This is the 8-Nov-96 revision of the FAQ for the alt.video.dvd Usenet
newsgroup.
Please send corrections, additions, and new questions to Jim Taylor <mailto:jhtaylor@videodiscovery.com>.
Where can I get this FAQ?
- It will be posted periodically to alt.video.dvd and news.answers as
"alt.video.dvd Frequently Asked Questions (FAQ)".
-
The most current version is on the Web at <http://www.videodiscovery.com/vdyweb/dvd/dvdfaq.html>.
DVD, which stands for Digital Video Disc, Digital Versatile Disc, or
nothing, depending on whom you ask, is the next generation of optical disc
storage technology. It's essentially a bigger, faster CD that can hold
video as well as audio and computer data. DVD aims to encompass home entertainment,
computers, and business information with a single digital format, eventually
replacing audio CD, videotape, laserdisc, CD-ROM, and perhaps even video
game cartridges. DVD has widespread support from all major electronics
companies, all major computer hardware companies, and most major movie
and music studios, which is unprecedented and says much for its chances
of success (or, pessimistically, the likelihood of it being forced down
our throats).
It's important to understand the difference between DVD-Video and DVD-ROM.
DVD-Video (often simply called DVD) holds video programs and is played
in a DVD player hooked up to a TV. DVD-ROM holds computer data and is read
by a DVD-ROM drive hooked up to a computer. The difference is similar to
that between Audio CD and CD-ROM. DVD-ROM also includes future variations
that are recordable one time (DVD-R) or many times (DVD-RAM). Most people
expect DVD-ROM to be initially much more successful than DVD-Video.
There's also a DVD-Audio format. The technical specifications for DVD-Audio
will not be finished for the first release of DVD.
[1.2] What are the features of DVD-Video?
- Over 2 hours of high-quality digital video.
- Support for widescreen movies and regular or widescreen TVs (4:3 and
16:9 aspect ratios).
- Up to 8 tracks of digital audio (for multiple languages), each with up
to 8 surround channels.
- Up to 32 subtitle/karaoke tracks.
- Automatic "seamless" branching of video (for different story
lines or ratings).
- Up to 9 viewer-selectable camera angles.
- Menus and simple interactive features (for games, quizzes, etc.).
- "Instant" rewind and fast forward, including search to title,
chapter, or track.
- Durability (no wear from playing, only from scratching).
- Not susceptible to magnetic fields.
Most players include additional features:
- Language choice (for automatic selection of video scenes, audio tracks,
subtitle tracks, and menus).
- Programmability (playback of selected sections in a desired sequence).
- Special effects playback (high speed, frame by frame, and slow motion).
- Parental lock (for denying playback of discs or scenes with objectionable
material).
- Search to any frame (by entering a timecode).
[1.3] What's the quality of DVD-Video?
DVD has the capability to produce near-studio-quality video and better-than-CD-quality
audio. DVD is vastly superior to videotape, and can be better than laserdisc
(see 2.8.). However, quality depends on many production
factors. Until compression knowledge and technology improves we will likely
see DVDs which are inferior to laserdiscs. Also, since large amounts of
video have already been encoded for VideoCD using MPEG-1, some early DVDs
will use that format (which is no better than VHS) instead of higher-quality
MPEG-2.
DVD video is compressed from studio CCIR-601 format to MPEG-2 format.
This is a "lossy" compression which attempts to remove redundant
information (such as sections of the picture that don't change) and information
that's not readily perceptible by the human eye. The resulting video, especially
when it is complex or changing quickly, may sometimes contain "artifacts"
such as blockiness or fuzziness. It depends entirely on the quality of
compression and how heavily the video is compressed. At average rates of
3.5 Mb/s (megabits/second), artifacts may be occasionally noticeable. Higher
data rates result in higher quality, with almost no perceptible difference
from the original master at rates above 6 Mb/s. As MPEG compression technology
improves, better quality will be achieved at lower rates.
One of DVD's audio formats is LPCM (linear pulse code modulation) with
sampling sizes and rates higher than audio CD. Audio can also be stored
as discrete multi-channel surround sound using Dolby Digital or MPEG-2
audio compression. These are similar to the surround sound formats used
in theaters but with higher compression. As with video, quality depends
very much on how well the encoding was done.
[1.4] What are the disadvantages of DVD?
- It can't record (yet).
- It can't play in reverse.
- It uses digital compression. Poorly compressed audio or video may be
blocky, fuzzy, harsh, or vague.
- It has built-in copy protection and regional lockout. (See 1.11
and 1.10)
- DVD players and drives may not be able to read CD-Rs. (See 2.4.3.)
- It will take years for movies and software to become widely available.
[1.5] When will DVD players and drives be available?
Some manufacturers, such as Thomson, originally announced that DVD players
would be available as early as the 2nd or 3rd quarter of 1996. These predictions
were woefully optimistic. Delivery has been held up mostly for "political"
reasons of copy protection demanded by movie studios. The first players
appeared from Matsushita (Panasonic) and Toshiba in Japan on November 1.
Samsung and LG Electronics will launch DVD players in Korea in November.
JVC, Philips, and Sony will not deliver at all until Spring 1997. JVC and
Philips will release in Japan and Europe in Summer 1997. Mitsubishi, Panasonic,
Pioneer, and Samsung players will not be available in the U.S. before early
1997. Toshiba says they will introduce players in the U.S. before 1997
only if there are enough DVD titles. Hitachi has delayed development and
will sell Pioneer-built players in the interim (in Japan).
Fujitsu released the first DVD-ROM-equipped computer on Nov. 6 in Japan.
Toshiba hopes to release a DVD-ROM-equipped computer and a DVD-ROM drive
in Japan in December. Toshiba plans to release by Christmas a DVD upgrade
kit in the U.S. for its Infinia line. Philips and Samsung have announced
that their DVD-ROM drives will be available in the 2nd quarter of 1997.
[1.6] When will DVD titles be available, and how
many?
As with hardware, rosy predictions of hundreds of movie titles for Christmas
of 1996 have failed to materialize. Time Warner originally announced they
would have 250 titles available for the launch of DVD, but they now say
only that they "hope" to have as many as 50 titles ready by the
first quarter of 1997.
At the November 1 launch of DVD players in Japan only 15 or so titles
were available. Toshiba EMI and Victor (JVC) delayed some DVD title releases
in Japan until mid-November to ensure compatibility with various DVD players.
Sony will release titles in the Spring when it launches its players.
The following are known to have been seen in demos, which may or may
not have anything to do with them being released first or ever: Batman
Forever, Cutthroat Island, Free Willy, The Fugitive, Grumpier Old Men,
Hell Freezes Over (Eagles tour), Outbreak, The Shadow, and Unforgiven.
DVD-ROM titles may begin appearing in late 1996. Approximately 40% of
CD-ROM producers have announced intentions to develop for DVD-ROM. As of
Aug. 1996, 30 DVD-ROM titles are supposedly in development for early 1997
release.
The first DVD-ROMs will probably be "PhoneDisc PowerFinder USA
One" (which filled 6 CD-ROMs) from Digital Directory Assistance Inc.,
and "Silent Steel" from Tsunami Media.
[1.7] How much do players and drives cost?
DVD movie players will initially cost $600 to $1,800. Within a few years
they may approach VCR prices.
DVD-ROM drives for computers will sell for around $400. (Philips has
announced an OEM price of $200 for Q2 1997). Prices will drop very quickly
to current CD-ROM drive levels.
[1.8] How much do discs cost?
It will vary. Many studios have promised that DVDs will be as cheap
or cheaper than videotapes (and much cheaper than laserdiscs). This remains
to be seen, especially for special editions with supplemental material
which cost much more to produce. Depending on how the DVD rental market
develops, new releases may initially be priced for rental (traditionally
around $80 for VHS). But existing titles, which have already made back
money, are expected to be priced below $25 on DVD.
DVD-ROMs will initially be more expensive than CD-ROMs since there is
more stored on them, they cost more to replicate, and the market is smaller.
But as costs drop and the installed base of drives grow, DVD-ROMs will
probably cost the same as CD-ROMs do today.
[1.9] How quickly will DVD become established?
Nobody knows. Here are a few predictions:
- Pioneer: 400,000 DVD-Video players in 1996, 11 million by 2000. 100,000
DVD-Audio players in 1996, 4 million by 2000.
- Time-Warner: 10 million DVD-Video players in the U.S. by 2002.
- C-Cube: 1 million players and drives in 1997.
- Dataquest: over 33 million shipments of DVD players and drives by 2000.
- Philips: 25 million DVD-ROM drives worldwide by 2000 (10% of projected
250 million optical drives).
- Pioneer: 500,000 DVD-ROM drives sold in 1997, 54 million sold in 2000.
- Toshiba: will no longer make CD-ROM drives in 2000.
- IDC: 10 million DVD-ROM drives sold in 1997, 70 million sold in 2000,
118 million sold in 2001.
- Intel: 70 million DVD-ROM drives by 1999 (sales will surpass CD-ROM drives
in 1998).
For comparison, there are about 600 million audio CD players and 100 million
CD-ROM drives worldwide. There are about 80 million VCRs in the U.S. [Anybody
know how many worldwide?]
[1.10] What are "regional codes," "country
codes," or "zone locks"?
Motion picture studios want to control the home release of movies in
different countries because theater releases aren't simultaneous (a movie
may come out on DVD in the U.S. when it's just hitting screens in Europe).
Therefore they have required that the DVD standard include codes which
can be used to prevent playback of certain discs in certain geographical
regions. Players sold in each region will have that region's code built
into the player. The player will refuse to play discs which are not allowed
in the region. This means that discs bought in one country may not play
on players bought in another country.
Regional codes are entirely optional. Discs without codes will play
on any player in any country. It's not an encryption system, it's just
one byte of information on the disc that the player checks. Some studios
have already announced that only their new releases will have regional
codes. Presumably, once a DVD movie has achieved worldwide release it could
be re-released without encoding.
There are 6 regions:
- North America
- Europe
- Japan
- Australia & Far East (except Japan)
- Africa & Middle East
- Central & South America
These are apparently not completely finalized. Rumors are that Mexico is
floating around.
Regional codes do not apply to DVD-ROMs or DVD-ROM drives. It's not
yet known if regional codes will apply to DVD-Audio. Since there is no
equivalent for CD Audio it's likely DVD-Audio will not use them
[1.11] What are the copy protection issues?
There are already two forms of copy protection specified by the DVD
standard:
1) Videotape (analog) copying is prevented with a Macrovision (or equivalent)
circuit in every player. Composite video output will have a rapidly modulated
colorburst signal along with pulses in the vertical blanking signal to
confuse the automatic-recording-level circuitry of VCRs. Unfortunately,
this can degrade the picture, especially with old or nonstandard equipment.
There are rumors that Macrovision can create problems for some line doublers.
[Can anyone confirm this?] It's not clear if Macrovision will be used on
component video output or S-video output. The discs themselves tell the
player whether or not to enable Macrovision. So just as with videotapes
now, some DVDs will be Macrovision-protected and some wont.
2) Digital copying is controlled by information on each disc specifying
how many times (if any) the data can be copied. This is a "serial"
copy generation management system (CGMS) designed to prevent copies of
copies. Of course, the equipment making the copy has to abide by the rules.
A third form of copy protection was *tentatively* agreed to on
Oct 29. Because of the potential to make perfect digital copies, paranoid
movie studios want to force a deeper copy protection requirement into the
DVD standard. Content Scrambling System (CSS) is a form of data encryption
that prevents reading the media files directly from the disc. Most players
will have a decryption circuit that decodes the data before displaying
it. It's unclear yet if this will affect output to a digital screen (such
as a DLP or plasma display). On the computer side, DVD-ROM drives and video
display/decoder hardware or software will exchange encryption keys so that
the video is decrypted just before display by the encoder.
Movie studios also want to make it illegal to defeat copy protection.
A co-chair of the legal group of the copy protection committee stated,
"in the video context, the contemplated legislation should also provide
some specific assurances that certain reasonable and customary home recording
practices will be permitted, in addition to providing penalties for circumvention."
It's not at all clear how this might be "permitted" by a player.
DVD-ROM will not use CSS for computer data. However, since DVD-ROM can
hold any form of computer data, any desired encryption scheme can be implemented.
All three forms of copy protection are optional for the producer of
a disc. Decryption is also optional for hardware and software playback
manufacturers: a player or computer without decryption capability will
not be able to play encrypted movies.
The copy protection schemes are designed to guard against casual copying
(which the studios claim causes billions of dollars in lost revenue). Even
the people who developed the copy protection standards admit that it won't
stop well-eqipped pirates.
[1.12] What about DVD-Audio or Music DVD?
The DVD Consortium has decided to seek additional input from the music
industry before defining the DVD-Audio format. If the final specification
includes features or formats not present in the current DVD specification,
then first-generation DVD players will not be able to play DVD-Audio discs.
Quotes from manufacturers indicate an odd separation of DVD-Video and
DVD-Audio. Many apparently plan to introduce DVD-Audio players independent
of DVD-Video players. Leaving out video circuitry results in slightly cheaper
players, but there's no reason to have two separate DVD-format players
in the same home setup. The separation makes more sense for audio-only
portable players. It remains to be seen how this will turn out.
[1.13] Which studios are supporting DVD? Didn't
some studios say they won't support it?
Time Warner, Sony (Columbia/Tristar), MCA, MGM, and Turner have announced
intentions to release movies on DVD. Disney has expressed concerns over
copying, but is closely involved in DVD development and will most likely
jump in once copy protection is resolved (see 1.11).
Paramount may hold back because of their connection to Blockbuster. Other
studios may also hold back, but if DVD is a success no studio would be
foolish enough to not jump on the bandwagon.
[1.14] Will DVD record from VCR/TV/etc?
Short Answer: No. (Not in this century.)
Long answer: The minimum requirement for reproducing audio and video
on DVD is an MPEG video stream and a PCM audio track. (Other streams such
as Dolby Digital audio, MPEG audio, and subpicture are not necessary for
the simplest case.) Basic DVD control codes are also needed. At the moment
it's difficult in real time to encode the video and audio, combine them
with the control codes, and write the whole thing to DVD. Even if you could
do all this in real time it would be too expensive. Prices for DVD production
systems are dropping from millions of dollars to thousands of dollars,
but they won't be in the <$500 range for home use for several years
yet. It's possible the first home DVD recorders will require a digital
source of already-compressed audio and video, such as DSS.
Don't be confused by DVD-R (write-once) systems, which will be available
soon and will cost several thousand dollars. These can record DVD-ROM type
data, but to create full-featured DVD-Videos would require additional hardware
and software to do video encoding (MPEG-2), audio encoding (Dolby Digital
or MPEG or LPCM), subpicture encoding (run-length-compressed bitmaps),
still frame encoding (MPEG-1 or MPEG-2), control code generation, and multiplexing.
And since this can't be done in real time, you'd also need a 5 to 9 GB
hard drive to premaster the data to.
Some people believe that recordable DVD-Video will never be practical
for consumers to record TV shows or home videos, since digital tape is
more cost effective. On the other hand, digital tape lacks many of the
advantages of DVD such as seamless branching, instant rewind/fast forward,
instant search, and durability, not to mention the coolness of small shiny
discs. So once the encoding technology is fast and cheap enough, and the
blank discs are cheap enough, recordable DVD may be a reality.
[1.15] What happens if I scratch the disc? Aren't
discs too fragile to be rented?
DVD includes a better error-correction system than CD. Most scratches
will cause minor raw data errors that are easily corrected. Major scratches
may cause unrecoverable errors that will show up as a momentary glitch
in the picture. However, there are schemes for correcting errors in MPEG
video that will probably be employed in players as they improve.
Consider that laserdiscs, music CDs, and CD-ROMs are likewise subject
to scratches, but many video stores and libraries rent them.
[1.16] VHS is good enough, why should I care about
DVD?
The primary advantages of DVD are quality and extra features (see 1.2).
DVD will not degrade with age or after many playings like videotape will
(which is an advantage for parents with kids who watch Disney videos twice
a week!). This is the "collectability" factor present with CDs
vs. cassette tapes.
If none of this matters to you, then VHS probably is good enough.
[1.17] Is the packaging different from CD?
Manufacturers are worried about customers assuming DVDs will play in
their CD player. Time Warner is promoting a package (similar in form to
the plastic and paper "eco" CD packages) which measures 14cm
wide x 19cm high x 1.25cm thick (5.5" x 7.5" x 0.5"). [I
measured it by hand, so this may not be exact.] This is about as wide as
a CD jewel box and about as tall as a VHS cassette box. There is also a
proposal from the Video Software Dealers Association for a package 5 5/8"
wide, 7 3/8" high and between 3/8" and 5/8" deep. However,
no one is being forced to use a larger package size. It remains to be seen
what becomes standard, especially for DVD-ROM.
[1.18] When will double-sided or dual-layer discs
appear? Will they work in all players?
Soon. Some replicators plan to produce double-sided discs, dual-layer
discs, and double-dual discs from day one. Obviously the prices will be
higher, but certain producers already require more space than is available
on a single side or single layer. All players will play dual-layer discs
-- it's required. All players will also play double-sided discs if you
flip the discs over. No manufacturer has announced a player that will play
both sides. (See 2.9 for note on reading both sides
simultaneously.)
[1.19] Is DVD a worldwide standard? Does it work
with NTSC, PAL and SECAM?
Not really. DVD supports two television systems: 525/60 (NTSC) and 625/50
(PAL). There are three differences between discs intended for different
markets: picture size (720x480 vs. 720x576), frame rate (29.97 vs 25),
and surround audio (Dolby Digital vs. MPEG-2). (See 3.3
and 3.5 for details.) However, a producer can choose
to include additional video and audio --at the expense of playing time--
so that all formats are covered. It's unknown if players will be able to
automatically recognize and play the correct format video in this case.
It's rumored that some studios will include Dolby Digital tracks on their
PAL releases.
It's possible to make a multi-standard player that will output NTSC
from a 525/60 disc and PAL from a 625/50 disc. This requires a multi-standard
TV that can display both. It's also possible to make a standards-converting
player that will output NTSC from a 625/50 disc or PAL from a 525/60 disc.
No manufacturer has yet announced a player of either kind.
[2] DVD's relationship to other products
[2.1] Will DVD replace VCRs?
Not any time soon. DVD is not yet recordable (see 1.14)
and it will take a while before the size of the market drives costs down
to VCR levels. However, DVD has many advantages over VCRs, including fundamentally
lower technology cost for hardware and disc production (which is appealing
to manufacturers), so if DVD is a commercial success it might replace VCRs
in fifteen to twenty years.
[2.2] Will DVD replace CD-ROM?
Yes. Some CD-ROM drive manufacturers have announced that they expect
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 forward migration
path.
[2.3] Can CD-R writers create DVDs?
No. DVD uses a smaller wavelength of laser to allow smaller pits in
tracks that are closer together. The DVD laser must also focus tighter
and at a different level. In fact, a disc made on a current CD-R writer
may not be readable by a DVD-ROM drive (see 2.4.3).
It's unlikely there will be "upgrades" to convert CD-R drives
to DVD-R, since this would probably cost more than purchasing a new DVD-R
drive.
[2.4] Is CD compatible with DVD?
This is actually many questions with many answers:
[Note the differentiation between DVD (general case)
and DVD-ROM (computer data).]
[2.4.1] Is CD audio (CD-DA) compatible with DVD?
Yes. All DVD players and drives will read audio CDs (Red Book). This
is not actually required by the DVD spec, but so far all manufacturers
have stated that their DVD hardware will read CDs. On the other hand, you
can't play a DVD in a CD player.
[2.4.2] Is CD-ROM compatible with DVD-ROM?
Yes. All DVD-ROM drives will read CD-ROMs (Yellow Book). However, DVD-ROMs
are not readable by CD-ROM drives.
[2.4.3] Is CD-R compatible with DVD-ROM?
Maybe. The problem is that CD-Rs (Orange Book Part II) are "invisible"
to the wavelength of laser required by DVD, because the dye used in CD-Rs
doesn't reflect the laser beam. Supposedly there will be new CD-R2 blanks
that will work with CD-ROM and DVD. A better solution, announced by Sony,
is a twin-laser pickup in which one laser is used for reading DVDs and
the other for reading CDs and CD-Rs. This provides complete backwards compatibility
with millions of CD-R discs. Philips has also stated that its DVD-ROM drives
will read CD-Rs.
[2.4.4] Is CD-RW compatible with DVD?
Partly. CD-Rewritable (Orange Book Part III) discs can not be read by
existing CD-ROM drives and CD players or first-generation DVD-ROM drives
and DVD players. CD-RW has a lower reflectivity difference, requiring automatic-gain-control
(AGC) circuitry. The new "MultiRead" standard addresses this
and some DVD manufacturers have already suggested they will support it.
CD-RW does not have the "invisibility" problem of CD-R (see 2.4.3).
[2.4.5] Is VideoCD compatible with DVD?
Probably. It's not required by the DVD spec, but it's trivial to support
the White Book standard since any MPEG-2 decoder can also decode MPEG-1
from a VideoCD. Most [?] manufacturers have announced that their DVD players
will play VideoCDs.
[2.4.6] Is Photo CD compatible with DVD?
Not yet. Since Photo CDs are usually on CD-R media, they may suffer
from the CD-R problem (see 2.4.3). That aside, DVD
players could support Photo CD with a few extra chips and a license from
Kodak. No one has announced such a player. Most likely all DVD-ROM drives
will read Photo CDs since it's trivial to support the Orange Book standard.
The more important question is, "Does the OS or application support
Photo CD?" but that's beyond the scope of this FAQ.
[2.4.7] Is CD-I compatible with DVD?
In general, no. Most DVD players will not play CD-I (Green Book) discs.
However, Philips, the inventor of CD-I, 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).
[2.4.8] Is Enhanced CD (CD Plus) compatible with
DVD?
Yes. DVD players will play music from Enhanced CDs, and DVD-ROM drives
will play music and read data from Enhanced CDs.
[2.4.9] Is CD+G compatible with DVD?
No DVD-Video players claim to support CD+G. Toshiba has announced that
its DVD-ROM drive supports CD+G, and it's likely that most other DVD-ROM
drives also will.
[2.4.10] Is CDV compatible with DVD?
Sort of. CDV, sometimes called Video Single, is actually a weird combination
of CD and laserdisc. Part of it contains 20 minutes of digital audio playable
on any CD or DVD player. The other part of it contains 5 minutes of analog
video (and digital audio) in laserdisc format, playable only on a CDV-compatible
system. However, Pioneer has announced combi players that will play DVDs,
laserdiscs, and CDVs.
[2.5] Is laserdisc compatible with DVD?
No. Most DVD players will not play laserdiscs, and you can't play a
DVD disc on any existing laserdisc player. (Laserdisc uses analog video,
DVD uses digital video; they are very different formats.) However, Pioneer
has announced combi players that will play DVDs and laserdiscs (and also
CDVs and Audio CDs).
[2.6] Will DVD replace laserdisc?
Probably, but not for a very long time. Laserdisc is well established
as a videophile format. There are over 9,000 laserdisc titles in the US
and over 30,000 [?] worldwide that can be played on over 3 million laserdisc
players. It will take DVD many years to reach this point. Until then laserdisc
has the superiority of tenure. Pioneer and other laserdisc companies have
committed to supporting it for years to come. There's no reason to stop
buying laserdiscs, especially rare titles that may not appear on DVD for
a long while if ever.
Unfortunately, anticipation of DVD is already hurting laserdisc. In
1996 laserdisc sales were down 36% even though sales of VCRs and hi-fi/surround
systems were up.
[2.7] How does DVD compare to laserdisc?
This is a dangerous question to answer, given the legions of laserdisc
fanatics who would rather have their laserdiscs pried from their cold dead
fingers than switch! But since I'm a bit fanatical myself,
having used laserdiscs since 1979 and currently working for a company whose
major product is laserdiscs, I'll give it a shot. <Putting on
flameproof suit....>
DVD improves on laserdisc in almost every aspect:
- Price: DVD hardware and discs are (or will be) cheaper. Studio representatives
have promised they will make DVDs as cheap or cheaper than videotape.
- Features: DVD has the same basic features as laserdisc (scan, slow, still,
search) but adds branching, multiple camera angles, video menus, interactivity,
etc. But unlike laserdisc, DVD can't play backwards.
- Convenience: DVD players can be portable -- similar to CD players. Discs
can be easily and cheaply sent through the mail.
- Audio: DVD has better audio. Laserdisc has 3 audio tracks: analog, digital,
and surround (AC-3 steals one channel of analog). DVD has up to 8 audio
tracks. Laserdisc uses LPCM audio sampled with 16 bits at 44 kHz. DVD LPCM
audio can use 16, 20, or 24 bit samples at 48 or 96 kHz. Laserdisc has
surround audio in Dolby Digital (AC-3) and DTS formats. DVD uses the same
Dolby Digital surround sound, but can actually go to a higher data rate
for better quality (448 Kb/s instead of 384).
- Video: DVD has the potential for better video. Laserdisc suffers from
degradation inherent in analog recording and in the composite NTSC or PAL
video signal. DVD uses digital video, and even though it's heavily compressed,
hundreds of video professionals have seen demos of MPEG-2 video and concluded
that properly and carefully encoded it's indistinguishable from studio
D-1 masters. Nevertheless, this doesn't mean that the video quality of
DVD, especially at first, WILL be better than laserdisc. Only that it CAN
be better. Also keep in mind that the average television is of insufficient
quality to show much difference between laserdisc and DVD. Home theater
systems are needed to take advantage of the improved quality.
- Support: There are more announced DVD players than there are laserdisc
players. Studios have said they will release more DVD titles than laserdisc
titles. Many new computers will be able to play DVD-Videos.
There are concerns that regional coding (see 1.10)
and Macrovision copy protection (see 1.11) will make
DVD less usable than laserdisc. This can't be confirmed until DVD is in
the hands of consumers.
[2.8] Can I modify or upgrade my laserdisc player
to play DVD?
It's not likely. DVD circuitry is completely different, the pickup laser
is a different wavelength, the tracking control is more precise, etc. No
hardware upgrades have been announced, and in any case they would probably
be more expensive than buying a DVD player to put next to the laserdisc
player.
[2.9] Will DVD support Digital TV (HDTV)?
HTDV is not supported by DVD, but the designers have it in mind. Since
HDTV uses MPEG-2 it will be easy to "upgrade" the DVD format.
The limited data rate of DVD may make it difficult to support high-quality
HDTV, but this can be solved by either increasing the spin rate (as with
multi-speed CD-ROM drives) or using higher-capacity blue lasers.
Some have speculated that a "double-headed" player reading
both sides of the disc at the same time could double the data rate. This
is impossible since the track spirals go in opposite directions. The DVD
specs would have to be changed to allow reverse spirals on the second side.
[3] DVD technical details
[3.1] What are the outputs of a DVD player?
Most DVD players will have the following output connections:
Video:
- RCA composite video (NTSC or PAL)
- S-video (NTSC or PAL)
Audio:
- Dual RCA stereo analog audio (with Pro Logic)
- Digital audio (coaxial FM and/or IEC-958 optical). Requires an external
decoder or an amplifier/receiver with built-in Dolby Digital or MPEG-2
audio or PCM (stereo) support.
Some players may have additional connections:
- Component (YCrCb; NTSC or PAL)
- RF video output for connecting to TV without direct input. (Panasonic
DVD-A300)
- 6 RCA jacks for surround sound output from built-in decoder. (Panasonic
DVD-A300, RCA.)
No player has been announced with digital video output, but it's expected
that at some point DVD players will include FireWire (IEEE 1394) connectors
(see <http://www.firewire.com>).
[3.2] What are the sizes and capacities of DVD?
There are many variations on the DVD theme. There are two physical sizes:
12 cm (4.7 inches) and 8 cm (3.1 inches), both 1.2 mm thick. This is the
same form factor as CD. A disc can be single-sided or double-sided. Each
side can have one or two layers of data. The amount of video a disc can
hold depends on how much audio accompanies it and how heavily the video
and audio are compressed. The oft-quoted figure of 133 minutes is apocryphal:
a standard DVD can actually hold up to 6 hours of video and audio if it's
heavily compressed (which reduces the quality).
DVD-ROM, DVD-Video, DVD-Audio:
For reference, a CD-ROM holds about 650 MB (megabytes), which is 0.63
GB (gigabytes).
- DVD-5 (12cm, single-layer) : 4.7 GB of data, over 2 hours of video
- DVD-9 (12cm, dual-layer): 8.54 GB, about 4 hours of video
- DVD-10 (12cm, double-sided, single-layer): 9.4 GB, about 4.5 hours of
video
- DVD-18 (12cm, double-sided, dual-layer): 17 GB, about 8 hours of video
- DVD-1? (8cm, single-layer) : 1.46 GB of data, about half an hour of video
- DVD-2? (8cm, dual-layer): 2.66 GB, about 1.5 hours of video
- DVD-3? (8cm, double-sided, single-layer): 2.92 GB, about 1.5 hours of
video
- DVD-4? (8cm, double-sided, dual-layer): 5.32 GB, about 2.5 hours of video
Tip: It takes about two gigabytes to store one hour of average video.
DVD-R (recordable) and DVD-RAM (erasable):
Most likely will only be available as 12cm, single-layer. The standards
aren't finalized and there will initially be different sizes varying from
2.5 to 3.8 gigabytes. The technology will improve to eventually support
4.7 gigabytes, which is crucial for desktop DVD production. Pioneer has
been showing working prototypes of DVD-R. Toshiba claims DVD-R will be
ready in Spring 1997 and DVD-RAM will be available in Fall 1997. (Don't
hold your breath.)
[3.3] What are the video details?
A disc has one track (stream) of MPEG-2 constant bitrate (CBR) or variable
bitrate (VBR) compressed digital video. A limited version of MPEG-2 Main
Profile at Main Level (MP@ML) is used. MPEG-1 CBR video is also supported.
525/60 (NTSC, 29.97 frames/sec) and 625/50 (PAL, 25 frames/sec) video systems
are supported.
Picture dimensions are max 720x480 (29.97 frames/sec) or 720x576 (25
frames/sec).
Maximum bitrate is 9.8 Mb/s (but will always be less to allow for audio).
The "average" bitrate is 3.5 but depends entirely on the length,
quality, amount of audio, etc. This is approximately a 70:1 reduction from
original 243 Mb/s CCIR 601 source. (But note that MPEG uses 4:2:0 format,
which is a 75% reduction from 4:2:2 before compression)
Raw channel data is read off the disc at a constant 26.16 Mb/s. After demodulation
it's down to 13.08 Mb/s. After error correction, the user data stream goes
into the track buffer at a constant 11.08 Mb/s. The track buffer feeds
system stream data out at a variable rate of up to 10.08 Mb/s. After system
overhead, the maximum rate of combined elementary streams (audio + video
+ subpicture) is 9.8.
Still frames (encoded as MPEG-2 I-frames) are supported and can be displayed
indefinitely. These are generally used for menus. Still frames can be accompanied
by audio [is this confirmed?].
A disc also can have up to 32 subpicture streams that overlay the video
for subtitles, karaoke, menus, simple animation, etc. These are full-screen,
run-length-encoded bitmaps limited to four contrast values and four colors
per pixel (contrast and color are selected for a group of subpictures from
palettes of 16). Subpicture includes built-in effects such as scroll and
fade.
[3.4] How do the aspect ratios work?
Video can be stored on a DVD in 4:3 format (standard TV shape) or 16:9
(widescreen). The 16:9 format is "anamorphic," meaning the picture
is squeezed horizontally to fit a 4:3 rectangle then unsqueezed during
playback. DVD players output widescreen video in three different ways:
- letterbox (for 4:3 screens)
- pan & scan (for 4:3 screens)
- anamorphic or unchanged (for wide screens)
Note: Some 16:9 discs are playable in widescreen and letterbox modes
only, if the producer chooses.
For letterbox mode the player uses a "letterbox filter" that
creates black bars at the top and the bottom of the picture (60 lines each
for NTSC, 72 for PAL). This leaves 3/4 of the height remaining, creating
a shorter but wider rectangle. In order to fit this shorter rectangle,
the picture is squeezed vertically by combining every 4 lines into 3. This
compensates for the original horizontal squeezing, resulting in the movie
being shown in its full width.
For pan & scan mode the video is unsqueezed to 16:9 and a portion
of the image is shown at full height on a 4:3 screen by following "center
of interest" coordinates that are encoded in the video stream according
to the preferences of the people who transferred the film to video.
For anamorphic mode the video is stretched back out by widescreen equipment
to its original width.
In widescreen or letterbox mode if a movie is wider than 16:9 (and most
are), additional thin black bars will be added to the top and bottom at
production time or the sides may be cropped (possibly with a small amount
of additional panning).
Video stored in 4:3 format is not changed by the player. It will appear
normally on a 4:3 screen. Widescreen systems will either stretch it horizontally
or add black bars to the sides.
Some producers may put 16:9 source on one side of the disc and 4:3 source
on the other, since "full-frame" 4:3 movies have additional picture
at the top and bottom rather than panning and scanning. (The cinematographer
has two sets of frame marks in his viewfinder, one for 4:3 and one for
1.85, so he can allow for both formats).
The 16:9 anamorphic format causes no problems with line doublers, since
they simply double the lines on their way to the widescreen display which
then stretches out the lines.
[3.5] What are the audio details?
The DVD-Audio format is not yet specified. These details are for audio
tracks on DVD-Video.
A disc can have up to 8 audio tracks (streams). Each track can be in one
of three formats:
- Dolby Digital (AC-3): 1 to 5.1 channels
- MPEG-2 audio: 1 to 7.1 channels
- LPCM: 1 to 8 channels.
This is extensible in the future to other formats such as DTS or Sony
SDDS/DSD.
The ".1" refers to a low-frequency effects (LFE) channel that
connects to a subwoofer.
All three audio formats support karaoke mode, which has two channels
for stereo (L and R) plus an optional melody channel (M) and two optional
vocal channels (V1 and V2).
Discs containing 525/60 (NTSC) video must use LPCM or Dolby Digital
on at least one track. Discs containing 625/50 (PAL) video must use LPCM
or MPEG-2 audio on at least one track. Additional tracks may be in any
format.
For stereo output, all players will do a downmix from 5.1 or 7.1 surround
sound (if present) to Dolby Pro Logic stereo. Both Dolby Digital and MPEG
support 2-channel Dolby Pro Logic as the source (for cases where the original
is in Pro Logic format and the producer can't or doesn't want to remix
with surround channels.)
LPCM is uncompressed (lossless) digital audio. It can be sampled at
48 or 96 kHz with 16, 20, or 24 bits/sample. (Audio CD is 44.1 kHz at 16
bits.) There can be 1, 2, 5, or 8 channels. The maximum bitrate is 6.0
Mb/s (not 6.144), which limits sample rates and bit sizes with 5 or 8 channels.
It's generally felt that the 96 dB dynamic range of 16 bits or even the
120 dB range of 20 bits combined with a frequency response of up to 22,000
Hz from 48 kHz sampling is more than adequate for high-fidelity sound reproduction.
24 bits and 96 kHz will probably be used only for "studio" archiving.
Dolby Digital is multi-channel digital audio, compressed using AC-3
coding technology from original PCM with a sample rate of 48 kHz at 16
bits. The bitrate is 64 Kb/s to 448 Kb/s, with 384 being the normal rate
for 5.1 channels and 192 being the normal rate for stereo (Dolby Pro Logic).
The channel combinations are (front/surround): 1/0, 1+1/0 (dual mono),
2/0, 3/0, 2/1, 3/1, 2/2, and 3/2. The LFE channel is optional with all
8 combinations. For details see ATSC document A/52 <http://www.atsc.org/document.html>.
MPEG audio is multi-channel digital audio, compressed from original
PCM format with sample rate of 48 kHz at 16 bits. Both MPEG-1 and MPEG-2
formats are supported. The bitrate is 32 Kb/s to 912 Kb/s, with 384 being
the normal rate. There can be 1, 2, 5.1 or 7.1 channels [any more?]. The
7.1 channel format adds left-center and right-center channels. MPEG-2 surround
channels are in an extension stream which is matrixed onto the MPEG-1 stereo
channels, which makes MPEG-2 audio backwards compatible with MPEG-1 hardware
(the MPEG-1 system will only see the two stereo channels.)
A DVD-5 with only one stereo ProLogic audio stream (at 192 Kb/s) can
hold over 55 hours of audio. A DVD-18 can hold over 200 hours!
[4] DVD and computers
[4.1] Can I play DVD movies on my computer?
Only if your computer has the right stuff. In addition to a DVD-ROM
drive, you must have extra hardware to decode MPEG-2 video and Dolby Digital/MPEG-2/LPCM
audio. You may also need software that can read the MicroUDF format used
to store DVD data files and interpret the DVD control codes. It's estimated
that 10-30% of new computers with DVD-ROM drives will include decoder hardware.
It can also be purchased separately for about $900.
Some DVD-Videos will be encoded using MPEG-1 instead of MPEG-2. Many
existing computers have MPEG-1 hardware built in or will be able to decode
MPEG-1 with software.
CompCore Multimedia <http://www.compcore.com>
and Mediamatics <http://www.mediamatics.com>
make software that can play DVD movies but both require at least a 200MHz
Pentium MMX to achieve film frame rates (24/sec) but not full video frame
rates. It's unknown if these software decoders will be able to decrypt
copy-protected movies (see 1.11).
Mediamatics is promoting a new standard called Motion Video Collaborative
Compression Architecture (MVCCA) which allows certain MPEG decompression
tasks to be performed by hardware on a video card and the remainder by
software. Video graphics controllers with this feature are being called
"DVD MPEG-2 accelerated."
[5] DVD production
[5.1] How much does it cost to produce a DVD? Isn't
DVD much more expensive than videotape, laserdisc, and CD-ROM?
These can't be compared in a straightforward manner. There are basically
three stages of costs: production, pre-mastering, and mastering/replication.
Production costs are not much more 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. Authoring and encoding
systems currently cost from $100,000 to over $2 million. These prices will
drop very rapidly in the next few years to where DVDs can be produced on
desktop computer systems using additional hardware costing less than $20,000.
The current estimate for producing a two-hour DVD movie is about $25,000.
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 $1,800 to master, and about $12 to replicate. DVD
currently costs a few thousand dollars to master and $2.50 to replicate.
Since DVD production equipment is very similar or the same as CD production
equipment, mastering and replication costs will quickly drop to CD levels.
Soon it will be cheaper to produce video titles on DVD than on videotape.
[5.2] What DVD authoring systems are available and
how much do they cost?
- DVD Creator (encoding) and Scenarist DVD (authoring) by Sonic Solutions.
$180,000 (full cost is about $250,000 with hard disks, DLT drive, PowerPC
(for Creator), SGI (for Scenarist), etc.) <http://www.sonic.com/html/dvd/products_dvd.html>
- Compressionist 250 from Minerva. $99,000. <http://www.minervasys.com>
- Panasonic, JVC, Toshiba, and Pioneer all have authoring systems under
development but nothing available at the moment.
[5.3] Who can produce a DVD for me?
- [A] CRUSH Digital Video* (NY), <mailto:info@CrushDV.com>
212-965-1501.
- [A] Digital Video Compression Corporation (CA), 818-777-5185.
- [R] Imation (formerly 3M) (WI), 612-704-4898.
- [A] KAO Infosystems* (CA), <www.kaoinfo.com>
510-657-8425.
- [R] LaserPacific (CA), <http://www.laserpacific.com>
213-462-6266.
- [A] NB Digital Solutions*, <http://www.nbeng.com/dvd.htm>
- [R] Nimbus Manufacturing. 804-985-1100.
- [R] Optical Disc Corporation, 310-946-3050. (Makes the LaserWave DirectCut
DVD recorder for creating single copies.)
- [R] Pacific Video Resources (CA), <http://www.pvr.inter.net>
415-864-5679.
- [R] Pioneer Video Manufacturing, Inc., 310-518-0710.
- [A] Rainmaker* (BC), 604-874-8700.
- [R] Warner Advanced Media Operations, 717-383-3291.
[A] Authoring (including compression and premastering).
[R] Replication (mastering and/or one-offs).
* Use Sonic Solutions' authoring system.
DVD is primarily the work of Toshiba, Philips, and Sony. There were
originally two next-generation standards for DVD. The MMCD format was backed
Sony, Philips, and others. The competing SD format was backed by Toshiba,
Time Warner, and others. A group of computer companies led by IBM insisted
that the DVD proponents agree on single standard. The combined DVD standard
was announced in September of 1995, avoiding a confusing and costly repeat
of the VHS vs. BetaMax videotape battle (or the quadraphonic sound battle
of the 1970s).
No single company "owns" DVD. The DVD Licensor Consortium
now comprises Hitachi, JVC, Matsushita, Mitsubishi, Philips, Pioneer, Sony,
Thomson, Time Warner, and Toshiba. (Visit Robert's DVD Info page <http://www.unik.no/~robert/hifi/dvd/>
for links to company Web pages.)
Any company making DVD products must license the technology, mostly
from a pool administered by Philips but also separately from Thomson. Matsushita
is licensing copy-protection encryption technology.
[6.2] Who is making or supporting DVD products?
The following companies have made official statements of products designed
to support the DVD format.
Consumer electronics:
Akai
Hitachi
JVC
LG Electronics
Matsushita (Panasonic/National/Technics/Quasar)
Mitsubishi
Philips (Magnavox)
Pioneer
Samsung
Sharp
Sony
Thomson (RCA/GE/Proscan/Ferguson/Nordmende/Telefunken/Saba/Brandt)
Time Warner (Warner Bros./Turner Broadcasting/HBO/CNN/Warner Music)
Toshiba
Zenith
Studios:
MCA
MGM
Pony Canyon
Sony (Columbia/Tristar)
Time Warner
Toshiba EMI
Turner
Victor Entertainment
Computer hardware/software:
Apple: DVD-ROM computers, drivers, and playback hardware and software
(QuickTime)
AST: DVD-ROM computers (with MMX-based playback software)
ATI Technologies: DVD-accelerated video audio/video cards
Creative Multimedia: DVD-accelerated audio/video cards
Fujitsu: DVD-ROM computers
Hitachi: DVD-ROM drives
JVC: DVD-ROM drives
Matsushita (Panasonic): DVD-ROM drives
Mediamatics: DVD playback software
Microsoft: DVD drivers and playback software (ActiveMovie)
Mitsubishi: DVD-ROM drives
Philips: DVD-ROM drives
Pioneer: DVD-ROM drives
S3: DVD-accelerated video controller chips
Sony: DVD-ROM computers and drives
Toshiba: DVD-ROM computers and drives
Trident Microsystems: DVD-accelerated video controller chips
Computer software on DVD-ROM:
Digital Directory Assistance: PhoneDisc PowerFinder USA One
Interactual Technologies: Star Trek VideoSaver
Tsunami Media: Silent Steel
Warner Advanced Media
- New questions: [1.18] When will double-sided or
dual-layer discs appear? Will they work in all players? [1.19]
Is DVD a worldwide standard? Does it work with NTSC, PAL and SECAM? [2.6]
Will DVD replace laserdisc? [2.9] Will DVD support Digital
TV (HDTV)? [6.2] Who is making or supporting DVD products?
- Better answers: [1.4] What are the disadvantages of
DVD? [1.11] What are the copy protection issues? [1.6]
When will DVD titles be available, and how many? [2.4.4]
Is CD-RW compatible with DVD? [2.4.10] Is CDV compatible
with DVD? [3.4] How do the aspect ratios work? [4.1]
Can I play DVD movies on my computer?
- Listed the six geographical regions (1.10). Thanks,
Dirk!
- Added brief explanation of streams and bitrates to video details (3.3).
- Added "panning & scanning" speculation to last section
of aspect ratios (3.4)
- Added CD+G compatibility information (2.4.9)
- Added a number of companies to section 5.3.
- Updated info about Sonic Solutions DVD authoring. Added info about Minerva
system. (5.2.)
[7.2] Remaining unanswered questions
(If you know the answer to any of these, please speak
up!)
- How exactly will copy protection encryption work? Is audio encrypted?
- Will CompCore's and Mediamatic's software DVD players play encrypted
movies?
- It would be nice if an expert made sure I got the streams and rates right
in 3.3.
- How will copy-protection affect digital video output?
- Does Macrovision cause problems with line doublers?
- Will Macrovision be used on component and s-video outputs (as opposed
to composite output only)?
- Will regional codes apply to DVD-Audio?
- Do any DVD players support CD+G?
- What are the digital audio outputs of DVD players?
- How are languages (of subtitle and audio streams) identified? ISO XXX?
- Display frame rates are 29.97 and 25. What internal frame rates (i.e.
for 3:2 pulldown) are allowed? The same as MP@ML or a subset?
- Are there official designations for 8 cm discs (DVD-1, DVD-2, etc.?)
[7.3] Acknowledgments
This FAQ is written and maintained by Jim Taylor. The following people
have contributed to the FAQ (either directly, by posting to alt.video.dvd,
or by me borrowing from their writing :-). Their contributions are deeply
appreciated. Information has also been taken from material distributed
at the April 1996 DVD Forum.
Robert Aas
Wayne Bundrick
Roger Dressler
Chad Fogg
Kilroy Hughes
Ralph LaBarge
Martin Leese
Dana Parker
Geoffrey Tully
----
This document may be freely redistributed only in its entirety with
authorship notice and acknowledgements intact. No part of it may be sold
for profit or incorporated in a commercial document without the permission
of the copyright holder. Permission is expressly granted for complete electronic
copies to be made available as an archive or mirror service. This document
is provided as is without any express or implied warranty.
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