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DVD Frequently Asked Questions (and Answers)

This is the May 9, 2000 revision of the official Internet DVD FAQ for the rec.video.dvd Usenet newsgroups.
(See below for what's new.) Please send corrections, additions, and new questions to Jim Taylor <jtfrog@usa.net>.

This FAQ is updated at least once a month. If you are looking at a version more than a month old, it's an out-of-date copy. The most current version is at DVD Demystified.


Recent changes (last posted to newsgroups on Feb 9):

[0] Where can I get the DVD FAQ?

[0.1] Has the DVD FAQ been translated into other languages?

Various translations of the DVD FAQ are available:

If you'd like to translate the DVD FAQ into another language (Klingon, anyone?), please contact Jim.

[0.2] This FAQ is too long and technical. Is there a simpler version?

Yup. Take a gander at Earl's Famous DVD Technology Exposition Web Page Extravaganza Supreme Deluxe <lonestar.texas.net/~bdub/earl/dvd.htm>.

[0.3] Is this FAQ any good? How do I know it's accurate?

Here are a few user comments on the DVD FAQ. It's the most accurate source of DVD information in this galaxy. If you find something you think is in error, please let Jim know.

Pointers to other DVD sites are scattered throughout the FAQ and in section 6.4

[1] General DVD

[1.1] What is DVD?

DVD, which once stood for Digital Video Disc or Digital Versatile Disc, is the next generation of optical disc storage technology. It's essentially a bigger, faster CD that can hold cinema-like video, better-than-CD audio, and computer data. DVD aims to encompass home entertainment, computers, and business information with a single digital format, eventually replacing audio CD, videotape, laserdisc, CD-ROM, and perhaps even video game cartridges. DVD has widespread support from all major electronics companies, all major computer hardware companies, and all major movie and music studios. With this unprecedented support, DVD has become the most successful consumer electronics product of all time in less than three years of its introduction.

It's important to understand the difference between the physical formats (such as DVD-ROM or DVD-R) and the application formats (such as DVD-Video or DVD-Audio). DVD-ROM is the base format that holds data. DVD-Video (often simply called DVD) defines how video programs are stored on disc and played in a DVD-Video player or a DVD computer (see 4.1). The difference is similar to that between CD-ROM and Audio CD. DVD-ROM includes recordable variations DVD-R, DVD-RAM, DVD-RW, and DVD+RW (see 4.3). The application formats include DVD-Video, DVD-Video Recording, DVD-Audio (see 1.23), DVD-Audio Recording, DVD Stream Recording, and SACD). There are also special application formats for game consoles such as Sony PlayStation II.

[1.2] What are the features of DVD-Video?

Note: Most discs do not contain all features (multiple audio/subtitle tracks, seamless branching, parental control, etc.), as each feature must be specially authored. Some discs may not allow searching or skipping.

Most players support a standard set of features:

* Must be supported by additional content on the disc.

Some players include additional features:

[1.3] What's the quality of DVD-Video?

DVD has the capability to produce near-studio-quality video and better-than-CD-quality audio. DVD is vastly superior to videotape and generally better than laserdisc (see 2.8.). However, quality depends on many production factors. As compression experience and technology improves we will see increasing quality, but as production costs decrease we will also see more shoddily produced discs. A few low-budget DVDs will even use MPEG-1 encoding (which is no better than VHS) instead of higher-quality MPEG-2.

DVD video is usually encoded from digital studio master tapes to MPEG-2 format. The encoding process uses lossy compression that removes redundant information (such as areas of the picture that don't change) and information that's not readily perceptible by the human eye. The resulting video, especially when it is complex or changing quickly, may sometimes contain visual flaws, depending on the processing quality and amount of compression. At average rates of 3.5 Mbps (million bits/second), compression artifacts may be occasionally noticeable. Higher data rates can result in higher quality, with almost no perceptible difference from the master at rates above 6 Mbps. As MPEG compression technology improves, better quality is being achieved at lower rates.

Video from DVD sometimes contains visible artifacts such as color banding, blurriness, blockiness, fuzzy dots, shimmering, missing detail, and even effects such as a face that "floats" behind the rest of the moving picture. It's important to understand that the term "artifact" refers to anything that was not originally present in the picture. Artifacts are sometimes caused by poor MPEG encoding, but artifacts are more often caused by a poorly adjusted TV, bad cables, electrical interference, sloppy digital noise reduction, improper picture enhancement, poor film-to-video transfer, film grain, player faults, disc read errors, etc. Most DVDs exhibit few visible MPEG compression artifacts on a properly configured system.. If you think otherwise, you are misinterpreting what you see.

Some early DVD demos were not very good, but this is simply an indication of how bad DVD can be if not properly processed and correctly reproduced. Many demo discs were rushed through the encoding process in order to be distributed as quickly as possible. Contrary to common opinion, and as stupid as it may seem, these demos were not carefully "tweaked" to show DVD at its best. In-store demos should be viewed with a grain of salt, since most salespeople are incapable of properly adjusting a television set. 

Most TVs have the sharpness set too high for the clarity of DVD. This exaggerates high-frequency video and causes distortion, just as the treble control set too high for a CD causes it to sound harsh. Many DVD players output video with a black-level setup of 0 IRE (Japanese standard) rather than 7.5 IRE (US standard). On TVs that are not properly adjusted this can cause some blotchiness in dark scenes. DVD video has exceptional color fidelity, so muddy or washed-out colors are almost always a problem in the display (or the original source), not in the DVD player or disc.

DVD audio quality is superb. DVD includes the option of PCM (pulse code modulation) digital audio with sampling sizes and rates higher than audio CD. Alternatively, audio for most movies is stored as discrete, multi-channel surround sound using Dolby Digital or DTS audio compression similar to the digital surround sound formats used in theaters. As with video, audio quality depends on how well the processing and encoding was done. In spite of compression, Dolby Digital and DTS can be close to or better than CD quality.

The final assessment of DVD quality is in the hands of consumers. Most viewers consistently rate it better than laserdisc, but no one can guarantee the quality of DVD, just as no one should dismiss it based on demos or hearsay. In the end it's a matter of individual perception and the level of quality delivered by the playback system.

[1.4] What are the disadvantages of DVD?

[1.5] What DVD players and drives are available?

Some manufacturers originally announced that DVD players would be available as early as the middle of 1996. These predictions were woefully optimistic. Delivery was initially held up for "political" reasons of copy protection demanded by movie studios, but was later delayed by lack of titles. The first players appeared in Japan in November, 1996, followed by U.S. players in March, 1997. Players slowly trickled in to other regions. Now, over two years after the initial launch, over a hundred models of DVD players are available from dozens of electronics companies. Prices for the first players were $1000 and up. By the middle of 1999, players were available for under $200 at discount retailers.

See section 6.2 for a list of companies that provide DVD players.

Fujitsu supposedly released the first DVD-ROM-equipped computer on Nov. 6 in Japan. Toshiba released a DVD-ROM-equipped computer and a DVD-ROM drive in Japan in early 1997 (moved back from December which was moved back from November). DVD-ROM drives from Toshiba, Pioneer, Panasonic, Hitachi, and Sony began appearing in sample quantities as early as January 1997, but none were to be available before May. The first upgrade kits (combination DVD-ROM drive and decoder hardware) became available from Creative Labs, Hi-Val, and Diamond Multimedia in April and May of 1997.

Today, every major PC manufacturer has models that include DVD-ROM drives. The price difference from the same system with a CD-ROM drive ranges from $30 to $200 (laptops have more expensive drives). Upgrade kits for older computers are available for $100 to $700 from Creative Labs, DynaTek, E4 (Elecede), Hi-Val, Leadtek, Margi Systems (for laptops), Media Forte, Pacific Digital, Sigma Designs, Sony, STB Systems, Toshiba, Utobia, and others. For more information about DVDs on computers, including writable DVD drives, see section 4.

Note: If you buy a player or drive from outside your country (e.g., a Japanese player for use in the US) you may not be able to play region-locked discs on it. (See 1.10.)

More information:

[1.5.1] Which player should I buy?

There are many good players available. Video and audio performance in all modern DVD players is excellent. Personal preferences, your budget, and your existing home theater setup all play a large role in what player is best for you. Unless you have a high-end home theater setup, a player that costs under $400 should be completely adequate. Make a list of things that are important to you (such as ability to play CD-Rs, ability to play Video CDs, 96 kHz/24-bit audio decoding, DTS Digital Out, internal 6-channel Dolby Digital decoder) to help you come up with a set of players. Then try out a few of the players in your price range, focusing on ease of use (remote control design, user interface, front-panel controls). Since there is not a big variation in picture quality and sound quality within a given price range, convenience features play a big part. The remote control, which you'll use all the time, can drive you crazy if it doesn't suit your style.

In certain cases, you might want to buy a DVD PC instead of a standard DVD player, especially if you want progressive video. See 1.40 and 4.1

Here are a few questions to ask yourself.

- Do I want selectable sound tracks and subtitles, multiangle viewing, aspect ratio control, parental/multirating features, fast and slow playback, great digital video, multichannel digital audio, compatibility with Dolby Pro Logic receivers, on-screen menus, dual-layer playback, and ability to play audio CDs? If so, this is the wrong question to ask yourself, since all DVD players have all of these features.
- Do I appreciate special deals? If so, look for free DVD coupons and free DVD rentals that are available with many players.
- Do I want DTS audio? If so, look for a player with the "DTS Digital Out" logo. (See 3.6.2.) 
- Do I want to play Video CDs? If so, check the specs for Video CD compatibility. (See 2.4.5.)
- Do I need a headphone jack?
- Do I want player setup menus in languages other than English? If so, look for multilanguage setup feature. (Note: the multilanguage menus on certain discs are supported by all players.)
- Do I want to play homemade CD-R audio discs? If so look for the "dual laser" feature. (See 2.4.3.)
- Do I want to replace my CD player? If so, you might want a changer that can hold 3, 5, or even hundreds of discs.
- Do I want to control all my entertainment devices with one remote control? If so, look for a player with a programmable universal remote, or make sure your existing universal remote is compatible with the DVD player.
- Do I want to zoom in to check details of the picture? If so, look for players with picture zoom.
- Do I want to play HDCDs? If so, check for the HDCD logo. (See 2.4.13.)
- Does my receiver have only optical or only coax digital audio inputs? If so, make sure the player has outputs to match. (See 3.2.)
- Do I care about black-level adjustment?

For more information, read hardware reviews at Web sites such as DVDFile, DVD Resource, and E-Town, or in magazines such as Widescreen Review. You may also want to read about user experiences in online forums at Home Theater Forum and DVDFile.

See sections 3.1 and 3.2 for specific information on what audio/video connections are needed to fit into your existing setup.

[1.6] What DVD titles are available?

As with hardware, rosy predictions of hundreds of movie titles for Christmas of 1996 failed to materialize. Only a handful of DVD titles, mostly music videos, were available in Japan for the November 1996 launch of DVD. Actual feature films began to appear in December. By April there were over 150 titles in Japan. Movies appeared in the US in March of 1997. Almost 19,000 discs were purchased in the first two weeks of the US launch -- more than expected. InfoTech predicted over 600 titles by the end of 1997 and more than 8,000 titles by 2000. By December 1997, over 1 million individual DVD discs were shipped. By June 1999, over 30 million discs had shipped. As of February 2000 there are just over 6,000 titles available in the US and over 9,000 worldwide. Compared to other launches (CD, LD, etc.) this is a huge number in a very short time.

See 6.3 for a list of Web sites where you can buy or rent DVDs.

Availability of DVD hardware and software in Europe runs about a year to 18 months behind the US. A number of launches were announced with little follow-through, but DVD began to become established around the end of 1998.

For an extensive, searchable database of movie titles available in the US and Canada see Jeff Phillips' <www.thedvdlist.com>. Perry Denton has a text list of region 1 titles at <www.surroundfreak.com/dvd/dvd1.htm>. For titles in Japan and Europe see Niels van Eijkelenburg's list at <www.surroundfreak.com/dvd/dvd2.htm>. Also check out the Internet Movie Database's DVD Browser or the searchable and downloadable database from the DVD Entertainment Group. New release lists and announcements are available at <www.image-entertainment.com/laserv.html>. For a list of widescreen-specific DVD titles, visit www.WidescreenReview.com>.

Concorde Video released a PAL-format 12 Monkeys in Germany at the end of March 1997. They were threatened by Philips with a lawsuit for not including a multichannel MPEG track, but the issue is now resolved (see 3.6).

DVD-ROM software will slowly appear. Approximately 50% of CD-ROM producers have announced intentions to develop for DVD-ROM. See 6.2 for a list. Many initial DVD-ROM titles are only be available as part of a hardware or software bundle until the market grows larger. IDC expected that over 13 percent of all software would be available in DVD-ROM format by the end of 1998, but reality didn't meet expectations. In one sense, DVD-ROMs are simply larger faster CD-ROMs and will contain the same material. But DVD-ROMs can also take advantage of the high-quality video and multi-channel audio capabilities being added to many DVD-ROM-equipped computers.

[1.7] How much do players and drives cost?

Mass-market DVD movie players currently list for $300 and up. (See 1.5 for models and prices.) Within a few years they may approach VCR prices. InfoTech predicts prices will be as low as $250 by the year 2000, and below $150 by 2005.

DVD-ROM drives and upgrade kits for computers sell for around $80 to $600. (OEM drive prices are under $70.) Prices are expected to drop quickly to current CD-ROM drive levels.

[1.8] How much do discs cost?

It varies, but most DVD movies list for $20 to $30 with street prices between $15 and $25, even those with supplemental material. Low-priced movies can be found for under $10. So far DVD has not followed the initial high rental price model of VHS.

DVD-ROMs will initially be slightly more expensive than CD-ROMs since there is more on them, they cost more to replicate, and the market is smaller. But once production costs drop and the installed base of drives grow, DVD-ROMs will cost about the same as CD-ROMs today.

[1.9] How quickly will DVD become established?

Not as fast as generally predicted, but faster than videotape, laserdisc, and CD. By the end of 1997 over 500,000 DVD-Video players shipped worldwide. 349,482 of these were in the US (with about 200,000 actually sold into homes). About 600 DVD video titles were available in the US, with over 5 million copies shipped and about 2 million sold. Around 330,000 DVD-ROM drives were shipped worldwide with about 1 million bundled DVD-ROM titles. Only 60 DVD-ROM titles were available by the end of 1997, most of them bundled with PCs or drive upgrade kits.

By the end of 1999, there were almost 5 million DVD-Video players in the US, and about 30 million DVD PCs.

Here are some predictions:

Here's reality:

For comparison, there were about 700 million audio CD players and 160 million CD-ROM drives worldwide in 1997. 1.2 billion CD-ROMs were shipped worldwide in 1997 from a base of about 46,000 different titles. There are about 80 million VCRs in the U.S. (89% of households) and about 400 million worldwide. 110,000 VCRs shipped in the first two years after release. Nearly 16 million VCRs were shipped in 1998. There are about 3 million laserdisc players in the U.S. There are about 270 million TVs in the U.S. and 1.3 billion worldwide.

[1.10] What are "regional codes," "country codes," or "zone locks"?

Motion picture studios want to control the home release of movies in different countries because theater releases aren't simultaneous (a movie may come out on video in the U.S. when it's just hitting screens in Europe). Also, studios sell distribution rights to different foreign distributors and would like to guarantee an exclusive market. Therefore they have required that the DVD standard include codes that can be used to prevent playback of certain discs in certain geographical regions. Each player is given a code for the region in which it's sold. The player will refuse to play discs that are not allowed in that region. This means that discs bought in one country may not play on players bought in another country. Some people believe that region codes could be considered an illegal restraint of trade, but there have been no legal cases to establish this.

Regional codes are entirely optional for the maker of a disc. Discs without codes will play on any player in any country. It's not an encryption system, it's just one byte of information on the disc that the player checks. Some studios originally announced that only their new releases will have regional codes, but so far almost all releases play in only one region. Region codes are a permanent part of the disc, they won't "unlock" after a period of time.

There are 8 regions (also called "locales"). Players and discs are identified by the region number superimposed on a world globe. If a disc plays in more than one region it will have more than one number on the globe.
1: U.S., Canada, U.S. Territories
2: Japan, Europe, South Africa, and Middle East (including Egypt)
3: Southeast Asia and East Asia (including Hong Kong)
4: Australia, New Zealand, Pacific Islands, Central America, Mexico, South America, and the Caribbean
5: Eastern Europe (Former Soviet Union), Indian subcontinent, Africa, North Korea, and Mongolia
6: China
7: Reserved
8: Special international venues (airplanes, cruise ships, etc.)
(See the map at <www.unik.no/~robert/hifi/dvd/world.html>.)

Some players can be modified to play discs regardless of their regional codes. This usually voids the warranty, but is probably not illegal. Some discs, such as those from Buena Vista/Touchstone/Miramax, MGM/Universal, and Polygram contain program code that checks for the proper region. These "smart discs" that do active region checking won't play on code-free players that have their region set to 0, but they can be played on code-switchable players that allow you to change the region using the remote control. They may also not work on auto-switching players that recognize and match the disc region. Information about modifying players can be found on the Internet (at sites such as Code Free DVD, dvdkits.com, DVD Upgrades, Link Electronics, PlanetDVD, 7thZone, Techtronics, Upgrade Heaven, and <www.brouhaha.com/~eric/video/dvd/>) and in the rec.video.dvd newsgroups (searchable at Deja.com).

Regional codes also apply to DVD-ROM systems, but are allowed for use only with DVD-Video discs, not DVD-ROM discs containing computer software. (See 1.11 below for more details). Computer playback systems check for regional codes before playing movies from a DVD-Video. Newer "RPC2" DVD-ROM drives let you change the region code several times. Once a drive has reached the limit (usually 5 changes) it can't be changed again unless the vendor or manufacturer resets it. The Drive Info utility can tell you if you have an RPC2 drive (it will say "This drive has region protection"). Drive Info and information about circumventing DVD-ROM region restrictions is available from Internet sites such as Visual Domain and DVD Infomatrix. After December 31, 1999, only RPC Phase II drives will be manufactured.

Regional codes do not apply to DVD-Audio.

[1.11] What are the copy protection issues?

There are four forms of copy protection used by DVD:

1) Analog CPS (Macrovision)
Videotape (analog) copying is prevented with a Macrovision 7.0 or similar circuit in every player. The general term is APS (Analog Protection System). Computer video cards with composite or s-video (Y/C) output must also use APS. Macrovision adds a rapidly modulated colorburst signal ("Colorstripe") along with pulses in the vertical blanking signal ("AGC") to the composite video and s-video outputs. This confuses the synchronization and automatic-recording-level circuitry in 95% of consumer VCRs. Unfortunately, it can degrade the picture, especially with old or nonstandard equipment. Macrovision may show up as stripes of color, distortion, rolling, black & white picture, and dark/light cycling. Macrovision creates problems for many line doublers. Macrovision is not present on analog component video output of early players, but is required on newer players (AGC only, since there is no burst in a component signal). The discs contain "trigger bits" telling the player whether or not to enable Macrovision AGC, with the optional addition of 2-line or 4-line Colorstripe. The triggers occur about once a second, which allows fine control over what part of the video is protected. The producer of the disc decides what amount of copy protection to enable and then pays Macrovision royalties accordingly (a few cents per disc). Just as with videotapes, some DVDs are Macrovision-protected and some aren't. (For a few Macrovision details see STMicroelectronics' NTSC/PAL video encoder datasheets at <www.st.com/stonline/books/>.)

Each disc also contains information specifying if the contents can be copied. This is a "serial" copy generation management system (SCMS) designed to prevent copies or copies of copies. The CGMS information is embedded in the outgoing video signal. For CGMS to work, the equipment making the copy must recognize and respect the CGMS. The analog standard (CGMS/A) encodes the data on NTSC line 21 (in the XDS service). The digital standard (CGMS/D) is not yet finalized, but will apply to digital connections such as IEEE 1394/FireWire. See section 4, below.

3) Content Scrambling System (CSS)
Because of the potential for perfect digital copies, paranoid movie studios forced a deeper copy protection requirement into the DVD standard. Content Scrambling System (CSS) is a data encryption and authentication scheme intended to prevent copying video files directly from the disc. CSS was developed primarily by Matsushita and Toshiba. Each CSS licensee is given a key from a master set of 400 keys that are stored on every CSS-encrypted disc. This allows a license to be revoked by removing its key from future discs. The CSS decryption algorithm exchanges keys with the drive unit to generate an encryption key that is then used to obfuscate the exchange of disc keys and title keys that are needed to decrypt data from the disc. DVD players have CSS circuitry that decrypts the data before it's decoded and displayed. On the computer side, DVD decoder hardware and software must include a CSS decryption module. All DVD-ROM drives have extra firmware to exchange authentication and decryption keys with the CSS module in the computer. Beginning in 2000, new DVD-ROM drives are required to support regional management in conjunction with CSS (see 1.10 and 4.1). Makers of equipment used to display DVD-Video (drives, decoder chips, decoder software, display adapters, etc.) must license CSS. There is no charge for a CSS license, but it's a lengthy process, so it's recommended that interested parties apply as soon as possible. Near the end of May 1997, CSS licenses were finally granted for software decoding. The license is extremely restrictive in an attempt to keep the CSS algorithm and keys secret. Of course, nothing that's used on millions of players and drives worldwide could be kept secret for long. In October 1999, the CSS algorithm was cracked and posted on the Internet, triggering endless controversies and legal battles (see 4.8).

4) Digital Copy Protection System (DCPS)
In order to provide for digital connections between components without allowing perfect digital copies, five digital copy protection systems have been proposed to CEMA. The frontrunner is DTCP (digital transmission content protection), which focuses on IEEE 1394/FireWire but can be applied to other protocols. The draft proposal (called 5C, for the five companies that developed it) was made by Intel, Sony, Hitachi, Matsushita, and Toshiba in February 1998. Sony released a DTCP chip in mid 1999. Under DTCP, devices that are digitally connected, such as a DVD player and a digital TV or a digital VCR, exchange keys and authentication certificates to establish a secure channel. The DVD player encrypts the encoded audio/video signal as it sends it to the receiving device, which must decrypt it. This keeps other connected but unauthenticated devices from stealing the signal. No encryption is needed for content that is not copy protected. Security can be "renewed" by new content (such as new discs or new broadcasts) and new devices that carry updated keys and revocation lists (to identify unauthorized or compromised devices). A competing proposal, XCA (extended conditional access), from Zenith and Thomson, is similar to DTCP but can work with one-way digital interfaces (such as the EIA-762 RF remodulator standard) and uses smart cards for renewable security. Other proposals have been made by MRJ Technology, NDS, and Philips. In all five proposals, content is marked with CGMS-style flags of "copy freely", "copy once," "don't copy," and sometimes "no more copies". Digital devices that do nothing more than reproduce audio and video will be able to receive all data (as long as they can authenticate that they are playback- only devices). Digital recording devices are only able to receive data that is marked as copyable, and they must change the flag to "don't copy" or "no more copies" if the source is marked "copy once." Digital CPS is designed for the next generation of digital TVs, digital receivers, and digital video recorders. It will require new DVD players with digital connectors (such as those on DV equipment). These new products won't appear until 2000. Since the encryption is done by the player, no changes are needed to the existing disc format.

The first three forms of copy protection are optional for the producer of a disc. Movie decryption is also optional for hardware and software playback manufacturers: a player or computer without decryption capability will only be able to play unencrypted movies. DCPS is performed by the DVD player, not by the disc developer.

These copy protection schemes are designed only to guard against casual copying (which the studios claim causes billions of dollars in lost revenue). The goal is to "keep the honest people honest." Even the people who developed the copy protection standards admit that they won't stop well-equipped pirates. There are inexpensive devices that defeat Macrovision, although only a few work with the new Colorstripe feature. These devices go under names such as Video Clarifier, Image Stabilizer, Color Corrector, and CopyMaster.

Movie studios have promoted legislation making it illegal to defeat DVD copy protection. The result is the World Intellectual Property Organization (WIPO) Copyright Treaty and the WIPO Performances and Phonograms Treaty (December 1996) and the compliant U.S. Digital Millennium Copyright Act (DMCA), passed into law in October 1998. Software intended specifically to circumvent copy protection is now illegal in the U.S. and many other countries. A co-chair of the legal group of the DVD copy protection committee stated, "in the video context, the contemplated legislation should also provide some specific assurances that certain reasonable and customary home recording practices will be permitted, in addition to providing penalties for circumvention." It's not at all clear how this might be "permitted" by a player or by studios that set the "don't copy" flag on all their discs.

DVD-ROM drives and computers, including DVD-ROM upgrade kits, are required to support Macrovision, CGMS, and CSS. PC video cards with TV outputs that don't support Macrovision will not work with encrypted movies. Computers with IEEE 1394/FireWire connections must support the final DCPS standard in order to work with other DCPS devices. Every DVD-ROM drive must include CSS circuitry to establish a secure connection to the decoder hardware or software in the computer, although CSS can only be used on DVD-Video content. Of course, since a DVD-ROM can hold any form of computer data, other encryption schemes can be implemented. See 4.1 for more information on DVD-ROM drives.

The Watermarking Review Panel (WaRP) --the successor to the Data-Hiding Sub-Group (DHSG)-- of the industry's Copy Protection Technical Working Group (CPTWG) is evaluating watermarking proposals. The original seven watermarking proposals that were merged into three: IBM/NEC, Hitachi/Pioneer/Sony, and Macrovision/Digimarc/Philips. On February 17, 1999, the first two groups combined to form the "Galaxy Group" and merged their technologies into a single proposal. The second group has dubbed their technology "Millennium." Watermarking, which is used for DVD-Audio and will be added to DVD-Video at some point, permanently marks each digital audio or video frame with noise that is supposedly undetectable by human ears or eyes. Watermark signatures can be recognized by playback and recording equipment to prevent copying, even when the signal is transmitted via digital or analog connections or is subjected to video processing. New players and other equipment will be required to support watermarking, but the DVD Forum intends to make watermarked discs compatible with existing players. There were reports that the early watermarking technique used by Divx caused visible "raindrop" or "gunshot" patterns, but the problem seemed to have been solved for later releases.

[1.12] What about DVD-Audio or Music DVD?

When DVD was released in 1996 there was no DVD-Audio format, although the audio capabilities of DVD-Video far surpassed CD. The DVD Forum sought additional input from the music industry before defining the DVD-Audio format. A draft standard was released by the DVD Forum's Working Group 4 (WG4) in January 1998, and version 0.9 was released in July. The final DVD-Audio 1.0 specification (minus copy protection) was approved in February 1999 and released in March. DVD-Audio products may show up in mid 2000. The delay is in part caused by the slow process of selecting copy protection features (encryption and watermarking), with complications introduced by the Secure Digital Music Initiative (SDMI). Proposals from Aris, Blue Spike, Cognicity, IBM, and Solana were evaluated by major music companies in conjunction with the 4C Entity, comprising IBM, Intel, Matsushita, and Toshiba. Aris and Solana merged to form a new company called Verance, whose Galaxy technology was chosen in August 1999. (In November 1999, Verance watermarking was also selected for SDMI.) The scheduled October release was delayed until mid 2000, ostensibly because of concerns caused by the CSS crack (see 4.8), but also because the hardware wasn't quite ready, production tools aren't up to snuff, and there is lackluster support from music labels.

Matsushita hopes to have Panasonic and Technics brand universal DVD-Audio/DVD-Video players available in mid 2000 , which will cost $700 to $1,200. Pioneer, JVC, Yamaha, and others may also release DVD-Audio players at the same time.

In the meantime, the DVD-Video standard includes surround sound audio and better-than-CD audio (see 3.6.2).

DVD-Audio is a separate format from DVD-Video. DVD-Audio discs can be designed to work in DVD-Video players, but it's possible to make a DVD-Audio disc that won't play at all in a DVD-Video player, since the DVD-Audio specification includes new formats and features, with content stored in a separate "DVD-Audio zone" on the disc (the AUDIO_TS directory) that DVD-Video players never look at. New DVD-Audio players are needed, or new "universal players" that can play both DVD-Video and DVD-Audio discs.

Plea to producers: Universal players won't be available for some time, but you can make universal discs today. With a small amount of effort, all DVD-Audio discs can be made to work on all DVD players by including a Dolby Digital version of the audio in the DVD-Video zone.
Plea to DVD-Audio authoring system developers: Make your software do this by default or strongly recommend this option during authoring.

DVD-Audio (and universal) players will work with existing receivers. They output PCM and Dolby Digital, and some will support the optional DTS and DSD formats. However, most current receivers can't decode the high-definition PCM audio (see 3.6.1 for details), and even if they could it can't be carried on standard digital audio connections. DVD-Audio players with high-end digital-to-analog converters (DACs) can only be hooked up to receivers with two-channel or 6-channel analog inputs, but some quality will be lost if the receiver converts back to digital for processing. Future receivers with improved digital connections such as IEEE 1394 (FireWire) will be needed to use the full digital resolution of DVD-Audio.

DVD audio is copyright protected by an embedding signaling or digital watermark feature. This uses signal processing technology to apply a digital signature and optional encryption keys to the audio in the form of supposedly inaudible noise so that new equipment will recognize copied audio and refuse to play it. Audiophiles claim this degrades the audio, but extensive test performed by the 4C indicate that even golden-eared listeners can't detect the watermarking noise.

Sony and Philips have developed a competing Super Audio CD format that uses DVD discs. (See 3.6.1 for details.) SACD is supposed to provide "legacy" discs that have two layers, one that plays in existing CD players, plus a high-density layer for DVD-Audio players, but technical difficulties have kept dual-format discs from being produced. Ironically, initial price for these dual-layer discs will be higher than for a standard CD plus a standard DVD. Sony released version 0.9 of the SACD spec in April 1998, the final version appeared in April (?) 1999. SACD technology is available to existing Sony/Philips CD licensees at no additional cost. Pioneer, which released the first DVD-Audio players in Japan at the end of 1999, included SACD support in their DVD-Audio players. If other manufacturers follow suit, the entire SACD vs. DVD-Audio standards debate will be moot, since DVD-Audio players will play both types of discs.

Sony released an SACD player in Japan in May 1999 at the tear-inducing price of $5,000. The player was released in limited quantities in the U.S. at the end of 1999. Initial SACD releases are mixed in stereo, not multichannel. About 40 SACD titles were available at the end of 1999, from studios such as DMP, Mobile Fidelity Labs, Pioneer, Sony, and Telarc.

[1.13] Which studios are supporting DVD?

When DVD players became available in early 1997, Warner and Polygram were the only major movie studios to release titles. Additional titles were available from small developers. The other studios gradually joined the DVD camp (see 6.2 for a full list, see 1.6 for movie info).

Dreamworks was the last significant studio to announce full DVD support. Paramount, Fox, and Dreamworks initially supported only Divx, but in summer 1998 they each announced support for open DVD.

[1.14] Can DVD record from VCR/TV/etc?

Short Answer: Not yet, but soon. Pioneer and Philips have announced DVD home video recorders. (See 4.3.)

Long answer: Recording analog video to DVD is a very tricky process. The minimum requirement for reproducing audio and video on DVD is an MPEG video stream and a PCM audio track. (Other streams such as Dolby Digital audio, MPEG audio, and subpicture are not necessary for the simplest case.) Basic DVD control codes are also needed. It's difficult in real time to encode the video and audio, combine them with DVD-Video info, and write the whole thing to a recordable DVD disc, especially in a form that's compatible with standard DVD-Video players. This is still extremely expensive for a home recorder, even though prices for DVD production systems have dropped over the space of three years from millions of dollars to thousands of dollars to hundreds of dollars for the simplest packages.

Other obstacles: Blank discs cost about $25 (although they will get cheaper over time). Real-time compression requires higher bit rates for decent quality, thus lowering capacity. MPEG-2 compression works much better with high-quality source, so recording from VHS or broadcast/cable may not give very good results (unless the DVD recorder has special prefilters, which increases the cost).

Don't be confused by DVD-R drives, DVD-RAM drives, or other recordable DVD drives for computers (see 4.3). These existing recorders can store data, but to create full-featured DVD-Videos requires additional hardware and software to do video encoding (MPEG), audio encoding (Dolby Digital, MPEG, or PCM), subpicture encoding (run-length-compressed bitmaps), still frame encoding (MPEG), navigation and control data generation, and multiplexing.

In spite of all the difficulties, many of the major DVD manufacturers are working on recordable DVD for the home. We will see various DVD video recorders in the year 2000. Early units, especially those that can record from analog video sources such as TV, will be expensive: probably $2,000 and up. There will also be cheaper units that can record only from a source of already-compressed digital audio and video, such as satellite, DTV, or digital cable. At some point, DVD recorder/players will be built into satellite and cable receivers. 

Some people believe that recordable DVD-Video will never be practical for consumers to record TV shows or home videos, since digital tape is more cost effective. On the other hand, digital tape lacks many of the advantages of DVD such as seamless branching, instant rewind/fast forward, instant search, and durability, not to mention the coolness of small shiny discs. Once the encoding technology is fast and cheap enough, and blank discs are cheap enough, recordable DVD will reach the mainstream.

[1.15] What happens if I scratch the disc? Aren't discs too fragile to be rented?

Most scratches will cause minor channel data errors that are easily corrected. That is, data is stored on DVDs using powerful error correction techniques that can recover from scratches as big as 6 millimeters with no loss of data. A common misperception is that a scratch will be worse on a DVD than on a CD because of higher storage density and because video is heavily compressed. DVD data density (say that fast ten times!) is physically four times that of CD-ROM, so it's true that a scratch will affect more data. But DVD error correction is at least ten times better than CD-ROM error correction and more than makes up for the density increase. It's also important to realize that MPEG-2 and Dolby Digital compression are partly based on removal or reduction of imperceptible information, so decompression doesn't expand the data as much as might be assumed. Major scratches may cause uncorrectable errors that will produce an I/O error on a computer or show up as a momentary glitch in DVD-Video picture. Paradoxically, sometimes the smallest scratches can cause the worst errors (because of the particular orientation and refraction of the scratch). There are many schemes for concealing errors in MPEG video, which may be used in future players (see section D.12 of <icib.igd.fhg.de/icib/it/iso/cd_13818-2/read1.html>).

See 1.39 for information on care and cleaning of DVDs.

The DVD computer advisory group specifically requested no mandatory caddies or other protective carriers. Consider that laserdiscs, music CDs, and CD-ROMs are likewise subject to scratches, but many video stores and libraries rent them. Major chains such as Blockbuster and West Coast Entertainment rent DVDs in many locations. So far most reports of rental disc performance are positive. A nice list of DVD rental outlets is at <home.earthlink.net/~tlfordham/rental.html>.

[1.16] VHS is good enough, why should I care about DVD?

The primary advantages of DVD are quality and extra features (see 1.2). DVD will not degrade with age or after many playings like videotape will (which is an advantage for parents with kids who watch Disney videos twice a week!). This is the "collectability" factor present with CDs vs. cassette tapes.

If none of this matters to you, then VHS probably is good enough.

[1.17] Is the packaging different from CD?

Manufacturers are worried about customers assuming DVDs will play in their CD player, so they would like the packaging to be different. There are a number of DVD packages that are as wide as a CD jewel box (about 5-5/8") and as tall as a VHS cassette box (about 7-3/8"), as recommended by the Video Software Dealers Association (VSDA). However, no one is being forced to use a larger package size. Some companies use standard jewel cases or paper and vinyl sleeves. Divx discs came in paperboard and plastic Q-Pack cases the same size as a CD jewel case.

Most movies are packaged in the Amaray "keep case," an all-plastic clamshell with clear vinyl pockets for inserts, that's popular among consumers. Time Warner's "snapper," a paperboard case with a plastic lip, is less popular. There's also a "super jewel box," the stretch-limo version of a CD jewel case, that's common in Europe. 

[1.18] What's a dual-layer disc? Will it work in all players?

A dual-layer disc has two layers of data, one of them semi-transparent so that the laser can focus through it and read the second layer. Since both layers are read from the same side, a dual-layer disc can hold almost twice as much as a single-layer disc, for over 4 hours of video (see 3.3 for more details). Many discs use dual layers. Initially only a few replication plants could make dual-layer discs, but most plants now have the capability. The second layer can use either a PTP (parallel track path) layout where both tracks run in parallel (for independent data or special switching effects), or an OTP (opposite track path) layout where the second track runs in an opposite spiral; that is, the pickup head reads out from the center on the first track then in from the outside on the second track. The OTP layout is designed to provide continuous video across both layers. The layer change can occur anywhere in the video; it doesn't have to be at a chapter point. There's no guarantee that the switch between layers will be seamless. The layer change is invisible on some players, but it can cause the video to freeze for a fraction of a second or up to 4 seconds on other players. The "seamlessness" depends as much on the way the disc is prepared as on the design of the player. OTP is also called RSDL (reverse-spiral dual layer). The advantage of OTP/RSDL is that long movies can use higher data rates for better quality than with a single layer. See 1.27 for layer change details.

There are various ways to recognize dual-layer discs: 1) the gold color, 2) a menu on the disc for selecting the widescreen or letterbox version, 3) two serial numbers on one side.

All DVD players and drives can read dual-layer discs -- it's required by the spec. All players and drives also play double-sided discs if you flip them over. No manufacturer has announced a model that will play both sides. The added cost is probably not justifiable since discs can hold over 4 hours of video on one side by using two layers. (Early discs used two sides because dual-layer production was not widely supported. This should no longer be a problem.) Pioneer LD/DVD players can play both sides of an LD, but not a DVD. (See 2.12 for note on reading both sides simultaneously.)

[1.19] Is DVD-Video a worldwide standard? Does it work with NTSC, PAL, and SECAM?

DVD has the same NTSC vs. PAL problem as videotape and laserdisc. The MPEG video on DVD is stored in digital format, but it's formatted for one of two mutually incompatible television systems: 525/60 (NTSC) or 625/50 (PAL/SECAM). There are three differences between discs intended for playback on different systems: picture size and pixel aspect ratio (720x480 vs. 720x576), display frame rate (29.97 vs. 25), and surround audio (Dolby Digital vs. MPEG). (See 3.4 and 3.6 for details.) Video from film is usually stored at 24 frames/sec but is preformatted for one of the two display rates. Movies formatted for PAL display are usually sped up by 4%, so the audio must be adjusted accordingly before being encoded. Unless the audio is digitally processed to shift the pitch back to normal, it will be slightly high. All PAL DVD players can play Dolby Digital audio tracks, but no NTSC players can play MPEG audio tracks. PAL and SECAM share the same scanning format, so discs are the same for both systems. The only difference is that SECAM players output the color signal in the format required for SECAM TVs.

Some players only play NTSC discs, some players only play PAL discs, and some play both. All DVD players sold in PAL countries play both. These multi-standard players partially convert NTSC to a 60Hz PAL (4.43 NTSC) signal. The player uses the PAL 4.43 MHz color subcarrier encoding format but keeps the 525/60 NTSC scanning rate. Most modern PAL TVs can handle this kind of "pseudo-PAL" 60-Hz signal. A few multi-standard PAL players output true 3.58 NTSC from 525/60 NTSC discs, which requires an NTSC TV or a multi-standard TV. Some players have a switch to choose 60-Hz PAL or NTSC output when playing NTSC discs. There are a few standards-converting PAL players (from Samsung and others) that convert from a 525/60 NTSC disc to standard PAL output. Proper standards conversion requires expensive hardware to handle scaling, temporal conversion, and object motion analysis. Because the quality of conversion in DVD players is poor, using 60Hz PAL output with a compatible TV provides a better picture. Most NTSC players can't play PAL discs. A very small number of NTSC players (such as the Apex) can convert 625/50 PAL to NTSC. External converter boxes are also available, such as the Emerson EVC1595 ($350). High-quality converters are available at TenLab.

A producer can choose to put 525/60 video on one side of the disc and 625/50 on the other. Most studios so far are including Dolby Digital audio tracks on their PAL discs.

There are actually three types of DVD players if you count computers. Most DVD PC software and hardware can play both NTSC and PAL video and both Dolby Digital and MPEG audio. Some PCs can only display the converted video on the computer monitor, but others can output it as a video signal for a TV.

[1.20] What about animation on DVD? Doesn't it compress poorly?

Some people claim that animation, especially hand-drawn cell animation such as cartoons and anime, does not compress well with MPEG-2 or even ends up larger than the original. Other people claim that animation is simple so it compresses better. Neither is true.

Supposedly the "jitter" between frames caused by differences in the drawings or in their alignment causes problems. An animation expert at Disney pointed out that this doesn't happen with modern animation techniques. And even if it did, the motion estimation feature of MPEG-2 would compensate for it.

Because of the way MPEG-2 breaks a picture into blocks and transforms them into frequency information it can have a problem with the sharp edges common in animation. This loss of high-frequency information can show up as "ringing" or blurry spots along edges (called the Gibbs effect). However, at the data rates commonly used for DVD this problem does not occur.

[1.21] Why do some discs require side flipping? Can't DVDs hold four hours per side?

Even though DVD's dual-layer technology (see 3.3) allows over four hours of continuous playback from a single side, some movies are split over two sides of a disc, requiring that the disc be flipped partway through. Most "flipper" discs exist because of producers who are too lazy to optimize the compression or make a dual-layer disc. Better picture quality is a cheap excuse for increasing the data rate; in many cases the video will look better if carefully encoded at a lower bit rate. Lack of dual-layer production capability is also a lame excuse; in 1997 very few DVD plants could make dual-layer discs, but this is no longer the case. No players can automatically switch sides, but it's not needed since most movies less than 4 hours long can easily fit on one dual-layer (RSDL) side.

There is a list of "flipper" discs in the Film Vault at DVD Review. Note: A flipper is not the same as a disc with a widescreen version on one side and a pan & scan version or supplements on the other. Please send additions to info@dvdreview.com. (The list has gotten too long to keep in this FAQ.)

[1.22] Why is the picture squished, making things look too skinny?

Answer: RTFM. You are watching an anamorphic picture intended for display only on a widescreen TV. (See 3.5 for technical details). You need to go into the player's setup menu and tell it you have a standard 4:3 TV, not a widescreen 16:9 TV. It will then automatically letterbox the picture so you can see the full width at the proper proportions.

In some cases you can change the aspect ratio as the disc is playing (by pressing the "aspect" button on the remote control). On most players you have to stop the disc before you can change aspect. Some discs are labeled with widescreen on one side and standard on the other. In order to watch the fullscreen version you must flip the disc over.

See Steve Tannehill's Why Does The Picture Look Squished? article for further explanation and pictures.

[1.23] Do all videos use Dolby Digital (AC-3)? Do they all have 5.1 channels?

Most DVD-Video discs contain Dolby Digital soundtracks. However, it's not required. Some discs, especially those containing only audio, have PCM tracks. It's also possible for a 625/50 (PAL) disc to contain only MPEG audio, but so far MPEG audio is not widely used.

Don't assume that the "Dolby Digital" label is a guarantee of 5.1 channels. A Dolby Digital soundtrack can be mono, dual mono, stereo, Dolby Surround stereo, etc. For example, Blazing Saddles and Caddyshack are mono movies, so the Dolby Digital soundtrack on these DVDs has only one channel. Some DVD packaging has small lettering or icons under the Dolby Digital logo that indicates the channel configuration. In some cases, there is more than one Dolby Digital version of a soundtrack: a 5.1-channel track and a track specially remixed for stereo Dolby Surround. It's perfectly normal for your DVD player to indicate playback of a Dolby Digital audio track while your receiver indicates Dolby Surround: it means that the disc contains a two-channel Dolby Surround signal encoded in Dolby Digital format.

See 3.6 for more audio details.

[1.24] Can DVDs have laser rot?

Laserdiscs are subject to what's commonly called laser rot: the deterioration of the aluminum layer due to oxidation or other chemical change. This often results from the use of insufficiently pure aluminum during replication, but can be exacerbated by mechanical shear stress due to bending, warping or thermal cycles (the large size of laserdiscs makes them flexible, so that movement along the bond between layers can break the seal). Deterioration of the data layer can be caused by chemical contaminants or gasses in the glue, or by moisture that penetrates the acrylic substrates.

Like laserdiscs, DVDs are made of two platters glued together, but DVDs are more rigid and use newer adhesives. DVDs are molded from polycarbonate, which absorbs about ten times less moisture than the slightly hygroscopic acrylic (PMMA) used for laserdiscs.

It's too early to know for sure, but DVDs will probably have few laser rot problems. There have been reports of a few discs going bad, possibly due to poor adhesive, chemical reactions, or oxidation of the aluminum layer. See www.mindspring.com/~yerington/.

[1.25] Which titles are pan & scan only? Why?

Some titles are available only in pan & scan because there was no letterbox or anamorphic transfer made from film. (See 3.5 for more info on pan & scan and anamorphic formats.) Since transfers cost $50,000 to $100,000, studios may not think a new transfer is justified. In some cases the original film or rights to it are no longer available for a new transfer. In the case of old movies, they were shot full frame in the 1.37 "academy" aspect ratio so there can be no widescreen version. Video shot with TV cameras, such as music concerts, is already in 4:3 format.

The list of pan & scan only titles has gotten too big to keep here. You can get a list from the Internet Movie Database (which also includes discs with both widescreen and pan & scan versions), and you can search by screen format (which includes disc with video shot in fullscreen 4:3) at The DVD List.

[1.26] How do I make the subtitles on my Pioneer player go away?

On the remote control, press Subtitle, then either Clear or 0 (zero). No need to use the menus.

[1.27] What is a layer change? Where is it on specific discs?

Some movies, especially those over two hours long or encoded at a high data rate, are spread across two layers on one side of the disc. When the player changes to the second layer, the video and audio may freeze for a moment. The length of the pause depends on the player and on the layout of the disc. The pause is not a defect in the player or the disc. See 1.18 for details.

There is a list of layer switch points in the Film Vault at DVD Review. Please send new times to info@dvdreview.com. (The list has gotten too long to keep in this FAQ.)

[1.28] The disc says Dolby Digital. Why do I get 2-channel surround audio?

Some discs (many from Columbia TriStar) have 2-channel Dolby Surround audio (or plain stereo) on track one and 5.1-channel audio on track two. Since some studios create separate sound mixes optimized for Dolby Surround or stereo, and they feel the default track should match the majority of sound systems in use. Unless you specifically select the 5.1-channel track (with the audio button on the remote or with the on-screen menu) the player will play the default 2-channel track. (Note: Some players such as the Sony 3000 have a feature to automatically select the first 5.1 track.)

Dolby Digital doesn't necessarily mean 5.1 channels. See 3.6.

[1.29] Why doesn't the repeat A-B feature work on some discs?

Almost all features of DVD such as search, pause, and scan can be disabled by the disc, which can prevent the operation the player needs to back up and repeat a segment. If the player uses time search to repeat a segment, then a disc with fancy non-sequential title organization may also block the repeat feature. In many cases the authors don't even realize they have prevented the use of this feature.

[1.30] What's the difference between first, second, and third generation DVD?

There is no good answer to this question, since you'll get a different response from everyone you ask. The terms "2nd generation" and "3rd generation," and so on refer both to DVD-Video players and to DVD-ROM drives. In general, they simply mean newer versions of DVD playback devices. The terms haven't been used (yet) to refer to DVD products that can record, play video games, or so on.

According to some people, second-generation DVD players came out in the fall of 1997 and third-generation players are those that came out in the beginning of 1998. According to others, the second generation of DVD will be "high-definition" players (see 2.12) that won't come out until 2003 or so. There are many confusing variations between these extremes, including the viewpoint that DTS-compatible players or Divx players or progressive-scan players constitute the third generation or fourth generation.

Things are a little more clear cut on the PC side, where second generation (DVD II) usually means 2x DVD-ROM drives that can read CD-Rs, and third generation (DVD III) usually means 5x (or sometimes 2x or 4.8x or 6x) DVD-ROM drives, a few of which can read DVD-RAMs, and some of which are RPC2 format. Some people refer to RPC2 drives or 10x drives as fourth generation. See section 4.2 for more speed info. See section 1.10 for RPC2 explanation.

[1.31] What's a hybrid DVD?

Do you really want the answer to this one? Ok, you asked for it...

  1. A disc that works in both DVD-Video players and DVD-ROM PCs. (The most common use of the term hybrid, but more accurately called an enhanced DVD)
  2. A DVD-ROM disc that runs on Windows and Mac OS computers. (More accurately called a cross-platform DVD.)
  3. A DVD-ROM or DVD-Video disc that also contains Web content for connecting to the Internet. (More accurately called a WebDVD or Web-connected DVD.)
  4. A disc that contains both DVD-Video and DVD-Audio content. (More accurately called a universal DVD.)
  5. A disc with two layers, one that can be read in DVD players and one that can be read in CD players. (More accurately called a legacy or CD-compatible disc.) There are at least three variations of this hybrid (none were commercially available as of 12/99):
    1. A 1.2mm CD substrate bonded to the back of a 0.6mm DVD substrate. One side can be read by CD players, the other side by DVD players. The resulting disc is 0.6mm thicker than a standard CD or DVD, which can cause problems in players with tight tolerances, such as portables. Sonopress, the first company to announce this type, calls it DVDPlus. It's colloquially known as a "fat" disc.
    2. A 0.6mm CD substrate bonded to the front of a semitransparent 0.6mm DVD substrate. Both layers are read from the same side, with the CD player being required to read through the semitransparent DVD layer, causing problems with some CD players.
    3. A 0.6mm CD substrate, with a special refractive coating that causes a 1.2mm focal depth, bonded to the back of a 0.6mm DVD substrate. One side can be read by CD players, the other side by DVD players.
  6. A disc with two layers, one containing pressed (DVD-ROM) data and one containing rewritable (DVD-RAM, etc.) media for recording and re-recording. (More accurately called a mixed-media or rewritable sandwich disc.)
  7. A disc with two layers on one side and one layer on the other. (More accurately called a DVD-14.)
  8. A disc with an embedded memory chip for storing custom usage data and access codes. (More accurately called a chipped DVD.)

Did I miss any?

[1.32] What's the deal with DTS and DVD?

Digital Theater Systems Digital Surround is an audio encoding format similar to Dolby Digital. It requires a decoder, either in the player or in an external receiver. See 3.6.2 for technical details. Some people claim that because of its lower compression level DTS sounds better than Dolby Digital. Others claim there is no meaningfully perceptible difference. Because of the many variances in production, mixing, decoding, and reference levels, it's almost impossible to accurately compare the two formats (DTS usually produces a higher volume level, causing it to sound better). 

DTS originally did all encoding in house, but as of October 1999 DTS encoders are available for purchase. DTS titles are generally considered to be specialty items intended for audio enthusiasts. It's expected that most DTS will also be available in a Dolby Digital-only version.

DTS is an optional format on DVD. Contrary to what some people claim, the DVD specification has included an ID code for DTS since 1996 (before the spec was even finalized). Because DTS was slow in releasing encoders and test discs, players made before mid 1998 (and many since) ignore DTS tracks. A few demo discs were created in 1997 by embedding DTS data into a PCM track (the same technique used with CDs and laserdiscs), and these are the only DTS DVD discs that work on all players. New DTS-compatible players arrived in mid 1998, but theatrical DTS discs using the proper DTS audio stream ID did not appear until January 7, 1999 (they were originally scheduled to arrive in time for Christmas 1997). Mulan, a direct-to-video animation (not the Disney movie) with DTS soundtrack did appear in November 1998. DTS-compatible players carry an official "DTS Digital Out" logo. A few manufacturers may provide upgrades to make existing players compatible with DTS discs.

Dolby Digital or PCM audio are required on 525/60 (NTSC) discs, and since both PCM and DTS together don't usually leave enough room for quality video encoding of a full-length movie, essentially every disc with a DTS soundtrack also carries a Dolby Digital soundtrack. This means that all DTS discs will work in all DVD players, but a DTS-compatible player and a DTS decoder are required to play the DTS soundtrack. DTS audio CDs work on all DVD players, since the DTS data is encapsulated into standard PCM tracks that are passed untouched to the digital audio output.

[1.33] Why is the picture black and white?

You are probably trying to play an NTSC disc in a PAL player, but your PAL TV is not able to handle the signal. If your player has a switch or on-screen setting to select the output format for NTSC discs, choosing PAL (60-Hz) may solve the problem. See section 1.19 for more information.

Or you may have connected one of the component outputs (Y, R-Y, or B-Y) of your DVD player to the composite input of your TV. See section 3.2 for hookup details. 

[1.34] Why are both sides fullscreen when one side is supposed to be widescreen?

Many DVD's are labeled as having widescreen (16:9) format video on one side and standard (4:3) on the other. If you think both sides are the same, you're probably seeing uncompressed 16:9 on the widescreen side. It seems to be 4:3 pan & scan, but if you look carefully you'll discover that the picture is horizontally compressed. The problem is that your player has been set for a widescreen TV. See 1.22 for details.

[1.35] Why are the audio and video out of sync?

There have been numerous reports of "lip sync" problems, where the audio lags slightly behind the video, and even reports of the audio coming before the video. Perception of a sync problem is highly subjective--some people are bothered by it while others can't discern it at all. Problems have been reported on a variety of players (notably the Pioneer 414 and 717 models, possibly all Pioneer models, some Sony models including the 500 series, new Toshiba models including the 3109, and some PC decoder cards). Certain discs are also more problematic (notably Lock, Stock, and Two Smoking Barrels; Lost In Space; TRON; The Parent Trap; and Austin Powers).

The cause of the sync problem is a complex interaction of as many as four factors

  1. Improper sync in audio/video encoding or DVD-Video formatting.
  2. Poor sync during film production or editing (especially post-dubbing or looping).
  3. Loose sync tolerances in the player.
  4. Delay in the external decoder/receiver.

Factor 1 or 2 usually must be present in order for factor 3 or 4 to become apparent. Some discs with severe sync problems have been reissued after being re-encoded to fix the problem. In some cases, the sync problem in players can be fixed by pausing or stopping playback and then restarting, or by turning the player off, waiting a few seconds, then turning it back on. Pioneer has stated that altering the audio-visual synchronization of their players "to compensate for the software quality would dramatically compromise the picture performance."

Unfortunately, there is no simple answer and no simple fix. More complaints from customers will motivate manufacturers to take the problem more seriously and hopefully correct it in future players or with firmware upgrades.

[1.36] Why does the picture alternate between light and dark?

You are seeing the effects of Macrovision copy protection (see 1.11), probably because you are running your DVD player through your VCR or VCR/TV combo (see 3.2.1).

[1.37] How do I find "Easter eggs" and other hidden features?

Some DVD movies contain hidden features, often called "Easter eggs." These are extra screens or video clips hidden in the disc by the developers. For example, Dark City includes scenes from Lost in Space and the Twin Peaks movie buried in the biography pages of William Hurt and Keifer Sutherland. There's also an amusing "Shell Beach" game entwined throughout the menus. On Mallrats, perhaps indicating that DVD has already become too postmodern for its own good, there's a hidden clip of the director telling you to stop looking for Easter eggs and do something useful.

It's more fun to search for hidden features on your own, but if you need some help, the best list is at DVD Review.

[1.38] How do I get rid of the black bars at the top and bottom?

The black bars are part of the letterbox process (see 3.5), and in many cases you can't get rid of them. If you set the display option in your player to pan & scan (sometimes called fullscreen or 4:3) instead of letterbox, it won't do you much good since no DVD movies have been released with this feature enabled.

In some cases, there may be both a fullscreen and a letterbox version of the movie on the same disc, with a variety of ways to get to the fullscreen version (usually only one works, so you may have to try all three):

  1. Check the other side of the disc (if it's two-sided)
  2. Look for a fullscreen choice in the main menu
  3. Use the "aspect" button on the remote control

DVD was designed to make movies look as good as possible on TV. Since most movies are wider than most TVs, letterboxing preserves the format of the theatrical presentation. (Nobody complains that the top and bottom of the picture are cut off in theaters.) DVD is ready for TVs of the future, which are widescreen. For these and other reasons, many movies on DVD are only available in widescreen format.

About two thirds of widescreen movies are filmed at 1.85 ("flat") aspect ratio or less. In this case, the actual size of the images on your TV are the same for a letterbox version and a full-frame version, unless the pan & scan technique is used to zoom in (which cuts off part of the picture). In other words, the picture is the same size, with extra stuff visible at the the top and bottom in the fullscreen version. In more other words, letterboxing covers over the part of the picture that was also covered in the theater, or it allows the entire widescreen picture to be visible for movies wider than 1.85, in which case the letterboxed picture is smaller and has less detail than a pan & scan version would.

For a detailed explanation of why most movie fans prefer letterboxing, see the Widescreen Cinema page and the Letterbox/Widescreen Advocacy Page. For an explanation of anamorphic widescreen and links to more information on other Web sites, see 3.5. For an anti-letterboxing viewpoint, see the FAQ About Letterboxing (Letterschlocking), after which you might want to read a rebuttal page.

The best solution to this entire mess is the FlikFX Digital Recomposition System, "the greatest advance in entertainment in 57 years."

[1.39] How should I clean and care for DVDs?

Since DVDs are read by a laser, they are resistant—to a point—to fingerprints, dust, smudges, and scratches (see 1.15 for more info). However, surface contaminants and scratches can cause data errors. On a video player, the effect of data errors ranges from minor video artifacts to frame skipping to complete unplayability. So it's a good idea to take care of your discs. In general treat them the same way as you would a CD.

Your player can't be harmed by a scratched or dirty disc, unless there are globs of nasty substances on it that might actually hit the lens. Still, it's best to keep your discs clean, which will also keep the inside of your player clean. Never attempt to play a cracked disc, as it could shatter and damage the player. It probably doesn't hurt to leave the disc in the player (even if it's paused and still spinning), but leaving it running unattended for long periods of time is not advisable.

In general, there's no need to clean the lens on your player, since the air moved by the rotating disc keeps it clean. However, if you commonly use a lens cleaning disc in your CD player, you may want to do the same with your DVD player. I recommend only using a cleaning disc designed for DVD players, since there are minor differences in lens positioning.

There is no need for periodic alignment of the pickup head. Sometimes the laser can drift out of alignment, especially after rough handling of the player, but this is not a regular maintenance item.

Care and feeding of DVDs

Handle only at the hub or outer edge. Don't touch the shiny surface with your popcorn-greasy fingers.

Store in a protective case when not in use. Do not bend the disc when taking it out of the case, and be careful not to scratch the disc when placing it in the case or in the player tray.

Make certain the disc is properly seated in the player tray before you close it.

Keep away from radiators/heaters, hot equipment surfaces, direct sunlight (near a window or in a car during hot weather), pets, small children, and other destructive forces. Magnetic fields have no effect on DVDs.

Coloring the outside edge of a DVD with a green marker makes no difference in video or audio quality. Data is read based on pit interference at 1/4 of the laser wavelength, a distance of less than 165 nanometers. A bit of dye that on average is more than 3 million times farther away is not going to affect anything.

Cleaning and repairing DVDs

If you notice problems when playing a disc, you may be able to correct them with a simple cleaning.

If you continue to have problems after cleaning the disc, you may need to attempt to repair one or more scratches. Sometimes even hairline scratches can cause errors if they just happen to cover an entire ECC block. Examine the disc, keeping in mind that the laser reads from the bottom. There are essentially two methods of repairing scratches: 1) fill or coat the scratch with an optical material; 2) polish down the scratch. There are many commercial products that do one or both of these, or you may wish to buy polishing compounds or toothpaste and do it yourself. The trick is to polish out the scratch without causing new ones. A mess of small polishing scratches can cause more damage than a big scratch. As with cleaning, polish only in the radial direction.

Libraries, rental shops, and other venues that need to clean a lot discs may want to invest in a commercial polishing machine that can restore a disc to pristine condition after an amazing amount of abuse. Keep in mind that the data layer on a DVD is only half as deep as on a CD, so a DVD can only be re-polished about half as many times.

[1.40] What's a progressive DVD player?

A progressive-scan DVD player converts the interlaced (480i) video from DVD into progressive (480p) format for connection to a progressive display (31.5 kHz or higher). (See 3.8 for an explanation of interlaced and progressive scanning.) Progressive players work with all standard DVD titles, but look best with film source. The result is a significant increase in vertical resolution, for a more detailed and film-like picture.

Toshiba developed the first progressive-scan player (SD5109, $800) in mid 1998, but didn't release it until fall of 1999 because of copy protection concerns. Panasonic also released a progressive-scan player (DVD-H1000, $3000) at about the same time. At the January 2000 CES show, most DVD player manufacturers talked about upcoming progressive players. It's also possible to buy an external line multiplier, such as the DVDO, to convert the output of a standard DVD player to progressive scanning. All DVD computers are progressive players, since the video is displayed on a progressive monitor, but quality varies a lot. (See 4.1 and 2.12.)

Converting interlaced DVD video to progressive video involves much more than putting film frames back together. There are essentially two ways to convert from interlaced to progressive:
1- Re-interleaving (also called weave). If the original video is from a progressive source, such as film, the two fields can be recombined into a single frame.
2- Line doubling (also called bob). If the original video is from an interlaced source, simply combining two fields will cause motion artifacts (the effect is reminiscent of a zipper), so each line of a single field is repeated twice to form a frame. Better line doublers use interpolation to produce new lines that are a combination of the lines above and below. The term line doubler is vague, since cheap line doublers only bob, while expensive line doublers (those that contain digital signal processors) can also weave.
(3- There's actually a third way, called field-adaptive de-interlacing, which examines individual pixels across three or more fields and selectively weaves or bobs regions of the picture as appropriate. Most systems that do this well cost $10,000 and up, so it will be a while before we see it in consumer DVD players.)
(4- And there's also a fourth way, called motion-adaptive de-interlacing, which examines MPEG-2 motion vectors or does massive image processing to identify moving objects in order to selectively weave or bob regions of the picture as appropriate. Most systems that do this well cost $50,000 and up (aside from the cool but defunct Chromatic Mpact2 chip).

There are three common kinds of de-interlacing systems:
1- Integrated. This is usually best, where the de-interlacer is integrated with the MPEG-2 decoder so that it can read MPEG-2 flags and analyze the encoded video to determine when to bob and when to weave. Most DVD computers use this method.
2- Internal. The digital video from the MPEG-2 decoder is passed to a separate deinterlacing chip. The disadvantage is that MPEG-2 flags and motion vectors are no longer available to help the de-interlacer determine the original format and cadence.
3- External. Analog video from the DVD player is passed to a separate line doubler or to a display with a built-in line doubler. In this case, the video quality is slightly degraded from being converted to analog, back to digital, and often back again to analog. However, for high-end projection systems, a separate line multiplier (which bobs, weaves, and interpolates to a variety of scanning rates) may achieve the best results.

(Note: from what I've been able to gather, the Panasonic DVD-H1000 and the Toshiba models (SD5109, SD9100, SD6200, SD9200) all use an internal Genesis gmVLX1A de-interlacing chip. The Princeton PVD-5000 uses a Sigma Designs decoder with integrated de-interlacing. Toshiba's "Super Digital Progressive" players and the Panasonic HD-1000 use 4:4:4 chroma oversampling, which provides a slight quality boost from DVD's native 4:2:0 format.)

A progressive DVD player has to determine whether the video should be line-doubled or re-interleaved. When re-interleaving film-source video, the player also has to deal with the difference between film frame rate (24 Hz) and TV frame rate (30 Hz). Since the 2-3 pulldown trick can't be used to spread film frames across video fields, there are worse motion artifacts than with interleaved video. However, the increase in resolution more than makes up for it. Advanced progressive players such as the Princeton PVD-5000 and DVD computers can get around the problem by displaying at multiples of 24 Hz such as 72 Hz, 96 Hz, and so on.

A progressive player also has to deal with problems such as video that doesn't have clean cadence (as when it's edited after being converted to interlaced video, when bad fields are removed during encoding, or when the video is speed-shifted to match the audio track). Another problem is that many DVDs are encoded with incorrect MPEG-2 flags, so the re-interleaver has to recognize and deal with pathological cases. In some instances it's practically impossible to determine if a sequence is 30-frame interlaced video or 30-frame progressive video. For example, the documentary on Apollo 13 is interlaced video encoded as if it were progressive. Other cases of improper encoding are Fargo and More Tales of the City.

A growing problem is that many TVs with progressive input don't allow the aspect ratio to be changed. When a non-anamorphic signal is sent to these TVs, they stretch it out! Before you buy an HDTV, make sure that it allows aspect ratio adjustment on progressive input.

Just as early DVD computers did a poor job of progressive-scan display of DVDs, the first generation of progressive consumer players are also a bit disappointing. But as techniques improve, and as DVD producers become more aware of the steps they must take to ensure good progressive display, and as more progressive displays appear in homes, the experience will undoubtedly improve, bringing home theaters closer to real theaters.

[1.41] Why doesn't disc X work in player Y?

The DVD specification is complex and open to interpretation. DVD-Video title authoring is also very complex. As with any new technology, there are compatibility problems here and there. The DVD-Video standard has not changed substantially since it was finalized in 1996, but many players don't properly support it. Discs have become more complex as authoring tools improve, so recent discs often uncover engineering flaws in players. A few discs have problems or wont play at all in certain players. In some cases, manufacturers can fix the problem with an upgrade to the player (check with tech support). In other cases, disc producers need to re-author the title to correct an authoring problem or to work around a player defect.

Below are problems reported by readers of this FAQ. The FAQ author has not verified these claims and takes no responsibility for their accuracy. Please report other confirmed problems.

Title Player Problem Solution
various Polygram titles early Toshiba and Magnavox models won't load or freezes upgrade available from Toshiba service centers
various Central Park Media (anime) titles similar problems as The Matrix
The Abyss, disc 2 early Toshiba models won't load or freezes upgrade available from Toshiba service centers
American Pie Philips 940 freezes at layer change (1:17:09)  
Arlington Road see Cruel Intentions
Armageddon Panasonic A115-U and A120-U won't load unplug player with disc inserted, plug in, turn on
Avenger's TV series (A&E) Toshiba SD-3108 locks up player upgrade available from Toshiba service centers
Philips 930, 935 won't load check with Philips for firmware upgrade
Cruel Intentions some JVC and Yamaha error in first release messes up parental controls, causing other discs to not play reset the player or get the corrected version of the disc or set parental country code to AD with password of 8888
Deep Blue Sea similar problems as The Matrix
Dragon's Lair Toshiba SD-2109/3109 various upgrade available from Toshiba service centers
most Samsung, Aiwa various check with Samsung (800-726-7864) or Aiwa for firmware upgrade
Entrapment JVC freezes check with JVC for firmware upgrade
Space Ace see Dragon's Lair
The Last Broadcast GE 1105P won't load  
Lost In Space Sharp freezes  
Creative DXR3 freezes, audio out of sync check for updated drivers
The Matrix various players various problems details at PCFriendly tech support
(for GE 1105-P, serial number beginning with 940 or lower, get upgrade from GE)
The Mummy Philips 930, 935 won't load  
Idle Hands see Cruel Intentions
Saving Private Ryan all players distortion (smearing, flares)  in beach scene at end of ch. 4 This is a deliberate camera effect in the film. Stop returning discs.
Space Ace Toshiba 2109, 3109 (before mid 1999) doesn't play correctly firmware update available from Toshiba 
Stargate SE Magnavox 400AT freezes in director's commentary  
Stargate SE Magnavox 400AT freezes in director's commentary  
Stuart Little Apex AD-600A won't play  
Tomorrow Never Dies Sharp 600U
Bush DVD2000
locks up player
won't load
Universal Soldier Wharfedale 750 picture breakup after ch. 30 might be a problem with the disc
Wild Wild West Samsung DVD 709; Philips 930, 935; GE 1105P  won't load check with Samsung (800-726-7864), Philips, or GE for firmware upgrade
You've Got Mail various players various problems details at PCFriendly tech support

For other DVD and home theater problems, try Ask Digital Man, Doc DVD, or DVD Digest's Tech Support Zone. For troubleshooting DVD on computers, see 4.6. The Dell Inspiron 7000 DVD Movie List has Inspiron-specific problems.

[1.42] How do the parental control and multi-rating features work?

DVD includes parental management features for blocking playback and for multiple versions of a movie on a single disc. Players (including software players on PCs) can be set to a specific parental level using the onscreen settings. If a disc with a rating above that level is put in the player, it won't play. In some cases, different programs on the disc have different ratings. The level setting can be protected with a password.

A disc can also be designed so that it plays a different version of the movie depending on the parental level that has been set in the player. By taking advantage of the seamless branching feature of DVD, objectionable scenes are automatically skipped over or replaced during playback. This requires that the disc be carefully authored with alternate scenes and branch points that don't cause interruptions or discontinuities in the soundtrack. There is no standard way to identify which discs have multi-rated content.

Unfortunately, very few multi-rating discs have been produced. Hollywood studios are not convinced that there is a big enough demand to justify the extra work involved (shooting extra footage, recording extra audio, editing new sequences, creating branch points, synchronizing the soundtrack across jumps, submitting new versions for MPAA rating, dealing with players that don't properly implement parental branching, having video store chains refuse to carry discs with unrated content, and much more). If this feature is important to you, let the studios know. A list of studio addresses is available at DVD File, and there's a Studio and Manufacturer Feedback area at Home Theater Forum.

Multi-ratings discs include Kalifornia, Crash, Damage, Embrace of the Vampire, Poison Ivy, Species II. Discs that use multi-story branching (not always seamless) for a director's cut or special edition version include Dark Star, Stargate SE, The Abyss, Independence Day, and Terminator 2 SE (2000 release).

Another option is to use a software player on a computer that can read a "play list" telling it where to skip scenes or mute the audio. Play lists can be created for the thousands of DVD movies that have been produced without parental control features. There was a shareware Cine-bit DVD Player that did this, but it has apparently been withdrawn because of legal threats from Nissim, who seem determined to stifle the very market they claim to support. A few other projects are under development.

Yet another option is TVGuardian or Curse Free TV, a device that attaches between the DVD player and the TV to filter out profanity and vulgar language. The box reads the closed caption text and automatically mutes the audio and provides substitute captions for objectionable words. (Note that current versions of these devices don't work with digital audio connections.)

[1.43] Which discs include multiple camera angles?

There's actually a euphemism in the DVD industry, where "multi-angle titles" --spoken with the right inflection-- means adult titles. However, apart from hundreds of X-rated discs, not very many DVDs have multiple angles, since it takes extra work and limits playing time (a segment with two angles uses up twice as much space on the disc).

Short Cinema Journal vol. 1 was one of the first to use camera angles, in the animated "Big Story," which is also available on the DVD Demystified sample disc. Ultimate DVD (Gold or Platinum) is another sample disc with examples of angles. King Crimson: Deja Vroom has excellent angles, allowing you to focus on any of the musicians. Other multi-angle music discs include Dave Matthews Band: Listener Supported, Metallica Cunning Stunts, Sarah McLachlan Mirrorball. Some movies, such as Detroit Rock City (KISS video), Ghostbusters SE, Mallrats, Suicide Kings, Terminator 2 SE, andTomorrow Never Dies SE use multiple angles in supplements.

You can get an incomplete list of multi-angle discs by doing an extended search at DVD File or a power search at DVD Express. To weed out the adult titles at DVD Express, select all entries in the category list (click top entry, Shift-click bottom entry) then deselect Adult (Ctrl-click).

[1.44] Is it ok to put labels or magnetic strips on DVDs?

Libraries and DVD rental outlets often want to label discs or attach magnetic strips for security. Rectangular labels and strips are a bad idea since they can unbalance the disc and cause errors, or even damage a player, especially if they peel off while the disc is spinning. It's best not to use stickers at all, but if you must, use a ring-shaped label that goes around the center of the disc. As long as the label doesn't interfere with the player clamping onto the hub, it should be fine. If you have to use a non-circular label, place it as close to the center as possible to minimize unbalancing. Placing a second label straight across from the center will also help.

In most cases a better alternative is a security case that can only be opened with special equipment at the sale or checkout counter. Barcodes, stickers, and security strips can be placed on the case without endangering the disc (or the player). This also accommodates double-sided discs, which have no space for stickers.

[2] DVD's relationship to other products

[2.1] Will DVD replace VCRs?

Not any time soon. Recordable DVD is for computer data only, not television video (see 1.14). It will take a while before the size of the market drives costs down to VCR levels. However, DVD has many advantages over VCRs, including fundamentally lower technology cost for hardware and disc production (which is appealing to manufacturers), so if DVD is a commercial success it might replace many VCRs in fifteen to twenty years.

[2.2] Will DVD replace CD-ROM?

Yes. Some CD-ROM drive manufacturers plan to cease CD-ROM drive production after a few years in favor of DVD-ROM drives. Because DVD-ROM drives can read CD-ROMs, there is a compatible forward migration path.

[2.3] Can CD-R writers create DVDs?

No. DVD uses a smaller wavelength of laser to allow smaller pits in tracks that are closer together. The DVD laser must also focus more tightly and at a different level. In fact, a disc made on a current CD-R writer may not be readable by a DVD-ROM drive (see 2.4.3). It's unlikely there will be "upgrades" to convert CD-R drives to DVD-R, since this would probably cost more than purchasing a new DVD-R drive.

[2.4] Is CD compatible with DVD?

This is actually many questions with many answers, covered in the following sections.
[Note the differentiation between DVD (general case) and DVD-ROM (computer data).]

[2.4.1] Is CD audio (CD-DA) compatible with DVD?

Yes. All DVD players and drives will read audio CDs (Red Book). This is not actually required by the DVD spec, but so far all manufacturers have stated that their DVD hardware will read CDs. 

On the other hand, you can't play a DVD in a CD player. (The pits are smaller, the tracks are closer together, the data layer is a different distance from the surface, the modulation is different, the error correction coding is new, etc.) Also, you can't put CD audio data onto a DVD and have it play in DVD players. (Red Book audio frames are different than DVD data sectors.)

[2.4.2] Is CD-ROM compatible with DVD-ROM?

Yes. All DVD-ROM drives will read CD-ROMs (Yellow Book). Software on a CD-ROM will run fine in a DVD-ROM system.

However, DVD-ROMs are not readable by CD-ROM drives.

[2.4.3] Is CD-R compatible with DVD?

Sometimes. The problem is that CD-Rs (Orange Book Part II) are "invisible" to DVD laser wavelength because the dye used in CD-Rs doesn't reflect the beam. Some first-generation DVD-ROM drives and many DVD players can't read CD-Rs. The formulation of dye used by different CD-R manufacturers also affects readability. The common solution is to use two lasers at different wavelengths: one for reading DVDs and the other for reading CDs and CD-Rs. Variations on the theme include Sony's "dual discrete optical pickup" with switchable pickup assemblies with separate optics, Sony's dual-wavelength laser (to be initially deployed on Playstation 2), Samsung's "annular masked objective lens" with a shared optical path, Toshiba's similar shared optical path using an objective lens masked with a coating that's transparent only to 650-nm light, Hitachi's switchable objective lens assembly, and Matsushita's holographic dual-focus lens. The MultiRead logo guarantees compatibility with CD-R and CD-RW media, but unfortunately, few manufacturers are using it.

Bottom line: If you want a DVD player that can read CD-R discs, look a "dual laser" or "dual optics" feature.

An effort to develop CD-R "Type II" media compatible with both CD and DVD wavelengths was abandoned.

DVD-ROM drives can't record on any media. There are a few combination DVD-ROM/CD-RW drives. Current writable DVD drives (see 4.3) can't record on CD-R or CD-RW, although future versions will.

[2.4.4] Is CD-RW compatible with DVD?

Usually. CD-Rewritable (Orange Book Part III) has a lower reflectivity difference, requiring new automatic-gain-control (AGC) circuitry. CD-RW discs can't be read by most existing CD-ROM drives and CD players. The new "MultiRead" standard addresses this, and some DVD manufacturers have suggested they will support it. The optical circuitry in even first-generation DVD-ROM drives and DVD players is usually able to read CD-RW discs, since CD-RW does not have the "invisibility" problem of CD-R (see 2.4.3).

Current writable DVD drives (see 4.3) can't record on CD-RW, although future versions will.

[2.4.5] Is Video CD compatible with DVD?

Sometimes. It's not required by the DVD spec, but it's trivial to support the Video CD (White Book) standard since any MPEG-2 decoder can also decode MPEG-1 from a Video CD. About two thirds of DVD players can play Video CDs. Panasonic, RCA, Samsung, and Sony models play Video CDs. Japanese Pioneer models play Video CDs but American models older than the DVL-909 don't. Toshiba players older than models 2100, 3107, and 3108 don't play Video CDs.

VCD resolution is 352x288 for PAL and 352x240 for NTSC. The way most DVD players and Video CD players deal with the difference is to chop off the extra lines or add blank lines. When playing PAL VCDs, the Panasonic and RCA NTSC players apparently cut 48 lines (17%) off the bottom. The Sony NTSC players scale all 288 lines to fit.

Because PAL VCDs are encoded for 25 fps playback of 24 fps film, there is usually a 4% speedup. Playing time is shorter, and the audio is shifted up in pitch (about one half of a semitone), unless it was digitally processed before encoding to shift the pitch back to normal. This also happens with PAL DVDs (see 1.19).

All DVD-ROM computers can play Video CDs (with the right software).

Standard VCD players can't play DVDs.

Note: Many Asian VCDs achieve two soundtracks by putting one language on the left channel and another on the right. The two channels are mixed together into babel on a stereo system unless you adjust the balance or disconnect one input to get only one channel.

For more on Video CD, see Glenn Sanderse's Video CD FAQ at CDPage.

[2.4.6] Is Super Video CD compatible with DVD?

Not generally. Super Video CD (SVCD) is an enhancement to Video CD that was developed by a Chinese government-backed committee of manufacturers and researchers, partly to sidestep DVD technology royalties and partly to create pressure for lower DVD player and disc prices in China. The final SVCD spec was announced in September 1998, winning out over C-Cube's China Video CD (CVD) and HQ-VCD (from the developers of the original Video CD). In terms of video and audio quality, SVCD is in between Video CD and DVD, using a 2x CD drive to support 2.2 Mbps VBR MPEG-2 video (at 480x480 (NSTC) or 480x576 (PAL) resolution) and 2-channel MPEG-2 Layer II audio. As with DVD, it can overlay graphics for subtitles. It's technically easy to make a DVD-Video player compatible with SVCD, but it's being done mostly on Asian DVD player models. The Philip's DVD170 player can be upgraded (using a special disc) to play SVCD discs. It's not likely that SVCD will be released outside of China and nearby countries.

SVCD players can't play DVDs, since the players are based on CD drives.

See Jukka Aho's Super Video CD Overview and Super Video CD FAQ for more info.


[2.4.7] Is Photo CD compatible with DVD?

Not yet. Since Photo CDs are usually on CD-R media, they may suffer from the CD-R problem (see 2.4.3). That aside, DVD players could support Photo CD with a few extra chips and a license from Kodak. No one has announced such a player. Most DVD-ROM drives will read Photo CDs (if they read CD-Rs) since it's trivial to support the XA and Orange Book multisession standards. The more important question is, "Does the OS or application support Photo CD?" but that's beyond the scope of this FAQ.

[2.4.8] Is CD-i compatible with DVD?

In general, no. Current DVD players do not play CD-i (Green Book) discs. Philips once announced that it would make a DVD player that supported CD-i, but it has yet to appear. Some people expect Philips to create a "DVD-i" format in an attempt to breathe a little more life into CD-i (and recover a bit more of the billion or so dollars they invested in it). A DVD-ROM PC with a CD-i card should be able to play CD-i discs.

There are also "CD-i movies" that use the CD-i Digital Video format that was the precursor to Video CD. Early CD-i DV discs won't play on DVD players or VCD players, but newer CD-i movies, which use standard VCD format, will play on any player that can play VCDs (see 2.4.5).

See Jorg Kennis' CD-i FAQ for more information on CD-i.

[2.4.9] Is Enhanced CD compatible with DVD?

Yes. DVD players will play music from Enhanced Music CDs (Blue Book, CD Plus, CD Extra), and DVD-ROM drives will play music and read data from Enhanced CDs. Older ECD formats such as mixed mode and track zero (pregap, hidden track) should also be compatible, but there is a problem with Microsoft and other CD/DVD-ROM drivers skipping track zero.

[2.4.10] Is CD+G compatible with DVD?

Only the Pioneer DVL-9 player and Pioneer karaoke DVD models DV-K800 and DVK-1000 are known to support CD+G. Most other DVD-V players probably won't support this mostly obsolete format. All DVD-ROM drives support CD+G, but special software is required to make use of it.

[2.4.11] Is CDV compatible with DVD?

Sort of. CDV, sometimes called Video Single, is actually a weird combination of CD and laserdisc. Part of the disc contains 20 minutes of digital audio playable on any CD or DVD player. The other part contains 5 minutes of analog video and digital audio in laserdisc format, playable only on a CDV-compatible system. Pioneer's combination DVD/laserdisc players are the only DVD players that can play CDVs.

LD/CDV players can't play DVDs. (See 2.5 for more LD info.)

[2.4.12] Is MP3 compatible with DVD?

Mostly no. MP3 is the MPEG-1 Layer 3 audio compression format. (MP3 is not MPEG-3, which doesn't exist.) The DVD-Video spec allows only Layer 2 for MPEG audio. MP3 can be played on computers with a DVD-ROM drive. A few DVD players (Apex/REC/VDDV, I-Jam, Lasonic, Nintaus, Raite [AV Phile/Hoyo/KiSS/Monica/Monyka/Tokai/Yamakawa], Sampo, Shinco) can play MP3 CDs. (See 6.2 for company Web sites.)

[2.4.13] Is HDCD compatible with DVD?

Yes. Pacific Microsonics' HDCD (high-definition compatible digital) is an encoding process that enhances audio CDs so that they play normally in standard CD and DVD players (and allegedly sound better than normal CDs) yet produce an extra 4 bits of precision (20 bits instead of 16) when played on CD and DVD players equipped with HDCD decoders.

[2.5] Is laserdisc compatible with DVD?

No. Standard DVD players will not play laserdiscs, and you can't play a DVD disc on any standard laserdisc player. (Laserdisc uses analog video, DVD uses digital video; they are very different formats.)

However, Pioneer produces combo players that play laserdiscs and DVDs (and also CDVs and audio CDs). Denon and Samsung are rumored to have LD/DVD players in the works also.

[2.6] Will DVD replace laserdisc?

When this question was first entered in the FAQ, before DVD was even available, people wondered if DVD would replace laserdisc (and some argued it never would -- that DVD would fail and it's adherents would come groveling back to laserdisc). After DVD was released, it became clear that it had doomed laserdisc to quick obscurity. Pioneer Entertainment, the long-time champion of laserdisc, abandoned it in June of 1999. This was sooner than even Pioneer thought possible, (in September 1998, Pioneer's president Kaneo Ito said the company expected laserdisc products to be in the market for another one-and-a-half to two years).

Laserdisc still fills important niches in education and training, but is fading very quickly as an entertainment format. Existing players and discs will still be around for a very long time, and new discs are still being produced, since laserdisc has become well established over 20 years as a videophile format. There are over 9,000 laserdisc titles in the US and a total of over 35,000 titles worldwide that can be played on over 7 million laserdisc players. It will take DVD several years to reach this level, and even then there's no reason for laserdisc player owners to stop buying or playing laserdiscs, especially rare titles that may not appear on DVD for a long while if ever. One bright point is that laserdiscs (especially used discs) can now be had at bargain prices.

[2.7] How does DVD compare to laserdisc?

For more laserdisc info, see Leopold's FAQ at <www.cs.tut.fi/~leopold/Ld/FAQ/index.html>, and Bob Niland's FAQs and overview at <www.frii.com/~rjn/laser/> (overview reprinted from Widescreen Review magazine).

[2.8] Can I modify or upgrade my laserdisc player to play DVD?

It's not likely. DVD circuitry is completely different, the pickup laser is a different wavelength, the tracking control is more precise, etc. No hardware upgrades have been announced, and in any case they would probably be more expensive than buying a DVD player to put next to the laserdisc player.

[2.9] Does DVD support HDTV (DTV)? Will HDTV make DVD obsolete?

Short answers: Partially. No.

First, some quick definitions: HDTV (high-definition TV) encompasses both analog and digital televisions that have a 16:9 aspect ratio and approximately 5 times the resolution of standard TV (double vertical, double horizontal, wider aspect). DTV (digital TV) applies to digital broadcasts in general and to the U.S. ATSC standard in specific. The ATSC standard includes both standard-definition (SD) and high-definition (HD) digital formats. The notation H/DTV is often used to specifically refer to high-definition digital TV.

In December of 1996 the FCC approved the U.S. DTV standard. HDTVs became available in late 1998, but they are very expensive and won't become widespread for many years. DVD will look better on HDTVs but it won't provide the highest resolutions.

DVD-Video does not directly support HDTV. No digital HDTV standards were finalized when DVD was developed. In order to be compatible with existing televisions, DVD's MPEG-2 video resolutions and frame rates are closely tied to NTSC and PAL/SECAM video formats (see 1.19). DVD does use the same 16:9 aspect ratio of HDTV and the Dolby Digital audio format of U.S. DTV.

HDTV in the US is part of the ATSC DTV format. The resolution and frame rates of DTV in the US generally correspond to the ATSC recommendations for SD (640x480 and 704x480 at 24p, 30p, 60p, 60i) and HD (1280x720 at 24p, 20p, and 60p; 1920x1080 at 24p, 30p and 60i). (24p means 24 progressive frames/sec, 60i means 60 interlaced fields/sec [30 frames/sec].) The current DVD-Video spec covers all of SD except 60p. It's expected that future DVD players will output digital video signals from existing discs in SDTV formats. The HD formats are 2.7 and 6 times the resolution of DVD, and the 60p version is twice the frame rate. The ITU-R is working on BT.709 HDTV standards of 1125/60 (1920x1035/30) (same as SMPTE 240M, similar to Japan's analog MUSE HDTV) and 1250/50 (1920x1152/25) which may be used in Europe. The latter is 5.3 times the resolution of DVD's 720x576/25 format. HD maximum data rate is usually 19.4 Mbps, almost twice the maximum DVD-Video data rate. In other words, DVD-Video does not currently support HDTV video content.

HDTV will not make DVD obsolete. Those who postpone purchasing a DVD player because of HDTV are in for a long wait. HDTV became available in late 1998 at very high prices (about $5000 and up). It will take many years before even a small percentage of homes have HDTV sets. CEA expects 10 percent of U.S. households to have HDTV in 2003, 20 percent by 2005, and 30 percent by 2006.

HDTV sets include analog video connectors (composite, s-video, and component) that will work with all DVD players and other existing video equipment such as VCRs. Existing DVD players and discs will work perfectly with HDTV sets, and will provide a much better picture than any other prerecorded consumer video format, especially once new progressive-scan players become available. Since the cheapest route to HDTV reception will be HDTV converters for existing TV sets, HDTV for many viewers will look no better than DVD.

At some point, HDTV displays will support component digital video connections (YCbCr) and digital data connections (FireWire/IEEE 1394). The digital connections will provide the best possible reproduction of DVD-Video, especially in widescreen mode. Once DVD players have digital outputs, they may be usable as "transports" which output any kind of A/V data (even formats developed after the player was built) to any sort of external display or converter.

The interesting thing many people don't realize is that DTV is happening soonest, fastest, and cheapest on PCs. A year before any consumer DTV sets came out you could buy a DVD PC with a 34" VGA monitor and get gorgeous progressive-scan movies for under $3000. The quality of a good DVD PC connected to a data-grade video projector beats $30,000 line-doubler systems. (See NetTV and Digital Connection for product examples. Video projectors are available from Barco, Dwin, Electrohome, Faroudja, InFocus, Projectavision, Runco, Sharp, Sony, Vidikron, and others.)

Eventually the DVD-Video format will be upgraded to an "HD-DVD" format. See 2.12.

[2.10] What was Divx?

Depending on whom you ask, Divx (once known as ZoomTV) was either an insidious evil scheme for greedy studios to control what you see in your own living room or an innovative approach to video rental with cheap discs you could get almost anywhere and keep for later viewings. On June 16, 1999, less than a year after initial product trials, Digital Video Express announced that it was closing down. Divx did not confuse or delay development of the DVD market nearly as much as many people predicted (including yours truly). In fact, it probably helped by stimulating Internet rental companies to provide better services and prices, by encouraging manufacturers to offer more free discs with player purchases, and by motivating studios to develop rental programs.

The company is offering $100 rebate coupons to all owners of Divx players. This actually makes the players a good deal, since they can play open DVDs just as well as other low-end players that cost more. The Divx billing computer will continue to operate normally until June 30th, 2001, after which all Divx discs will presumably become unplayable. Divx discs can no longer be upgraded to unlimited play.

Developed by Circuit City and a Hollywood law firm, Divx was supported by Disney (Buena Vista), Twentieth Century Fox, Paramount, Universal, MGM, and DreamWorks SKG, all of which also released discs in "open DVD" format, since the Divx agreement was non-exclusive. Harman/Kardon, JVC, Kenwood, Matsushita (Panasonic), Pioneer, Thomson (RCA/Proscan/GE), and Zenith announced Divx players, though some never came to market. The studios and hardware makers supporting Divx were given incentives in the form of guaranteed licensing payments totaling over $110 million. Divx discs were manufactured by Nimbus, Panasonic, and Pioneer. Circuit City lost over $114 million (after tax writeoffs) on Divx.

Divx was a pay-per-viewing-period variation of DVD. Divx discs sold for $4.50. Once inserted into a Divx player the disc would play normally (allowing the viewer to pause, rewind, even put in another disc before finishing the first disc) for the next 48 hours, after which the "owner" had to pay $3.25 to unlock it for another 48 hours. A Divx DVD player, which cost about $100 more than a regular player, had to be hooked up to a phone line so it could call an 800 number for about 20 seconds during the night once each month to upload billing information. Most Divx discs could be converted to DivxSilver status by paying an additional fee (usually $20) to allow unlimited plays on a single account (as of Dec 1998, 85% of Divx discs were convertible). Unlimited-playback DivxGold discs were announced but never produced. Divx players can also play regular DVD discs, but Divx discs do not play in standard DVD players. Divx discs are serialized (with a barcode in the standard Burst Cutting Area) and in addition to normal DVD copy protection (see 1.11) they employ watermarking of the video, modified channel modulation, and triple DES encryption (three 56-bit keys) of serial communications. Divx technology never worked on PCs, which undoubtedly contributed to its demise. Because of the DES encryption, Divx technology may not have been allowed outside the U.S.

Divx was originally announced for Summer 1998 release. Limited trials began June 8, 1998 in San Francisco, CA and Richmond, VA. The only available player was from Zenith (which at the time was in Chapter 11 bankruptcy), and the promised 150 movies had dwindled to 14. The limited nationwide rollout (with one Zenith player model and 150 movies in 190 stores) began on September 25, 1998. By the end of 1998 about 87,000 Divx players (from four models available) and 535,000 Divx discs were sold (from about 300 titles available). The company apparently counted the five discs bundled with each player, which means only 100,000 additional discs were sold. By March 1999, 420 Divx titles were available (compared to over 3,500 open DVD titles).

Advantages of Divx:

Disadvantages of Divx :

For more information, see the Anti Divx page at <www.dvdresource.com/divx>.

[2.11] How can I record from DVD to videotape?

Why in the world would you want to degrade DVD's beautiful digital picture by copying it to analog tape? Especially since you lose the interactive menus and other nice features.

If you really want to do this, hook the audio/video outputs of the TV player to the audio/video inputs of your VCR, then record the disc to tape. You'll discover that most of the time the resulting tape is garbled and unwatchable. This is because of the Macrovision feature designed to prevent you from doing this. See 1.11.

[2.12] Will high-definition DVD or 720p DVD make current players and discs obsolete?

Not for a long time. HD-DVD "technology demonstrations" being made by various companies do not mean that HD-DVD is around the corner (the demonstrations mean only that companies are busy jockeying for technology and patent positions in developing the future DVD format). Consider that U.S. HDTV was widely anticipated to be available in 1989, yet was not finalized until 1996, and did not appear until 1998. And has it made your current TV obsolete yet?

HD-DVD (HD stands for both high-density and high-definition) may be available in 2003 at the very earliest, though 2006 is more likely. It will use blue or violet lasers to read smaller pits, increasing data capacity to around 20 GB per layer. MPEG-2 Progressive Profile--or perhaps another format such as H.263--will probably be used to encode the video. All ATSC and DVB formats will be supported, possibly with the addition of 1080p24. HD-DVD players will play current DVD discs and will make them look even better (with progressive-scan video and picture processing), but new HD-DVD discs won't be playable in older DVD players (unless one side is HD and the other standard DVD).

Ironically, computers will support HDTV before settop players do, since 2x DVD-ROM drives coupled with appropriate playback and display hardware meet the 19 Mbps data rate needed for HDTV. This has led to various "720p DVD" projects, which use the existing DVD format to store video in 1280x720 resolution at 24 progressive frames per second. It's possible that 720p DVDs can be made compatible with existing players (which would only play the 480-line line data).

Note: The term HDVD has already been taken for "high-density volumetric display."

Some have speculated that a "double-headed" player reading both sides of the disc at the same time could double the data rate or provide an enhancement stream for applications such as HDTV. This is currently impossible since the track spirals go in opposite directions (unless all four layers are used). The DVD spec would have to be changed to allow reverse spirals on layer 0. Even then, keeping both sides in sync, especially with MPEG-2's variable bit rate, would require independently tracking heads, precise track and pit spacing, and a larger, more sophisticated track buffer.

See 2.9 for more information about HDTV and DVD.

[2.13] What effect will FMD have on DVD?

Who knows? So far Constellation 3D's FMD (fluorescent multilayer disc) isn't out of the lab. You can be sure only that the reports of FMD causing the early death of DVD are wildly exaggerated and not founded in reality.

Fluorescent multilayer technology, which can be used in cards or discs, aims a laser at fluorescent recording material, causing it to emit light. Since it doesn't depend on reflected laser light, it's possible to create many data layers (C3D has prototyped 50 layers in its lab). It can use the same 650nm laser as DVD, so FMD drives could be made to read DVDs. 

FMD is a new technology, with no track record, supported by one small company. DVD is based on decades of optical storage technology development by dozens of companies. It's possible that FMD could become established in few years, but by then DVD will be so entrenched that FMD drives will have to read DVDs in order to succeed. So there is little worry of DVD becoming obsolete any time soon. Perhaps FMD will be the third generation of the DVD format, following the high-density blue-laser version currently under development (see 2.12)

[3] DVD technical details

[3.1] What are the outputs of a DVD player?

Video outputs

Most DVD players have the following video output connections, which can carry an NTSC, PAL, or SECAM signal.

Some players may have additional video connections:

Most of the DVD players with component video outputs use YUV (Y'PbPr), which is incompatible with RGB equipment. European players with SCART connectors have RGB outputs. YUV to RGB transcoders are rumored to be available for $200-$300, but seem hard to track down. A $700 converter is available from avscience, and $900 converter, the CVC 100, is available from Extron. Converters are also available from Altinex, Kramer, Monster Cable, and others. For progressive scan you need a converter that can handle 31.5 kHz signals. Converters from s-video are also an option (Markertek Video Supply, 800-522-2025).

Note: The correct term for analog color-difference output is Y'Pb'Pr', not Y'Cb'Cr' (which is digital, not analog). To simplify things, this FAQ uses the term YUV in the generic sense to refer to analog color difference signals.

No DVD players have yet been announced with digital video outputs, but digital output will soon be available using FireWire (IEEE 1394) connectors.

Audio outputs

Most DVD players have the following audio output connections.

Some players may have additional audio connections:

Some players and receivers support only S/P DIF or only Toslink. If your player and receiver don't match, you'll need a converter such as the Audio Authority 977 Midiman C02, COP 1, or POF.

Some players can output 96/24 PCM audio using a non-standard variation of IEC-958 running at 6.2 MHz (6.144 Mbps) instead of the normal limit of 3.1 MHz. Note: The DVD license restricts digital PCM output of CSS-protected material to 48kHz/24-bit signals.

[3.2] How do I hook up a DVD player?

It depends on your audio/video system and your DVD player. Most DVD players have 2 or 3 video hookup options and 3 audio hookup options. Choose the option with the best quality (indicated below) that is supported by your video and audio systems. See 3.1 for output connector details.

Video hookup

Warning: If you connect your DVD player to a VCR and then to your TV, you may have problems with discs that enable the player's Macrovision circuit. See 3.2.1.

Warning: Some video projectors don't recognize the 4.43 NTSC signal from NTSC discs in PAL players (see 1.19). They see the 60Hz scanning frequency and switch to NSTC even though the color subcarrier is in PAL format.

Note: Most DVD players support widescreen signaling, which tells a widescreen display what the aspect ratio is so that it can automatically adjust. One standard (ITU-R BT.1119, used mostly in Europe) includes information in a video scanline. Another standard, for Y/C connectors, adds a 5V DC signal to the chroma line to designate a widescreen signal. Unfortunately, some switchers and amps throw away the DC component instead of passing it on to the TV.

Audio hookup

Note: All DVD players have either a built-in Dolby Digital (AC-3) or MPEG audio decoder, or both. The decoder translates multi-channel audio into PCM audio. This is fed to the digital output and also converted to analog for standard audio output. Most players have only a 2-channel-output decoder, but some provide 6-channel output (details below).

[3.2.1] Will I have problems connecting my VCR between my TV and my DVD player?

It's not a good idea to route the video from your DVD player through your VCR. Most movies use Macrovision protection (see 1.11), which causes problems such as a repeated darkening and lightening of the picture. If your TV doesn't have a direct video input, you may need a separate RF converter (see 3.2). Or better yet, get a new TV with s-video inputs.

You may also have problems with a TV/VCR combo, since many of them route the video input through the VCR circuitry. The only solution is to get a box to strip Macrovision (see 1.11). 

[3.2.2] Why is the audio or video bad?

If you get audio hum or noisy video, it's probably caused by interference or a ground loop. Try a shorter cable. Make sure the cable is adequately shielded. Try turning off all equipment except the pieces you are testing. Try moving things farther apart. Try plugging into a different circuit. Wrap your entire house in tinfoil. Make sure all equipment is plugged into the same outlet. For more on ground loops, see http://www.hut.fi/Misc/Electronics/docs/groundloop/.

[3.3] What are the sizes and capacities of DVD?

There are many variations on the DVD theme. There are two physical sizes: 12 cm (4.7 inches) and 8 cm (3.1 inches), both 1.2 mm thick. These are the same form factors as CD. A DVD disc can be single-sided or double-sided. Each side can have one or two layers of data. The amount of video a disc can hold depends on how much audio accompanies it and how heavily the video and audio are compressed. The oft-quoted figure of 133 minutes is apocryphal: a DVD with only one audio track easily holds over 160 minutes, and a single layer can actually hold up to 9 hours of video and audio if it's compressed to VHS quality.

At a rough average rate of 4.7 Mbps (3.5 Mbps for video, 1.2 Mbps for three 5.1-channel soundtracks), a single-layer DVD can hold a little over two hours. A two-hour movie with three soundtracks can average 5.2 Mbps. A dual-layer disc can hold a two-hour movie at an average of 9.5 Mbps (very close to the 10.08 Mbps limit).

A DVD-Video disc containing mostly audio can play for 13 hours (24 hours with dual layers) using 48/16 PCM (slightly better than CD quality). It can play 160 hours of audio (or a whopping 295 hours with dual layers) using Dolby Digital 64 kbps compression of monophonic audio, which is perfect for audio books.

Capacities of DVD:

For reference, a CD-ROM holds about 650 megabytes, which is 0.64 gigabytes or 0.68 billion bytes. In the list below, SS/DS means single-/double-sided, SL/DL/ML means single-/dual-/mixed-layer (mixed means single layer on one side, double layer on the other side), gig means gigabytes (2^30), G means billions of bytes (10^9). See note about giga vs. billion in section 7.2.

Tip: It takes about two gigabytes to store one hour of average video.

The increase in capacity from CD-ROM is due to: 1) smaller pit length (~2.08x), 2) tighter tracks (~2.16x), 3) slightly larger data area (~1.02x), 4) more efficient channel bit modulation (~1.06x), 5) more efficient error correction (~1.32x), 6) less sector overhead (~1.06x). Total increase for a single layer is about 7 times a standard CD-ROM. There's a slightly different explanation at <www.mpeg.org/MPEG/DVD/General/Gain.html>.

The capacity of a dual-layer disc is slightly less than double that of a single-layer disc. The laser has to read "through" the outer layer to the inner layer (a distance of 20 to 70 microns). To reduce inter-layer crosstalk, the minimum pit length of both layers is increased from .4 um to .44 um. To compensate, the reference scanning velocity is slightly faster -- 3.84 m/s, as opposed to 3.49 m/s for single layer discs. Longer pits, spaced farther apart, are easier to read correctly and are less susceptible to jitter. The increased length means fewer pits per revolution, which results in reduced capacity per layer.

See 4.3 for details of recordable DVD (DVD-R and DVD-RAM).

[3.3.1] When will double-sided, dual-layer discs (DVD-18) be available?

The first commercial DVD-18 title, The Stand, was released in October 1999. It will still take a while for these super-size discs to become common. A DVD-18 requires a completely different way of creating two layers. A single-sided, dual-layer disc (DVD-9) is produced by putting one data layer on each substrate and gluing the halves together with transparent adhesive so that the pickup laser can read both layers from one side. But in order to get four layers, each substrate needs to hold two. This requires stamping a second data layer on top of the first, a much more complicated prospect. Even after new equipment is developed and installed in production lines, the yield (number of usable discs compared to bad discs) will be quite low until the process is fine tuned.

WAMO and others continue to announce progress with DVD-18 processes, but given how long it took for production of dual-layer, single-sided discs to become practical, it will take even longer before the yields of DS/DL discs can meet the replication demands of mainstream movie distribution, especially since low yields mean higher replication costs. In the interim we'll see DVD-14s (two layers on one side, one layer on the other side), since they're a little easier to produce.

(My prediction in this FAQ, as of December 1998, was that we wouldn't see commercial DVD-18 discs until fall 1999, in spite of many rumors that they would appear sooner.)

[3.4] What are the video details?

DVD-Video is an application of DVD-ROM. DVD-Video is also an application of MPEG-2. This means the DVD format defines subsets of these standards to be applied in practice as DVD-Video. DVD-ROM can contain any desired digital information, but DVD-Video is limited to certain data types designed for television reproduction.

A disc has one track (stream) of MPEG-2 constant bit rate (CBR) or variable bit rate (VBR) compressed digital video. A restricted version of MPEG-2 Main Profile at Main Level (MP@ML) is used. SP@ML is also supported. MPEG-1 CBR and VBR video is also allowed. 525/60 (NTSC, 29.97 interlaced frames/sec) and 625/50 (PAL, 25 interlaced frames/sec) video display systems are expressly supported. Coded frame rates of 24 fps progressive from film, 25 fps interlaced from PAL video, and 29.97 fps interlaced from NTSC video are typical. MPEG-2 progressive_sequence is not allowed, but interlaced sequences can contain progressive pictures and progressive macroblocks. In the case of 24 fps source, the encoder embeds MPEG-2 repeat_first_field flags into the video stream to make the decoder either perform 2-3 pulldown for 60Hz (59.94) displays or 2-2 pulldown (with resulting 4% speedup) for 50Hz displays. In other words, the player doesn't really "know" what the encoded rate is, it simply follows the MPEG-2 encoder's instructions to produce the predetermined display rate of 25 fps or 29.97 fps. (Very few players convert from PAL to NTSC or NTSC to PAL. See 1.19.) It's interesting to note that even interlaced source video is often encoded as progressive-structured MPEG pictures, with interlaced field-encoded macroblocks used only when needed for motion. A computer can mostly ignore the repeat_first_field flags and re-interleave (weave) the video fields back into full-resolution progressive frames, which works especially well at 72 Hz refresh rate (3x24). Computers can improve the quality of interlaced source by doubling the lines in fields (bobbing) and displaying them as progressive frames at twice the normal rate. Most film source is encoded progressive (the inverse telecine process in the encoder removes duplicate 2-3 pulldown fields from videotape source); most video sources are encoded interlaced. These may be mixed on the same disc, such as an interlaced logo followed by a progressive movie. 

See 3.8 for an explanation of progressive and interlaced scanning. See 1.40 for progressive-scan players. See the MPEG page <www.mpeg.org> for more information on MPEG-2 video.

Picture dimensions are max 720x480 (for 525/60 NTSC display) or 720x576 (for 625/50 PAL/SECAM display). Pictures are subsampled from 4:2:2 ITU-R BT.601 down to 4:2:0, allocating an average of 12 bits/pixel in Y'CbCr format. (Color depth is 24 bits, since color samples are shared across 4 pixels.) The uncompressed source is 124.416 Mbps for video source (720x480x12x30 or 720x576x12x25), or either 99.533 or 119.439 Mbps for film source (720x480x12x24 or 720x576x12x24). Using the traditional (and rather subjective) television measurement of "lines of horizontal resolution" DVD can theoretically produce 540 lines on a standard TV (720/1.33) and 405 on a widescreen TV (720/1.78). In practice, most DVD players provide about 500 lines because of filtering and low-quality digital-to-analog converters. VHS has about 230 (172 widescreen) lines and laserdisc has about 425 (318 widescreen). Note that lines of horizontal resolution (visually resolvable vertical lines per picture height) are not the same as total horizontal pixels (720) or horizontal scan lines (480). In analog output signal terms, typical luma frequency response maintains full amplitude to between 5.0 and 5.5 MHz. This is below the 6.75 MHz native frequency of the MPEG-2 digital signal (in other words, most players fall short of reproducing the full quality of DVD). Chroma frequency response is half that of luma.

Different players use different numbers of bits for the video digital-to-analog converter. Current best-quality players use 10 bits. This has nothing to do with the MPEG decoding process, since each original component signal is limited to 8 bits per sample. More bits in the player provide more "headroom" and more signal levels during digital-to-analog conversion, which can help produce a better picture.

Maximum video bit rate is 9.8 Mbps. The "average" video bit rate is 3.5 but depends entirely on the length, quality, amount of audio, etc. This is a 36:1 reduction from uncompressed 124 Mbps video source (or a 28:1 reduction from 100 Mbps film source). Raw channel data is read off the disc at a constant 26.16 Mbps. After 8/16 demodulation it's down to 13.08 Mbps. After error correction the user data stream goes into the track buffer at a constant 11.08 Mbps. The track buffer feeds system stream data out at a variable rate of up to 10.08 Mbps. After system overhead, the maximum rate of combined elementary streams (audio + video + subpicture) is 10.08. MPEG-1 video rate is limited to 1.856 Mbps with a typical rate of 1.15 Mbps.

Still frames (encoded as MPEG-2 I-frames) are supported and can be displayed for a specific amount of time or indefinitely. These are generally used for menus. Still frames can be accompanied by audio.

A disc also can have up to 32 subpicture streams that overlay the video for subtitles, captions for the hard of hearing, captions for children, karaoke, menus, simple animation, etc. These are full-screen, run-length-encoded bitmaps with two bits per pixel, giving four color values and four transparency values. For each group of subpictures, four colors are selected from a palette of 16 (from the YCbCr gamut), and four contrast values are selected out of 16 levels from transparent to opaque. Subpicture display command sequences can be used to create effects such as scroll, move, color/highlight, and fade. The maximum subpicture data rate is 3.36 Mbps, with a maximum size per frame of 53220 bytes.

In addition to subtitles in subpicture streams, DVD also supports NTSC Closed Captions. Closed Caption text is stored in the video stream as MPEG-2 user data (in packet headers) and is regenerated by the player as a line-21 analog waveform in the video signal, which then must be decoded by a Closed Caption decoder in the television. Although the DVD-Video spec mentions NTSC only, there is no technical reason PAL/SECAM DVD players could not be made to output the Closed Caption text in World System Teletext (WST) format; the only trick is to deal with frame rate differences. Unfortunate note: DVD Closed Caption MPEG-2 storage format is slightly different than the ATSC format. See the Closed Caption FAQ for more about Closed Captions.

[3.5] What's widescreen? How do the aspect ratios work?

Video can be stored on a DVD in 4:3 format (standard TV shape) or 16:9 (widescreen). The width-to-height ratio of standard televisions is 4 to 3; in other words, 1.33 times wider than high. New widescreen televisions, specifically those designed for HDTV, have a ratio of 16 to 9; that is, 1.78 times wider than high.

DVD is specially designed to support widescreen displays. Widescreen 16:9 video, such as from a 16:9 video camera, can be stored on the disc in anamorphic form, meaning the picture is squeezed horizontally to fit the standard 4:3 rectangle, then unsqueezed during playback.

Things get more complicated when film is transferred to video, since most movies today have an aspect ratio of 1.66, 1.85 ("flat"), or 2.40 ("scope"). Since these don't match 1.33 or 1.78 TV shapes, two processes are employed to make various movie pegs fit TV holes:

Letterbox (often abbreviated to LBX) means the video is presented in its theatrical aspect ratio, which is wider than standard or widescreen TV. Black bars, called mattes, are used to cover the gaps at the top and bottom. A 1.85 movie that has been letterboxed for 1.33 display has thinner mattes than a 2.4 movie letterboxed to 1.33 (28% of display height vs. 44%), although the former are about the same thickness as those of a 2.4 movie letterboxed to 1.78 (26% of display height). The mattes used to letterbox a 1.85 movie for 1.78 display are so thin (2%) that they're hidden by the overscan of most widescreen TVs. Some movies, especially animated features and European films, have an aspect ratio of 1.66, which can be letterboxed for 1.33 display or sideboxed for 1.78 display.

Pan & scan means the thinner TV "window" is panned and zoomed across the wider movie picture, chopping off the sides. However, most movies today are shot soft matte, which means a full 1.33 aspect film frame is used. (The cinematographer has two sets of frame marks in her viewfinder, one for 1.33 and one for 1.85, so she can allow for both formats.) The top and bottom are masked off in the theater, but when the film is transferred to video the full 1.33 frame can be used in the pan & scan process. Pan & scan is primarily used for 1.33 formatting, not for 1.78 formatting, since widescreen fans prefer that letterboxing be used to preserve the theatrical effect.

For more details and nice visual aids see Leopold's How Film Is Transferred to Video page. A list of movie aspect ratios is at <cheezmo.com/wsmc>.

Once the video is formatted to full-frame or widescreen form, it's encoded and stored on DVD discs. DVD players have four playback modes, one for 4:3 video and three for 16:9 video:

Video stored in 4:3 format is not changed by the player. It will appear normally on a standard 4:3 display. Widescreen systems will either enlarge it or add black bars to the sides. 4:3 video may have been formatted with letterboxing or pan & scan before being transferred to DVD. All formatting done to the video prior to it being stored on the disc is transparent to the player. It merely reproduces it as a standard 4:3 TV picture. Video that is letterboxed before being encoded can be flagged so that the player will tell a widescreen TV to automatically expand the picture. Unfortunately, some discs (such as Fargo) do not flag the video properly. And worse, some players ignore the flags.

The beauty of anamorphosis is that less of the picture is wasted on letterbox mattes. DVD has a frame size designed for 1.33 display, so the video still has to be made to fit, but because it's only squeezed horizontally, 33% more pixels (25% of the total pixels in a video frame) are used to store active picture instead of black. Anamorphic video is best displayed on widescreen equipment, which stretches the video back out to its original width. Alternatively, many new 4:3 TV's can reduce the vertical scan area to restore the proper aspect ratio without losing resolution (an automatic trigger signal is sent to European TVs on SCART pin 8). Even though almost all computers have 4:3 monitors, they have higher resolution than TVs so they can display the full widescreen picture in a window (854x480 pixels or bigger for NTSC; 1024x576 or bigger for PAL).

Anamorphic video can be converted by the player for display on standard 4:3 TVs in letterbox or pan & scan form. If anamorphic video is shown unchanged on a standard 4:3 display, people will look tall and skinny as if they have been on a crash diet. The setup options of DVD players allow the viewer to indicate whether they have a 16:9 or 4:3 TV. In the case of a 4:3 TV, a second option lets the viewer indicate a preference for how the player will reformat anamorphic video. The two options are detailed below.

For automatic letterbox mode, the player generates black bars at the top and the bottom of the picture (60 lines each for NTSC, 72 for PAL). This leaves 3/4 of the height remaining, creating a shorter but wider rectangle (1.78:1). In order to fit this shorter rectangle, the anamorphic picture is squeezed vertically using a letterbox filter that combines every 4 lines into 3, reducing the vertical resolution from 480 scan lines to 360. (If the video was already letterboxed to fit the 1.78 aspect, then the mattes generated by the player will extend the mattes in the video.) The vertical squeezing exactly compensates for the original horizontal squeezing so that the movie is shown in its full width. Some players have better letterbox filters than others, using weighted averaging to combine lines (scaling 4 lines into 3 or merging the boundary lines) rather than simply dropping one out of every four lines. Widescreen video can be letterboxed to 4:3 on expensive studio equipment before it's stored on the disc, or it can be stored in anamorphic form and letterboxed to 4:3 in the player. If you compare the two, the letterbox mattes will be identical but the picture quality of the studio version may be slightly better.

For automatic pan & scan mode, the anamorphic video is unsqueezed to 16:9 and the sides are cropped off so that a portion of the image is shown at full height on a 4:3 screen by following a center of interest offset that's encoded in the video stream according to the preferences of the people who transferred the film to video. The pan & scan "window" is 75% of the full width, which reduces the horizontal pixels from 720 to 540. The pan & scan window can only travel laterally. This does not duplicate a true pan & scan process in which the window can also travel up and down and zoom in and out. Auto pan & scan has three strikes against it: 1) it doesn't provide the same artistic control as studio pan & scan, 2) there is a loss of detail when the picture is scaled up, and 3) equipment for recording picture shift information is not widely available. Therefore, no anamorphic movies have been released with auto pan & scan enabled, although a few discs use the pan & scan feature in menus so that the same menu video can be used in both widescreen and 4:3 mode. In order to present a quality full-screen picture to the vast majority of TV viewers, yet still provide the best experience for widescreen owners, some DVD producers choose to put two versions on a single disc: 4:3 studio pan & scan and 16:9 anamorphic.

Playback of widescreen material can be restricted by the producer of the disc. Programs can be marked for the following display modes:
- 4:3 full frame
- 4:3 LB (for sending letterbox expand signal to widescreen TV)
- 16:9 LB only (player not allowed to pan & scan on 4:3 TV)
- 16:9 PS only (player not allowed to letterbox on 4:3 TV)
- 16:9 LB or PS (viewer can select pan & scan or letterbox on 4:3 TV)

You can usually tell if a disc contains anamorphic video if the packaging says "enhanced for 16:9 widescreen" or something similar. If all it says is "widescreen," it may be letterboxed to 4:3, not 16:9. The Laserviews Web site has a list of anamorphic DVD titles.

Additional explanations of how anamorphic video works can be found at Greg Lovern's What's an Anamorphic DVD? page, Bill Hunt's Ultimate Guide to Anamorphic Widescreen DVD, and Dan Ramer's What the Heck Is Anamorphic? article. There are excellent animated illustrations at DVD Web (requires Flash). More information can be found at the Anamorphic Widescreen Support Page. See 1.38 for further discussion of letterboxing.

Anamorphosis causes no problems with line doublers and other video scalers, which simply duplicate the scan lines before they are stretched out by the widescreen display.

For anamorphic video, the pixels are fatter. Different pixel aspect ratios (none of them square) are used for each aspect ratio and resolution. 720-pixel and 704-pixel sizes have the same aspect ratio because the first includes overscan. Note that "conventional" values of 1.0950 and 0.9157 are for height/width (and are tweaked to match scanning rates). The table below uses less-confusing width/height values (y/x * h/w).

      720x480   720x576

      704x480   704x576   352x480   352x576

4:3     0.909     1.091     1.818     2.182

16:9    1.212     1.455     2.424     2.909

[3.6] What are the audio details?

There are two home-entertainment flavors of DVD: DVD-Video and DVD-Audio. Each supports high-definition multichannel audio. DVD-Audio includes higher-quality PCM audio.

[3.6.1] DVD-Audio details

LPCM is mandatory, with up to 6 channels at sample rates of 48/96/192 kHz (also 44.1/88.2/176.4 kHz) and sample sizes of 16/20/24 bits. This allows theoretical frequency response of up to 96 kHz and dynamic range of up to 144 dB. Multichannel PCM is downmixable by the player, although at 192 and 176.4 kHz only two channels are available. Sampling rates and sizes can vary for different channels by using a predefined set of groups. The maximum data rate is 9.6 Mbps.

The WG4 decided to include lossless compression (it's about time!), and on August 5, 1998 approved Meridian's MLP (Meridian Lossless Packing) scheme, already licensed by Dolby. MLP removes redundancy from the signal to achieve a compression ratio of about 2:1 while allowing the PCM signal to be completely recreated by the MLP decoder (required in all DVD-Audio players). MLP allows playing times of about 74 to 135 minutes of 6-channel 96kHz/24-bit audio on a single layer (compared to 45 minutes without packing). Two-channel 192kHz/24-bit playing times are about 120 to 140 minutes (compared to 67 minutes without packing).

Other audio formats of DVD-Video (Dolby Digital, MPEG audio, and DTS, described below) are optional on DVD-Audio discs, although Dolby Digital is required for audio content that has associated video. A subset of DVD-Video features (no angles, no seamless branching, etc.) is allowed. It's expected that shortly after DVD-Audio players appear, new universal DVD players will also support all DVD-Audio features.

DVD-Audio includes specialized downmixing features for PCM channels. Unlike DVD-Video, where the decoder controls mixing from 6 channels down to 2, DVD-Audio includes coefficent tables to control mixdown and avoid volume buildup from channel aggregation. Up to 16 tables can be defined by each Audio Title Set (album), and each track can be identified with a table. Coefficients range from 0dB to 60dB. This feature goes by the horribly contrived name of SMART (system-managed audio resource technique). (Dolby Digital, supported in both DVD-Audio and DVD-Video, also includes downmixing information that can be set at encode time.)

DVD-Audio allows up to 16 still graphics per track, with a set of limited transitions. On-screen displays can be used for synchronized lyrics and navigation menus. A special simplified navigation mode can be used on players without a video display.

Sony and Philips are promoting SACD, a competing DVD-based format using Direct Stream Digital (DSD) encoding with sampling rates of up to 100 kHz. DSD is based on the pulse-density modulation (PDM) technique that uses single bits to represent the incremental rise or fall of the audio waveform. This supposedly improves quality by removing the brick wall filters required for PCM encoding. It also makes downsampling more accurate and efficient. DSD provides frequency response from DC to over 100 kHz with a dynamic range of over 120 dB. DSD includes a lossless encoding technique that produces approximately 2:1 data reduction by predicting each sample and then run-length encoding the error signal. Maximum data rate is 2.8 Mbps.

SACD includes a physical watermarking feature. Pit signal processing (PSP) modulates the width of pits on the disc to store a digital watermark (data is stored in the pit length). The optical pickup must contain additional circuitry to read the PSP watermark, which is then compared to information on the disc to make sure it's legitimate. Because of the requirement for new watermarking circuitry, SACD discs are not playable in existing DVD-ROM drives.

SACD includes text and still graphics, but no video. Sony says the format is aimed at audiophiles and is not intended to replace the audio CD format. A special dual-layer format that would allow SACDs to play in existing compact disc players was originally planned, but was dropped in 1999 because of technical problems. It may be revived when yields are high enough that it no longer costs more to make a hybrid SACD disc than to press both an SACD DVD and a CD. See 1.12 for player info.

See E-Town's two-part DVD-Audio vs. SACD article for more on DVD-Audio and SACD.

[3.6.2] Audio details of DVD-Video

The following details are for audio tracks on DVD-Video. Some DVD manufacturers such as Pioneer are developing audio-only players using the DVD-Video format. Some DVD-Video discs contain mostly audio with only video still frames.

A DVD-Video disc can have up to 8 audio tracks (streams). Each track can be in one of three formats:

Two additional optional formats are provided: DTS and SDDS. Both require external decoders and are not supported by all players.

The ".1" refers to a low-frequency effects (LFE) channel that connects to a subwoofer. This channel carries an emphasized bass audio signal.

Linear PCM is uncompressed (lossless) digital audio, the same format used on CDs and most studio masters. It can be sampled at 48 or 96 kHz with 16, 20, or 24 bits/sample. (Audio CD is limited to 44.1 kHz at 16 bits.) There can be from 1 to 8 channels. The maximum bit rate is 6.144 Mbps, which limits sample rates and bit sizes when there are 5 or more channels. It's generally felt that the 96 dB dynamic range of 16 bits or even the 120 dB range of 20 bits combined with a frequency response of up to 22,000 Hz from 48 kHz sampling is adequate for high-fidelity sound reproduction. However, additional bits and higher sampling rates are useful in studio work, noise shaping, advanced digital processing, and three-dimensional sound field reproduction. DVD players are required to support all the variations of LPCM, but some of them may subsample 96 kHz down to 48 kHz, and some may not use all 20 or 24 bits. The signal provided on the digital output for external digital-to-analog converters may be limited to less than 96 kHz and less than 24 bits.

Dolby Digital is multi-channel digital audio, using lossy AC-3 coding technology from original PCM with a sample rate of 48 kHz at up to 24 bits. The bitrate is 64 kbps to 448 kbps, with 384 being the normal rate for 5.1 channels and 192 being the normal rate for stereo (with or without surround encoding). (Most Dolby Digital decoders support up to 640 kbps.) The channel combinations are (front/surround): 1/0, 1+1/0 (dual mono), 2/0, 3/0, 2/1, 3/1, 2/2, and 3/2. The LFE channel is optional with all 8 combinations. For details see ATSC document A/52 <www.atsc.org/document.html>. Dolby Digital is the format used for audio tracks on almost all DVDs.

MPEG audio is multi-channel digital audio, using lossy compression from original PCM format with sample rate of 48 kHz at 16 bits. Both MPEG-1 and MPEG-2 formats are supported. The variable bitrate is 32 kbps to 912 kbps, with 384 being the normal average rate. MPEG-1 is limited to 384 kbps. Channel combinations are (front/surround): 1/0, 2/0, 2/1, 2/2, 3/0, 3/1, 3/2, and 5/2. The LFE channel is optional with all combinations. The 7.1 channel format adds left-center and right-center channels, but will probably be rare for home use. MPEG-2 surround channels are in an extension stream matrixed onto the MPEG-1 stereo channels, which makes MPEG-2 audio backwards compatible with MPEG-1 hardware (an MPEG-1 system will only see the two stereo channels.) MPEG Layer III (MP3) and MPEG-2 AAC (aka NBC or unmatrix) are not supported by the DVD-Video standard.

DTS (Digital Theater Systems) Digital Surround is an optional multi-channel (5.1) digital audio format, using lossy compression from PCM at 48 kHz at up to 20 bits. The data rate is from 64 kbps to 1536 kbps, with typical rates of 768 and 1536. (The DTS Coherent Acoustics format supports up to 4096 kbps variable data rate for lossless compression, but this isn't supported by DVD.). Channel combinations are (front/surround): 1/0, 2/0, 3/0, 2/1, 2/2, 3/2. The LFE channel is optional with all 6 combinations. The DVD standard includes an audio stream format reserved for DTS, but many players ignore it. According to DTS, existing DTS decoders work with DTS DVDs. The DTS format used on DVDs is different from the one used in theaters (Audio Processing Technology's apt-X, an ADPCM coder, not a psychoacoustic coder). All DVD players can play DTS audio CDs, since the standard PCM stream holds the DTS code. See 1.32 for general DTS information. For more info visit <www.dtstech.com> and read Adam Barratt's article for Movie Sound Page.

SDDS (Sony Dynamic Digital Sound) is an optional multi-channel (5.1 or 7.1) digital audio format, compressed from PCM at 48 kHz. The data rate can go up to 1280 kbps. SDDS is a theatrical film soundtrack format based on the ATRAC compression format that is also used by Minidisc. Sony has not announced any plans to support SDDS on DVD.

THX (Tomlinson Holman Experiment) is not an audio format. It's a certification and quality control program that applies to sound systems and acoustics in theaters, home equipment, and digital mastering processes. The LucasFilm THX Digital Mastering program uses a patented process to track video quality through the multiple video generations needed to make a final format disc or tape, setup of video monitors to ensure that the filmmaker is seeing a precise rendition of what is on tape before approval of the master, and other steps along the way. THX-certified "4.0" amplifiers enhance Dolby Pro Logic: crossover sends bass from front channels to subwoofer; re-equalization on front channels (compensates for high-frequency boost in theater mix designed for speakers behind the screen); timbre matching on rear channels; decorrelation of rear channels; bass curve that emphasizes low frequencies. THX-certified "5.1" amplifiers enhance Dolby Digital and improve on 4.0: rear speakers are now full range, so crossover sends bass from both front and rear to subwoofer; decorrelation is turned on automatically when rear channels have the same audio, but not during split-surround effects, which don't need to be decorrelated. More info at Home THX Program Overview.

Discs containing 525/60 video (NTSC) must use PCM or Dolby Digital on at least one track. Discs containing 625/50 video (PAL/SECAM) must use PCM or MPEG audio or Dolby Digital on at least one track. Additional tracks may be in any format. A few first-generation players, such as those made by Matsushita, can't output MPEG-2 audio to external decoders.

The original spec required either MPEG audio or PCM on 625/50 discs. There was a brief scuffle led by Philips when early discs came out with only two-channel MPEG and multichannel Dolby Digital, but the DVD Forum clarified in May 1997 that only stereo MPEG audio was mandatory for 625/50 discs. In December 1997 the lack of MPEG-2 encoders (and decoders) was a big enough problem that the spec was revised to allow Dolby Digital as the only audio track on 625/50 discs.

For stereo output (analog or digital), all players have a built-in 2-channel Dolby Digital decoder that downmixes from 5.1 channels (if present on the disc) to Dolby Surround stereo (i.e., 5 channels are phase matrixed into 2 channels to be decoded to 4 by an external Dolby Pro Logic processor). PAL players also have an MPEG or MPEG-2 decoder. Both Dolby Digital and MPEG-2 support 2-channel Dolby Surround as the source in cases where the disc producer can't or doesn't want to remix the original onto discrete channels. This means that a DVD labeled as having Dolby Digital sound may only use the L/R channels for surround or "plain" stereo. Even movies with old monophonic soundtracks may use Dolby Digital -- but only 1 or 2 channels. Sony players can optionally downmix to non-surround stereo. If surround audio is important to you, you will hear significantly better results from multichannel discs if you have a Dolby Digital system.

The new Dolby Digital Surround EX (DD-SEX?) format, which adds a rear center channel, is compatible with DVD discs and players, and with existing Dolby Digital decoders. The new DTS Digital Surround ES (DTS-ES) format, which likewise adds a rear center channel, works fine with existing DTS decoders and with DTS-compatible DVD players. However, for full use of both new formats you need a new decoder to extract the rear center channel, which is phase matrixed into the two standard rear channels in the same way Dolby Surround is matrixed into standard stereo channels. Without a new decoder, you'll get the same 5.1-channel audio you get now. Because the additional rear channel isn't a full-bandwidth discrete channel, it's appropriate to call the new formats "5.2-channel" digital surround.

The Dolby Digital downmix process does not usually include the LFE channel and may compress the dynamic range in order to improve dialog audibility and keep the sound from becoming "muddy" on average home audio systems. This can result in reduced sound quality on high-end audio systems. The dynamic range compression (DRC) feature, often called midnight mode, reduces the difference between loud and soft sounds so that you can turn the volume down to avoid disturbing others yet still hear the detail of quiet passages. Some players have the option to turn off DRC. The downmix is auditioned when the disc is prepared, and if the result is not acceptable the audio may be tweaked or a separate L/R Dolby Surround track may be added. Experience has shown that minor tweaking is sometimes required to make the dialog more audible within the limited dynamic range of a home stereo system, but that a separate track is not usually necessary.

Dolby Digital also includes a feature called dialog normalization, which could more accurately be called volume standardization. DN is designed to keep the sound level the same when switching between different sources. This will become more important as additional Dolby Digital sources (digital satellite, DTV, etc) become common. Each Dolby Digital track contains loudness information so that the receiver can automatically adjust the volume, turning it down, for example, on a loud commercial. (Of course the commercial makers can cheat and set an artificially low DN level, causing your receiver to turn up the volume during the commercial!) Turning DN on or off on your receiver has no effect on dynamic range or sound quality, its effect is no different than turning the volume control up or down.

All five DVD-Video audio formats support karaoke mode, which has two channels for stereo (L and R) plus an optional guide melody channel (M) and two optional vocal channels (V1 and V2).

A DVD-5 with only one surround stereo audio stream (at 192 kbps) can hold over 55 hours of audio. A DVD-18 can hold over 200 hours.

Many people complain that the audio level from DVD players is too low. In truth the audio level is too high on everything else. Movie soundtracks are extremely dynamic, ranging from near silence to intense explosions. In order to support an increased dynamic range and hit peaks (near the 2V RMS limit) without distortion, the average sound volume must be lower. This is why the line level from DVD players is lower than from almost all other sources. So far, unlike on CDs and LDs, the level is much more consistent between discs. If the change in volume when switching between DVD and other audio sources is annoying, you can adjust the output signal level on some players, or the input signal level on some receivers, but other than that, there's not much you can do.

For more information about multichannel surround sound, see Bobby Owsinski's FAQ at <www.surroundassociates.com/safaq.html>.

[3.7] How do the interactive features work?

DVD-Video players (and software DVD-Video navigators) support a command set that provides rudimentary interactivity. The main feature is menus, which are present on almost all discs to allow content selection and feature control. Each menu has a still-frame graphic and up to 36 highlightable, rectangular "buttons" (only 12 if widescreen, letterbox, and pan & scan modes are used). Remote control units have four arrow keys for selecting onscreen buttons, plus numeric keys, select key, menu key, and return key. Additional remote functions may include freeze, step, slow, fast, scan, next, previous, audio select, subtitle select, camera angle select, play mode select, search to program, search to part of title (chapter), search to time, and search to camera angle. Any of these features can be disabled by the producer of the disc.

Additional features of the command set include simple math (add, subtract, multiply, divide, modulo, random), bitwise and, bitwise or, bitwise xor, plus comparisons (equal, greater than, etc.), and register loading, moving, and swapping. There are 24 system registers for information such as language code, audio and subpicture settings, and parental level. There are 16 general registers for command use. A countdown timer is also provided. Commands can branch or jump to other commands. Commands can also control player settings, jump to different parts of the disc, and control presentation of audio, video, subpicture, camera angles, etc.

DVD-V content is broken into "titles" (movies or albums), and "parts of titles" (chapters or songs). Titles are made up of "cells" linked together by one or more "program chains" (PGC). A PGC can be on of three types: sequential play, random play (may repeat), or shuffle play (random order but no repeats). Individual cells may be used by more than one PGC, which is how parental management and seamless branching are accomplished: different PGCs define different sequences through mostly the same material.

Additional material for camera angles and seamless branching is interleaved together in small chunks. The player jumps from chunk to chunk, skipping over unused angles or branches, to stitch together the seamless video. Since angles are stored separately, they have no direct effect on the bitrate but they do affect the playing time. Adding 1 camera angle for a program roughly doubles the amount of space needed (and cuts the playing time in half). Examples of branching (seamless and non-seamless) include Kalifornia, Dark Star, and Stargate SE.

[3.8] What is the difference between interlaced and progressive video?

There are basically two ways to display video: interlaced scan or progressive scan. Progressive scan, used in computer monitors and digital television, displays all the horizontal lines of a picture at one time, as a single frame. Interlaced scan, used in standard television formats NTSC, PAL, and SECAM, displays only half of the horizontal lines at a time (the first field, containing the odd-numbered lines, is displayed, followed by the second field, containing the even-numbered lines). Interlacing relies on the persistence of vision characteristic of our eyes (which may only be psychological, not physical), as well as the phosphor persistence of the TV tube to blur the fields together into a seemingly single picture. The advantage of interlaced video is that a high refresh rate (50 or 60 Hz) can be achieved with only half the amount of data. The disadvantage is that the horizontal resolution is essentially cut in half because the video must be filtered to avoid flicker and other artifacts.

It may help to understand the difference by considering how the source images are captured. A film camera shoots 24 frames per second, while a video camera alternately scans fields of odd and even lines in 1/60 of a second intervals. (Unlike projected film, which shows the entire frame in an instant, most progressive-scan displays trace a series of lines from top to bottom, but the end result is about the same.)

DVD is specifically designed to be displayed on interlaced-scan displays, which covers 99.9% of the 1 billion TVs worldwide. However, most DVD content comes from film, which is inherently progressive. To make film content work in interlaced form, the video from each film frame is split into two video fields —240 lines in one field, and 240 lines in the other— and encoded as separate fields in the MPEG-2 stream. Another complication is that film runs at 24 frames/second, while TV runs at 30 frames (60 fields) per second for NTSC or 25 frames (50 fields) per second for PAL and SECAM. For PAL/SECAM display, the simple solution is to show the film frames at 25/second, which is a 4% speedup, and speed up the audio to match. For NTSC display, the solution is to spread 24 frames across 60 fields by alternating the display of the first film frame for 2 video fields and the next film frame for 3 video fields. This is called 2-3 pulldown. The sequence works as shown below, where A-D represent film frames; A1, A2, B1, etc. represent the separation of each film frame into two video fields; and 1-5 represent the final video frames.

Film frames:   |  A  |   B    |  C  |   D    |

Video fields:  |A1 A2|B1 B2|B1 C2|C1 D2|D1 D2|

Video frames:  |  1  |  2  |  3  |  4  |  5  |

For MPEG-2 encoding, repeated fields (B1 and D2) are not actually stored twice. Instead, a flag is set to tell the decoder to repeat the field. (The apparently inverted order of  C2-C1 and D2-D1 are because of the requirement that top and bottom fields alternate.) MPEG-2 also has a flag to indicate when a frame is progressive (that the two fields come from the same instant in time). For film content, the progressive_frame flag should be true for every frame. See 3.4 for more MPEG-2 details.

As you can see, there are a couple of problems: 1) some film frames are shown for a longer period of time than others, causing judder, or jerkiness, that shows up especially in smooth pans; and 2) if you freeze the video on the third or fourth video frame when there is motion in the picture you will see two separate images combined in a flickering mess. Most DVD players avoid the second problem, although some allow you to freeze on flicker-frames. (This is what the frame/field still option in the player's setup menu refers to.)

Most DVD players are hooked up to interlaced TVs, so there's not much that can be done about artifacts from film conversion. However, see 1.40 for information about progressive DVD players.

[3.9] What is edge enhancement?

When films are transferred to video in preparation for DVD encoding, they are commonly run through digital processes that attempt to clean up the picture. These processes include noise reduction (DVNR) and image enhancement. Enhancement increases contrast (similar to the effect of the "sharpen" filter in PhotoShop), but can tend to overdo areas of transition between light and dark or different colors, causing a "chiseled" look or a ringing effect like the haloes you see around streetlights when driving in the rain.

Video noise reduction is a good thing, when done well, since it can remove scratches, spots, and other defects from the original film. Enhancement, which is rarely done well, is a bad thing. The video may look sharper and clearer to the casual observer, but fine tonal details of the original picture are altered and lost.

[3.10] Does DVD work with barcodes?

If your humble FAQ author and other long-time developers of laserdisc had prevailed, all DVD players would support barcodes. This would have made for really cool printed supplements and educational discs. But the rejection of our recommendations after an all-star meeting in August 1995 is another story for another day.

So the answer is "mostly no." A few industrial players, the Pioneer LD-V7200, Pioneer LD-V7400, and Philips ProDVD-170 support barcodes, including compatibility with the LaserBarCode standard. The DVD must be authored with one_sequential_PGC titles in order for timecode search to work. More info can be found in the Pioneer technical manuals.

[4] DVD and computers

[4.1] Can I play DVD movies on my computer?

Yes, if your computer has the right stuff. The computer operating system or playback software must support regional codes and be licensed to descramble copy-protected movies. If the computer has TV video out, it must support Macrovision in order to play copy-protected movies. You may also need software that can read the MicroUDF file system format used by DVDs. You don't need special drivers for Windows, since the existing CD-ROM drivers work fine with DVD-ROM drives. In addition to a DVD-ROM drive you must have extra hardware to decode MPEG-2 video and Dolby Digital or MPEG-2 audio, or your computer must be fast enough to handle software decoding. Good-quality software-only playback requires a 350-MHz Pentium II or a Mac G4. Less than 10% of new computers with DVD-ROM drives include decoder hardware, since software decoding is now possible on even the cheapest new models. Hardware upgrade kits can be purchased for existing computers (usually minimum 133 MHz Pentium or G3), starting at $150. See <www.brouhaha.com/~eric/video/dvd> for a list of drives and upgrade kits.

If you're having problems playing movies on your PC, see section 4.6.

Certain MPEG decoding tasks such as motion compensation and IDCT (inverse discrete cosine transform) can be performed by additional circuitry on a video graphics card, improving the performance of software decoders. This is called hardware decode acceleration or hardware motion comp. All modern graphics cards also provide hardware colorspace conversion (YCbCr to RGB) and videoport overlay.

Microsoft Windows 98 and Windows 2000 includes DirectShow, which provides standardized support for DVD-Video and MPEG-2 playback. DirectShow can also be installed in Windows 95 (it's available for download). DirectShow creates a framework for DVD applications, but a third-party hardware or software decoder is required (see below). Windows NT 4.0 supports DVD-ROM drives for data, but has very little support for playing DVD-Video discs. Margi DVD-To-Go, Sigma Designs Hollywood Plus, and the related Creative Labs Dxr3 are among the few hardware decoders that work in NT 4.0. InterVideo WinDVD software works in NT 4.0 (Mediamatics DVD Express and MGI SoftDVD Max also work in NT 4.0, but they aren't available retail.) Windows 2000 uses essentially the same WDM drivers and DirectShow software as Windows 98, so it fully supports movie playback and DVD applications, including WebDVD. Internet Explorer 5.0 includes version 6.1 of Windows Media Player that enables scriptable DVD playback in an HTML page. Windows 98 and newer can read UDF discs. Adaptec provides a free filesystem driver, UDF Reader, for Windows 95/98/NT. Software Architects sells Read DVD for Windows 95.

Apple QuickTime 4 is partially ready for DVD-Video and MPEG-2 but does not yet have full decoding or DVD-Video playback support in place. Mac OS 8.1 or newer can read UDF discs. Adaptec provides a free utility, UDF Volume Access, that enables Mac OS 7.6 and newer to read UDF discs. Software Architects sells UDF reading software for Mac OS called DVD-RAM TuneUp.

Note: The QuickTime MPEG Extension for Mac OS is for MPEG-1 only and does not play MPEG-2 DVD-Video.

Some DVD-ROMs and a few DVD-Videos use video encoded using MPEG-1 instead of MPEG-2. Most recent computers have MPEG-1 hardware built in or are able to decode MPEG-1 with software.

DVD player applications (using either software or hardware decoding) are virtual DVD players. They support most DVD-Video features (menus, subpictures, etc.) and emulate the functionality of a DVD-Video player remote control. Many player applications include additional features such as bookmarks, chapter lists, and subtitle language lists.

Software decoders and DVD player applications for Microsoft Windows PCs:

Software decoders need at least a 350 MHz Pentium II and a DVD-ROM drive with bus mastering DMA to play without dropped frames. Anything slower than a 400 MHz Pentium III will benefit quite a bit from hardware decode acceleration in the graphics card. An AGP graphics card (rather than PCI) also improves the performance of software decoders.

Hardware decoder cards and DVD-ROM upgrade kits for Microsoft Windows PCs:

All but the Sigma Designs decoder (including Creative Dxr3) have WDM drivers for DirectShow. The Sigma Designs decoder card is used in hardware upgrade kits from Hitachi, HiVal, Panasonic, Phillips, Sony, Toshiba, and VideoLogic. The advantage of hardware decoders is that they don't eat up CPU processing power, and they often produce better quality video than software decoders. The Chromatic Mpact2 chip does 3-field analysis to produce exceptional progressive-scan video from DVDs (unfortunately, Chromatic was bought by ATI and the chip is no longer supported — but see Tony Lai's Mpact2 FAQ at pegasus.ign.com.au/.) Hardware decoders use video overlay to insert the video into the computer display. Some use analog overlay, which takes the analog VGA signal output from the graphics card and keys in the video, while others use video port extension (VPE), a direct digital connection to the graphics adapter via a cable inside the computer. Analog overlay may degrade the quality of the VGA signal. See 4.4 for more overlay info.

Macintosh G4's and some iMacs come standard with DVD-ROM or DVD-RAM drives. They use the Velocity Engine (AltiVec) portion of the PowerPC chip for video and audio decoding. Unfortunately, there are numerous problems with Apple's software decoding. Apple released five software updates in the first four months. Check MacFixit and MacInTouch for the latest info. A few models of the iMac, PowerBook, and G3 lines can be ordered with DVD-ROM drives and hardware decoders. DVD-ROM upgrade kits and decoder cards for Macintoshes are made by E4 (Elecede) (Cool DVD, C-Cube chip) [E4 has gone out of business], EZQuest (BOA Mac DVD), Fantom Drives (DVD Home Theater kit: DVD-ROM or DVD-RAM drive with Wired MPEG-2 card), and Wired (Wired 4DVD, Sigma EM8300 chip [same card as Hollywood plus]; MasonX [can't play encrypted movies]; DVD-To-Go [out of production]; Wired has been acquired by Media100). There's a beta version of a shareware DVD software player that can play unencrypted movies.

The Sigma Designs NetStream 2000 DVD decoder card will support Linux DVD playback.

Computers have the potential to produce better video than settop DVD-Video players by using progressive display and higher scan rates, but many current systems don't look as good as a home player hooked up to a quality TV

If you want to hook a DVD computer to a TV, the decoder card or the VGA card must have a TV output (composite video or s-video). Video quality is much better with s-video. Alternatively, you can connect a scan converter to the VGA output. The quality of the video will depend on the decoder, the TV encoder chip, and other factors, but will usually be a little inferior to a good consumer DVD player. The RGB output of the VGA card in computers is at a different frequency than standard component RGB video, so it can't be directly connected to most RGB video monitors. If the decoder card or the sound card has Dolby Digital or DTS output, you can connect to your A/V receiver to get multichannel audio.

A DVD PC connected to a progressive-scan monitor or video projector, instead of a standard TV, usually looks much better than a consumer player. See 2.9. Also see the Home Theater Computers forum at AVS.

For remote control of DVD playback on your PC, check out Animax Anir Multimedia Magic, Evation IRMan, InterAct WebRemote, Multimedia Studio Miro MediaRemote, Packard Bell RemoteMedia, RealMagic Remote Control, and X10 MouseRemote. Many remotes are supported by Visual Domain's Remote Selector software.

[4.2] What are the features and speeds of DVD-ROM drives?

Unlike CD-ROM drives, which took years to move up to 2x, 3x, and faster spin rates, faster DVD-ROM drives began appearing in the first year. 1x DVD-ROM drives provide a data transfer rate of 1.321 MB/s (11.08*10^6/8/2^20) with burst transfer rates of up to 12 MB/s or higher. The data transfer rate from a DVD-ROM disc at 1x speed is roughly equivalent to a 9x CD-ROM drive (1x CD-ROM data transfer rate is 150 KB/s, or 0.146 MB/s). DVD physical spin rate is about 3 times faster than CD (that is, 1x DVD spin ~ 3x CD spin), but most DVD-ROM drives increase motor speed when reading CD-ROMs, achieving 12x or faster performance.  A drive listed as "16x/40x" spins a DVD at 16 times normal, or a CD at 40 times normal. DVD-ROM drives are available in 2x, 4x, 4.8x, 5x, 6x, 8x, 10x, and 16x speeds, although they usually don't achieve sustained transfer at their full rating. The "max" in DVD and CD speed ratings means that the listed speed only applies when reading data at the outer edge of the disc, which moves faster. The average data rate is lower than the max rate. Most 1x DVD-ROM drives have a seek time of 85-200 ms and access time of 90-250 ms.

DVD drive speed Data rate Equivalent CD rate Actual CD speed
1x 11.08 Mbps (1.32 MB/s) 9x 8x-18x
2x 22.16 Mbps (2.64 MB/s) 18x 20x-24x
4x 44.32 Mbps (5.28 MB/s) 36x 24x-32x
5x 55.40 Mbps (6.60 MB/s) 45x 24x-32x
6x 66.48 Mbps (7.93 MB/s) 54x 24x-32x
8x 88.64 Mbps (10.57 MB/s) 72x 32x-40x
10x 110.80 Mbps (13.21 MB/s) 90x 32x-40x
16x 177.28 Mbps (21.13 MB/s) 144x 32x-40x

The bigger the cache (memory buffer) in a DVD-ROM drive, the faster it can supply data to the computer. This is useful primarily for data, not video. It may reduce or eliminate the pause during layer changes, but has no effect on video quality.

In order to maintain constant linear density, typical CD-ROM and DVD-ROM drives spin the disc more slowly when reading near the outside where there is more physical surface in each track. (This is CLV, constant linear velocity.) Some faster drives keep the rotational speed constant and use a buffer to deal with the differences in data readout speed. (This is CAV, constant angular velocity.) In CAV drives, the data is read fastest at the outside of the disc, which is why specifications often list "max speed."

Note: When playing movies, a fast DVD-ROM drive gains you nothing more than possibly smoother scanning and faster searching. Speeds above 1x do not improve video quality from DVD-Video discs. Higher speeds only make a difference when reading computer data, such as when playing a multimedia game or when using a database.

Connectivity is similar to that of CD-ROM drives: EIDE (ATAPI), SCSI-2, etc. All DVD-ROM drives have audio connections for playing audio CDs. No DVD-ROM drives have been announced with DVD audio or video outputs (which would require internal audio/video decoding hardware). In order to hook a DVD-ROM PC to a television and a stereo receiver, the decoder card or the video card must have a TV video output and an audio output. Some cards have SP/DIF outputs to connect to digital audio receivers. If there's no video output, a TV scan converter can be connected to the VGA output.

Almost all DVD-Video and DVD-ROM discs use the UDF Bridge format, which is a combination of the DVD MicroUDF and ISO 9660 file systems. The OSTA UDF file system will eventually replace the ISO 9660 system originally designed for CD-ROMs, but the bridge format provides backwards compatibility until more operating systems support UDF.

[4.3] What about recordable DVD: DVD-R, DVD-RAM, DVD-RW, and DVD+RW?

There are five recordable versions of DVD-ROM: DVD-R/authoring, DVD-R/general, DVD-RAM, DVD-RW, and DVD+RW. All can read DVD-ROM and DVD-Video discs, but each uses a different type of disc for recording. DVD-R can record data once (sequentially only), while DVD-RAM, DVD-RW, and DVD+RW can be rewritten thousands of times. Final versions of the DVD-R and DVD-RAM version 1.0 specifications were published in August 1997 (see 6.1). DVD-RW 1.0 and DVD-R 2.0 are being finalized in early 2000. DVD+RW will be available in early 2001. Most recordable media are not currently usable for home video recording (see 1.14), though home DVD recorders became available in Japan at the beginning of 2000. The three erasable formats (DVD-RAM, DVD-RW, and DVD+RW) are essentially in competition with each other. The market will determine which of them succeed. DVD-RAM has a head start of more than a year.

Toshiba, Panasonic, and others released combination DVD-ROM/CD-RW drives near the end of 1999.

Each writable DVD format is covered briefly below. For more on writable DVD, see Dana Parker's article at <www.emediapro.net/EM1999/parker1.html>. If you're interested in writable DVD for data storage, visit Steve Rothman's DVD-DATA page for FAQ and mailing list info.


DVD-R uses organic dye polymer technology, like CD-R, and is compatible with most DVD drives and players. First-generation capacity was 3.95 billion bytes, but was later extended to 4.7 billion bytes. Matching the 4.7G capacity of DVD-ROM was crucial for desktop DVD-ROM and DVD-Video production. In early 2000, the format was split into an "authoring" version and a "general" version. The general version will use a 650nm laser (instead of 635nm) for future ability to write DVD-RAM.

DVD-RW (formerly DVD-R/W and also briefly known as DVD-ER) is a phase-change erasable format that became available at the end of 1999. Developed by Pioneer based on DVD-R, using the similar track pitch, mark length, and rotation control, DVD-RW will be playable in most DVD drives and players. (Some drives and players are confused by DVD-RW media's lower reflectivity into thinking it's a dual-layer disc. Simple firmware upgrades will be required to solve the problem.) DVD-RW uses groove recording with address info on land areas for synchronization at write time (land data is unnecessary during reading). Capacity is 4.7 billion bytes. DVD-RW can be rewritten about 1,000 times. DVD-R discs are expected to last anywhere from 50 to 250 years, about as long as CD-R discs. DVD-RW discs won't last quite as long. See <www.ee.washington.edu/conselec/CE/kuhn/otherformats/95x9.htm> and <www.cd-info.com/CDIC/Technology/CD-R/Media/Kodak.html> for more info. For comparison, magnetic media (tapes and disks) lasts 10 to 30 years, high-quality acid neutral paper can last a hundred years or longer, and archival-quality microfilm is projected to last 300 years or more. Note that optical media can become technically obsolete within 20 to 30 years, long before it physically deteriorates.

Pioneer released 3.95G DVD-R 1.0 drives in October 1997 (about 6 months late) for $17,000. New 4.7G DVD-R 1.9 drives appeared in limited quantities in May 1999 (about 6 months late) for $5,400. A future version of the drive will support DVD-R 2.0 media and DVD-RW media. Price for blank DVD-Rs is about $40. Initial DVD-RW prices will be about the same. Blank media is being made by Eastman Kodak, Hitachi Maxell, Mitsubishi, Mitsui, Pioneer, Ricoh, Ritek, TDK, Verbatim, and Victor. Ricoh, Yamaha, Sony, and others will join Pioneer in making 4.7G DVD-R/RW drives.

In December 1999, Pioneer released DVD-RW home video recorders in Japan. The unit costs 250,000 yen (about $2,500) and blank discs cost 3,000 yen (about $30). Since the recorder uses the new DVD-VR (video recording) format, the discs won't play in existing players (the discs are physically compatible, but not logically compatible). Recording time varies from 1 hour to 6 hours, depending on quality. The player is expected to be released in the U.S. and elsewhere around the middle of 2000. Sharp announced a $2,200 DVD-RW recorder, and Zenith (LG) announced a $2,000 DVD-RW recorder, both expected near the end of 2000. DVD video recorders will not copy protected DVD movie discs.

The advantages of DVD-R and DVD-RW drives, which are used primarily for DVD production, are higher capacity and compatibility with most DVD players and drives.

The DVD-R 1.0 format is standardized in ECMA-279.


DVD-RAM, with an initial storage capacity of 2.58 billion bytes, uses phase-change (PD) technology with some MO features mixed in. It is not compatible with most drives and players (because of defect management, reflectivity differences, and minor format differences). A wobbled groove is used to provide clocking data, with marks written in both the groove and the land between grooves. The grooves and pre-embossed sector headers are molded into the disc during manufacturing. Single-sided DVD-RAM discs come with or without cartridges. There are two types of cartridges: type 1 is sealed, type 2 allows the disc to be removed. Discs can only be written while in the cartridge. Double-sided DVD-RAM discs are available in sealed cartridges only. Cartridge dimensions are 124.6mm x 135.5mm x 8.0mm. DVD-RAM can be rewritten about 100,000 times, and the discs are expected to last at least at least 30 years.

DVD-RAM drives appeared in June 1998 (about 6 months late) for $500 to $800, with blank discs at about $30 for single-sided and $45 for double-sided. Disc prices were under $20 by August 1998, and retail drive prices were under $250 by November 1999. The first DVD-ROM drive to read DVD-RAM discs was released by Panasonic in 1999 (SR-8583, 5x DVD-ROM, 32x CD). Hitachi's GD-5000 drive, released in late 1999, also reads DVD-RAM discs. Blank DVD-RAM media is manufactured by Hitachi Maxell, Eastman Kodak, Mitsubishi, Mitsui, Ritek, and TDK. 

DVD-RAM version 2.0, with a capacity of 4.7 billion bytes per side, was published in October 1999. The first drives will appear in mid 2000 at about the same price as current DVD-RAM 1.0 drives. DVD-RAM 2.0 also specifies 8cm discs and cartridges for portable uses such as digital camcorders. Future DVD-RAM discs may use a contrast enhancement layer and a thermal buffer layer to achieve higher density.

Samsung and C-Cube made a technology demonstration (not a product announcement) in October 1999 of a DVD-RAM video recorder using the new DVD-VR format (see DVD-R/RW section above for DVD-VR details). Panasonic demonstrated a $3,000 DVD-RAM video recorder at CES in January 2000, with expected availability in late 2000. Samsung said its $2,000 DVD-RAM-based recorder would be out around the same time. Hitachi showed a camcorder that uses the smaller DVD-RAM discs, to be available for $3,000 in late 2000.

The DVD-RAM 1.0 format is standardized in ECMA-272 and ECMA-273.


Phase-Change Rewritable DVD is an erasable format announced by Philips, Sony, Hewlett-Packard and others based on CD-RW technology. It will become available in early 2001. DVD+RW is not supported by the DVD Forum (even though the DVD+RW companies are members), but the Forum has no power to set standards. DVD+RW drives will read DVD-ROMs and CDs, and probably DVD-Rs and DVD-RWs, but will not read or write DVD-RAM discs. The drives are expected to write CD-Rs and CD-RWs. DVD+RW discs, which hold 4.7 billion bytes (4.4 gigabytes) per side, should be readable in about 70% of the existing DVD-Video players and DVD-ROM drives.

DVD+RW backers claimed in 1997 that it would be used only for computer data, not home video, but this was apparently a smokescreen intended to placate the DVD Forum and competitors. The original 1.0 format, which held 3 billion bytes (2.8 gigabytes) per side and was incompatible with all existing players and drives, was abandoned in late 1999.

The DVD+RW format uses phase-change technology with a high-frequency wobbled groove that allows it to eliminate linking sectors. This, plus the option of no defect management, allows DVD+RW discs to be written in a way that should be compatible with many existing DVD readers. DVD+RW discs can be recorded in either CLV format for sequential video access (read at CAV speeds by drive) or CAV format for random access. DVD+RW media can be rewritten about 1,000 times (down from 100,000 times in the original version), and the discs are expected to last at least 30 years.

Media will be produced by MCC/Verbatim. Ricoh and Yamaha have also announced support for the DVD+RW format.

Philips announced a DVD+RW home video recorder, to be available "after mid 2000." [Jim's prediction (Jan 2000): we won't see it until early 2001.] Unlike the Pioneer DVD-RW recorder, the Philips recorder will use the DVD-Video format, so discs will play in many existing players.

More DVD+RW information is at <www.dvdrw.org>. The obsolete DVD+RW 1.0 format is standardized in ECMA-274.


Other upcoming potential competitors to recordable DVD include AS-MO (formerly MO7), which holds 5 to 6 billion bytes, and NEC's Multimedia Video Disc (MVDisc, formerly MMVF, Multimedia Video File), which holds 5.2 billion bytes and is targeted at home recording. ASMO are expected to read DVD-ROM but not DVD-RAM or first-generation DVD+RW. MVDisc is similar to DVD-RW and DVD+RW, using two bonded 0.6mm phase-change substrates, land and groove recording, and a 640nm laser, but contrary to initial reports, the drives won't be able to read DVD-ROM or compatible discs.

[4.4] Why can't I take a screenshot of DVD video? Why do I get a pink or black square?

Most DVD PCs, even those with software decoders, use video overlay hardware to insert the video directly into the VGA signal. This an efficient way to handle the very high bandwidth of full-motion video. Some decoder cards, such as the Creative Labs Encore Dxr series and the Sigma Designs Hollywood series, use a pass-through cable that overlays the video into the analog VGA signal after it comes out of the video display card. Video overlay uses a technique called colorkey to selectively replace a specified pixel color (often magenta or near-black) with video content. Anywhere a colorkey pixel appears in the computer graphics video, it's replaced by video from the DVD decoder. This process occurs "downstream" from the computer's video memory, so if you try to take a screenshot (which grabs pixels from video RAM), all you get is a solid square of the colorkey color.

Some decoders write to normal video memory. In this case, utilities such as Creative Softworx, HyperSnap, and SD Capture can grab still pictures. Some player applications can also take screenshots.

[4.5] Why can't I play movies copied to my hard drive?

Almost all movies are encrypted with CSS copy protection (see 1.11). Decryption keys are stored in the normally inaccessible lead-in area of the disc. If you copy the contents of an encrypted DVD to a hard drive, the keys will not be copied. If you try to play the VOB files, the decoder will request the keys from the DVD-ROM drive and will fail. You may get the message "Cannot play copy-protected files".

[4.6] Why do I have problems playing DVDs on my computer?

There are thousands of answers to this question, but here are some basic troubleshooting steps to help you track down problems such as jerky playback, pauses, error messages, and so on.

More information on specific graphics cards and driver updates:

[4.7] Can I stream DVD over a network or the Internet?

Short answer: usually not.

With a fast enough network (100 Mbps or better, with good performance and low traffic) and a high-performance server, it's possible to stream DVD-Video from a server to client stations. If the source on the server is a DVD-ROM drive (or jukebox), then more than one user simultaneously accessing the same disc will cause breaks in the video unless the server has a fast DVD-ROM drive and a very good caching system designed for streaming video.

A big problem is that CSS-encrypted movies (see 1.11) are difficult to remotely source because of security issues. The CSS license does not allow decrypted video to be sent over an accessible bus or network, so the decoder has to be on the remote PC. If the decoder has a secure channel to perform authentication with the drive on the server, then it's possible to stream encrypted video over a network to be decrypted and decoded remotely.

An alternative is to decode the video at the server and send it to individual stations via separate cables (usually RF). The advantage is that performance is very good, but the disadvantage is that that DVD interactivity is usually limited, and every viewer connected to a single drive/decoder must watch the same thing at the same time.

Many companies provide support for streaming MPEG-1 and MPEG-2 video over LANs, but only from files or realtime encoders, not from DVD-Video discs.

The Internet is a different matter. It takes over a week to download the contents of a single-layer DVD using a 56k modem. It takes about 7 hours on a T1 line. Cable modems theoretically cut the time down to a few hours, but if other users in the same neighborhood have cable modems, bandwidth could drop significantly. [Jim's prediction: the average DVD viewing household won't have sufficiently fast Internet connections before 2007 at the earliest. Around that time there will be a new high-definition version of DVD with double the data rate, which will once again exceed the capacity of the typical Internet connection.]

[4.8] What is DeCSS?

CSS (Content Scrambling System) is an encryption and authentication scheme intended to prevent DVD movies from being digitally copied. See 1.11 for details. DeCSS refers to the general process of defeating CSS, as well as to DeCSS source code and programs.

Computer software to decrypt CSS was released to the Internet in October 1999 (see Dana Parker's article at www.emediapro.net/news99/news111.html), although other "ripping" methods were available before that (see www.7thzone.com, go.to/dvdsoft, and www.neophile.net). The difference between circumventing CSS encryption with DeCSS and intercepting decrypted, decompressed video with a DVD ripper is that DeCSS can be considered illegal under the DMCA and the WIPO treaties. The DeCSS information can be used to "guess" at master keys, such that a standard PC can generate the entire list of 400 keys, rendering the key secrecy process useless.

In any case, there's not much appeal to being able to copy a set of movie files (without menus and other DVD special features) that would take over a week to download on a 56K modem and would fill up a 6G hard disk or a dozen CD-Rs. The supporters of DeCSS point out that it was only developed to allow DVD movies to be played on the Linux operating system, which had been excluded from CSS licensing because of its open-source nature. This is specifically allowed by DMCA and WIPO laws. What most DeCSS proponents fail to acknowledge (or perhaps fail to realize) is that the DeCSS.exe program being posted on the Internet is a Windows application that is clearly intended for copying movies. This lack of differentiation between the DeCSS process in Linux and the DeCSS.exe Windows application is hurting the cause of DeCSS backers. See OpenDVD.org for more information on DeCSS. 

Worthy of note is that DVD piracy was around long before DeCSS. Serious DVD pirates can copy the disc bit for bit, including the normally unreadable lead in (possible only with specially modified drives), or copy the video output from a standard DVD player, or get a copy of the video from another source such as laserdisc, VHS, or a camcorder smuggled into a theater. It's certainly true that DVD piracy is problem, but DeCSS has little to do with it. 

Shortly after the appearance of DeCSS, the DVD CCA filed a lawsuit and requested a temporary injunction in an attempt to prevent Web sites from posting (or even linking to!) DeCSS information. The request was denied by a California court on December 29, 1999. On January 14, 2000, the seven top U.S. movie studios (Disney, MGM, Paramount, Sony [Columbia/TriStar], Time Warner, Twentieth Century Fox, and Universal), backed by the MPAA, filed lawsuits in Connecticut and New York in a further attempt to stop the distribution of DeCSS on Web sites in those states. On January 21, the judge for the New York suit granted a preliminary injunction, and on January 24, the judge for the CCA suit in California reversed his earlier decision and likewise granted a preliminary injunction. In both cases, the judges ruled that the injunction applied only to sites with DeCSS information, not to linking sites. (Good thing, since this FAQ links to DeCSS sites!) The CCA suit is based on misappropriation of trade secrets (somewhat shaky ground), while the MPAA suits are based on copyright circumvention. On January 24, 16-year old Jon Johansen, the Norwegian programmer who first distributed DeCSS, was questioned by local police who raided his house and confiscated his computer equipment and cell phone. Johansen says the actual cracking work was done by two anonymous programmers, one German and one Dutch, who call themselves Masters of Reverse Engineering (MoRE).

This all seems to be a losing battle, since the DeCSS source code is available on a T-shirt and was made publicly available by the DVD CCA itself in court records--oops! See Fire, Work With Me for a facetious look at the broad issue.

[4.9] How do I play DVD video in HTML, PowerPoint, Director, VB, etc.?

A variety of multimedia development/authoring programs can be extended to play video from a DVD, either as titles and chapters from a DVD-Video volume, or as MPEG-2 files. In Windows, this is usually done with ActiveX controls. On the Mac, until DVD-Video support is added to QuickTime, the options are limited. 

DVD-Video and MPEG-2 video can be played back in an HTML page in Microsoft Internet Explorer using Windows Media Player (docs on DVD scripting are in the Windows Media SDK), InterActual PC Friendly, or SpinWare PortaLink. Netscape Navigator doesn't work, since it doesn't support ActiveX objects.

MPEG-2 video can be played in PowerPoint, Visual Basic, or other ActiveX hosts using Windows Media Player. Because of an annoying reliance on IE, WMP must be embedded into an HTML page, then controlled with the Browser ActiveX control in order to play DVD-Video. Zuma Digital's ActiveDVD (using the PC Friendly engine), Daikin's Enhanced DVD Kit (also using the PC Friendly engine), and Visible Lights' OnStage DVD ActiveX provide ActiveX-based DVD playback.

A number of Xtras are (or will soon be) available for DVD playback in Director. Tabuleiro's DirectMediaXtra plays MPEG-2 files (the older MpegXtra uses MCI, which doesn't work well for MPEG-2 and DVD). LBO's Xtra DVD and Visible Light's OnStage DVD Xtra plays DVD-Video volumes.

Of course, if you simply treat DVD-ROM as a bigger, faster CD-ROM, you can create projects using traditional tools (Director, Flash, Toolbook, HyperCard, VB, HTML, etc.) and traditional media types (CinePak, Sorenson, Indeo, etc. in QuickTime or AVI format) and they'll work just fine from DVD. You can even raise the data rate for bigger or better quality video. But it still won't look as good as MPEG-2.

[4.10] What are .IFO, .VOB, and .AOB files? How can I play them?

The DVD-Video and DVD-Audio specifications define how audio and video data are stored in specialized files. The .IFO (and backup .BUP) files contain menus and other information about the video and audio. The .VOB files (for DVD-Video) and .AOB files (for DVD-Audio) are MPEG-2 program streams with additional packets containing navigation and search information. 

Since a .VOB file is just a specialized MPEG-2 file, most MPEG-2 decoders and players can play them. However, any special features such as angles or branching will cause strange effects. The best way to play a .VOB file is to use a DVD player application to play the entire volume (or to open the VIDEO_TS.IFO file), since this will make sure all the DVD-Video features are used properly.

The DVD Video Recording format will introduce .SOB files <snigger>.

Most .VOB files won't play when copied to your hard drive. See 4.5.

[5] DVD production

DVD production has two basic phases: development and replication. Development is different for DVD-ROM and DVD-Video, replication is essentially the same for both.

DVD-ROMs can be developed with traditional software development tools such as Macromedia Director, Asymetrix Toolbook, HyperCard, Quark mTropolis, and C++. Discs, including DVD-R check discs, can be created with UDF formatting software (see 5.3). DVD-ROMs that take advantage of DVD-Video's MPEG-2 video and multichannel Dolby Digital or MPEG-2 audio require video and audio encoding (see 5.3).

DVD-Video development has three basic parts: encoding, authoring (design, layout, and testing), and premastering (formatting a disc image). The entire development process is sometimes referred to as authoring. Development facilities are provided by many service bureaus (see 5.5). If you intend to produce numerous DVD-Video titles (or you want to set up a service bureau), you may want to invest in encoding and authoring systems (see 5.3 and 5.4).

Replication (including mastering) is usually a separate job done by large plants that also replicate CDs (see 5.5). DVD replication equipment typically costs millions of dollars. A variety of machines are used to create a glass master, create metal stamping masters, stamp substrates in hydraulic molds, apply reflective layers, bond substrates together, print labels, and insert discs in packages. Most replication plants provide "one-off" or "check disc" services, where one to a hundred discs are made for testing before mass duplication. Unlike DVD-ROM mastering, DVD-Video mastering may include an additional step for CSS encryption, Macrovision, and regionalization. There is more information on mastering and replication at Panasonic Disc Services and Technicolor.

For projects requiring less than 50 copies, it can be cheaper use DVD-R. Automated machines can feed DVD-R blanks into a recorder, and even print labels on each disc. This is called duplication, as distinguished from replication.

[5.1] How much does it cost to produce a DVD? Isn't it more expensive than videotape, laserdisc, and CD-ROM?

Videotape, laserdisc, and CD-ROM can't be compared to DVD in a straightforward manner. There are basically three stages of costs: production, pre-mastering (authoring, encoding, and formatting), and mastering/replication.

DVD video production costs are not much higher than for VHS and similar video formats unless the extra features of such as multiple sound tracks, camera angles, seamless branching, etc. are employed.

Authoring and pre-mastering costs are proportionately the most expensive part of DVD. Video and audio must be encoded, menus and control information have to be authored and encoded, it all has to be multiplexed into a single data stream, and finally encoded in low level format. Typical charges for compression are $80/min for video, $20/min for audio, $6/min for subtitles, plus formatting and testing at about $30/min. A ballpark cost for producing a Hollywood-quality two-hour DVD movie with motion menus, multiple audio tracks, subtitles, trailers, and a few info screens is about $20,000. Alternatively, many facilities charge for time, at rates of around $400/hour. A simple two-hour DVD-Video title with menus and various video clips can cost as low as $3,000. If you want to do it yourself, authoring and encoding systems can be purchased at prices from $400 to over $2 million. Prices for software and hardware will drop very rapidly in the next few years to where DVDs can be produced on a desktop computer system that costs less than $20,000.

Videotapes don't really have a mastering cost, and they run about $2.40 for replication. CDs cost about $1,000 to master and $0.50 to replicate. Laserdiscs cost about $3,000 to master and about $8 to replicate. As of the beginning of 2000, DVDs cost about $1000 to master and about $1.60 to replicate. Since DVD production is based mostly on the same equipment used for CD production, mastering and replication costs will drop to CD levels. Double-sided or dual-layer discs cost about $1 more to replicate, since all that's required is stamping data on the second substrate (and using transparent glue for dual layers). Double-sided, dual-layer discs (DVD-18s) are more difficult and more expensive. (See 3.3.1.)

[5.2] What DVD-ROM formatting tools are available?

Features to look for in DVD formatters:

[5.3] What video and audio encoding tools are available?

Video encoding tools

Audio encoding tools

Other production tools

[5.4] What DVD-Video authoring systems are available?

[5.5] Who can produce a DVD for me?

[A] = authoring (including encoding, DVD-R copies, and premastering).
[R] = replication (mastering and check discs).

Also see DVD Insider professional services directory and Medialine Weblinks.

[5.6] What testing/verification services and tools are available?

[5.7] Can I put DVD-Video content on a CD-R or CD-RW?

[Note: This section refers to creating original DVD-Video content, not copying from DVD to CD. The latter is impractical, since it takes 7 to 14 CDs to hold one side of a DVD. Also, most DVD movies are encrypted so that the files can't be copied without special software.]

There are many advantages to creating a DVD-Video volume using inexpensive recordable CD rather than expensive recordable DVD. The resulting "MiniDVD" is perfect for testing and for short video programs. Unfortunately, you can put DVD-Video files on CD-R or CD-RW media but as yet there is no settop player that can play the disc. There are a number of reasons DVD-Video players can't play DVD-Video content from CD media:
1) checking for CD media is a fallback case after DVD focus fails, at which point the players are no longer looking for DVD-Video content
2) it's simpler and cheaper for players to spin CDs at 1x speed rather than the 9x speed required for DVD-Video content
3) many players can't read CD-R discs (see 2.4.3).

Computers are more forgiving. DVD-Video files from any source with fast enough data rates, including CD-R or CD-RW, with or without UDF formatting, will play back on any DVD-ROM PC as long as the drive can read the media (all but early model DVD-ROM drives can read CD-Rs). Author the DVD-Video content as usual (see 5.4) then burn the VIDEO_TS directory to the root drive of a CD-R or CD-RW. To be compatible with future settop players that might read MiniDVDs, turn on the UDF filesystem option of the CD burning software. To achieve longer playing times, encode the video in MPEG-2 half-D1 format (352x480 or 352x576) or in MPEG-1 format.

An alternative is to put Video CD or Super Video CD content on CD-R or CD-RW media for playback in a DVD player. Settop players that are VCD or SVCD capable and can read recordable media will be able to play such discs (see 2.4.5). The limitations of VCD apply (MPEG-1 video and audio, 1.152 Mbps, 74 minutes of playing time). All DVD-ROM PCs able to read recordable CD media can play recorded VCD discs. An MPEG-2 decoder (see 4.1) is need to play SVCDs. See 5.8 for more on creating Video CDs.

[5.8] How do I copy my home videos/movies/slides to DVD?

If you're rich enough, put together a system with the following components

Then take the following steps

Otherwise, if you're like most of us and you make less money in year than Bill Gates does in a day, then wait until sometime in 2001 when all the above functionality is available for only a few thousand dollars. Or, in the meantime, find someone who has the above system and will transfer your video for a reasonable fee (in March 2000, the rate was around $700 for 1 hour). Or, if MPEG-1 video quality is sufficient for your needs, get MPEG-1 encoding software and a CD-R/RW formatting application that supports Video CD (such as Easy CD Creator or Toast from Adaptec, MPEG Maker-2 from VITEC, Nero Burning ROM from Ahead, NTI CD-Maker from NTI, InternetDiscWriter from Query [beware the seizure-inducing Web design], or WinOnCD from Cequadrat). Quality won't be as good, and playing time won't be as long, but software, hardware, and blank discs will be much cheaper. Just make sure that any players you intend to play the disc on can read CD-Rs (see 2.4.3) and can play Video CDs (see 2.4.5). A variation on this last strategy is to make Super Video CDs (see 2.4.6), which have better quality but shorter playing time. SVCD support is being added to a few of the authoring/formatting tools listed above.

[5.9] How do I get a job making DVDs?

Read this FAQ through a few times. For extra credit read my book, DVD Demystified, and visit some of the DVD information sources list in section 6.4. Then attend a conference such as DVD Pro, DVD Summit (Europe) or DVD Production to learn more and to make contacts in the DVD industry. Consider joining the DVDA. If you can, volunteer to be an intern at a DVD production house (see section 5.4).

Once you have a little experience, you'll be in great demand! Register at DVDJobsUSA.com and check the listings at DVDArtist.

[6] Miscellaneous

[6.1] Who invented DVD and who owns it? Whom to contact for specifications and licensing?

DVD is the work of many companies and many people. There were originally two competing proposals. The MMCD format was backed by Sony, Philips, and others. The SD format was backed by Toshiba, Matsushita, Time Warner, and others. A group of computer companies led by IBM insisted that the factions agree on a single standard. The combined DVD format was announced in September of 1995, avoiding a confusing and costly repeat of the VHS vs. Betamax videotape battle or the quadraphonic sound battle of the 1970s.

No single company "owns" DVD. The official specification was developed by a consortium of ten companies: Hitachi, JVC, Matsushita, Mitsubishi, Philips, Pioneer, Sony, Thomson, Time Warner, and Toshiba. Representatives from many other companies also contributed in various working groups. In May 1997, the DVD Consortium was replaced by the DVD Forum, which is open to all companies, and as of February 2000 had over 220 members. Time Warner originally trademarked the DVD logo, and has since assigned it to the DVD Format/Logo Licensing Corporation. The term "DVD" is too common to be trademarked or owned. See section 6.2 and visit Robert's DVD Info page for links to Web sites of companies working with DVD.

The official DVD specification books are available after signing a nondisclosure agreement and paying a $5,000 fee. One book is included in the initial fee; additional books are $500 each. Manufacture of DVD products and use of the DVD logo for non-promotional purposes requires additional format and logo licenses, at $10,000 per format. (E.g., a DVD-Video player manufacturer must license DVD-ROM and DVD-Video for $20,000.) Contact DVD Format/Logo Licensing Corporation (DVD FLLC), Shiba Shimizu Building 5F, Shiba-daimon 2-3-11, Minato-ku, Tokyo 105-0012, tel: 03-5777-2883, fax: 03-5777-2884. Before April 14, 2000, logo/format licensing was administered by Toshiba.

ECMA has developed international standards for DVD-ROM (part 1, the smallest part of the DVD spec), available for free download as ECMA-267 and ECMA-268 from www.ecma.ch. ECMA has also standardized DVD-R in ECMA-279, DVD-RAM in ECMA-272 and ECMA-273, and DVD+RW as ECMA-274 (see 4.3). Unfortunately, ECMA has the annoying habit of spelling "disc" wrong. Also confusing, if you're not from Europe, is ECMA's use of a comma instead of a period for the decimal point.

The specification for the UDF file system used by DVD is available from www.osta.org.

Any company making DVD products must license essential technology patents from a Philips/Pioneer/Sony pool (3.5% per player, minimum $5; additional $2.50 for Video CD compatibility; 5 cents per disc), a Hitachi/Matsushita/Mitsubishi/Time Warner/Toshiba/Victor pool (4% per player or drive, minimum $4; 4% per DVD decoder, minimum $1; 7.5 cents per disc) and from Thomson. Patent royalties may also be owed to Discovision Associates.

The licensor of CSS encryption technology is DVD CCA (Copy Control Association), a non-profit trade association with offices at 225 B Cochrane Circle, Morgan Hill, CA. There is a $10,000 initial licensing fee, but no per-product royalties. Send license requests to css-license@lmicp.com, technical info requests to css-info@lmicp.com. Before December 15, 1999, CSS licensing was administered on an interim basis by Matsushita.

Macrovision licenses its analog anti-recording technology to hardware makers. There is a $30,000 initial charge, with a $15,000 yearly renewal fee. The fees support certification of players to ensure widest compatibility with televisions. There are no royalty charges for player manufacturers. Macrovision charges a royalty to content publishers (approximately 3 to 6 cents per disc).

Dolby licenses Dolby Digital decoders for $0.26 per channel. Philips, on behalf of CCETT and IRT, also charges $0.20 per channel (maximum of $0.60 per player) for Dolby Digital patents, along with $0.003 per disc.

An MPEG-2 patent license may also be required, from MPEG LA (MPEG Licensing Adminstrator). Cost is about $4 for a DVD player or decoder card and 4 cents for each DVD disc, although there seems to be disagreement on whether content producers owe royalties for discs.

Nissim claims 25 cents per player for parental management patents, but there is disagreement on whether the patents apply to DVD and if they are valid.

Various licensing fees add up to over $30 in royalties for a $300 DVD player, and about $0.20 per disc. Disc royalties are paid by the replicator.

[6.2] Who is making or supporting DVD products?

[6.2.1] Consumer electronics

[6.2.2] Studios, video publishers, and distributors

DVD File maintains a list of studio addresses, as well as DVD producer and distributor information.

[6.2.3] Hardware and computer components

[6.2.4] Computer software titles on DVD-ROM

[6.3] Where can I buy (or rent) DVDs and players?

For local DVD rental outlets, see the list at DVD Post.

You can search for lowest prices and online discount coupons at DVD Price Search and DiVerse DVD.

[6.4] Where can I get more information about DVD?

Here are a few of the top DVD info sites.

You might also want to take a look at the book DVD Demystified, by the author of this FAQ. More info at <dvddemystified.com>.

[7] Leftovers

[7.1] Unanswered questions

(If you know the answer to any of these, please speak up!)

[7.2] Notation and units

There's an unfortunate confusion of units of measurement in the DVD world. For example, a single-layer DVD holds 4.7 billion bytes (G bytes), not 4.7 gigabytes (GB). It only holds 4.38 gigabytes. Likewise, a double-sided, dual-layer DVD holds only 15.90 gigabytes, which is 17 billion bytes.

The problem is that "kilo," "mega," and "giga" generally represent multiples of 1000 (10^3, 10^6, and 10^9), but when used in the computer world to measure bytes they generally represent multiples of 1024 (2^10, 2^20, and 2^30). Both Windows and Mac OS list volume capacities in "true" megabytes and gigabytes, not millions and billions of bytes

Most DVD figures are based on multiples of 1000, in spite of using notation such as GB and KB/s that traditionally have been based on 1024. The "G bytes" notation does seem to consistently refer to 10^9. The closest I have been able to get to an unambiguous notation is to use "kbps" for thousands of bits/sec, "Mbps" for millions of bits/sec, "kilobytes" for 1024 bytes, "megabytes" for 1,048,576 bytes, and "gigabytes" for 1,073,741,824 bytes.

This may seem like a meaningless distinction, but it's not trivial to someone who prepares 4.7 gigabytes of data (according to the OS) and then wastes a DVD-R or two learning that they really hold only 4.4 gigabytes!

To make things worse, data transfer rates when measured in bits per second are almost always multiples of 1000, but when measured in bytes per second are sometimes multiples of 1024. For example, a 1x DVD drive transfers data at 11.08 million bits per second (Mbps), which is 1.385 million bytes per second, but only 1.321 megabytes per second. The 150 KB/s 1x data rate listed for CD-ROM drives is "true" kilobytes per second, since the data rate is actually 153.6 thousand bytes per second.

In 1999, the IEC produced new prefixes for binary multiples: kibibytes (KiB), mebibytes (MiB), gibibytes (GiB), and so on. These prefixes may never catch on, or they may cause even more confusion, but they are a valiant effort to solve the problem. The big strike against them is that they sound a bit silly.

[7.3] Acknowledgments

This FAQ is written and maintained by Jim Taylor. The following people have contributed to the FAQ (either directly, by posting to alt.video.dvd, or by me borrowing from their writing :-). Their contributions are deeply appreciated. Information has also been taken from material distributed at the April 1996 DVD Forum, May 1997 DVD-R/DVD-RAM Conference, and October 1998 DVD Forum Conference.

Robert Lundemo Aas
Adam Barratt
David Boulet
Espen Braathen
Wayne Bundrick
Roger Dressler
Chad Fogg
Dwayne Fujima
Robert "Obi" George
Henrik "Leopold" Herranen
Irek Defee
Kilroy Hughes
Ralph LaBarge
Martin Leese
Dana Parker
Eric Smith
Steve Tannehill
Geoffrey Tully

Thanks to Videodiscovery for hosting this FAQ for the first two and a half years.


Copyright 1996-2000 by Jim Taylor. This document may be redistributed only in its entirety with version date, authorship notice, and acknowledgements intact. No part of it may be sold for profit or incorporated in a commercial document without the permission of the copyright holder. Permission will be granted for complete electronic copies to be made available as an archive or mirror service on the condition that the author be notified and that the copy be kept up to date. This document is provided as is without any express or implied warranty.


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