This is the 21-Mar-97 revision of the FAQ for the alt.video.dvd Usenet newsgroup. (See below for what's new.)
Please send corrections, additions, and new questions to Jim Taylor <mailto:jhtaylor@videodiscovery.com>.
Recent significant changes (last posted to newsgroups on Mar. 8):
DVD, which stands for Digital Video Disc, Digital Versatile Disc, or nothing, depending on whom you ask, is the next generation of optical disc storage technology. It's essentially a bigger, faster CD that can hold video as well as 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 most major movie and music studios, which is unprecedented and says much for its chances of success (or, pessimistically, the likelihood of it being forced down our throats).
It's important to understand the difference between DVD-Video and DVD-ROM. DVD-Video (often simply called DVD) holds video programs and is played in a DVD player hooked up to a TV. DVD-ROM holds computer data and is read by a DVD-ROM drive hooked up to a computer. The difference is similar to that between Audio CD and CD-ROM. DVD-ROM also includes future variations that are recordable one time (DVD-R) or many times (DVD-RAM). Most people expect DVD-ROM to be initially much more successful than DVD-Video. Most new computers with DVD-ROM drives will also be able to play DVD-Videos (see 6.1).
There's also a DVD-Audio format. The technical specifications for DVD-Audio are not yet determined.
Note: Most discs will not contain all features (multiple audio/subtitle tracks, seamless branching, parental control, etc.).
Most players support a standard set of features:DVD has the capability to produce near-studio-quality video and better-than-CD-quality audio. DVD is vastly superior to videotape, and can be better than laserdisc (see 2.8.). However, quality depends on many production factors. Until compression experience and technology improves we may often see DVDs which are inferior to laserdiscs. Also, since large amounts of video have already been encoded for VideoCD using MPEG-1, some early DVDs will use that format (which is no better than VHS) instead of higher-quality MPEG-2.
DVD video is compressed from studio ITU-R 601 format to MPEG-2 format. This is a "lossy" compression which removes redundant information (such as sections 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 "artifacts" such as blockiness or fuzziness depending on the processing quality and amount of compression. At average rates of 3.5 Mbps (million bits/second), artifacts may be occasionally noticeable. Higher data rates result in higher quality, with almost no perceptible difference from the original master at rates above 6 Mbps. As MPEG compression technology improves, better quality will be achieved at lower rates.
Some DVD demos have visible artifacts such as blockiness, color banding, blurriness, missing detail, and even detail such as a face which "floats" behind the rest of the moving picture. This is sometimes caused by poor MPEG encoding, but is just as often cause by bad digital noise reduction during film-to-tape transfer or before encoding. The Free Willy and Twister excerpts on the Panasonic demo disc are good examples of this. In any case, bad demos are not an indication that DVD quality is bad, since other demos show no artifacts or other problems. Bad demos are simply an indication of how bad DVD can be if not properly processed and correctly reproduced. Early demos were shown on prototype players based on prerelease hardware and firmware. Many demo discs were rushed through the encoding process in order to be distributed as quickly as possible. Contrary to popular opinion, and as stupid as it may seem, these demos are not carefully "tweaked" to show DVD at its best. Also, 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 the high-frequency video and causes distortion, just as the treble control set too high for a CD causes it to sound harsh. DVD video has exceptional color fidelity, so muddy or washed out colors are almost always a problem in the display, not in the DVD player or disc.
DVD audio quality is excellent. One of DVD's audio formats is LPCM (linear pulse code modulation) with sampling sizes and rates higher than audio CD. Alternately, audio for most movies is stored as discrete multi-channel surround sound using Dolby Digital or MPEG-2 audio compression similar to the surround sound formats used in theaters. As with video, audio quality depends on how well the encoding was done. Most audio on DVD will be in Dolby Digital format, which is close to CD quality.
The final assessment can't be made until DVD is in the hands of consumers. No one can yet guarantee the quality of DVD, just as no one should dismiss it based on demos or hearsay. And in the end it's a matter of individual perception.
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.
Available players:
Projected player releases (1997):
Fujitsu supposedly released the first DVD-ROM-equipped computer on Nov. 6 in Japan. Toshiba hopes to release a DVD-ROM-equipped computer and a DVD-ROM drive in Japan in January (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 are expected to be available before May. Samsung drives (and PCs with drives) were available in Korea in January, a few months later elsewhere. Philips and LG drives will be available in the 2nd quarter. Toshiba's Infinia DVD-ROM-equipped PC will be available Spring 1997. Compaq and Sony DVD-PCs are scheduled for April. Sony's DVD-PCs will be out by Summer.
Note: If you buy a player 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.)
As with hardware, rosy predictions of hundreds of movie titles for Christmas of 1996 have failed to materialize. Warner Home Video originally announced they would have 250 titles available for the launch of DVD, but now plan to release only 25 in March. Info-Tech predicts over 600 titles by the end of 1997 and more than 8,000 titles by 2000.
At the November launch of DVD players in Japan, only 15 or so titles were available, mostly music. Toshiba EMI and Victor (JVC) delayed some DVD title releases in Japan until mid-November to ensure compatibility with various DVD players. Papillon was released in Japan on December 5 by AMUSE Video. Other titles, such as Adventures of Priscilla Queen of the Desert, Farinelli, Chunking Express, and Les Adventuriers were also released but are allegedly low-quality MPEG-1 versions.
Warner Home Video began sales in Japan on December 20 with four major titles: The Assassin, Blade Runner, Eraser, and The Fugitive. Warner released another four titles on January 23: Batman Forever, Interview with a Vampire, Outbreak, and Unforgiven. A few other DVD titles (not from Warner!) released in January included Nutts About Butts, Yum Yum I Love Cum, and Super Nice Body's Water Melon.
Concorde Video is releasing 12 Monkeys in Germany at the end of February. This is a special edition, dubbed in German, limited to 5000 copies, priced at DM49,95. Call +49-711-182-1229 or email mpsbestell@aol.com.
Lumivision will release 4 titles on March 19 at $24.95: Tropical Rainforest (IMAX), Antarctica: An Adventure of a Different Nature (IMAX), Africa: The Serengeti (IMAX), and Animation Greats (from the National Film Board of Canada). Lumivision plans to have 20 titles on DVD by the end of 1997.
Warner Home Video will release movies in March priced at $24.98, over half of which include extras such as running director commentary, behind-the-scenes footage, storyboards, Internet browser capability, director's cut versions, screen tests, and interviews with cast and crew (those running less than 125 minutes): Batman, Blade Runner: The Director's Cut, The Bodyguard, The Bridges of Madison County, Bonnie and Clyde, Casablanca, The Color Purple, Doctor Zhivago, Eraser, The Exorcist, The Fugitive, The Glimmer Man, Gone with the Wind, GoodFellas, Interview with the Vampire, JFK: Special Edition Director's Cut, Lethal Weapon, The Road Warrior, Singin' in the Rain, Space Jam, A Streetcar Named Desire: The Director's Cut, A Time to Kill, Twister, Unforgiven, and Woodstock: The Director's Cut. Additional titles to be release later concurrent with VHS: Mars Attacks!, Michael, Michael Collins (4/25), My Fellow Americans, and Sleepers (4/1); on 4/29: Batman Returns, Disclosure, Driving Miss Daisy, Long Kiss Goodnight, Tin Cup; on 5/20: Batman Forever, Blazing Saddles, Chariots of Fire, Strangers on a Train, 10, The Wild Bunch.
Warner Bros. Records Inc. will release three music video titles for $24.98 each in April: Eric Clapton - Unplugged, Madonna's The Girlie Show - Live Down Under, and R.E.M.'s Road Movie. All three feature 5.1-channel audio remixed from original multitracks. Warner will release five more music titles in 1997.
New Line Home Video will release The Mask, Dumb and Dumber, Seven, Rumble In The Bronx, Mortal Kombat and The Player starting at the end of April with about 25 titles planned for release in the next year. New Line intends to release selected titles at the same time as the VHS versions and at sell-through prices.
Sony's Columbia TriStar Home Video will begin releasing feature film titles in North America on April 24 to match the delivery of Sony DVD players. Retail prices are expected to be $24.98 to $26.98, and most will include options such as dubs in Spanish and French, subtitles in Spanish and Korean, and English closed-captions. Additional releases will follow every six to eight weeks. Release 1: Fly Away Home, In the Line of Fire, Jumanji, and Legends of the Fall. Release 2: Bad Boys, Desperado, Matilda, and Taxi Driver. Release 3: Bram Stoker's Dracula, First Knight, A League of Their Own, and Sleepless in Seattle. Release 4: The Cable Guy, The Craft, Little Women, and Sense and Sensibility. Additional titles include Cliffhanger, Close Encounters of the Third Kind: Special Edition, Ghostbusters, Glory, The Last Action Hero, The Net, and Philadelphia. Sony Music Entertainment/Sony Wonder will release Sesame Street's 25th Anniversary: A Musical Celebration, Tony Bennett's MTV Unplugged, Streetfighter II -- the Animated Movie, Odyssey into the Mind's Eye, and Beavis & Butt-head's The Final Judgement.
MGM Home Entertainment will release 10 titles at sell-through pricing in April, with another 30 before the end of the year. The first 10 are Species, Raging Bull, Poltergeist, Rain Man, The Wizard of Oz, GoldenEye, The Birdcage, Get Shorty, Rocky, and Midnight Cowboy. Additional titles include Singin' in the Rain, and Casablanca. Most MGM titles will include soundtracks in English, Spanish, and French.
Polygram Video (Philips partner) will release 10 titles in the US in the Spring, and another 10 by the end of the year. Nine will be sell-through priced at $30 to $40: Dead Man Walking, Fargo, The Usual Suspects, Four Weddings and a Funeral, Lord of the Dance, Three Tenors, U2 Live from Sydney, Short Cinema, and Ghost in the Shell. The Portrait of a Lady will be available on DVD the same day as the VHS release, and both will be priced for rental at about $90.
Live Entertainment will release in May: The Arrival, Cutthroat Island, and Stargate; in June: Reservoir Dogs, The Substitute, and Total Recall; in July: The Doors, Madonna: Truth or Dare, and Red Heat; and in August: Dirty Dancing, Terminator 2, and Basic Instinct.
Playboy Home Video will release approximately 30 DVD titles a year, beginning in May with 1997 Playmate of the Year.
DVD-ROM software will slowly appear. Approximately 50% of CD-ROM producers have announced intentions to develop for DVD-ROM. As of Aug. 1996, 30 DVD-ROM titles are supposedly in development for early 1997 release. IDC expects over 13 percent of all software will be available in DVD-ROM format by the end of 1998. 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 MPEG video and multi-channel audio capabilities being added to many DVD-ROM-equipped computers.
The first DVD-ROMs will probably be "The Union Catalogue of Belgian Research Libraries" from IVS, "PhoneDisc PowerFinder USA One" (which filled 6 CD-ROMs) from Digital Directory Assistance Inc., and "Silent Steel" from Tsunami Media.
Mass-market DVD movie players currently list for $600 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.
DVD-ROM drives for computers sell for around $400 to $500. (OEM prices are under $350.) Prices are expected to drop quickly to current CD-ROM drive levels.
It will vary. Many studios have promised that DVDs will be as cheap or cheaper than videotapes (and much cheaper than laserdiscs). This remains to be seen, especially for special editions with supplemental material which cost much more to produce. Some new releases will initially be priced for rental (near $80, the same as VHS). But existing titles, which have already made back money, are expected to be priced below $25 on DVD. Time Warner has set a price of $24.98 in the U.S. (3,000 yen in Japan). Polygram's sell-trhough discs are $29.99. Columbia TriStar says its feature film DVDs will be somewhere between VHS and laserdisc prices.
DVD-ROMs will initially be slightly more expensive than CD-ROMs since there is more stored on them, they cost more to replicate, and the market is smaller. But as costs drop and the installed base of drives grow, DVD-ROMs will probably cost the same as CD-ROMs do today.
Nobody knows. Here are a few predictions:
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). Therefore they have required that the DVD standard include codes which can be used to prevent playback of certain discs in certain geographical regions. Players sold in each region will include a built-in code. The player will refuse to play discs which are not allowed in the region. This means that discs bought in one country may not play on players bought in another country.
Regional codes are entirely optional. 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 have already announced that only their new releases will have regional codes. Presumably, once a DVD movie has achieved worldwide release it could be re-released without coding.
There are 6 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: North America
2: Japan, Europe, Middle East, South Africa
3: Southeast Asia (including Hong Kong)
4: Australia, New Zealand, Central/South America
5: Northwest Asia (including Korea?), North Africa
6: China
(See the map at <http://www.unik.no/~robert/hifi/dvd/world.html>.)
It's rumored that Chinese and Hong Kong companies have already developed chips to defeat the regional coding of a player, and that a Chinese-made player will play discs regardless of their regional codes. The MPAA and consumer electronics companies are pursuing legislation to make such devices illegal in the U.S.
Regional codes also apply to DVD-ROM systems, but will probably not be used for software. However, operating systems including upcoming versions of Windows and MacOS will check for regional codes before playing movies from a DVD-Video. It's not yet known if regional codes will apply to DVD-Audio.
There are three forms of copy protection used by DVD:
1) 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. With Macrovision, composite video and s-video output will have a rapidly modulated colorburst signal along with pulses in the vertical blanking signal designed to confuse the automatic-recording-level circuitry in 95% of consumer VCRs. Unfortunately, this can degrade the picture, especially with old or nonstandard equipment. Macrovision creates severe problems for some line doublers. Macrovision is not present on analog component video output of first-generation players, but is expected to be required for future players (AGC only, since there is no colorburst in a component signal). The discs themselves tell the player whether or not to enable Macrovision AGC with or without Colorstripe. The producer of the disc decides what amount of copy protection to enable and then pays Macrovision royalties accordingly. Just as with videotapes, some DVDs are Macrovision-protected and some aren't. (For Macrovision details see SGS/Thomson's video encoder datasheet at <http://www.st.com/stonline/books/ascii/docs/4570.htm>.)
2) Digital video copying is controlled by information on each disc specifying if the data can be copied. This is a "serial" copy generation management system (CGMS) designed to prevent copies or copies of copies. Of course, the equipment making the copy has to abide by the rules. The CGMS information is also encoded into the analog video signal (on NTSC line 21) so that digital recorders with analog inputs can recognize it.
3) Because of the potential for perfect digital copies, paranoid movie studios forced a deeper copy protection requirement into the DVD-Video standard. Content Scrambling System (CSS) is a form of data encryption that prevents reading the media files directly from the disc. Most players will have a decryption circuit that decodes the data before displaying it. No unscrambled digital output is allowed until work in progress for secure digital connections is finished. On the computer side, DVD-ROM drives and video display/decoder hardware or software will exchange encryption keys so that the video is decrypted just before display by the encoder. This means that many DVD-ROM drives and video display boards have extra hardware (and cost) for movie copy protection. Makers of equipment used to display DVD-Video (drives, chips, display boards, etc.) must license CSS. There is no charge for a CSS license, but it's currently a lengthy process, so it's recommended that interested parties apply as soon as possible. As of mid March, no CSS licenses allow software decoding because of Hollywood's concerns.
Movie studios and consumer electronics companies want to make it illegal to defeat DVD copy protection. A co-chair of the legal group of the 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.
DVD-ROM can use CSS for computer data, even though it's designed for audio and video. However, since DVD-ROM can hold any form of computer data, any desired encryption scheme could be implemented.
All 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.
These copy protection schemes are designed 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 it won't stop well-equipped pirates. There are inexpensive devices that defeat analog copy protection, but Macrovision claims none of the devices are effective against the new Colorstripe feature (yet).
The DVD Consortium has decided to seek additional input from the music industry before defining the DVD-Audio format. An audio standard probably won't appear until the end of 1997 at the earliest. If the final specification includes features or formats not present in the current DVD specification, existing DVD players may not be able to play new DVD-Audio discs.
Sony is pushing for its Direct Stream Digital (DSD) format, with the support of Philips. Other organizations such as Acoustic Renaissance for Audio (ARA) prefer lossless compressed PCM that's more appropriate for studio work and archiving.
There are rumors that the DVD Consortium is pushing for an 8 cm (CD-single) size, while the audio industry wants a 12 cm size. (The existing DVD physical spec allows both sizes.) The audio industry also wants "legacy" discs which will play on one side in existing CD players and on the other side in DVD players. There are technical difficulties in doing this, but it may be possible.
The music industry is also requesting an "embedding signalling" or "digital watermark" copy protection feature. This applies a digital signature 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.
In the meantime, the DVD-Video standard includes surround sound audio and better-than-CD audio (see 3.6). Pioneer is developing audio-only players based on the audio portion of DVD-Video.
Warner, Columbia TriStar, MGM, Polygram, and others are releasing movies on DVD (see 1.6). Others have announced support but no movies yet (see 6.2 for a full list). Disney has expressed concerns over copying, but is closely involved in DVD development and will most likely jump in once copy protection is resolved (see 1.11). Paramount and 20th Century Fox have no immediate plans for DVD. Other studios may hold back, but if DVD is a success no studio would be foolish enough to not jump on the bandwagon.
Short Answer: No. (Not in this century.)
Long answer: 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. At the moment it's difficult in real time to encode the video and audio, combine them with the control codes, and write the whole thing to DVD. Even if you could do all this in real time it would be too expensive. Prices for DVD production systems are dropping from millions of dollars to thousands of dollars, but they won't be in the <$500 range for home use for several years yet. It's possible the first home DVD recorders will require a digital source of already-compressed audio and video, such as DBS.
Other obstacles: Price of blank discs may initially be as high as $50 for record-once, and even higher for erasable. The first generation of recordable media will hold only about 3/4 as much as pre-recorded discs. Realtime compression will require higher bit rates for decent quality, lowering capacity even more. 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 prefilters, which raises the cost).
Don't be confused by DVD-R and DVD-RAM systems, which will be available soon and will cost over $10,000 (see 4.3). These can record data, but to create full-featured DVD-Videos would require additional hardware and software to do video encoding (MPEG-2), audio encoding (Dolby Digital or MPEG or LPCM), subpicture encoding (run-length-compressed bitmaps), still frame encoding (MPEG-1 or MPEG-2), control code generation, and multiplexing. And since this can't be done in real time, you'd also need a 5 to 9 GB hard drive to premaster the data to.
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. So once the encoding technology is fast and cheap enough, and the blank discs are cheap enough, recordable DVD may be a reality. It will be an interesting contest between DVD and digital video tape (DV). DV is out already, but decks cost $4,000.
Most scratches will cause minor channel data errors that are easily corrected. 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 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 cause an I/O error on a computer or show up as a momentary glitch in DVD-Video picture. However, there are many schemes for concealing errors in MPEG video (see section D.12 of <http://icib.igd.fhg.de/icib/it/iso/cd_13818-2/read1.html>.
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. West Coast Entertainment will be renting (and selling) DVDs and renting players beginning on March 25th in 57 stores in the New Jersey and New York markets. Sony and Blockbuster are placing DVD demo kiosks in select Blockbuster stores. Sony's DVD player includes coupons for free DVD rentals at Blockbuster.
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. Time Warner is promoting a "Snapper" package (similar in form to the plastic and paper "eco" CD packages) which measures 14cm wide x 19cm high x 1.25cm thick (5.5" x 7.5" x 0.5"). [I measured it by hand, so this may not be exact.] This is about as wide as a CD jewel box and about as tall as a VHS cassette box. There is also a proposal from the Video Software Dealers Association for a package 5 5/8" wide, 7 3/8" high and between 3/8" and 5/8" deep. However, no one is being forced to use a larger package size and many companies will undoubtedly use standard jewel cases. It remains to be seen if any package becomes standard, especially for DVD-ROM.
Dual-layer discs are already available. Some replicators plan to produce double-sided discs, dual-layer discs, and double-dual discs from day one. Obviously the prices will be higher, but certain producers already require more space than is available on a single side or single layer.
All DVD players and drives will play dual-layer discs -- it's required by the spec. All players and drives will also play double-sided discs if you flip them over. No manufacturer has announced a model that will play both sides. Pioneer LD/DVD players can play both sides of an LD, but not a DVD. (See 2.9 for note on reading both sides simultaneously.)
DVD-V has the same NTSC vs. PAL problem as videotape and laserdisc. DVD-V supports two mutually-incompatible television systems: 525/60 (NTSC) and 625/50 (PAL). There are three differences between discs intended for playback on different systems: picture size (720x480 vs. 720x576), display frame rate (29.97 vs 25), and surround audio (Dolby Digital vs. MPEG-2). (See 3.4 and 3.6 for details.) Movies are stored at 24 frames/sec but are encoded for one of the two display rates.
However, a producer can choose to include additional video and audio --at the expense of playing time-- so that all formats are covered. It's unknown if players will be able to automatically recognize and play the correct video track. Some studios include Dolby Digital tracks along with the MPEG audio tracks on their PAL discs.
Some players will only play NTSC discs, some players will only play PAL discs, and some will play both. Multi-standard players will output NTSC from a 525/60 disc and PAL from a 625/50 disc. This requires two TVs or a multi-standard TV that can display both. Some players partially convert NTSC to 60 Hz PAL, which requires a 60 Hz PAL TV. It's also possible to make a standards-converting player that will output standard NTSC from a 625/50 disc or standard PAL from a 525/60 disc, but so far no such players have been announced.
There are actually three types of DVD players if you count computers. Most DVD playback software and hardware can play both NTSC and PAL from a DVD-Video.
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.
Not any time soon. DVD is not yet recordable (see 1.14) and 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.
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.
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.
This is actually many questions with many answers:
[Note the differentiation between DVD (general case) and DVD-ROM (computer data).]
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.)
Yes. All DVD-ROM drives will read CD-ROMs (Yellow Book). However, DVD-ROMs are not readable by CD-ROM drives.
Maybe. 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. This problem is being addressed in many ways. Sony has developed a twin-laser pickup in which one laser is used for reading DVDs and the other for reading CDs and CD-Rs. Samsung has also announced dual-laser using a holographic annular masked lens. These solutions provide complete backwards compatibility with millions of CD-R discs. Philips has also stated that its DVD-ROM drives will read CD-Rs. In addition, new CD-R Type II blanks that will work with CD-ROM and DVD are supposedly in development. In the meantime, some first-generation DVD-ROM drives and many first-generation DVD-Video players will not read CD-R media.
Supposedly. CD-Rewritable (Orange Book Part III) discs can not be read by existing CD-ROM drives and CD players. CD-RW has a lower reflectivity difference, requiring automatic-gain-control (AGC) circuitry. The new "MultiRead" standard addresses this and some DVD manufacturers have already suggested they will support it. Supposedly the optical circuitry of DVD-ROM drives and DVD players is good enough to read CD-RW. CD-RW does not have the "invisibility" problem of CD-R (see 2.4.3).
Probably. It's not required by the DVD spec, but it's trivial to support the White Book standard since any MPEG-2 decoder can also decode MPEG-1 from a VideoCD. All Panasonic and Sony models play VideoCDs. Japanese Pioneer models play VideoCDs but American models don't. Toshiba players don't play VideoCDs. Most computers with DVD-ROM drives will be able to play VideoCDs (with the right software).
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.
In general, no. Most DVD players will not play CD-i (Green Book) discs. However, Philips has announced that it will make a DVD player that supports CD-i. Some people expect Philips to create a "DVD-i" format in attempt to breathe a little more life into CD-i (and recover a bit more of the billion or so dollars they've invested in it).
Yes. DVD players will play music from Enhanced CDs (Blue Book, CD Plus, CD Extra), and DVD-ROM drives will play music and read data from Enhanced CDs.
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.
Sort of. CDV, sometimes called Video Single, is actually a weird combination of CD and laserdisc. Part 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. However, Pioneer and others have announced combination players that will play DVDs, laserdiscs, and CDVs.
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 and Samsung have announced combo players that will play laserdiscs and DVDs (and also CDVs and audio CDs). Denon is rumored to have an LD/DVD player in the works also.
DVD will probably replace laserdisc, but not for a very long time. Laserdisc is well established as a videophile format. There are over 9,000 laserdisc titles in the US and a total of over 35,000 worldwide that can be played on over 7 million laserdisc players. It will take DVD many years to reach this point. Until then laserdisc has the superiority of tenure. Pioneer and other laserdisc companies have committed to supporting it for years to come. There's no reason to stop buying laserdiscs, especially rare titles that may not appear on DVD for a long while if ever. Even laserdisc owners who buy DVD will not immediately replace their collection. Laserdisc and DVD will co-exist for a long while.
In December of 1996 the FCC approved the U.S. DTV standard. HDTVs may appear as early as 1998 but they will be very expensive and won't become widespread for many years. DVD will look better on HDTVs but it won't provide high resolutions (see 2.9).
The answer to this question depends on you. If you need to be the first on your block with the latest gadget, you may want to get a DVD player or a combination LD/DVD player now. If you prefer to wait until DVD prices drop and bugs get worked out, you may have a lengthy wait. If you think DVD isn't a big enough improvement and decide to hold out for HTDV, you'll be in for an even longer wait. In the meantime you could be enjoying the large selection of laserdisc titles. Or you could start saving now for DVD (which won't be too expensive) or HDTV (which will be). If you buy a laserdisc player, a surround sound system, and speakers, they will be still be useful even after DVD and HDTV come out. HDTV will require a new TV set, but it will be compatible with the rest of your gear.
Unfortunately, anticipation of DVD is already hurting laserdisc. In 1996 laserdisc player sales were down 37% even though sales of VCRs and hi-fi/surround systems were up. But silver lining in this cloud is that disc prices may come down. (Laserdisc movie sales were only down 2.5% in 1996.)
This is a dangerous question to answer, given the legions of laserdisc fanatics who would rather have their laserdiscs pried from their cold dead fingers than switch! But I'm a bit fanatical myself: I've used laserdiscs since 1979 and I work for a company whose major product is laserdiscs; so I'll give it a shot. <Putting on flameproof suit....>
There are concerns that regional coding (see 1.10) and Macrovision copy protection (see 1.11) will make DVD less usable than laserdisc. This may be confirmed when DVD is in the hands of consumers.
Again, it will take years for DVD to reach the number of titles, installed base, and even quality of production that laserdisc has. DVD and laserdisc will coexist for at least another decade. But the potential of DVD can't be ignored -- it's the most likely long-term successor to laserdisc.
For more laserdisc info, see the Laserdisc FAQ at <http://www.cs.tut.fi/~leopold/Ld/FAQ/index.html>.
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.
HTDV is not directly supported by DVD-Video, but the designers have it in mind. HDTV standards were not finalized when DVD was developed, so DVD's MPEG-2 video resolutions and frame rates are closely tied to NTSC and PAL video formats. DVD does support the 16:9 ratio of HDTV. Since HDTV uses MPEG-2 it could be easy to "upgrade" the DVD format. The limited data rate of DVD may make it difficult to support high-quality HDTV, but this might be solved by increasing the spin rate (a double-speed DVD-ROM drive exceeds the 19 Mbps US ATV data rate) or by using higher-capacity blue or purple lasers. Either case will require new players and additional standards. There are rumors that future DVD players will convert existing DVD-Video to the standard-resolution progressive scan ATV format (704x480x30P).
The resolution of ATV in the US will probably correspond to the ATSC recommendations: 1280x720/60, 1920x1080/30. These are 2.7 and 6 times the resolution of DVD, and the first is twice the frame rate. There's also an SDTV (standard definition) mode of 704x480/60 which is similar to DVD's 720x480/30 mode but double 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.
It's quite likely that HDTV displays will support component digital video connections (YCrCb) or digital data connections (FireWire/IEEE 1394). This will provide the best possible reproduction of DVD-Video, especially in widescreen mode. Once DVD players have digital connections they may be able to ouput any kind of data (even formats newer than the player) to any sort of external display or converter.
Some have speculated that a "double-headed" player reading both sides of the disc at the same time could double the data rate 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. Keeping both sides in sync would require independently tracking heads, precise track and pit spacing, and a larger, more sophisticated track buffer.
Ironically, DVD-ROM computers will support HDTV before DVD-Video players, since 2x drives coupled with appropriate playback and display hardware can meet the requirements of HDTV.
Most DVD players will have the following output connections:
Video:
- Composite video (CVBS) RCA/Cinch (NTSC or PAL)
- Y/C (s-video) (NTSC or PAL)
Audio:
- Dual RCA stereo analog audio (with Dolby Surround encoding)
- Digital audio (IEC-958 II RCA coax (S/P DIF) or EIAJ CP-340 optical (Toslink)). Raw digital audio (AC-3, MPEG-2, PCM, or optional DTS or SDDS) requires an external decoder or an amplifier/receiver with built-in decoder. (Note: The digital AC-3 audio output is not the same as the RF AC-3 output on laserdisc players.)
Some players may have additional connections:
- Component analog video, NTSC or PAL (YUV: 3 RCA connectors, RGB: SCART connector or 3 RCA)
- RF video output for connecting via channel 3 or 4 to TV without direct input. (Panasonic DVD-A300)
- 6 RCA jacks for analog surround sound output. (Panasonic DVD-A300, RCA)
- AC-3 RF output on combo LD/DVD players. LD AC-3 on RF output only, DVD AC-3 on coax/optical outputs only. (Pioneer DVL-90, DV-50/DV-500)
Most of the DVD players with component outputs use YUV, which is incompatible with RGB. European players with SCART connectors have RGB outputs. YUV to RGB transcoders are available for $200-$300.
No DVD players have yet been announced with digital video outputs, but it's expected that at some point digital output will be available using FireWire (IEEE 1394) connectors (see <http://firewire.org>).
Note: All DVD players have either a built-in Dolby Digital (AC-3) or MPEG-1 audio decoder, or both. MPEG-2 audio decoders are not currently available. 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.
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. This is the same form factor as CD. A 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 6 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 holds around 135 minutes. 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 9.8 Mbps limit).
Tip: It takes about two gigabytes to store one hour of average video.
Most likely will only be available as 12cm, single-layer. The standards still aren't finalized and there may initially be different sizes varying from 2.6 to 4 G bytes. See 4.2 for 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 limited 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 supported. 525/60 (NTSC, 29.97 interlaced frames/sec) and 625/50 (PAL, 25 interlaced frames/sec) video systems are supported. Coded frame rates of 24 fps progressive or interlaced scan from film, 25 fps interlaced scan from PAL video, and 29.97 fps interlaced scan from NTSC video are supported. In the case of 24 fps, the data includes MPEG-2 repeat_first_field flags to tell the decoder to perform 3-2 pulldown for 60 (59.94) Hz displays and 2-2 pulldown for 50 Hz displays. (No current players convert from PAL to NTSC or NTSC to PAL. See 1.19.)
See the MPEG page <http://www.mpeg.org> for more information on MPEG-2 video.
Picture dimensions are max 720x480 (29.97 frames/sec) or 720x576 (25 frames/sec). Pictures are subsampled from ITU-R 601 at 4:2:0, which allocates an average of 12 bits/pixel. The uncompressed source is 124.416 Mbps (720x480x12x30 or 720x576x12x25). Using the traditional (and rather subjective) television measurement of "horizontal lines of resolution" DVD has 540 lines on a standard TV (720/(4/3)) and 405 on a widescreen TV (720/(16/9)). VHS has about 230 lines and laserdisc has about 425.
Maximum bitrate is 9.8 Mbps (but will always be less to allow for audio). The "average" bitrate is 3.5 but depends entirely on the length, quality, amount of audio, etc. This is a 36:1 reduction from uncompressed 124 Mbps. 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 9.8. MPEG-1 video rate is limited to 1.856 Mbps.
Still frames (encoded as MPEG-2 I-frames) are supported and can be displayed 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, karaoke, menus, simple animation, etc. These are full-screen, run-length-encoded bitmaps limited to four contrast values and four colors per pixel (contrast and color are selected for a group of subpictures from palettes of 16). Subpicture includes built-in effects such as scroll, move, and fade. The maximum subpicture data rate is 3.36 Mbps, with a maximum size per frame of 52 k bytes.
Video can be stored on a DVD in 4:3 format (standard TV shape) or 16:9 (widescreen). The 16:9 format is "anamorphic," meaning the picture is squeezed horizontally to fit a 4:3 rectangle then unsqueezed during playback. DVD players output widescreen video in three different ways:
Note: Playback of widescreen material can be restricted. Programs can be marked for the following display modes:
- 4:3 full frame
- 4:3 LB (for automatically setting letterbox expand mode on 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)
For letterbox mode the player uses a "letterbox filter" that creates 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. In order to fit this shorter rectangle, the picture is squeezed vertically by combining every 4 lines into 3. This compensates for the original horizontal squeezing, resulting in the movie being shown in its full width. The vertical resolution is reduced from 480 lines to 360.
For pan & scan mode the video is unsqueezed to 16:9 and a portion of the image is shown at full height on a 4:3 screen by following "center of interest" coordinates that are 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.
For anamorphic mode the video is stretched back out by widescreen equipment to its original width.
Video stored in 4:3 format is not changed by the player. It will appear normally on a 4:3 screen. Widescreen systems will either enlarge it or add black bars to the sides.
This gets even more complicated because most movies today are shot with a "soft matte." (The cinematographer has two sets of frame marks in her viewfinder, one for 1.33 (4:3) and one for 1.85, so she can allow for both formats). A few movies are even wider, such as the 2.35 ratio of Panavision. Since most movies are wider than 1.78 (16:9), one of at least 3 methods must be used during transfer to make it fit the 1.78 rectangle: 1) add additional thin black bars to the top and bottom; 2) include a small amount of extra picture at the top and bottom from the soft matte area; 3) crop the sides, possibly with a small amount of pan & scan. With the first two methods, the difference between 1.85 and 1.78 is so small that the letterbox bars or extra picture are hidden in the overscan area of most televisions. Nevertheless, and especially with 2.35 movies, some DVD producers put 16:9 source on one side (or layer) of the disc and 4:3 source on the other. This way the full-frame version of the film can be used for a horizontal and vertical pan & scan & zoom process with no letterbox bars and no reduction in resolution.
The 16:9 anamorphic format causes no problems with line doublers, since they simply double the lines on their way to the widescreen display which then stretches out the lines.
For anamorphic video, the pixels are fatter. Different pixel aspect ratios (none of them square) are used for each aspect ratio and resolution:
720x480 720x576 4:3 0.889 1.067 16:9 1.185 1.422
The DVD-Audio format is not yet specified. 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.
A disc can have up to 8 audio tracks (streams). Each track can be in one of three formats:
Two additional optional formats are supported: DTS and SDDS. Both require external decoders.
The ".1" refers to a low-frequency effects (LFE) channel that connects to a subwoofer.
All five audio formats support karaoke mode, which has two channels for stereo (L and R) plus an optional melody channel (M) and two optional vocal channels (V1 and V2).
Discs containing 525/60 (NTSC) video must use PCM or Dolby Digital on at least one track. Discs containing 625/50 (PAL) video must use PCM or MPEG-2 audio on at least one track. Additional tracks may be in any format. Many MPEG-2 discs include Dolby Digital.
For stereo output (analog or digital), all NTSC players and most PAL players have a built-in Dolby Digital decoder which downmixes from 5.1 channels (if present on the disc) to Dolby Surround stereo (i.e., 5 channels are matrixed into 2 channels to be decoded to 4 by an external Dolby Pro Logic processor). 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 labelled 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.
The downmix process is auditioned when the disc is prepared, and if the quality is not adequate the audio can be tweaked or a separate L/R Dolby Surround track can be added. Tests have shown that neither is usually necessary.
Linear PCM is uncompressed (lossless) digital audio, the same format used on CDs. 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 1, 2, 5, or 8 channels. The maximum bitrate is 6.144 Mbps, which limits sample rates and bit sizes with 5 or 8 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 entire signal is provded on the digital output for external digital-to-analog converters to support up to 96 kHz/24 bits.
Dolby Digital is multi-channel digital audio, compressed using AC-3 coding technology from original PCM with a sample rate of 48 kHz at 16 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). 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 <http://www.atsc.org/document.html>.
MPEG audio is multi-channel digital audio, compressed 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. There can be 1, 2, 5.1 or 7.1 channels [any more?]. 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.)
DTS is an optional multi-channel (5.1) digital audio format, compressed from PCM at 48 kHz. The data rate is from 64 kbps to 1536 kbps. 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.
SDDS 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.
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.
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 p&s; 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 defined as 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 it requires (and cuts the playing time in half).
Only if your computer has the right stuff. In addition to a DVD-ROM drive, you must have extra hardware to decode MPEG-2 video and Dolby Digital/MPEG-2/PCM audio. The computer operating system or playback system must support regional codes and be licensed to decrypt copy-protected movies. You may also need software that can read the MicroUDF format used to store DVD data files and interpret the DVD control codes. It's estimated that 10-30% of new computers with DVD-ROM drives will include decoder hardware, and that most of the remaining DVD-ROM computers will include movie playback software. Hardware upgrade kits can also be purchased separately for $400 to $1,000. (OEM price for playback hardware is about $200.)
Note: The recently released QuickTime MPEG Extension for MacOS is for MPEG-1 only and does NOT play MPEG-2 DVD-Video.
Some DVD-Videos and many DVD-ROMs will use video encoded using MPEG-1 instead of MPEG-2. Many existing computers have MPEG-1 hardware built in or are able to decode MPEG-1 with software.
CompCore Multimedia and Mediamatics make software to play DVD-Video movies (SoftDVD, DVD Express). Both require at least a 233 MHz Pentium MMX with AGP and an IDE/SCSI DVD-ROM drive with bus mastering DMA support to achieve about 20 frame/sec film rates (or better than 300 MHz for 30 frame/sec video), and can decrypt copy-protected movies (see 1.11). Oak's software requires hardware support. The software "navigators" support most DVD-Video features (menus, subpictures, etc.) and can emulate a DVD-Video remote control.
CompCore, Mediamatics, and Oak Technology have defined standards to allow certain MPEG decoding tasks to be performed by hardware on a video card and the remainder by software. Video graphics controllers with this feature are being called "DVD MPEG-2 accelerated." (The Mediamatics standard is called MVCCA.)
If you have at least a 433 MHz Alpha workstation you'll be able to play DVD movies at full 30 fps in software.
Most DVD-ROM drives have a seek time of 150-200 ms, access time of 200-250 ms, and data transfer rate of 1.2 MB/s (10.08*10^6/8/2^20) with burst transfer rates of up to 12 MB/s or higher. The data transfer rate from DVD-ROM discs is roughly equivalent to an 8x CD-ROM drive. DVD spin rate is about 3 times faster than CD, so when reading CD-ROMs, some DVD-ROM drives transfer data at 3x speed while others are faster. 2x and 3x DVD-ROM drives are already in the works. Hitachi is shipping samples of a 2x DVD-ROM drive which also reads CDs at 20x.
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).
DVD-ROMs use a MicroUDF/ISO 9660 bridge file system. The OSTA UDF file system will eventually replace the ISO 9660 system of CD-ROMs, but the bridge format provides backwards compatibility until operating systems support UDF.
There are two recordable versions of DVD-ROM: DVD-R (recordable once) and DVD-RAM (erasable and recordable many times), with capacities varying from 2.6 to 3.95 G bytes. DVD-R is close to finalization, and is expected to be compatible with all DVD drives. Two competing formats have been proposed for DVD-RAM. DVD-R will use organic dye polymer technology like CD-R. DVD-RAM will probably use phase-change technology. DVD-RAM discs are supposed to be readable by all DVD-ROM drives and DVD-Video players, but current proposals may require support for defect lists, which is not in the initial DVD spec, so first-generation DVD drives and players probably won't read DVD-RAM discs. The technology will improve to eventually support 4.7 G bytes, which is crucial for desktop DVD-ROM and DVD-Video production.
Initial price for DVD-R drives is expected to start at about $11,000 and drop within a year to around $2,000. DVD-RAM drives will be even more expensive. Initial price for blank DVD-Rs will be $40-$50, with DVD-RAMs at $50 or more. Pioneer plans to release a 3.95 G byte commercial DVD-R drive around July. Toshiba originally claimed DVD-R would be ready in Spring 1997 and DVD-RAM would be available in Fall 1997. Now they say DVD-R will be available in Summer 1997 and DVD-RAM in 1998. (Don't hold your breath.)
DVD-R/DVD-RAM are not currently designed for home video recording (see 1.14).
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, and mastering/replication.
DVD production costs are not much higher than for existing media, unless the extra features of DVD-Video such as multiple sound tracks, camera angles, etc. are employed.
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. Warner's charges for compression are $120/min for video, $20/min for audio, $6/min for subtitles, plus formatting and testing at about $30/min. A ballpark estimate for producing a two-hour DVD movie is about $30,000. If you want to do pre-mastering yourself, authoring and encoding systems can be purchased from $100,000 to over $2 million. These prices will drop very rapidly in the next few years to where DVDs can be produced on desktop computer systems using additional hardware costing 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. DVDs currently cost a few thousand dollars to master and about $2.40 to replicate. Since DVD production is based mostly on the same equipment used for CD production, mastering and replication costs will quickly drop to CD levels.
Double-sided or dual-layer discs cost slightly 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 are more difficult.
Authoring can also be done by many service bureaus (see below) for around $300/hour.
[A] Authoring (including compression and premastering).
[R] Replication (mastering and/or one-offs).
[S] Use Sonic Solutions' authoring system.
See Robert's DVD Info page <http://www.unik.no/~robert/hifi/dvd/> for more pointers.
DVD is the work of Toshiba, Matsushita, Philips, Sony, and others. There were originally two next-generation standards for DVD. The MMCD format was backed Sony, Philips, and others. The competing SD format was backed by Toshiba, Time Warner, and others. A group of computer companies led by IBM insisted that the DVD proponents agree on 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 DVD Consortium now comprises Hitachi, JVC, Matsushita, Mitsubishi, Philips, Pioneer, Sony, Thomson, Time Warner, and Toshiba. (Visit Robert's DVD Info page <http://www.unik.no/~robert/hifi/dvd/> for links to company Web pages.)
Any company making DVD products must license the technology, partly from a pool administered by Philips but also separately from Thomson and others. Matsushita licenses the CSS encryption technology free of charge. Macrovision licenses its analog anti-recording technology free of charge to hardware makers, but charges a per-copy royalty to content publishers.
The following companies have made official statements of products specifically designed for the DVD format.
At last count (in Feb 1997), there were 139 registered Internet domain names with DVD in them. (Thanks to Robert for this interesting tidbit.)
Here are a few of the top DVD info pages. For more extensive pointers go to Robert's page, which has all the links you will ever need.
(If you know the answer to any of these, please speak up!)
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 1,000 (10^3, 10^6, and 10^9), but when used in the computer world to measure bytes they represent multiples of 1,024 (2^10, 2^20, and 2^30).
Most DVD figures are based on 1,000, not 1,024, in spite of using notation such as GB and KB/s. 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, KB for 1024 bytes, MB for 1,048,576 bytes, and GB for 1,073,741,824 bytes. Feedback on any sort of notation standards would be helpful.
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.
Robert Lundemo Aas
David Boulet
Espen Braathen
Wayne Bundrick
Roger Dressler
Chad Fogg
Dwayne Fujima
Henrik "Leopold" Herranen
Irek Defee
Kilroy Hughes
Ralph LaBarge
Martin Leese
Dana Parker
Geoffrey Tully
This document may be freely redistributed only in its entirety with 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 is expressly granted for complete electronic copies to be made available as an archive or mirror service on the condition that the copy be kept up to date. This document is provided as is without any express or implied warranty.
