Hier finden Sie die aktuellen Infos zur DVD Technologie. Der
schwerpunkt liegt bei DVD-Video+Audio.
Eine deutsche Übersetzung ist in Vorbereitung.
www.home-cinema.de hier mehr über DVDPlayer speziell codefree und Macrovision off Player
www.home-cinema.com hier alles über progressive scan DVDPlayer (METROPOLIS MEDIA ONE)
www.dvd-info.com allgemeine Info Seite DVD AUDIO, VIDEO und Computeranwendung (DVD-ROM, DVD RAM)
This is the April 30, 1999 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>.
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 about half of the 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 recordable variations (DVD-R, DVD-RAM, DVD-RW, DVD+RW; see 4.3). Most people expect DVD-ROM to be initially much more successful than DVD-Video. Most new computers with DVD-ROM drives can also play DVD-Videos (see 6.1).
There's also the DVD-Audio format that was introduced in 1999 (see 1.23 and 3.6.1).
Note: Most discs do not contain all features (multiple audio/subtitle tracks, seamless branching, parental control, etc.), as each feature must be specially authored. Some discs may not allow searching or skipping.
Most players support a standard set of features:
* Must be supported by additional content on the disc.
Some players include additional features:
DVD has the capability to produce near-studio-quality video and better-than-CD-quality audio. DVD is vastly superior to videotape and generally better than laserdisc (see 2.8.). However, quality depends on many production factors. Until compression experience and technology improves we will occasionally see DVDs that are inferior to laserdiscs. Also, since large amounts of video have already been encoded for Video CD using MPEG-1, a few low-budget DVDs will use that format (which is no better than VHS) instead of higher-quality MPEG-2.
DVD video is compressed from digital studio master tapes to MPEG-2 format. This "lossy" compression 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 "artifacts" such as blockiness, fuzziness, and video noise depending on the processing quality and amount of compression. At average rates of 3.5 Mbps (million bits/second), compression artifacts may be occasionally noticeable. Higher data rates can result in higher quality, with almost no perceptible difference from the master at rates above 6 Mbps. As MPEG compression technology improves, better quality is being achieved at lower rates.
Video from DVD sometimes contains visible artifacts such as color banding, blurriness, blockiness, fuzzy dots, shimmering, missing detail, and even effects such as a face that "floats" behind the rest of the moving picture. It's important to understand that the term "artifact" refers to anything that was not originally present in the picture. Artifacts are sometimes caused by poor MPEG encoding, but artifacts are more often caused by a poorly adjusted TV, bad cables, electrical interference, sloppy digital noise reduction or 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 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. 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 are 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, 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. Alternatively, audio for most movies is stored as discrete multi-channel surround sound using Dolby Digital or DTS audio compression similar to the surround sound formats used in theaters. As with video, audio quality depends on how well the processing and encoding was done. In spite of compression, Dolby Digital and DTS can be close to or better than CD quality.
The final assessment of DVD quality is in the hands of consumers. Most viewers consistently rate it better than laserdisc, but no one can guarantee the quality of DVD, just as no one should dismiss it based on demos or hearsay. In the end it's a matter of individual perception and the level of quality delivered by the playback system.
Some manufacturers originally announced that DVD players would be available as early as the middle of 1996. These predictions were woefully optimistic. Delivery was initially held up for "political" reasons of copy protection demanded by movie studios, but was later delayed by lack of titles.
Available players:
Projected player releases:
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. Creative Labs' PC-DVD
upgrade kit (Matsushita drive and A/V decoder board; Warner DVD-V sampler) went on sale in
the U.S. in April 1997 for $500. Samsung drives (and PCs with drives) were available in
Korea in January. Hi-Val's $799 PC-DVD upgrade kit (Toshiba drive, Quadrant decoder; 6
DVD-ROMS including Silent Steel, Daedalus Encounter, and Xiphias Encyclopedia Electronica)
became available in May 1997, as did Diamond Multimedia's $599 kit. STB Systems DVD
Theater Upgrade Kit was be available in July for $699. DynaTek announced a $649 upgrade
kit with 6 titles. Toshiba's Infinia DVD-ROM-equipped PC become available Summer 1997.
Creative's new "Encore" 2x DVD-ROM kit is available for under $100. Hi-Val's
2nd-generation kit is $380. E4's CoolDVD upgrade kit for Macintoshes became available for
$499 in July 1998. Sigma Designs also makes playback cards.
For drive details see http://www.brouhaha.com/~eric/video/dvd/.
WebShopper has a good report
(dated Sep 16, 1998).
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.)
As with hardware, rosy predictions of hundreds of movie titles for Christmas of 1996 failed to materialize. Only a handful of DVD titles, mostly music videos, were available in Japan for the November 1996 launch of DVD. Actual feature films began to appear in December. By April there were over 150 titles in Japan. Movies appeared in the US in March of 1997. Currently (Apr 1998) there are about 800 titles available in the US and over 1200 worldwide. Compared to other launches (CD, LD, etc.) this is a huge number. 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.
A concerted launch of DVD hardware and software in Europe is planned for the second quarter of 1998. Over 100 titles are expected to be available by March, with over 250 available by the end of 1998. Time Warner's official launch of DVD in Australia (region 4) is planned for Easter of 1998.
For an extensive, searchable list of titles available in the US and Canada see Jeff Phillips' list at <http://www.thedvdlist.com/>. For titles in Japan and Europe see Niels van Eijkelenburg's list at <http://www.surroundfreak.com/dvd/dvd2.htm> or Robert's list at <http://www.unik.no/~robert/hifi/dvd/film2.html>. Also check out the Internet Movie Database's DVD Browser <http://us.imdb.com/Sections/DVDs>. Christoph Steinecke's extensive list of region 1 titles is at <http://www.surroundfreak.com/dvd/dvd1.htm>. New release lists and announcements are available at <http://www.image-entertainment.com/laserv.html>. For a list of widescreen-specific DVD titles, visit http://www.widescreenreview.com/>.
Concorde Video released a PAL-format 12 Monkeys in Germany at the end of March 1997. They were threatened by Philips with a lawsuit for not including a multichannel MPEG track, but the issue is now resolved (see 3.6).
DVD-ROM software will slowly appear. Approximately 50% of CD-ROM producers have announced intentions to develop for DVD-ROM. See 6.2 for a list. Many initial DVD-ROM titles are only be available as part of a hardware or software bundle until the market grows larger. IDC expects that 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 high-quality video and multi-channel audio capabilities being added to many DVD-ROM-equipped computers.
Mass-market DVD movie players currently list for $300 and up. (See 1.5 for models and prices.) Within a few years they may approach VCR prices. InfoTech predicts prices will be as low as $250 by the year 2000, and below $150 by 2005.
DVD-ROM drives and upgrade kits for computers sell for around $80 to $600. (OEM drive prices are under $70.) Prices are expected to drop quickly to current CD-ROM drive levels.
It varies, but most DVD movies list for $20 to $30 with street prices between $15 and $25, even those with supplemental material. Low-priced movies can be found for under $10. So far DVD has not followed the initial high rental price model of VHS.
DVD-ROMs will initially be slightly more expensive than CD-ROMs since there is more on them, they cost more to replicate, and the market is smaller. But once production costs drop and the installed base of drives grow, DVD-ROMs will cost about the same as CD-ROMs today.
Not as fast as generally predicted, but faster than videotape, laserdisc, and CD. By the end of 1997 over 500,000 DVD-Video players shipped worldwide. 349,482 of these were in the US (with about 200,000 actually sold into homes). About ?? DVD video titles were available worldwide, with ?? million copies shipped. About 600 DVD video titles were available in the US, with over 5 million copies shipped and about 2 million sold. Around 330,000 DVD-ROM drives were shipped worldwide with about 1 million bundled DVD-ROM titles. Only 60 DVD-ROM titles were available by the end of 1997, most of them bundled with PCs or drive upgrade kits.
Here are some predictions:
Here's reality:
For comparison, there are about 700 million audio CD players and 160 million CD-ROM drives worldwide in 1997. 1.2 billion CD-ROMs were shipped worldwide in 1997 from a base of about 46,000 different titles. There are about 80 million VCRs in the U.S. (89% of households) and about 400 million worldwide. 110,000 VCRs shipped in the first two years after release. Nearly 16 million VCRs were shipped in 1998. There are about 3 million laserdisc players in the U.S. There are about 250 million TVs in the U.S. and 1.2 billion worldwide.
Motion picture studios want to control the home release of movies in different countries because theater releases aren't simultaneous (a movie may come out on video in the U.S. when it's just hitting screens in Europe). Also, studios sell distribution rights to different foreign distributors and would like to guarantee an exclusive market. Therefore they have required that the DVD standard include codes that can be used to prevent playback of certain discs in certain geographical regions. Each player is given a code for the region in which it's sold. The player will refuse to play discs that are not allowed in that region. This means that discs bought in one country may not play on players bought in another country.
Regional codes are entirely optional for the maker of a disc. Discs without codes will play on any player in any country. It's not an encryption system, it's just one byte of information on the disc that the player checks. Some studios originally announced that only their new releases will have regional codes, but so far almost all releases play in only one region. Region codes are a permanent part of the disc, they won't "unlock" after a period of time.
There are 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: Canada, U.S., U.S. Territories
2: Japan, Europe, South Africa, Middle East (including Egypt)
3: Southeast Asia, East Asia (including Hong Kong)
4: Australia, New Zealand, Pacific Islands, Central America, Mexico, South America,
Caribbean
5: Former Soviet Union, Indian Subcontinent, Africa (also North Korea, Mongolia)
6: China
(See the map at <http://www.unik.no/~robert/hifi/dvd/world.html>.)
Some players can be modified to play discs regardless of their regional codes. This usually voids the warranty. Some discs, such as those from Buena Vista/Touchstone/Miramax, MGM/Universal, and Polygram contain program code that checks for the proper region. These discs won't play on "code-free" players that have their region set to 0, but they can be played on "code-switchable" players that allow you to change the region using the remote control. Information about modifying players can be found on the Internet (including sites such as Code Free DVD and <http://www.brouhaha.com/~eric/video/dvd/>) and in the rec.video.dvd newsgroups (searchable at Deja News).
Regional codes also apply to DVD-ROM systems, but are allowed for use only with DVD-Video discs, not DVD-ROM discs containing computer software. (See 1.11 below for more details). Computer playback systems check for regional codes before playing movies from a DVD-Video. Newer "RPC2" DVD-ROM drives let you change the region code several times. Once a drive has reached the limit (usually 5 to 9 changes) it can't be changed again unless the vendor or manufacturer resets it.
Regional codes will not apply to DVD-Audio.
There are four forms of copy protection used by DVD:
1) Analog CPS (Macrovision)
Videotape (analog) copying is prevented with a Macrovision 7.0 or similar circuit in every
player. The general term is APS (Analog Protection System). Computer video cards with
composite or s-video (Y/C) output must also use APS. Macrovision adds a rapidly modulated
colorburst signal ("Colorstripe") along with pulses in the vertical blanking
signal ("AGC") to the composite video and s-video outputs. This confuses the
synchronization and automatic-recording-level circuitry in 95% of consumer VCRs.
Unfortunately, it can degrade the picture, especially with old or nonstandard equipment.
Macrovision may show up as stripes of color, distortion, rolling, black & white
picture, and dark/light cycling. Macrovision creates severe problems for most 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" in the header of each sector telling
the player whether or not to enable Macrovision AGC, with the optional addition of 2-line
or 4-line Colorstripe. This allows fine control over which sections are copy 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 <http://www.st.com/stonline/books/>.)
2) CGMS
Each disc also contains information specifying if the contents can be copied. This is a
"serial" copy generation management system (SCMS) designed to prevent copies or
copies of copies. The CGMS information is embedded in the outgoing video signal. For CGMS
to work, the equipment making the copy must recognize and respect the CGMS. The analog
standard (CGMS/A) encodes the data on NTSC line 21 (in the XDS service). The digital
standard (CGMS/D) is not yet finalized, but will apply to digital connections such as IEEE 1394/FireWire. See section 4, below.
3) Content Scrambling System (CSS)
Because of the potential for perfect digital copies, paranoid movie studios forced a
deeper copy protection requirement into the DVD-Video standard. Content Scrambling System
(CSS) is a form of data encryption to discourage reading media files directly from the
disc. Most players 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 exchange encryption keys so that the video is decrypted just before
being displayed by the encoder. This means that many DVD-ROM drives and video display
boards have extra hardware (and cost) for movie copy protection. In 1999, all DVD-ROM
drives will be required to support regional management in conjunction with CSS. Some
drives may allow the user to reset the region a limited number of times; other drives will
self-program after a certain number of movies have been played. 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. Near the end of May 1997, CSS licenses were
finally granted for software decoding.
4) Digital Copy Protection System (DCPS)
In order to provide for digital connections between components without allowing perfect
digital copies, five digital copy protection systems have been proposed to CEMA. The frontrunner is DTCP (digital transmission content protection), which
focuses on IEEE 1394/FireWire but can be applied to other protocols. The draft proposal
(called 5C, for the five companies that developed it) was made by Intel, Sony, Hitachi,
Matsushita, and Toshiba in February 1998. In December 1998, Sony announced the development
of a DTCP chip planned for release in spring 1999. Under DTCP, devices that are digitally
connected, such as a DVD player and a digital TV or a digital VCR, exchange keys and
authentication certificates to establish a secure channel. The DVD player encrypts the
encoded audio/video signal as it sends it to the receiving device, which must decrypt it.
This keeps other connected but unauthenticated devices from stealing the signal. No
encryption is needed for content that is not copy protected. Security can be
"renewed" by new content (such as new discs or new broadcasts) and new devices
that carry updated keys and revocation lists (to identify unauthorized or compromised
devices). A competing proposal, XCA (extended conditional access), from Zenith and
Thomson, is similar to DTCP but can work with one-way digital interfaces (such as the
EIA-762 RF remodulator standard) and uses smart cards for renewable security. Other
proposals have been made by MRJ Technology, NDS, and Philips. In all five proposals,
content is marked with CGMS-style flags of "copy freely", "copy once,"
"don't copy," and sometimes "no more copies". Digital devices that do
nothing more than reproduce audio and video will be able to receive all data (as long as
they can authenticate that they are playback- only devices). Digital recording devices are
only able to receive data that is marked as copyable, and they must change the flag to
"don't copy" or "no more copies" if the source is marked "copy
once." Digital CPS is designed for the next generation of digital TVs, digital
receivers, and digital video recorders. It will require new DVD players with digital
connectors (such as those on DV equipment). These new products won't appear before mid
1999. Since the encryption is done by the player, no changes are needed to the existing
disc format.
Movie studios and consumer electronics companies want to make it illegal to defeat DVD copy protection, and have promoted legislation in the U.S. and other countries. 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 Millenium Copyright Act (DMCA), passed into law in October 1998. 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 or by studios that set the "don't copy" flag 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 compute, 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.
The first three forms of copy protection are optional for the producer of a disc. Movie decryption is also optional for hardware and software playback manufacturers: a player or computer without decryption capability will only be able to play unencrypted movies. DCPS is performed by the DVD player, not by the disc developer.
These copy protection schemes are designed only to guard against casual copying (which the studios claim causes billions of dollars in lost revenue). The goal is to "keep the honest people honest." Even the people who developed the copy protection standards admit that they won't stop well-equipped pirates. There are inexpensive devices that defeat analog copy protection, although only a few work with the new Macrovision Colorstripe feature. These devices go under names such as Video Clarifier, Image Stabilizer, and CopyMaster.
The Data-Hiding Sub-Group (DHSG) of the industry's Copy Protection Technical Working Group (CPTWG) is evaluating watermarking proposals. The original seven watermarking proposals that were merged into three: IBM/NEC, Hitachi/Pioneer/Sony, and Macrovision/Digimarc/Philips. On February 17, 1999, the first two groups combined to form the "Galaxy Group" and merged their technologies into a single proposal. Watermarking, which will be added to DVD at some point, permanently marks each digital video frame with noise that is supposedly visually undetectable. Watermark signatures can be recognized by video playback and recording equipment to prevent copying, even when the video 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 are reports that the watermarking technique used by Divx causes visible "raindrop" or "gunshot" patterns. The problem seems to have been solved with newer discs.
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 was approved in February 1999 and released in March. DVD-Audio products will show up in late 1999 at the earliest. The delay is being caused by the slow process of selecting copy protection features (encryption and watermarking). It's possible that the RIAA's Secure Digital Music Initiative (SDMI) could push the introduction of DVD-Audio into 2000.
DVD-Audio is a separate format from DVD-Video. DVD-Audio discs can be designed to work in DVD-Video players, but its possible to make a DVD-Audio disc that won't play at all in a DVD-Video player, since the DVD-Audio specification includes new formats and features, with content stored in a separate "DVD-Audio zone" on the disc (the AUDIO_TS directory) that DVD-Video players never look at. New DVD-Audio players are needed, or new "universal players" that can play both DVD-Video and DVD-Audio discs.
Plea to producers: Universal players won't be
available for some time, but you can make "universal discs" today. With a small
amount of effort, all DVD-Audio discs can be made to work on all DVD
players by including a Dolby Digital version of the audio in the DVD-Video zone.
Plea to DVD-Audio authoring system developers: Make
your software do this by default or have it strongly recommend this option during
authoring.
DVD-Audio (and universal) players will work with existing receivers. They output PCM and Dolby Digital, and some will support the optional DTS and DSD formats. However, most current receivers can't decode the high-definition PCM audio (see 3.6.1 for details), and even if they could it can't be carried on standard digital audio connections. DVD-Audio players with high-end digital-to-analog converters (DACs) can be hooked up to receivers with two-channel or 6-channel analog inputs, but some quality will be lost if the receiver converts back to digital for processing. Future receivers with improved digital connections such as IEEE 1394 (FireWire) will be required to use the full digital resolution of DVD-Audio.
The music industry has requested an "embedding signalling" or "digital watermark" copy protection feature. This uses signal processing technology to apply a digital signature and optional encryption keys to the audio in the form of supposedly inaudible noise so that new equipment will recognize copied audio and refuse to play it. Audiophiles claim this degrades the audio.
In the meantime, the DVD-Video standard includes surround sound audio and better-than-CD audio (see 3.6.2).
Sony and Philips have developed a competing Super Audio CD format. (See 3.6.1 for details.) SACD provides "legacy" discs that have two layers, one that plays in existing CD players, plus a high-density layer for DVD-Audio players. Ironically, initial price for these dual-layer discs will be higher than for a standard CD plus a standard DVD. Sony released version 0.9 of the SACD spec in April 1998, the final version is expected in April 1999. SACD technology will be available to existing Sony/Philips CD licensees at no additional cost.
When DVD players became available in early 1997, Warner and Polygram were the only major movie studios to release titles. Additional titles were available from small developers. The other studios gradually joined the DVD camp (see 6.2 for a full list, see 1.6 for movie info).
Dreamworks was the last significant studio to announce full DVD support. Paramount, Fox, and Dreamworks initially supported only Divx, but in summer 1998 they each announced support for open DVD.
Short Answer: 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 DVD-V info, and write the whole thing to DVD. Even if you could do all this in a home recorder, it would be extremely 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. In June 1997, Hitachi demonstrated a home DVD video recorder containing a DVD-RAM drive, a hard disk drive (as a buffer), two MPEG-1 encoders, and an MPEG-2 decoder. No production date was mentioned. 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 initially will be $30 and up. The first generation of recordable media will hold less than 3/4 as much as prerecorded discs. Realtime compression requires 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, which came out in Sep 1997 for $17,000; or DVD-RAM, which came out in June for around $500; or other recordable variations of DVD (see 4.3). These can record data, but to create full-featured DVD-Videos requires additional hardware and software to do video encoding (MPEG), audio encoding (Dolby Digital, MPEG, or PCM), subpicture encoding (run-length-compressed bitmaps), still frame encoding (MPEG), navigation and control data generation, and multiplexing. And since this can't yet 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 formats. DV (aka DVC) is out already, but decks cost $4,000. D-VHS and other Digital VCR technologies are just becoming available.
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. There are many schemes for concealing errors in MPEG video, which may be used in future players (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. Major chains such as Blockbuster and West Coast Entertainment rent DVDs in many locations. So far most reports of rental disc performance are positive. A nice list of DVD rental outlets is at <http://www.dvdpost.com/rental.html>.
The primary advantages of DVD are quality and extra features (see 1.2). DVD will not degrade with age or after many playings like videotape will (which is an advantage for parents with kids who watch Disney videos twice a week!). This is the "collectability" factor present with CDs vs. cassette tapes.
If none of this matters to you, then VHS probably is good enough.
Manufacturers are worried about customers assuming DVDs will play in their CD player, so they would like the packaging to be different. There are a number of DVD packages such as the "keep case" and Time Warner's "Snapper" that are about as wide as a CD jewel box and about as tall as a VHS cassette box. 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.
A dual-layer disc has two layers of data, one of them semi-transparent so that the laser can focus through it and read the second layer. Since both layers are readable from the same side, a dual-layer disc can hold almost twice as much as a single-layer disc, for over 4 hours of video (see 3.3 for more details). Many dual-layer discs are currently available (such as Contact, Goldeneye, Species, Raging Bull, and Rain Man). Initially only a few replication plants could make dual-layer discs, but most plants now have the capability. The second layer can either have a "PTP" track that runs in parallel to the first track (for independent data or special switching effects), or an "OTP" tracks that runs opposite to the first track; that is the pickup head reads out from the center on the first track then in from the outside on the second track. This is designed to provide continuous video across both layers. There's no guarantee that the switch between layers will be seamless. Non-seamless switches cause the video to freeze for less than half a second on most players but up to 4 seconds on some. The "seamlessness" depends as much on the way the disc is prepared as on the design of the player. OTP is also called RSDL (Reverse-Spiral Dual Layer). The advantage of OTP (RSDL) is that longer movies can use higher data rates for better quality than with a single layer. See 1.26 for layer change details.
All DVD players and drives can read dual-layer discs -- it's required by the spec. All players and drives also play double-sided discs if you flip them over. No manufacturer has announced a model that will play both sides. The added cost is probably not justifiable since discs can hold over 4 hours of video on one side by using two layers. (Early discs used two sides because dual-layer production was not widely supported. This should no longer be a problem.) Pioneer LD/DVD players can play both sides of an LD, but not a DVD. (See 2.9 for note on reading both sides simultaneously.)
There are various ways to recognize dual-layer discs: 1) the gold color, 2) a menu on the disc for selecting the widescreen or letterbox version, 3) two serial numbers on one side.
DVD-V has the same NTSC vs. PAL problem as videotape and laserdisc. The MPEG video on DVD is stored in digital format, but it's formatted for one of two mutually incompatible television systems: 525/60 (NTSC) or 625/50 (PAL/SECAM). There are three differences between discs intended for playback on different systems: picture size and pixel aspect ratio (720x480 vs. 720x576), display frame rate (29.97 vs 25), and surround audio (Dolby Digital vs. MPEG). (See 3.4 and 3.6 for details.) Video from film is usually stored at 24 frames/sec but is preformatted for one of the two display rates. Movies formatted for PAL display are usually sped up by 4%, so the audio must be adjusted accordingly before being encoded. All PAL DVD players can play Dolby Digital audio tracks, but no NTSC players can play MPEG audio tracks.
Some players will only play NTSC discs, some players will only play PAL discs, and some will play both. All DVD players sold in PAL countries play both. These multi-standard players partially convert NTSC to a 60-Hz PAL (4.43 NTSC) signal, which requires a PAL TV that can handle 60-Hz signals. In this case the player uses the PAL 4.43 color encoding format but keeps the 525/60 NTSC scanning rate. Most modern PAL TVs can handle this kind of signal. A few multi-standard PAL players output true 3.58 NTSC from a 525/60 NTSC discs, which requires an NTSC TV or a multi-standard TV. Some players have a switch to choose between 60-Hz PAL and NTSC output when playing NTSC discs. 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. A few players that convert 525/60 NTSC to 625/50 PAL have been announced.
A producer can choose to include additional video and audio --at the expense of playing time-- so that all formats are covered. It's unclear if players will be able to automatically recognize and play the correct video track. Of course it's always possible to put 525/60 video on one side of the disc and 625/50 on the other. Most studios so far are including Dolby Digital tracks along with the MPEG audio tracks on their PAL discs.
There are actually three types of DVD players if you count computers. Most DVD PC software and hardware can play both NTSC and PAL video and both Dolby Digital and MPEG audio. Some PCs can only display the converted video on the computer monitor, but others can output it as a video signal for a TV.
Some people claim that animation, especially hand-drawn cell animation such as cartoons and anime, does not compress well with MPEG-2 or even ends up larger than the original. Other people claim that animation is simple so it compresses better. Neither is true.
Supposedly the "jitter" between frames caused by differences in the drawings or in their alignment causes problems. An animation expert at Disney pointed out that this doesn't happen with modern animation techniques. And even if it did, the motion estimation feature of MPEG-2 would compensate for it.
Because of the way MPEG-2 breaks a picture into blocks and transforms them into frequency information it can have a problem with the sharp edges common in animation. This loss of high-frequency information can show up as "ringing" or blurry spots along edges (called the Gibbs effect). However, at the data rates commonly used for DVD this problem does not occur.
Even though DVD's dual-layer technology (see 3.3) allows over four hours of continuous playback, some movies are split over two sides of a disc, requiring that the disc be flipped partway through. Most "flipper" discs exist because of producers who are too lazy to optimize the compression or make a dual-layer disc. Better picture quality is a lame excuse for increasing the data rate; in many cases the video will look better if carefully encoded at a lower bit rate. Lack of dual-layer production capability is also a lame excuse; in 1997 very few DVD plants could make dual-layer discs, but this is no longer the case. No players can automatically switch sides, but it's not needed since most movies less than 4 hours long can easily fit on one dual-layer (RSDL) side.
The following discs are "flippers." (Note: This is not the same as a disc with a widescreen version on one side and a pan & scan version or supplements on the other.)
Answer: RTFM. You are watching an anamorphic picture intended for display only on a widescreen TV. (See 3.5 for technical details). You need to go into the player's setup menu and tell it you have a standard 4:3 TV, not a widescreen 16:9 TV. It will then automatically letterbox the picture so you can see the full width at the proper proportions.
In some cases you can change the aspect ratio as the disc is playing (by pressing the "aspect" button on the remote control). On most players you have to stop the disc before you can change aspect. Some discs are labeled with widescreen on one side and standard on the other. In order to watch the fullscreen version you must flip the disc over.
See Steve Tannehill's Why Does The Picture Look Squished? article for further explanation and pictures.
Most DVD-Video discs contain Dolby Digital soundtracks. However, it's not required. Some discs, especially those containing only audio, have PCM tracks. It's also possible for a 625/50 (PAL) disc to contain only MPEG audio, but so far MPEG audio is not widely used.
Don't assume that the "Dolby Digital" label is a guarantee of 5.1 channels. A Dolby Digital soundtrack can be mono, dual mono, stereo, Dolby Surround stereo, etc. For example, Blazing Saddles and Caddyshack are mono movies, so the Dolby Digital soundtrack on these DVDs has only one channel. Some DVD packaging has small lettering or icons under the Dolby Digital logo that indicates the channel configuration. In some cases, there is more than one Dolby Digital version of a soundtrack: a 5.1-channel track and a track specially remixed for stereo Dolby Surround. It's perfectly normal for your DVD player to indicate playback of a Dolby Digital audio track while your receiver indicates Dolby Surround: it means that the disc contains a two-channel Dolby Surround signal encoded in Dolby Digital format.
See 3.6 for more audio details.
Laserdiscs are subject to what's commonly called laser rot: the deterioration of the aluminum layer due to oxidation. The large size of laserdiscs makes them flexible, so that movement along the bond between sides can break the seal. Like laserdiscs, DVDs are made of two platters glued together, but DVDs are more rigid and use newer adhesives. Also, DVDs are molded from polycarbonate, which absorbs about ten times less moisture than the PMMA used for laserdiscs. It's too early to know for sure, but DVD's will probably have few or no laser rot problems.
Some titles are available only in pan & scan because there was no letterbox or anamorphic transfer made from film. (See 3.5 for more info on pan & scan and anamorphic formats.) Since transfers cost $50,000 to $100,000, studios may not think a new transfer is justified. In some cases the original film or rights to it are no longer available for a new transfer. In the case of old movies, they were shot full frame in the 1.37 "academy" aspect ratio so there can be no widescreen version. Video shot with TV cameras, such as music concerts, is already in 4:3 format.
The list of pan & scan only titles has gotten too big to keep here. You can get a list from the Internet Movie Database (which also includes discs with both widescreen and pan & scan versions), and you can search by screen format (which includes disc with video shot in fullscreen 4:3) at The DVD List.
On the remote control, press Subtitle, then either Clear or 0 (zero). No need to use the menus.
Some movies over 2 hours long may be spread across two layers on a disc. When the player changes to the second layer, the video and audio may freeze for a moment. The length of the pause depends on the player and on the layout of the disc. The pause is not a defect in the player or the disc. See 1.18 for details.
Layer switch points on RSDL discs:
Some discs (many from Columbia TriStar) put 2-channel Dolby Surround audio on track one and 5.1-channel audio on track two. Unless you intervene, the player will play the default 2-channel track. Use the audio button on the remote or select the 5.1 track from the menu. (Note: The Sony 3000 has a feature to automatically select the first 5.1 track.)
Dolby Digital doesn't necessarily mean 5.1 channels. See 3.6.
Almost all features of DVD such as search, pause, and scan can be disabled by the disc, which can prevent the operation the player needs to back up and repeat a segment. If the player uses time search to repeat a segment, then a disc with fancy non-sequential title organization may also block the repeat feature. In many cases the authors don't even realize they have prevented the use of this feature.
There is no good answer to this question, since you'll get a different response from everyone you ask. The terms "2nd generation" and "3rd generation" are used refer both to DVD-Video players and to DVD-ROM drives. In general, they simply mean newer versions of basic DVD playback systems. The terms haven't been used (yet) to refer to DVD systems that can record, play video games, or so on.
According to some people, second-generation DVD players came out in the fall of 1997 and third-generation players are those that came out in the beginning of 1998. According to others, the second generation of DVD will be "high-definition" players (see 2.9) that won't come out until 2003 or so. There are many confusing variations between these extremes, including the viewpoint that DTS-compatible players or Divx players or progressive-scan players constitute the third generation.
Things are a little more clear cut on the PC side, where second generation (DVD II) usually means 2x DVD-ROM drives that can read CD-Rs, and third generation (DVD III) usually means 5x (or sometimes 2x or 4.8x or 6x) DVD-ROM drives, a few of which can read DVD-RAMs, and some of which are RPC2 format. See section 4.2 for more speed info. See section 1.10 for RPC2 explanation.
Hah, hah, hah! Do you really want the answer to this one? Ok, you asked for it...
Did I miss any?
Digital Theater Systems Digital Surround is an audio encoding format similar to Dolby Digital. It requires a decoder, either in the player or in an external receiver. See 3.6.2 for technical details. Some people claim that because of its lower compression level DTS sounds better than Dolby Digital. Others claim there is no meaningful difference. DTS discs are produced only by DTS, under license from movie studios, and are generally considered to be specialty items intended for audio enthusiasts. It's expected that discs produced by DTS will also be available in standard DVD format.
DTS is an optional format on DVD. The original DVD specification developed in 1996 provides an ID code for DTS, but players made before mid 1998 (and many since) ignore DTS tracks. A few demo discs were created by embedding DTS data into a PCM track (the same technique used with CDs and laserdiscs), and these are the only DTS DVD discs that work on all players. New DTS-compatible players arrived in mid 1998, but theatrical DTS discs using the DTS audio stream ID specified by the DVD-Video standard did not appear until January 7, 1999 (they were originally scheduled to arrive in time for Christmas 1997). Mulan, a direct-to-video animation (not the Disney movie) with DTS soundtrack did apear in November 1998. DTS-compatible players will carry an official "DTS Digital Out" logo. A few manufacturers may provide upgrades to make existing players compatible with DTS discs.
Dolby Digital or PCM audio are required on 525/60 (NTSC) discs, and since both PCM and DTS together don't usually leave enough room for quality video encoding, essentially every disc with a DTS soundtrack will also carry a Dolby Digital soundtrack. This means that all DTS discs will work in all DVD players, but a DTS-compatible player and a DTS decoder are required to play the DTS soundtrack. DTS audio CDs will work on all DVD players, since the DTS data is encapsulated as standard PCM tracks that are passed untouched to the digital audio output(s).
You are probably trying to play an NTSC disc in a PAL player, but your PAL TV is not able to handle the signal. If your player has a switch or onscreen setting to select the output format for NTSC discs, choosing PAL (60-Hz) may solve the problem. See section 1.19 for more information.
Many DVD's are labeled as having widescreen (16:9) format video on one side and standard (4:3) on the other. If you think both sides are the same, you're probably seeing uncompressed 16:9 on the widescreen side. It seems to be 4:3 pan & scan, but if you look carefully you'll discover that the picture is horizontally compressed. The problem is that your player has been set for a widescreen TV. See 1.22 for details.
Not any time soon. Recordable DVD is for computer data only, not television video (see 1.14). It will take a while before the size of the market drives costs down to VCR levels. However, DVD has many advantages over VCRs, including fundamentally lower technology cost for hardware and disc production (which is appealing to manufacturers), so if DVD is a commercial success it might replace many VCRs in fifteen to twenty years.
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). Software on a CD-ROM will run fine in a DVD-ROM system. However, DVD-ROMs are not readable by CD-ROM drives.
Sometimes. The problem is that CD-Rs (Orange Book Part II) are "invisible" to DVD laser wavelength because the dye used in CD-Rs doesn't reflect the beam. Some first-generation DVD-ROM drives and many DVD players can't read CD-Rs. The common solution is to use two lasers at different wavelengths: one for reading DVDs and the other for reading CDs and CD-Rs. Variatons on the theme include Sony's "dual discrete optical pickup" with switchable pickup assemblies with separate optics, Samsung's "annular masked objective lens" with a shared optical path, Toshiba's similar shared optical path using an objective lens masked with a coating that's transparent only to 650-nm light, Hitachi's switchable objective lens assembly, and Matsushita's holographic dual-focus lens. Look for drives with the MultiRead label, which guarantees compatibility with CD-R and CD-RW media.
An effort to develop CD-R "Type II" media compatible with both CD and DVD wavelengths has been abandoned.
DVD-ROM drives can't record on any media. Current writable DVD drives (see 4.3) can't record on CD-R, although future versions may be able to.
Usually. CD-Rewritable (Orange Book Part III) has a lower reflectivity difference, requiring new automatic-gain-control (AGC) circuitry. CD-RW discs can't be read by most existing CD-ROM drives and CD players. The new "MultiRead" standard addresses this, and some DVD manufacturers have suggested they will support it. The optical circuitry in even first-generation DVD-ROM drives and DVD players is usually able to read CD-RW discs, since CD-RW does not have the "invisibility" problem of CD-R (see 2.4.3).
Current writable DVD drives (see 4.3) can't record on CD-RW, although future versions may be able to.
Sometimes. It's not required by the DVD spec, but it's trivial to support the Video CD (White Book) standard since any MPEG-2 decoder can also decode MPEG-1 from a Video CD. Panasonic, RCA, Samsung, and Sony models play Video CDs. Japanese Pioneer models play Video CDs but American models older than the DVL-909 don't. Toshiba players older than models 2100, 3107, and 3108 don't play Video CDs.
VCD resolution is 352x288 for PAL and 352x240 for NTSC. The way most DVD players and Video CD players deal with the difference is to chop off the extra lines or add blank lines. When playing PAL VCDs, the Panasonic and RCA NTSC players apparently cut 48 lines (17%) off the bottom. The Sony NTSC players apparently scale all 288 lines to fit.
Most DVD-ROM computers can play Video CDs (with the right software), since its already possible with current-model CD-ROM computers.
Note: Many Asian VCDs achieve "two" soundtracks by putting one language on the left channel and another on the right. They will be mixed together into babel on a stereo system unless you adjust the balance to get only one channel.
Not currently. Super Video CD (SVCD) is an enhancement to Video CD that was developed by a Chinese government-backed committee of manufacturers and researchers, partly to sidestep DVD technology royalties and partly to create pressure for lower DVD player and disc prices in China. The final SVCD spec was announced in September 1998, winning out over C-Cube's China Video CD (CVD) and HQ-VCD (from the developers of the original Video CD). In terms of video and audio quality, SVCD is in between Video CD and DVD, using a 2x CD drive to support 2.2 Mbps VBR MPEG-2 video (at 480x567 resolution) and 2-channel MPEG-2 Layer II audio. As with DVD, it can overlay graphics for subtitles. Since it's technically easy to make a DVD-Video player compatible with SVCD, it will probably happen soon, but perhaps only on Asian DVD player models. It's not likely that SVCD will be released outside of China and nearby countries.
SVCD players can't play DVDs, since the players are based on CD drives.
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 Music CDs (Blue Book, CD Plus, CD Extra), and DVD-ROM drives will play music and read data from Enhanced CDs. Older ECD formats such as mixed mode and track zero (pregap, hidden track) should also be compatible, but there may be a problem with DVD-ROM drivers skipping track zero (as has been the case with some new CD-ROM drivers).
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. MP3 is MPEG-1 Layer 3 audio compression. (MP3 is not MPEG-3.) The DVD-Video spec allows Layer 2 only. MP3 can be played on a computer with a DVD-ROM drive, but not in a DVD-Video player.
Yes. Pacific Microsonics' HDCD (high-definition compatible digital) is an encoding process that enhances audio CDs so that they play normally in standard CD and DVD players (and allegedly sound better than normal CDs) yet produce an extra 4 bits of precision (20 bits instead of 16) when played on CD and DVD players equipped with HDCD decoders.
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.
In a way, DVD has already replaced laserdisc, since it's the clear choice for new buyers interested in high-quality video. But laserdisc will still be around for a very long time, since it's well established as a videophile format. There are over 9,000 laserdisc titles in the US and a total of over 35,000 titles worldwide that can be played on over 7 million laserdisc players. It will take DVD several years to reach this point. Until then laserdisc has the superiority of tenure. Pioneer and other laserdisc companies have committed to supporting it (on Sep. 7, 1998, Pioneer's president Kaneo Ito said the company expects laserdisc products to be in the market for another one-and-a-half to two years). There's no reason for laserdisc player owners to stop buying laserdiscs, especially rare titles that may not appear on DVD for a long while if ever. Even laserdisc collectors 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 became available in late 1998, but they are very expensive and won't become widespread for many years. DVD will look better on HDTVs but it won't provide the highest resolutions. See 2.9 for more information on DVD and HDTV.
The final 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 can probably jump in around the end of 1999. 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 isn't too expensive) or HDTV (which is). 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, laserdisc was hurt by anticipation of DVD before it even came out. In 1996 laserdisc player sales were down 37% even though sales of VCRs and hi-fi/surround systems were up. The silver lining in this cloud is that disc prices came down. (Laserdisc movie sales were only down 2.5% in 1996.)
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 Leopold's FAQ at <http://www.cs.tut.fi/~leopold/Ld/FAQ/index.html>, and Bob Niland's FAQs and overview at <http://www.frii.com/~rjn/laser/> (overview reprinted from Widescreen Review magazine).
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.
Short answers: Partially. No.
First, some quick definitions: HDTV (high-definition TV) encompasses both analog and digital televisions that have a 16:9 aspect ratio and approximately 5 times the resolution of standard TV (double vertical, double horizontal, wider aspect). DTV (digital TV) applies to digital broadcasts in general and to the U.S. ASTC standard in specific. The ATSC standard includes both standard-definition (SD) and high-definition (HD) digital formats.
DVD-Video does not directly support HDTV. No digital HDTV standards were finalized when DVD was developed. In order to be compatible with existing televisions, DVD's MPEG-2 video resolutions and frame rates are closely tied to NTSC and PAL/SECAM video formats (see 1.19). DVD does use the same 16:9 aspect ratio of HDTV and the Dolby Digital audio format of U.S. DTV.
HDTV in the US is part of the new ATSC DTV format. The resolution and frame rates of DTV in the US generally correspond to the ATSC recommendations for SD (640x480 and 704x480 at 24p, 30p, 60p, 60i) and HD (1280x720 at 24p, 20p, and 60p; 1920x1080 at 24p, 30p and 60i). (24p means 24 progressive frames/sec, 60i means 60 interlaced frames/sec.) The current DVD-Video spec covers all of SD except 60p. It's expected that future DVD players will output digital video signals from existing discs in SDTV formats. The HD formats are 2.7 and 6 times the resolution of DVD, and the 60p version is twice the frame rate. The ITU-R is working on BT.709 HDTV standards of 1125/60 (1920x1035/30) (same as SMPTE 240M, similar to Japan's analog MUSE HDTV) and 1250/50 (1920x1152/25) which may be used in Europe. The latter is 5.3 times the resolution of DVD's 720x576/25 format. HD maximum data rate is usually 19.4 Mbps, almost twice the maximum DVD-Video data rate. In other words, DVD-Video does not currently support HDTV video content.
HDTV will not make DVD obsolete. Those who postpone purchasing a DVD player because of HDTV are in for a long wait. HDTV became available in late 1998 at very high prices (about $5000 and up). It will take many years before even a small percentage of homes have HDTV sets. CEMA expects 10 percent of U.S. households to have HDTV in 2003, 20 percent by 2005, and 30 percent by 2006.
HTDV sets include analog video connectors (composite, s-video, and component) that will work with all DVD players and other existing video equipment such as VCRs. Existing DVD players and discs will work perfectly with HDTV sets, and will provide a much better picture than any other prerecorded consumer video format, especially once new progressive-scan players become available. Since the cheapest route to HDTV reception will be HDTV converters for existing TV sets, HDTV for many viewers will look no better than DVD.
At some point, HDTV displays will support component digital video connections (YCrCb) and digital data connections (FireWire/IEEE 1394). The digital connections will provide the best possible reproduction of DVD-Video, especially in widescreen mode. Once DVD players have digital outputs, they may be usable as "transports" which output any kind of A/V data (even formats developed after the player was built) to any sort of external display or converter.
The interesting thing many people don't realize is that DTV is happening soonest, fastest, and cheapest on PCs. A year before any consumer DTV sets came out you could buy a DVD PC with a 34" VGA monitor and get gorgeous progressive-scan movies. All for under $3000. The quality of a good DVD PC connected to a data-grade video projector beats $30,000 line-doubler systems. (See NetTV and Digital Connection for example product info.)
Eventually the DVD-Video format will be upgraded to a "DVD-HD" format, probably around 2003 at the earliest, based on higher-capacity discs and blue or purple lasers (already demonstrated by many DVD manufacturers). New DVD-HD players will play current DVD discs and will make them look even better, but new DVD-HD discs won't be playable in older DVD players (unless one side is HD and the other SD). Ironically, DVD computers will support HDTV before DVD-Video players, since 2x DVD-ROM drives coupled with appropriate playback and display hardware meet the 19 Mbps data rate needed for HDTV.
Note: The term "HDVD" has already been taken for "high-density volumetric display."
Some have speculated that a "double-headed" player reading both sides of the disc at the same time could double the data rate for applications such as HDTV. This is currently impossible since the track spirals go in opposite directions (unless all four layers are used). The DVD spec would have to be changed to allow reverse spirals on layer 0. Even then, keeping both sides in sync, especially with MPEG-2's variable bit rate, would require independently tracking heads, precise track and pit spacing, and a larger, more sophisticated track buffer.
Depending on whom you ask, Divx (formerly ZoomTV) is either an insidious evil scheme for greedy studios to control what you see in your own living room or an innovative approach to video rental that lets you get cheap discs almost anywhere and keep them for later viewings. Regardless, Divx is confusing consumers and delaying the acceptance of DVD. Developed by Circuit City and a Hollywood law firm, Divx is supported by Disney (Buena Vista), Twentieth Century Fox, Paramount, Universal, MGM, and DreamWorks SKG, all of which also release discs in "open DVD" format, since the Divx agreement is non-exclusive. Harman/Kardon, JVC, Kenwood, Matsushita (Panasonic), Pioneer, Thomson (RCA/Proscan/GE), and Zenith are developing Divx players. The studios and hardware makers supporting Divx have been offered incentives in the form of guaranteed licensing payments totalling over $110 million.
Divx is a pay-per-viewing-period variation of DVD. Divx discs sell for $4.50. Once inserted into a Divx player the disc plays normally (allowing the viewer to pause, rewind, even put in another disc before finishing the first disc) for the next 48 hours, after which the "owner" must pay $3.25 to unlock it for another 48 hours. A Divx DVD player, which costs about $100 more than a regular player, must be hooked up to a phone line so it can call an 800 number for about 20 seconds during the night once each month to upload billing information. Most Divx discs can be converted to DivxSilver status by paying an additional fee (usually $20) to allow unlimited plays on a single account (as of Dec 1998, 85% of Divx discs were convertible). Unlimited-playback DivxGold discs may also be offered for sale at a price similar to regular "open" DVDs. Divx players also play regular DVD discs, but Divx discs do not play in standard DVD players. Divx discs are serialized (with a barcode in the standard Burst Cutting Area) and in addition to normal DVD copy protection (see 1.11) they employ watermarking of the video and triple DES encryption (three 56-bit keys) of serial communications. No computer support of Divx has been announced, and in any case special decryption hardware may be required since DES is too complex for realtime software decoding. Because of the DES encryption, Divx technology may not be allowed outside the U.S.
Divx was originally announced for Summer 1998 release. Limited trials began June 8, 1998 in San Francisco, CA and Richmond, VA. The only available player was from Zenith (which at the time was in Chapter 11 bankruptcy), and the promised 150 movies had somehow dwindled to 14. The limited nationwide rollout (with one Zenith player model and 150 movies in 190 stores) began on September 25, 1998. By the end of 1998 about 87,000 Divx players (from four models available) and 535,000 Divx discs were sold (from about 300 titles available). If Divx is counting the five discs bundled with each player, then only 100,000 additional discs were sold.
For more information, see the Divx FAQ at <http://www.divx.com/> and the Anti Divx page at <http://www.dvdresource.com/divx>.
Most DVD players have the following output connections:
Video:
- Composite video (CVBS) RCA (NTSC or PAL)
- Y/C (s-video) (NTSC or PAL)
Audio:
- Dual RCA stereo analog audio (with Dolby Surround encoding)
- Digital audio (IEC-958 Type 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 interlaced analog video, NTSC or PAL (YUV: 3 RCA connectors, RGB: SCART
connector or 3 RCA).
- Component progressive analog video, NTSC or PAL (YUV, 3 connectors). (Toshiba SD7108)
- RF video output for connecting via channel 3 or 4 to TV without direct input. (Panasonic
DVD-A300, RCA 5500P)
- 6 RCA jacks for analog surround sound output. (Panasonic DVD-A300, RCA 5500P, Samsung
DVD905)
- 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, DVL-700)
Some players and receivers support only S/P DIF or only Toslink. If your player and receiver don't match, you'll need a converter such as the Midiman C02.
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 rumored to be available for $200-$300, but seem hard to track down. A $700 converter is available from avscience, and $900 converter, the CVC 100, is available from Extron.
Note: The correct term for analog color-difference output is Y'Pb'Pr', not Y'Cb'Cr' (which is digital, not analog). To simplify things, this FAQ uses the term YUV in its generic sense to refer to color difference signals.
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/>).
It depends on your audio/video system and your DVD player. Most DVD players have 2 or 3 video hookup options and 3 audio hookup options. Choose the option with the best quality (indicated below) that is supported by your video and audio systems.
Warning: If you connect your DVD player to a VCR and then to your TV, you may have problems with discs that enable the player's Macrovision circuit. See 3.2.1.
Note: Most DVD players support widescreen signalling, which tells a widescreen display what the aspect ratio is so that it can automatically adjust. One standard (ITU-R BT.1119, used mostly in Europe) includes information in a video scanline. Another standard, for Y/C connectors, adds a 5V DC signal to the chroma line to designate a widescreen signal. Unfortunately, some switchers and amps throw away the DC component instead of passing it on to the TV.
Note: All DVD players have either a built-in Dolby Digital (AC-3) or MPEG audio decoder, or both. The decoder translates multi-channel audio into PCM audio. This is fed to the digital output and also converted to analog for standard audio output. Most players have only a 2-channel-output decoder, but some provide 6-channel output (details below).
It's generally not a good idea to route the video from your DVD player through your VCR. Most movies use Macrovision protection, which will cause problems such as a repeated darkening and lightening of the picture. See 1.11 and the Video RF section of 3.2 and for more info.
There are many variations on the DVD theme. There are two physical sizes: 12 cm (4.7 inches) and 8 cm (3.1 inches), both 1.2 mm thick. These are the same form factors as CD. A DVD disc can be single-sided or double-sided. Each side can have one or two layers of data. The amount of video a disc can hold depends on how much audio accompanies it and how heavily the video and audio are compressed. The oft-quoted figure of 133 minutes is apocryphal: a DVD with only one audio track easily holds over 160 minutes, and a single layer can actually hold up to 9 hours of video and audio if it's compressed to VHS quality.
At a rough average rate of 4.7 Mbps (3.5 Mbps for video, 1.2 Mbps for three 5.1-channel soundtracks), a single-layer DVD 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 10.08 Mbps limit).
For reference, a CD-ROM holds about 650 megabytes, which is 0.64 gigabytes or 0.68 billion bytes. In the list below, SS/DS means single-/double-sided, SL/DL/ML means single-/dual-/mixed-layer (where mixed means single layer on one side, double layer on the other side), gig means gigabytes (2^30), G means billions of bytes (10^9). (See note about giga vs. billion in section 7.2.)
Tip: It takes about two gigabytes to store one hour of average video.
The increase in capacity from CD-ROM is due to: 1) smaller pit length (~2.08x), 2) tighter tracks (~2.16x), 3) slightly larger data area (~1.02x), 4) more efficient channel bit modulation (~1.06x), 5) more efficient error correction (~1.32x), 6) less sector overhead (~1.06x). Total increase for a single layer is about 7 times a standard CD-ROM. There's a slightly different explanation at <http://www.mpeg.org/MPEG/DVD/General/Gain.html>.
The capacity of a dual-layer disc is slightly less than double that of a single-layer disc. The laser has to read "through" the outer layer to the inner layer (a distance of 20 to 70 microns). To reduce inter-layer crosstalk, the minimum pit length of both layers is increased from .4 um to .44 um. In addition, the reference scanning velocity is slightly faster -- 3.84 m/s, as opposed to 3.49 m/s for single layer discs. Longer pits, spaced farther apart, are easier to read correctly and are less susceptible to jitter. The increased length means fewer pits per revolution, which means reduced capacity per layer.
See 4.3 for details of recordable DVD (DVD-R and DVD-RAM).
Not as soon as most people hope (including Jim Cameron). DVD-18 technology is not yet out of the laboratory. It requires a completely different way of creating two layers. Single-sided, dual-layer discs are produced by putting one data layer on each substrate and gluing the halves together with transparent adhesive so that the pickup laser can read both layers from one side. But in order to get four layers, each substrate needs to hold two. This requires stamping a second data layer on top of the first, a much more complicated prospect. Even after new equipment is developed and installed in production lines, the yield (number of usable discs compared to bad discs) will be quite low until the process is fine tuned.
WAMO and others have announced progress with DVD-18 processes, but given how long it took for production of dual-layer, single-sided discs to become practical, it will take even longer before the yields of DS/DL discs can meet the replication demands of mainstream movie distribution, especially since low yields mean higher replication costs. In the interim we'll see DVD-14s (two layers on one side, one on the other), since they're a little easier to produce.
(My personal prediction is that we won't see commercial DVD-18 discs until fall 1999.)
DVD-Video is an application of DVD-ROM. DVD-Video is also an application of MPEG-2. This means the DVD format defines subsets of these standards to be applied in practice as DVD-Video. DVD-ROM can contain any desired digital information, but DVD-Video is limited to certain data types designed for television reproduction.
A disc has one track (stream) of MPEG-2 constant bit rate (CBR) or variable bit rate
(VBR) compressed digital video. A restricted version of MPEG-2 Main Profile at Main Level
(MP@ML) is used. SP@ML is also supported. MPEG-1 CBR and VBR video is also allowed. 525/60
(NTSC, 29.97 interlaced frames/sec) and 625/50 (PAL, 25 interlaced frames/sec) video
display systems are expressly supported. Coded frame rates of 24 fps progressive from
film, 25 fps interlaced from PAL video, and 29.97 fps interlaced from NTSC video are
typical. MPEG-2 progressive_sequence is not allowed, but interlaced sequences can contain
progressive pictures and progressive macroblocks. In the case of 24 fps source, the
encoder embeds MPEG-2 repeat_first_field flags into the video stream to make the decoder
either perform 3-2 pulldown for 60 (59.94) Hz displays or 2-2 pulldown (with 4% speedup)
for 50 Hz displays. In other words, the player doesn't really "know" what the
encoded rate is, it simply follows the MPEG-2 encoder's instructions to produce the
predetermined display rate of 25 fps or 29.97 fps. (No current players convert from PAL to
NTSC or NTSC to PAL. See 1.19.) It's
interesting to note that even interlaced source video is usually encoded as
progressive-structured MPEG pictures, with interlaced field-encoded macroblocks used only
when needed for motion. On a computer, which is not tied to the display refresh rate, the
repeat_first_field flags can be mostly ignored and the video can be shown as progressive
frames at the original rate. Computers can also improve the quality of interlaced source
by doubling fields and displaying them as progressive frames at twice the normal rate.
Most film source is encoded progressive; most video sources are encoded interlaced. These
may be mixed on the same disc, such as an interlaced logo followed by a progressive movie.
See 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 4:2:2 ITU-R 601 down to 4:2:0, allocating an average of 12 bits/pixel. (Color depth is still 24 bits, since color samples are shared across 4 pixels.) The uncompressed source is 124.416 Mbps for video source (720x480x12x30 or 720x576x12x25), or either 99.533 or 119.439 Mbps for film source (720x480x12x24 or 720x576x12x24). Using the traditional (and rather subjective) television measurement of "lines of horizontal resolution" DVD can theoretically produce 540 lines on a standard TV (720/(4/3)) and 405 on a widescreen TV (720/(16/9)). In practice, most DVD players provide about 500 lines because of filtering. VHS has about 230 (172 w/s) lines and laserdisc has about 425 (318 w/s).
Different players use different numbers of bits for the video digital-to-analog converter. Current best-quality players use 10 bits. This has nothing to do with the MPEG decoding process, since each original component signal is limited to 8 bits per sample. More bits in the player provide more "headroom" and more signal levels during digital-to-analog conversion, which can help produce a better picture.
Maximum video bitrate is 9.8 Mbps. 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 (or a 28:1 reduction from 100 Mbps film source). Raw channel data is read off the disc at a constant 26.16 Mbps. After 8/16 demodulation it's down to 13.08 Mbps. After error correction the user data stream goes into the track buffer at a constant 11.08 Mbps. The track buffer feeds system stream data out at a variable rate of up to 10.08 Mbps. After system overhead, the maximum rate of combined elementary streams (audio + video + subpicture) is 10.08. MPEG-1 video rate is limited to 1.856 Mbps with a typical rate of 1.15 Mbps.
Still frames (encoded as MPEG-2 I-frames) are supported and can be displayed for a specific amount of time or indefinitely. These are generally used for menus. Still frames can be accompanied by audio.
A disc also can have up to 32 subpicture streams that overlay the video for subtitles, captions for the hard of hearing, captions for children, karaoke, menus, simple animation, etc. These are full-screen, run-length-encoded bitmaps limited to four pixel types. For each group of subpictures, four colors are selected from a palette of 16 (from the YCrCb gamut), and four contrast values are selected out of 16 levels from transparent to opaque. Subpicture display command sequences can be used to create effects such as scroll, move, color/highlight, and fade. The maximum subpicture data rate is 3.36 Mbps, with a maximum size per frame of 53220 bytes.
In addition to subtitles in subpicture streams, DVD also supports NTSC Closed Captions. Closed Caption text is stored in the video stream as MPEG-2 user data (in packet headers) and is regenerated by the player as a line-21 analog waveform in the video signal, which then must be decoded by a Closed Caption decoder in the television. Although the DVD-Video spec mentions NTSC only, there is no technical reason PAL/SECAM DVD players could not be made to output the Closed Caption text in World System Teletext (WST) format; the only trick is to deal with frame rate differences. Unfortunate note: DVD Closed Caption MPEG-2 storage format is slightly different than the ATSC format.
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 can output video in four
different ways:
Letterbox (often abbreviated to LBX) means the video is shown in its theatrical aspect ratio, usually 1.85:1 or 2.40:1. Since this is wider than standard 4:3 TV, black bars must be added to the top and bottom. Pan & scan means the smaller TV "window" is panned and zoomed around the wider movie picture, chopping off the sides. However, most movies are shot soft matte, which means the full TV-sized film frame is used, with the top and bottom masked off in the theater. When transferred to video, the extra picture on the film can be included during the pan & scan process. For more details and nice visual aids see Leopold's "How Film Is Transferred to Video" page, <http://www.cs.tut.fi/~leopold/Ld/FilmToVideo>. A list of movie aspect ratios is at <http://cheezmo.com/wsmc>.
Video stored in 4:3 format is not changed by the player. It will appear normally on a standard 4:3 display. Widescreen systems will either enlarge it or add black bars to the sides. 4:3 video may have been formatted in various ways before being transferred to DVD. For example, it may have been letterboxed to hold video with a wider shape. Or it may have been panned & scanned from film composed for a wider theatrical presentation. All formatting done to the video prior to it being stored on the disc is transparent to the player. It merely reproduces the signal in standard 4:3 form.
Anamorphic (16:9) video can be displayed on widescreen equipment, which stretches the video back out to its original width. Alternatively, many new European standard TV's can reduce the vertical scan area to restore the proper aspect ratio without losing resolution (an automatic trigger signal is sent on SCART pin 8). If anamorphic video is shown unchanged on a standard 4:3 display, people will look tall and skinny as if they have been on a crash diet. Widescreen mode is 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 4 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; 4) pan & scan with a 1.78 window. 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, many 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 Laserviews Web site has a list of anamorphic DVD titles. Additional explanations of how anamorphic video works can be found at Greg Lovern's What's an Anamorphic DVD? page and Bill Hunt's The Big Squeeze: The ABCs of Anamorphic DVD article. More information can be found at the Anamorphic Widescreen Support Page.
Anamorphic video can also be converted by the player for display on standard 4:3 TVs in letterbox or pan & scan form. The conversion options available for each disc are determined by the producer of the disc.
For automatic letterbox mode, the player 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 using a "letterbox filter" that combines 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. Some players have better letterbox filters than others, using weighted averaging to combine lines (scaling 4 lines into 3 or merging the 3rd and 4th lines) rather than simply dropping one out of every four lines.
For automatic 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 a "center of interest" offset that's encoded in the video stream according to the preferences of the people who transferred the film to video. The pan & scan "window" is 75% of the full width, which reduces the horizontal pixels from 720 to 540. The pan & scan window can only travel laterally. This does not duplicate a true pan & scan process in which the window can also travel up and down and zoom in and out. Therefore, many DVD producers choose to put a separate pan & scan version on the disc in addition to the widescreen version. For this reason, and because because equipment for storing the picture shift information is not widely available, no movies have been released with auto pan & scan enabled, although a few discs use the pan & scan feature in menus so that the same menu video will work in both widescreen and 4:3 mode.
Anamorphosis causes no problems with line doublers and other video scalers, which simply duplicate the scan lines before they are stretched out by the widescreen display.
For anamorphic video, the pixels are fatter. Different pixel aspect ratios (none of them square) are used for each aspect ratio and resolution. 720-pixel and 704-pixel sizes have the same aspect ratio because the first includes overscan. Note that "conventional" values of 1.0950 and 0.9157 are for height/width (and are tweaked to match scanning rates). The table below uses less-confusing width/height values (y/x * h/w).
720x480 720x576
704x480 704x576 352x480 352x576
4:3 0.909 1.091 1.818 2.182
16:9 1.212 1.455 2.424 2.909
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)
There are two home-entertainment flavors of DVD: DVD-Video and DVD-Audio. Each supports high-definition multichannel audio. DVD-Audio includes higher-quality PCM audio.
LPCM is mandatory, with up to 6 channels at sample rates of 48/96/192 kHz (also 44.1/88.2/176.4 kHz) and sample sizes of 16/20/24 bits. This allows theoretical frequency response of up to 96 kHz and dynamic range of up to 144 dB. Multichannel PCM will be downmixable by the player, although at 192 and 176.4 kHz only two channels are available. Sampling rates and sizes can vary for different channels by using a predefined set of groups. The maximum data rate is 9.6 Mbps.
The WG4 decided to include lossless compression (it's about time!), and on August 5, 1998 approved Meridian's MLP (Meridian Lossless Packing) scheme, already licensed by Dolby. MLP removes redundancy from the signal to achieve a compression ratio of about 2:1 while allowing the PCM signal to be completely recreated by the MLP decoder (required in all DVD-Audio players). MLP allows playing times of about 74 to 135 minutes of 6-channel 96kHz/24-bit audio on a single layer (compared to 45 minutes without packing). Two-channel 192kHz/24-bit playing times are about 120 to 140 minutes (compared to 67 minutes without packing).
Other audio formats of DVD-Video (Dolby Digital, MPEG audio, and DTS, described below) are optional on DVD-Audio discs, although Dolby Digital is required for audio content that has associated video. A subset of DVD-Video features (no angles, no seamless branching, etc.) is allowed. It's expected that shortly after DVD-Audio players appear, new universal DVD players will also support all DVD-Audio features.
DVD-Audio includes specialized downmixing features. Unlike DVD-Video, where the decoder controls mixing from 6 channels down to 2, DVD-Audio includes coefficent tables to control mixdown and avoid volume buildup from channel aggregation. Up to 16 tables can be defined by each Audio Title Set (album), and each track can be identified with a table. Coefficients range from 0dB to 60dB. This feature goes by the horribly contrived name of SMART (system-managed audio resource technique).
DVD-Audio allows up to 16 still graphics per track, with a set of limited transitions. On-screen displays can be used for synchronized lyrics and navigation menus. A special simplified navigation mode can be used on players without a video display.
Sony and Philips are promoting SACD, a competing format based on Direct Stream Digital (DSD) with sampling rates of up to 100 kHz. DSD is based on the pulse-density modulation (PDM) technique that uses single bits to represent the incremental rise or fall of the audio waveform. This supposedly improves quality by removing the brick wall filters required for PCM encoding. It also makes downsampling more accurate and efficient. DSD provides frequency response from DC to over 100 kHz with a dynamic range of over 120 dB. DSD includes a lossless encoding technique that produces approximately 2:1 data reduction by predicting each sample and then run-length encoding the error signal. Maximum data rate is 2.8 Mbps.
SACD includes a physical watermarking feature. Pit signal processing (PSP) modulates the width of pits on the disc to store a digital watermark (data is stored in the pit length). The optical pickup must contain additional circuitry to read the PSP watermark, which is then compared to information on the disc to make sure it's legitimate. Because of the requirement for new watermarking circuitry, SACD discs are not playable in existing DVD-ROM drives.
SACD includes text and still graphics, but no video.
The following details are for audio tracks on DVD-Video. Some DVD manufacturers such as Pioneer are developing audio-only players using the DVD-Video format. Some DVD-Video discs contain mostly audio with only video still frames.
A DVD-Video disc can have up to 8 audio tracks (streams). Each track can be in one of
three formats:
Two additional optional formats are provided: DTS and SDDS. Both require external decoders and are not supported by all players.
The ".1" refers to a low-frequency effects (LFE) channel that connects to a subwoofer. This channel carries an emphasized bass audio signal.
Linear PCM is uncompressed (lossless) digital audio, the same format used on CDs and most studio masters. It can be sampled at 48 or 96 kHz with 16, 20, or 24 bits/sample. (Audio CD is limited to 44.1 kHz at 16 bits.) There can be from 1 to 8 channels. The maximum bitrate is 6.144 Mbps, which limits sample rates and bit sizes with 5 or more channels. It's generally felt that the 96 dB dynamic range of 16 bits or even the 120 dB range of 20 bits combined with a frequency response of up to 22,000 Hz from 48 kHz sampling is adequate for high-fidelity sound reproduction. However, additional bits and higher sampling rates are useful in studio work, noise shaping, advanced digital processing, and three-dimensional sound field reproduction. DVD players are required to support all the variations of LPCM, but some of them may subsample 96 kHz down to 48 kHz, and some may not use all 20 or 24 bits. The signal provided on the digital output for external digital-to-analog converters may be limited to less than 96 kHz and less than 24 bits.
Dolby Digital is multi-channel digital audio, using lossy AC-3 coding technology from original PCM with a sample rate of 48 kHz at up to 24 bits. The bitrate is 64 kbps to 448 kbps, with 384 being the normal rate for 5.1 channels and 192 being the normal rate for stereo (with or without surround encoding). (Most Dolby Digital decoders support up to 640 kbps.) The channel combinations are (front/surround): 1/0, 1+1/0 (dual mono), 2/0, 3/0, 2/1, 3/1, 2/2, and 3/2. The LFE channel is optional with all 8 combinations. For details see ATSC document A/52 <http://www.atsc.org/document.html>. Dolby Digital is the format used for audio tracks on almost all DVDs.
MPEG audio is multi-channel digital audio, using lossy compression from original PCM format with sample rate of 48 kHz at 16 bits. Both MPEG-1 and MPEG-2 formats are supported. The variable bitrate is 32 kbps to 912 kbps, with 384 being the normal average rate. MPEG-1 is limited to 384 kbps. Channel combinations are (front/surround): 1/0, 2/0, 2/1, 2/2, 3/0, 3/1, 3/2, and 5/2. The LFE channel is optional with all combinations. The 7.1 channel format adds left-center and right-center channels, but will probably be rare for home use. MPEG-2 surround channels are in an extension stream matrixed onto the MPEG-1 stereo channels, which makes MPEG-2 audio backwards compatible with MPEG-1 hardware (an MPEG-1 system will only see the two stereo channels.) MPEG Layer III (MP3) and MPEG-2 AAC (aka NBC, aka unmatrix) are not supported by the DVD-Video standard.
DTS (Digital Theater Systems) Digital Surround is an optional multi-channel (5.1) digital audio format, using lossy compression from PCM at 48 kHz at up to 20 bits. The data rate is from 64 kbps to 1536 kbps (though the DTS Coherent Acoustics format supports up to 4096 kbps for lossless compression). Channel combinations are (front/surround): 1/0, 2/0, 3/0, 2/1, 2/2, 3/2. The LFE channel is optional with all 6 combinations. The DVD standard includes an audio stream format reserved for DTS, but many players ignore it. According to DTS, existing DTS decoders will work with DTS DVDs. All DVD players can play DTS audio CDs. See 1.32 for general DTS information. For more info visit <http://www.dtstech.com/>.
SDDS (Sony Dynamic Digital Sound) is an optional multi-channel (5.1 or 7.1) digital audio format, compressed from PCM at 48 kHz. The data rate can go up to 1280 kbps. SDDS is a theatrical film soundtrack format based on the ATRAC compression format that is also used by Minidisc. Sony has not announced any plans to support SDDS on DVD.
THX (Tomlinson Holman Experiment) is not an audio format. It's simply an additional set of processes applied by THX-certified surround sound amplifiers. "THX 4.0" processing is added to Dolby Pro Logic: crossover sends bass from front channels to subwoofer; re-equalization on front channels; timbre matching on rear channels; decorrelation of rear channels; bass curve that emphasizes low frequencies. "THX 5.1" processing is added to Dolby Digital and improves on 4.0: rear speakers are now full range, so crossover sends bass from both front and rear to subwoofer; decorrelation is turned on automatically when rear channels have the same audio, but not during split-surround effects, which don't need to be decorrelated.
Discs containing 525/60 video (NTSC) must use PCM or Dolby Digital on at least one track. Discs containing 625/50 video (PAL/SECAM) must use PCM or MPEG audio or Dolby Digital on at least one track. Additional tracks may be in any format. A few first-generation players, such as those made by Matsushita, can't output MPEG-2 audio to external decoders.
The original spec required either MPEG audio or PCM on 625/50 discs. There was a brief scuffle led by Philips when early discs came out with only two-channel MPEG and multichannel Dolby Digital, but the DVD Forum clarified in May 1997 that only stereo MPEG audio was mandatory for 625/50 discs. In December 1997 the lack of MPEG-2 encoders (and decoders) was a big enough problem that the spec was revised to allow Dolby Digital as the only audio track on 625/50 discs.
For stereo output (analog or digital), all players have a built-in 2-channel Dolby Digital decoder that downmixes from 5.1 channels (if present on the disc) to Dolby Surround stereo (i.e., 5 channels are matrixed into 2 channels to be decoded to 4 by an external Dolby Pro Logic processor). PAL players also have an MPEG or MPEG-2 decoder. Both Dolby Digital and MPEG-2 support 2-channel Dolby Surround as the source in cases where the disc producer can't or doesn't want to remix the original onto discrete channels. This means that a DVD 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. Sony players can optionally downmix to non-surround stereo.
The Dolby Digital downmix process does not usually include the LFE channel and may compress the dynamic range in order to improve dialog audibility and keep the sound from becoming "muddy" on average home audio systems. This can result in reduced sound quality on high-end audio systems. Some players have the option to turn off the dynamic range compression. The downmix is auditioned when the disc is prepared, and if the result is not acceptable the audio may be tweaked or a separate L/R Dolby Surround track may be added. Experience has shown that minor tweaking is sometimes required to make the dialog more audible within the limited dynamic range of a home stereo system, but that a separate track is not usually necessary. If surround audio is important to you, you will hear significantly better results from multichannel discs if you have a Dolby Digital system.
All five audio formats support karaoke mode, which has two channels for stereo (L and R) plus an optional guide melody channel (M) and two optional vocal channels (V1 and V2).
A DVD-5 with only one surround stereo audio stream (at 192 kbps) can hold over 55 hours of audio. A DVD-18 can hold over 200 hours.
Many people complain that the audio level from DVD players is too low. In truth the audio level is too high on everything else. Movie soundtracks are extremely dynamic, ranging from near silence to intense explosions. In order to support an increased dynamic range and hit peaks (near the 2V RMS limit) without distortion, the average sound volume must be lower. This is why the line level from DVD players is lower than from almost all other sources. And so far, unlike on CDs and LDs, the level is much more consistent between discs.
For more information about multichannel surround sound, see Bobby Owsinski's FAQ at <http://www.surroundassociates.com/safaq.html>.
DVD-Video players (and software DVD-Video navigators) support a command set that provides rudimentary interactivity. The main feature is menus, which are present on almost all discs to allow content selection and feature control. Each menu has a still-frame graphic and up to 36 highlightable, rectangular "buttons" (only 12 if widescreen, letterbox, and pan & scan modes are used). Remote control units have four arrow keys for selecting onscreen buttons, plus numeric keys, select key, menu key, and return key. Additional remote functions may include freeze, step, slow, fast, scan, next, previous, audio select, subtitle select, camera angle select, play mode select, search to program, search to part of title (chapter), search to time, and search to camera angle. Any of these features can be disabled by the producer of the disc.
Additional features of the command set include simple math (add, subtract, multiply, divide, modulo, random), bitwise and, bitwise or, bitwise xor, plus comparisons (equal, greater than, etc.), and register loading, moving, and swapping. There are 24 system registers for information such as language code, audio and subpicture settings, and parental level. There are 16 general registers for command use. A countdown timer is also provided. Commands can branch or jump to other commands. Commands can also control player settings, jump to different parts of the disc, and control presentation of audio, video, subpicture, camera angles, etc.
DVD-V content is broken into "titles" (movies or albums), and "parts of titles" (chapters or songs). Titles are made up of "cells" linked together by one or more "program chains" (PGC). A PGC can be 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 needed (and cuts the playing time in half).
Yes, if your computer has the right stuff. The computer operating system or playback software must support regional codes and be licensed to descramble copy-protected movies. If the computer has TV video out, it must support Macrovision in order to play copy-protected movies. You may also need software that can read the MicroUDF file system format used by DVDs. In addition to a DVD-ROM drive you must have extra hardware to decode MPEG-2 video and Dolby Digital or MPEG-2 audio, or your computer must be fast enough to handle software decoding. Decent software-only playback requires a 300-MHz Pentium II or Mac G3. It's estimated that 10-30% of new computers with DVD-ROM drives include decoder hardware, and that most of the remaining DVD-ROM computers will include decoder software. Hardware upgrade kits can be purchased for existing computers (usually minimum 133 MHz Pentium), starting at $150. See <http://www.brouhaha.com/~eric/video/dvd> for a list of drives and upgrade kits.
Certain MPEG decoding tasks such as motion compensation and IDCT (inverse discrete cosine transform) can be performed by additional circuitry on a video graphics card, improving the performance of software decoders. This is called hardware decode acceleration or hardware motion comp.
Microsoft Windows 98 includes DirectShow 5.2, which provides standardized support for DVD-Video and MPEG-2 playback. DirectShow can also be installed in Windows 95. DirectShow 6.0 is available for download. DirectShow provides a standardized framework for DVD playback, but a third-party hardware or software decoder is still required (see below). Windows NT 4.0 doesn't support DVD-Video well at all, but Windows 2000 will use the same WDM drivers and DirectShow software as Windows 98. Internet Explorer 5.0 includes a new version of Windows Media Player that enables scriptable DVD plyaback in an HTML page. Windows 98 and newer can read UDF discs. Adaptec provides a free filesystem driver, UDF Reader, for Windows 95/98/NT. Software Architects sells Read DVD for Windows 95.
Apple QuickTime 3.0 is partially ready for DVD-Video and MPEG-2 but does not yet have full decoding or DVD-Video playback support in place. Mac OS 8.1 or newer can read UDF discs. Adaptec provides a free utility, UDF Volume Access, that enables Mac OS 7.6 and newer to read UDF discs. Software Architects sells UDF reading software for Mac OS called DVD-RAM TuneUp.
Note: The QuickTime MPEG Extension for MacOS is for MPEG-1 only and does not play MPEG-2 DVD-Video.
Some DVD-ROMs and a few DVD-Videos use video encoded using MPEG-1 instead of MPEG-2. Most recent computers have MPEG-1 hardware built in or are able to decode MPEG-1 with software.
DVD player applications (using either software or hardware decoding) are virtual DVD players. They support most DVD-Video features (menus, subpictures, etc.) and emulate the functionality of a DVD-Video player remote control. Many player applications include additional features such as bookmarks, chapter lists, and subtitle language lists.
Software decoders and DVD player applications for Microsoft Windows PCs are made by CyberLink (PowerDVD), InterVideo, Mediamatics (DVD Express), MGI, NEC, Odyssey, QI (Software CineMaster), Xing, Zoran (SoftDVD), and others. Only CyberLink, Odyssey, and Xing decoders are available for retail purchase, the others are bundled with OEM DVD PCs. A special low-cost version of the QI software decoder is available for download from the ATI web site for use with ATI video cards. CyberLink, InterVideo, and Odyssey don't yet support DirectShow. Software decoders need at least a 233 MHz Pentium II and an IDE/SCSI DVD-ROM drive with bus mastering DMA to achieve about 24 frames/sec film rates, or require better than 350 MHz for 30 frames/sec video. An AGP video card and hardware video acceleration improve performance of software decoders.
Hardware decoder cards and DVD-ROM upgrade kits for Microsoft Windows PCs are made by Creative Technology (Encore, C-Cube chip), E4 (Elecede) (Cool DVD, C-Cube chip) [E4 has apparently gone out of business], IBM (ThinkPad laptops, IBM chip), LeadTek (WinFast 3D S800, Mpact2 chip), Margi (DVD-to-Go, ZV PC card for laptops), QI (Hardware Cinemaster, C-Cube chip), Sigma Designs (Hollywood, Sigma chip), STB (DVD Theater, Mpact2 chip), Toshiba (Tecra laptops, Toshiba chip), and others. The Sigma Designs decoder card is used in decoder upgrade kits from Hitachi, HiVal, Panasonic, Phillips, Sony, and Toshiba. The advantage of hardware decoders is that they don't eat up CPU processing power, and they often produce better quality video than software decoders.
A few models of Macintosh PowerBook and G3 lines can be ordered with DVD-ROM drives and hardware decoders. DVD-ROM upgrade kits and decoder cards for Macintoshes are made by E4 (Elecede) (Cool DVD, C-Cube chip) [E4 has apparently gone out of business], EZQuest (BOA Mac DVD), and Wired (Wired 4DVD Sigma EM8300 chip; MasonX [can't play encrypted movies!]; DVD-To-Go [out of production]).
If you have at least a 433 MHz Alpha workstation you'll be able to play DVD movies at full 30 fps in software.
Unfortunately, even though computers have the potential to produce better video than settop DVD-Video players by using progressive display and higher scan rates, many current systems don't look as good as a home player hooked up to a quality TV.
If you want to hook a DVD computer to a TV, the decoder card or the VGA card must have a TV output (composite video or s-video). Alternatively, you can connect a scan converter to the VGA output. The quality of the video will depend on the decoder, the TV encoder chip, and other factors, but will usually be a little inferior to a good consumer DVD player.
For remote control of DVD playback on your PC, check out the Animax Anir Multimedia Magic infrared remote control.
Unlike CD-ROM drives, which took years to move up to 2x, 3x, and faster spin rates, faster DVD-ROM drives began appearing in the first year. Most 1x DVD-ROM drives have a seek time of 90-200 ms and access time of 100-250 ms. 1x DVD-ROM drives provide a data transfer rate of 1.321 MB/s (11.08*10^6/8/2^20) with burst transfer rates of up to 12 MB/s or higher. The data transfer rate from a DVD-ROM disc at 1x speed is roughly equivalent to a 9x CD-ROM drive (1x CD-ROM data transfer rate is 150 KB/s, or 0.146 MB/s). DVD spin rate is about 3 times faster than CD (that is, 1x DVD ~ 3x CD), but almost all DVD-ROM drives increase motor speed when reading CD-ROMs, achieving 12x or faster performance. 2x DVD-ROM drives are available (providing a transfer rate of 22.2 Mbps or 2.6 MB/s from DVDs, equivalent to an 18x CD-ROM rate). Most 2x DVD-ROM drives read CD-ROMs at 20x (max) speeds and higher. 4x, 4.8x, 5x, and 6x drives are also appearing, although they usually don't achieve a sustained transfer rate at their full rating. A 5x drive can theoretically transfer data at 55.4 Mbps or 6.4 MB/s, equivalent to a 45x CD-ROM data rate. Most 4x and faster DVD-ROM drives read CD-ROMs at 32x (max).
Note: When playing movies, a fast DVD-ROM drive gains you nothing more than possibly smoother scanning and faster searching. Speeds above 1x do not improve video quality from DVD-Video discs. Higher speeds only make a difference when reading computer data, such as when playing a multimedia game or when using a database.
Connectivity is similar to that of CD-ROM drives: EIDE (ATAPI), SCSI-2, etc. All DVD-ROM drives have audio connections for playing audio CDs. No DVD-ROM drives have been announced with DVD audio or video outputs (which would require internal audio/video decoding hardware). In order to hook a DVD-ROM PC to a television and a stereo receiver, the decoder card or the video card must have a TV video output and an audio output. Some cards have SP/DIF outputs to connect to digital audio receivers. If there's no video output, a TV scan converter can be connected to the VGA output.
Almost all DVD-Video and DVD-ROM discs use the UDF Bridge format, which is a combination of the DVD MicroUDF and ISO 9660 file systems. The OSTA UDF file system will eventually replace the ISO 9660 system originally designed for CD-ROMs, but the bridge format provides backwards compatibility until more operating systems support UDF.
There are four recordable versions of DVD-ROM: DVD-R, DVD-RAM, DVD-RW, and DVD+RW. DVD-R can record data once (sequentally only), while DVD-RAM, DVD-RW, and DVD+RW can be rewritten thousands of times. Final versions of the DVD-R and DVD-RAM version 1.0 specifications were published in August 1997 (see 6.1). DVD-RW 1.0 and DVD-R 2.0 are being finalized in early 1999. These recordable media are not currently usable for home video recording (see 1.14), though home DVD recorders will eventually become available. The three erasable formats (DVD-RAM, DVD-RW, and DVD+RW) are essentially in competition with each other. The market will determine which of them succeed. At the moment, DVD-RAM has a one-year head start.
Each format is reviewed briefly below. For more on writable DVD, see Dana Parker's article at <http://www.emediapro.net/EM1999/parker1.html>.
DVD-R uses organic dye polymer technology, like CD-R, and is compatible with almost all DVD drives and players (the Sony DVP-S7000 and DVP-S3000 being notable exceptions). First-generation capacity is 3.95 billion bytes, but will be extended to 4.7 billion bytes around mid 1999. Matching the 4.7G capacity of DVD-ROM is crucial for desktop DVD-ROM and DVD-Video production.
DVD-RW (formerly DVD-R/W and also briefly known as DVD-ER) is a phase-change erasable format that will be available around the middle of 1999. Developed by Pioneer based on DVD-R, using the similar track pitch, mark length, and rotation control, DVD-RW will be playable in most DVD drives and players. (Some drives and players are confused by DVD-RW media's lower reflectivity into thinking its a dual-layer disc. Simple firmware upgrades will be required to solve the problem.) DVD-RW uses groove recording with address info on land areas for synchronization at write time (land data is unnecessary during reading). Initial capacity will be 4.7 billion bytes.
Pioneer released DVD-R drives in October 1997 (about 6 months late) for $17,000. The price will drop to less than $5,000 for the new 4.7G drives that combine DVD-R and DVD-RW. Price for blank DVD-Rs is about $40. Initial DVD-RW prices will be about the same. Blank media is being made by Eastman Kodak, Hitachi Maxell, Mitsubishi, Mitsui, Pioneer, Ricoh, TDK, and Victor. Ricoh, Yamaha, and Sony will join Pioneer in making 4.7G DVD-R/RW drives.
The advantages of DVD-R and DVD-RW drives, which are used primarily for DVD production, are higher capacity and compatibility with most DVD players and drives.
DVD-R and DVD-RW discs are expected to last anywhere from 50 to 300 years, about as long as CD-R discs. See <http://www.ee.washington.edu/conselec/CE/kuhn/otherformats/95x9.htm> for more info.
The DVD-R format is standardized in ECMA-279.
DVD-RAM, with an initial storage capacity of 2.58 billion bytes, uses phase-change (PD) technology with some MO features mixed in and is not compatible with current drives (because of defect management, reflectivity differences, and minor format differences). A wobbled groove is used to provide clocking data, with marks written in both the groove and the land between grooves. The grooves and pre-embossed sector headers are molded into the disc during manufacturing. Single-sided DVD-RAM discs come with or without cartridges. There are two types of cartridges: type 1 is sealed, type 2 allows the disc to be removed. Discs can only be written while in the cartridge. Double-sided DVD-RAM discs are available in sealed cartridges only. Cartridge dimensions are 124.6mm x 135.5mm x 8.0mm. Blank DVD-RAM media is manufactured by Hitachi Maxell, Mitsubishi, Mitsui, and TDK. Future DVD-RAM discs may use a contrast enhancement layer and a thermal buffer layer to achieve higher density. Hitachi has announced reaching 4.7 billion bytes by reducing mark size from 0.41/0.43 microns to 0.28/0.30 microns and track pitch from 0.74 microns to 0.59 microns.
DVD-RAM drives appeared in June 1998 (about 6 months late) for $500 to $800, with blank discs at about $30 for single-sided and $45 for double-sided. Disc prices were under $20 by August 1998. The first DVD-ROM drive that can read DVD-RAM discs is being released by Panasonic in late 1998 (SR-8583, 5x DVD-ROM, 32x CD).
The DVD-RAM format is standardized in ECMA-272 and ECMA-273.
Phase-Change Rewritable, officially called +RW in standards documents, is a competing erasable format announced by Philips, Sony, Hewlett-Packard and others based on DVD and CD-RW technology. DVD+RW is not supported by the DVD Forum (even though the DVD+RW companies are members), but the Forum has no power to set standards. DVD+RW drives will read DVD-ROMs and CDs, and probably DVD-Rs and DVD-RWs, but will not be compatible with DVD-RAM discs. Because of reflectivity differences, linking sectors, and defect management, DVD+RW discs can't be read by existing DVD-Video players or DVD-ROM drives, except for the very newest drives from Sony and Philips. So far none of the three major DVD-ROM drive makers (Hitachi, Matsushita, and Toshiba, all backers of DVD-RAM) have announced plans to make their drives read DVD+RW discs. The DVD+RW format, which holds 3 billion bytes (2.8 gigabytes) per side, uses phase-change technology with wobbled groove and either CLV format for sequential video access (read at CAV speeds by drive) or CAV format for random access. DVD+RW will not be ready for production until mid 1999 at the earliest. Its backers claimed in 1997 that it would be used only for computer data, not home video, but recent developments indicate that this was a smokescreen intended to placate the DVD Forum and competitors. Second-generation DVD+RW drives, which will appear around mid 2000, will support 4.7 billion bytes and are expected to write CD-Rs and CD-RWs. The 4.7G DVD+RW format will use a high-frequency wobbled groove that allows it to eliminate linking sectors. This change, plus the option of no defect management, allows DVD+RW discs to be written in a way that should be compatible with most existing DVD-Video players and DVD-ROM drives, as well as DVD-R, DVD-RW, and DVD-RAM drives. More DVD+RW information is at <http://www.dvdrw.org/>
The DVD+RW format is standardized in ECMA-274.
Other upcoming potential competitors to recordable DVD include AS-MO (formerly MO7), which holds 5 to 6 billion bytes, and NEC's MMVF (Multimedia Video Format), which holds 5.2 billion bytes and is targeted at home recording. Both are expected to read DVD-ROM but not DVD-RAM or first-generation DVD+RW. MMVF is similar to DVD-RW and DVD+RW, using two bonded 0.6mm phase-change substrates, land and groove recording, and a 640nm laser.
Most DVD PCs, even those with software decoders, use video overlay hardware to insert the video directly into the VGA signal. This an efficient way to handle the very high bandwidth of full-motion video. Some systems, such as the Creative Labs Encore Dxr decoder, use a pass-through cable that overlays the video into the analog VGA signal after it comes out of the video display card. Video overlay uses a technique called colorkey to selectively replace a specified pixel color (often magenta or near black) with video content. Anywhere a colorkey pixel appears in the computer graphics video, it's replaced by video from the DVD decoder. This process occurs "downstream" from the computer's video memory, so if you try to take a screenshot (which grabs pixels from video RAM), all you get is a solid square of the colorkey color.
Almost all movies are encrypted with CSS copy protection. (See 1.11). Decryption keys are stored in a normally inaccessible area of the disc. If you copy the contents of an encrypted DVD to a hard drive, the keys will not be copied. If you try to play the VOB files, the decoder will request the keys from the DVD-ROM drive and will fail. You may get the message "Cannot play copy protected files".
DVD production has two basic phases: development and replication. Development is different for DVD-ROM and DVD-Video, replication is essentially the same for both.
DVD-ROMs can be developed with traditional software development tools such as Macromedia Director, Asymetrix Toolbook, HyperCard, Quark mTropolis, and C++. Discs, including DVD-R check discs, can be created with UDF formatting software (see 5.3). DVD-ROMs that take advantage of DVD-Video's MPEG-2 video and multichannel Dolby Digital or MPEG-2 audio require video and audio encoding (see 5.3).
DVD-Video development has three basic parts: encoding, authoring (design, layout, and testing), and premastering (formatting a disc image). The entire development process is sometimes referred to as authoring. Development facilities are provided by many service bureaus (see 5.5). If you intend to produce numerous DVD-Video titles (or you want to set up a service bureau), you may want to invest in encoding and authoring systems (see 5.3 and 5.4).
Replication (including mastering) is usually a separate job done by large plants that also replicate CDs (see 5.5). DVD replication equipment typically costs millions of dollars. Most replication plants provide "one-off" or "check disc" services, where one to a hundred discs are made for testing before mass duplication. Unlike DVD-ROM, DVD-Video mastering may include an additional step for CSS encryption, Macrovision, and regionalization.
Videotape, laserdisc, and CD-ROM can't be compared to DVD in a straightforward manner. There are basically three stages of costs: production, pre-mastering (authoring, encoding, and formatting), and mastering/replication.
DVD 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 $20,000. If you want to do pre-mastering yourself, authoring and encoding systems can be purchased at prices from $50,000 to over $2 million. These will drop very rapidly in the next few years to where DVDs can be produced on a desktop computer system that costs less than $20,000.
Videotapes don't really have a mastering cost, and they run about $2.40 for replication. CDs cost about $1,000 to master and $0.50 to replicate. Laserdiscs cost about $3,000 to master and about $8 to replicate. As of July 1998, DVDs cost about $2000 to master and about $1.70 to replicate. Since DVD production is based mostly on the same equipment used for CD production, mastering and replication costs will drop to CD levels. Pre-mastering costs are mostly for authoring systems and encoding systems which cost tens of thousands of dollars, but these too will get much cheaper in the next few years.
Double-sided or dual-layer discs cost only a little more to replicate, since all that's required is stamping data on the second substrate (and using transparent glue for dual layers). Double-sided, dual-layer discs (DVD-18s) are more difficult and not yet commercially available. (See 3.3.1.)
Features to look for in DVD formatters:
[A] Authoring (including encoding, DVD-R copies, and premastering).
[R] Replication (mastering and/or one-offs).
See Robert's DVD Info page <http://www.unik.no/~robert/hifi/dvd/>
for more pointers.
DVD is the work of Matsushita, Toshiba, 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, Matsushita, 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 standard was developed by a consortium of 10 companies: Hitachi, JVC, Matsushita, Mitsubishi, Philips, Pioneer, Sony, Thomson, Time Warner, and Toshiba. Working groups with representatives from many other companies also contributed. In May 1997 the Consortium was replaced by the DVD Forum, which is open to all companies (more info at <http://www.dvdforum.com/>). Visit Robert's DVD Info page <http://www.unik.no/~robert/hifi/dvd/> for links to Web pages of companies working with DVD.)
The official DVD specification books are available from Toshiba after signing a nondisclosure agreement and paying a $5000 fee. Contact Toshiba DVD Products 1-1 Shibaru 1-Chome, Minato-ku, Tokyo 105-01, Japan, 81-3-3457-2473, fax 81-3-5444-9401. ECMA has developed international standards for DVD-ROM (the smallest part of the DVD spec), available for free download as ECMA-267 and ECMA-268 from http://www.ecma.ch/. ECMA has also standardized DVD-R in ECMA-279, DVD-RAM in ECMA-272 and ECMA-273, and DVD+RW as ECMA-274 (see 4.3). Unfortunately, ECMA has the annoying habits of spelling disc wrong and (if you're from the U.S.) using a comma instead of a period for the decimal point. The UDF file system used by DVD is available from http://www.osta.org/.
Any company making DVD products must license the patented technology from a Philips/Pioneer/Sony pool, a Hitachi/Matsushita/Mitsubishi/Time Warner/Toshiba/Victor pool, and from Thomson. Total royalties are about 5% for a DVD-Video player, $6 for a DVD-ROM drive and decoder, and 10 cents for a DVD disc. Matsushita licenses the CSS encryption technology free of charge; contact CSS Interim License Organization, 2-15 Matsuba-cho, Kadoma, Osaka 571 Japan, 81-6-905-4155, fax 81-6-901-9299. Macrovision licenses its analog anti-recording technology free of charge to hardware makers, but charges a per-copy royalty to content publishers. The DVD format and logo must also be licensed; contact Toshiba DVD Business Promotion and Support: 81-3-5444-9580, fax 81-3-5444-9430. An MPEG-2 patent license may also be required, from MPEG LA (Licensing Adminstrator). Cost is about $4 for a DVD player or decoder card and 4 cents for each DVD disc, although there seems to be disagreement on whether content producers owe royalties for discs. Contact MPEG LA for more info: <http://www.mpegla.com/>.
A list of studio addresses is available at <http://www.high-rez.com/contacts.htm>
Here are a few of the top DVD info pages.
You might also want to take a look at the book DVD Demystified, by the author of this FAQ. More info at <http://www.videodiscovery.com/dvd>.
(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 1000 (10^3, 10^6, and 10^9), but when used in the computer world to measure bytes they generally represent multiples of 1024 (2^10, 2^20, and 2^30). Both Windows and Mac OS list volume capacities in "true" megabytes and gigabytes, not millions and billions of bytes
Most DVD figures are based on multiples of 1000, in spite of using notation such as GB and KB/s that traditionally have been based on 1024. The "G bytes" notation does seem to consistently refer to 10^9. The closest I have been able to get to an unambiguous notation is to use "kbps" for thousands of bits/sec, "Mbps" for millions of bits/sec, "kilobytes" for 1024 bytes, "megabytes" for 1,048,576 bytes, and "gigabytes" for 1,073,741,824 bytes.
This FAQ is written and maintained by Jim Taylor. The following people have contributed to the FAQ (either directly, by posting to alt.video.dvd, or by me borrowing from their writing :-). Their contributions are deeply appreciated. Information has also been taken from material distributed at the April 1996 DVD Forum, May 1997 DVD-R/DVD-RAM Conference, and October 1998 DVD Forum Conference.
Robert Lundemo Aas
David Boulet
Espen Braathen
Wayne Bundrick
Roger Dressler
Chad Fogg
Dwayne Fujima
Robert "Obi" George
Henrik "Leopold" Herranen
Irek Defee
Kilroy Hughes
Ralph LaBarge
Martin Leese
Dana Parker
Eric Smith
Steve Tannehill
Geoffrey Tully
----
This document may be freely redistributed only in its entirety with version date, authorship notice, and acknowledgements intact. No part of it may be sold for profit or incorporated in a commercial document without the permission of the copyright holder. Permission is 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.
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