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DVD Frequently Asked Questions (and Answers)

This is the June 18, 2001 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 If you are looking at a version more than a month old, it's an out-of-date copy.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.


Contents


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?

The following translations of the DVD FAQ are available. Translations to a few other languages are in progress.

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?

You betcha. 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.

[0.4] How big is this thing?

Since you asked, here are the stats as of Jan, 2001:

Size: 433 KB (443,727 bytes)
Number of words: 54,506
Number of links: 1030

If you're wondering why it's all in one big piece instead of broken into smaller pieces that would load faster, the main reason is so you can use the find feature of your browser to easily search the entire FAQ.


[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 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 1.12), DVD-Audio Recording, DVD Stream Recording, and SACD. There are also special application formats for game consoles such as Sony PlayStation 2.

[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 consumer 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 video data rates of 3.5 to 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, almost four years after the initial launch, over two hundred models of DVD players are available from dozens of electronics companies. Prices for the first players were $1000 and up. By the end of 2000, players were available for under $100 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.

Some players, especially cheaper models, don't properly play all discs. Before buying a player, you may want to test it with a few complex discs such as The Matrix, The Abyss, Independence Day, and DVD Demystified. See 1.41 for more information.

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 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?
- Do I appreciate special deals? If so, look for free DVD coupons and free DVD rentals that are available with many players.

For more information, read hardware reviews at Web sites such as DVDFile or in magazines such as Widescreen Review. You may also want to read about user experiences at Audio Review and in online forums at Home Theater Forum and DVDFile. There's more advice at DVDBuyingGuide and at eCoustics.com, which also has a list of links to reviews on other sites.

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 Japan in December. By April there were over 150 titles in Japan. The first titles released in the U.S., on March 19, 1997, by Lumivision, were Africa: The Serengeti, Antarctica, The Rainforest, and Animation Greats. The Warner Bros. U.S. launch happened on March 24, but was limited to seven cities.  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 the end of 1999, over 100 million discs had shipped. By the end of 2000 there were over 10,000 titles available in the US and over 15,000 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.

Doug MacLean has a searchable and downloadable database of region 1 movie titles at <www.hometheaterinfo.com/dvdlist.htm>. Perry Denton has a text list of region 1 titles at <www.surroundfreak.com/dvd/dvd1.htm>. 7th Zone has a searchable list of region 1 and region 2 titles. Also check out the Internet Movie Database's DVD Browser or the searchable and downloadable database from the DVD Entertainment Group. There are also good searchable databases at DVD File, Express.com, and DVD Planet. For a list of widescreen-specific DVD titles, visit Widescreen Review.

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 was resolved (see 3.6).

DVD-ROM software is slowly appearing. 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.

[1.6.1] Where can I read reviews of DVDs?

The following sites have reviews of at least 600 discs. Also see the list of DVD review sites at Yahoo.

[1.6.2] How do I find out when a movie will be available on DVD?

First, check one of the lists and databases mentioned in 1.6 to make sure it's not already available. Then check the upcoming release lists at DVD Review and Laser Scans. There's also the LaserViews DVD Calendar and release list at Image Entertainment. A good source of info about unannounced titles is The Digital Bits Rumor Mill.

[1.7] How much do players and drives cost?

Mass-market DVD movie players currently list for $140 to $3000. (See 1.5 for more information.) DVD-ROM drives and upgrade kits for computers sell for around $50 to $600. (OEM drive prices are around $60.) Prices are expected to eventually drop 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 are usually 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 is DVD doing? Where can I get statistics?

DVD did not take off quite as fast as some early predictions, but it has sold faster than videotape, CD, and laserdisc. In fact, before its third birthday in March 2000, DVD had become the most successful consumer electronics entertainment product ever.

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 were 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. In 2000 there were about 270 million TVs in the U.S. and 1.3 billion worldwide.When DVD came out in 1997 there were about 3 million laserdisc players in the U.S. 

For latest U.S. player sales statistics, see the CEA page at The Digital Bits. Other DVD statistics and forecasts can be found at IRMA, MediaLine, Twice. Industry analyses and forecasts can be purchased from Adams Media Research, British Video Association, Cahners In-stat, Centris, Datamonitor, Dataquest, DVD Intelligence, eBrain, International Data Corporation (IDC), InfoTech, Jon Peddie Associates (JPA), Paul Kagan Associates, Screen Digest, SIMBA Information, Strategy Analytics, and others.

[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 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 coded for its region. This means that discs bought in one country may not play on players bought in another country. Some people believe that region codes are 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 region locks 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 would have regional codes, but so far almost all Hollywood releases play in only one region. Region codes are a permanent part of the disc, they won't "unlock" after a period of time. Region codes do not apply to DVD-Audio.

There are 8 regions (also called "locales"). Players and discs are often 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>.)

Technically there is no such thing as a region 0 disc or a region 0 player. There is such thing as an all-region disc. There are also all-region players. Some players can be "hacked" with special command sequences from the remote control to switch regions or play all regions. Some players can be physically modified ("chipped") to play discs regardless of the regional codes on the disc. This usually voids the warranty, but is not illegal in most countries. (The only thing that requires player manufacturers to region-code their players is the CSS license. See 1.11) On Feb. 7, 2001, NASA sent two multiregion DVD players to the International Space Station.

Some discs from Fox, Buena Vista/Touchstone/Miramax, MGM/Universal, Polygram, and Columbia TriStar contain program code that checks for the proper region setting in the player. (There's Something About Mary and Psycho are examples.) In late 2000, Warner Bros. began using the same active region code checking that other studios had been using for over a year. They called it "region code enhancement" (RCE, also known as REA), and it received much publicity. RCE was first added to discs such as The Patriot and Charlie's Angels. "Smart discs" with active region checking won't play on code-free players that are set for all regions (FFh), but they can be played on manual code-switchable players that allow you to change the region using the remote control. They may not work on auto-switching players that recognize and match the disc region. (It depends on the default region setting of the player. An RCE disc has all its region flags set so that the player doesn't know which one to switch to, then it queries the player for the region setting and aborts if it's the wrong one. A default player setting of region 1 will fool RCE discs from region 1. Playing a region 1 disc for a few seconds will set most auto-switching players to region 1 and allow them to play an RCE disc.) When an RCE disc detects the wrong region or an all-region player, it will usually put up a message saying that the player may have been altered and that the disc is not compatible with the player. A serious side effect is that some legitimate players fail the test, such as the Fisher DVDS-1000.

There was much wailing and gnashing of teeth when RCE first appeared, but DVD fans quickly learned that it only affected some players. Makers of player modification kits that didn't work with RCE soon modified their chips to get around it. For every higher wall there is a taller ladder. See DVDTalk's RCE FAQ for more info and workarounds.

Information about modifying players and buying region-free players can be found on the Internet (at sites such as Code Free DVD, Region Free DVD, dvdkits.com, DVD Upgrades, DVD In the World, DVDoverseas, Link Electronics, PlanetDVD, 7thZone, Techtronics, Upgrade Heaven, and <www.brouhaha.com/~eric/video/dvd/>; for Mac: DVD Utilities for Macintosh) and in the rec.video.dvd newsgroups (searchable at Deja.com). There's more codefree player info at DVDCity.

Regional codes apply to game consoles such as PlayStation 2 and Xbox, but only for DVD-Video (movie) discs (although the PlayStation has a separate regional lockout scheme for games). Regional codes also apply to DVD-ROM systems, but affect only DVD-Video discs, not DVD-ROM discs containing computer software. Computer playback systems check for regional codes before playing movies from a CSS-protected DVD-Video (see 1.11 for CSS info). Newer RPC2 DVD-ROM drives let you change the region code several times. (RPC stands for region protection control.) Once an RPC2 drive has reached the limit of 5 changes it can't be changed again unless the vendor or manufacturer resets the drive. 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, as well as links listed above. After December 31, 1999, only RPC2 drives are being manufactured.

[1.11] What are the copy protection issues?

CPSA (content protection system architecture) is the name given to the overall framework for security and access control across the entire DVD family. Developed by the "4C" entity (Intel, IBM, Matsushita, and Toshiba) in cooperation with the Copy Protection Technical Working Group (CPTWG), it covers encryption, watermarking, protection of analog and digital outputs, and so on. There are six forms of content protection that apply to 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), also sometimes called copyguard. 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/>.) 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. Or you can build your own. APS affects only video, not audio. 

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 20 or line 21 (in the XDS service). CGMS/A is recognized by most digital camcorders and by some computer video capture cards (they will flash a message such as "recording inhibited"). The digital standard (CGMS/D) is not yet finalized, but will apply to digital connections such as IEEE 1394/FireWire. See section 6, 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 early. 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) Content Protection for Prerecorded Media (CPPM)
CPPM replaces CSS for DVD-Audio. Keys are stored in the lead-in area, but there are no title keys in the sector headers. The disc key is replaced by an "album identifier." The authentication mechanism is the same as for CSS, so no changes are required to existing drives. A disc may contain both CSS and CPPM content. (More info to come....)

5) Content Protection for Recordable Media (CPRM)
CPRM is a mechanism that ties a recording to the media on which it is recorded. It is supported by all DVD recorders released after 1999. Each blank recordable DVD has a unique 64-bit disc ID etched in the BCA (see 3.11). When protected content is recorded onto the disc, it can be encrypted with a 56-bit C2 (Cryptomeria) cipher derived from the disc ID. During playback, the disc ID is read from the BCA and used to generate a key to decrypt the contents of the disc. If the contents of the disc are copied to other media, the ID will be absent or wrong and the data will not be decryptable.

6) Digital Copy Protection System (DCPS)
In order to provide for digital connections between components without allowing perfect digital copies, five digital copy protection systems were proposed to the CEA. 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." DCPS in general 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 2001 at the earliest. Since the encryption is done by the player, no changes are needed to existing discs.

The first four 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. CPRM is handled automatically by DVD recorders. 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.

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 CPTWG selected a watermarking system that has been approved by the DVD Forum. The original seven watermarking proposals 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, but products were delayed in part by the slow process of selecting copy protection features (encryption and watermarking), with complications introduced by the Secure Digital Music Initiative (SDMI). The scheduled October 1999 release was further 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. Pioneer released some early models of DVD-Audio players in Japan in late 1999, but they don't play copy-protected discs.

Matsushita released Panasonic and Technics brand universal DVD-Audio/DVD-Video players available in July 2000 for $700 to $1,200. Pioneer, JVC, Yamaha, and others released DVD-Audio players in fall 2000 and early 2001. By the end of 2000 there were about 50 DVD-Audio titles available.