|
||
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 If you are looking at a version more than a month old, it's an out-of-date copy.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):
99-12-11: New questions:
[1.42] How do the parental control and multi-ratings
features work?
[3.9] What is edge enhancement?
[4.7] Can I stream DVD over a network or the Internet?
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.
Yup. Take a gander at Earl's Famous DVD Technology Exposition Web Page Extravaganza Supreme Deluxe <lonestar.texas.net/~bdub/earl/dvd.htm>.
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.
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.
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:
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.
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:
aus.dvd (Australia/New Zealand/region 4 player info)
WebShopper report on DVD-ROM drives (Sep 16, 1998)
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.
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.
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.
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.
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.
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.
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/>.)
2) CGMS
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.
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.
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.
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.
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>.
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.
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.
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.)
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.
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.
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 dis