DVD FAQ


What's the Story With This DVD Thing Anyway?

There are plenty of things that set DVD apart from other home video formats: The brilliant sharpness of the picture, the better-than-CD-quality audio, even the convenient small size of the disc. DVD also allows audiences to go behind the scenes with added features in the form of commentary tracks and outtakes. With DVD, as with all new technologies, there is some technical information you'll need to know to make your viewing experience more enjoyable.

There is actually a lot more to DVD technology than meets the eye, which is why it is taking so long for many of the major Anime studios to release their titles on DVD, and why some of them are going broke doing it! Here are answers to a few questions that I am frequently asked:


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What is DVD?

DVD, which once stood for Digital Video Disc or Digital Versatile Disc, is the next generation of optical disc storage technology. It's essentially a bigger, faster CD that can hold cinema-like video, better-than-CD audio, and computer data. DVD aims to encompass home entertainment, computers, and business information with a single digital format, eventually replacing audio CD, videotape, laserdisc, CD-ROM, and perhaps even video game cartridges. DVD has widespread support from all major electronics companies, all major computer hardware companies, and now most of the major domestic Anime studios.

It's important to understand the difference between the physical formats (such as DVD-ROM or DVD-R) and the application formats (such as DVD-Video or DVD-Audio). DVD-ROM is the base format that holds data. DVD-Video (often simply called DVD) defines how video programs are stored on disc and played in a DVD-Video player or a DVD computer. The difference is similar to that between CD-ROM and Audio CD. DVD-ROM includes recordable variations DVD-R, DVD-RAM, DVD-RW, and DVD+RW. The application formats include DVD-Video, DVD-Video Recording, DVD-Audio, DVD-Audio Recording, DVD Stream Recording, and SACD). There are also special application formats for game consoles such as Sony PlayStation II.

DVD Quality

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. However, quality depends on many production factors. As compression experience and technology improves we will see increasing quality, but as production costs decrease we will also see more shoddily produced discs. A few low-budget DVDs will even use MPEG-1 encoding (which is no better than VHS) instead of higher-quality MPEG-2.

DVD video is usually encoded from digital studio master tapes to MPEG-2 format. The encoding process uses lossy compression that removes redundant information (such as areas of the picture that don't change) and information that's not readily perceptible by the human eye. The resulting video, especially when it is complex or changing quickly, may sometimes contain visual flaws, depending on the processing quality and amount of compression. At average rates of 3.5 Mbps (million bits/second), compression artifacts may be occasionally noticeable. Higher data rates can result in higher quality, with almost no perceptible difference from the master at rates above 6 Mbps. As MPEG compression technology improves, better quality is being achieved at lower rates.

Video from DVD sometimes contains visible artifacts such as color banding, blurriness, blockiness, fuzzy dots, shimmering, missing detail, and even effects such as a face that "floats" behind the rest of the moving picture. It's important to understand that the term "artifact" refers to anything that was not originally present in the picture. Artifacts are sometimes caused by poor MPEG encoding, but artifacts are more often caused by a poorly adjusted TV, bad cables, electrical interference, sloppy digital noise reduction, improper picture enhancement, poor film-to-video transfer, film grain, player faults, disc read errors, etc. Most DVDs exhibit few visible MPEG compression artifacts on a properly configured system.. If you think otherwise, you are misinterpreting what you see.

Some early DVD demos were not very good, but this is simply an indication of how bad DVD can be if not properly processed and correctly reproduced. Many demo discs are rushed through the encoding process in order to be distributed as quickly as possible. Contrary to common opinion, and as stupid as it may seem, these demos were not carefully "tweaked" to show DVD at its best.

Most TVs have the sharpness set too high for the clarity of DVD. This exaggerates high-frequency video and causes distortion, just as the treble control set too high for a CD causes it to sound harsh. Many DVD players output video with a black-level setup of 0 IRE (Japanese standard) rather than 7.5 IRE (US standard). On TVs that are not properly adjusted this can cause some blotchiness in dark scenes. DVD video has exceptional color fidelity, so muddy or washed-out colors are almost always a problem in the display (or the original source), not in the DVD player or disc.

DVD audio quality is superb. DVD includes the option of PCM (pulse code modulation) digital audio with sampling sizes and rates higher than audio CD. Alternatively, audio for most movies is stored as discrete, multi-channel surround sound using Dolby Digital or DTS audio compression similar to the digital surround sound formats used in theaters. As with video, audio quality depends on how well the processing and encoding was done. In spite of compression, Dolby Digital and DTS can be close to or better than CD quality.

The final assessment of DVD quality is in the hands of consumers. Most viewers consistently rate it better than laserdisc, but no one can guarantee the quality of DVD, just as no one should dismiss it based on demos or hearsay. In the end it's a matter of individual perception and the level of quality delivered by the playback system.

Regional Encoding

There are 8 regions (also called "locales"). Players and discs are identified by the region number superimposed on a world globe printed on the disk or the disk case. If a disc plays in more than one region it will have more than one number on the globe.

  • Region 1 - U.S., Canada, U.S. Territories

  • Region 2 - Japan, Europe, South Africa, and Middle East (including Egypt)

  • Region 3 - Southeast Asia and East Asia (including Hong Kong)

  • Region 4 - Australia, New Zealand, Pacific Islands, Central & South America, Mexico, the Caribbean

  • Region 5 - Eastern Europe (Former Soviet Union), Indian subcontinent, Africa, North Korea, and Mongolia

  • Region 6 - China

  • Region 7 - Reserved

  • Region 8 - Special international venues (airplanes, cruise ships, etc.)

Some players can be modified to play discs regardless of their regional codes. This usually voids the warranty, but is probably not illegal. Some discs, such as those from Buena Vista/Touchstone/Miramax, MGM/Universal, and Polygram contain program code that checks for the proper region. These "smart discs" that do active region checking won't play on code-free players that have their region set to 0, but they can be played on code-switchable players that allow you to change the region using the remote control. They may also not work on auto-switching players that recognize and match the disc region.

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. Computer playback systems check for regional codes before playing movies from a DVD-Video. Newer "RPC2" DVD-ROM drives let you change the region code several times. Once a drive has reached the limit (usually 5 changes) it can't be changed again unless the vendor or manufacturer resets it. The Drive Info utility can tell you if you have an RPC2 drive (it will say "This drive has region protection"). Drive Info and information about circumventing. After December 31, 1999, only RPC Phase II drives will be manufactured.

Regional codes do not apply to DVD-Audio.

Should I Get Rid of my VCR?

No, not yet! The primary advantages of DVD are quality and extra features. DVD will not degrade with age or after many playings like videotape will (which is an advantage for fans who might watch a particular Anime a few hundred times). Another perk is most Anime titles released on DVD include BOTH an English language (dubbed) track, and a Japanese language track with English subtitles, so you can watch it both ways without having to buy 2 separate video tapes.

If DVD features don't matter to you, then VHS is good enough. Also, it will take many YEARS for the majority of Anime titles to be released on DVD. Because of sell through issues, most of the attention placed on DVD from studios will be on new releases, and some existing older titles may NEVER see a DVD release.

Is DVD-Video a worldwide standard? What about NTSC, PAL, and SECAM?

DVD has the same NTSC vs. PAL problem as videotape and laserdisc. The MPEG video on DVD is stored in digital format, but it's formatted for one of two mutually incompatible television systems: 525/60 (NTSC) or 625/50 (PAL/SECAM). There are three differences between discs intended for playback on different systems: picture size and pixel aspect ratio (720x480 vs. 720x576), display frame rate (29.97 vs. 25), and surround audio (Dolby Digital vs. MPEG). Video from film is usually stored at 24 frames/sec but is preformatted for one of the two display rates. Movies formatted for PAL display are usually sped up by 4%, so the audio must be adjusted accordingly before being encoded. Unless the audio is digitally processed to shift the pitch back to normal, it will be slightly high. All PAL DVD players can play Dolby Digital audio tracks, but no NTSC players can play MPEG audio tracks. PAL and SECAM share the same scanning format, so discs are the same for both systems. The only difference is that SECAM players output the color signal in the format required for SECAM TVs.

Some players only play NTSC discs, some players only play PAL discs, and some play both. All DVD players sold in PAL countries play both. These multi-standard players partially convert NTSC to a 60Hz PAL (4.43 NTSC) signal. The player uses the PAL 4.43 MHz color subcarrier encoding format but keeps the 525/60 NTSC scanning rate. Most modern PAL TVs can handle this kind of "pseudo-PAL" 60-Hz signal. A few multi-standard PAL players output true 3.58 NTSC from 525/60 NTSC discs, which requires an NTSC TV or a multi-standard TV. Some players have a switch to choose 60-Hz PAL or NTSC output when playing NTSC discs. There are a few standards-converting PAL players (from Samsung and others) that convert from a 525/60 NTSC disc to standard PAL output. Proper standards conversion requires expensive hardware to handle scaling, temporal conversion, and object motion analysis. Because the quality of conversion in DVD players is poor, using 60Hz PAL output with a compatible TV provides a better picture. Most NTSC players can't play PAL discs. A very small number of NTSC players (such as the Apex) can convert 625/50 PAL to NTSC. External converter boxes are also available.

A producer can choose to put 525/60 video on one side of the disc and 625/50 on the other. Most studios so far are including Dolby Digital audio tracks on their PAL discs.

There are actually three types of DVD players if you count computers. Most DVD PC software and hardware can play both NTSC and PAL video and both Dolby Digital and MPEG audio. Some PCs can only display the converted video on the computer monitor, but others can output it as a video signal for a TV.

I heard that Anime (animation) compresses poorly on the DVD format.

Some people claim that animation, especially hand-drawn cell animation such as Japanese 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.

What is a Hybrid DVD?

Do you really want the answer to this one? Ok, you asked for it...

  1. A disc that works in both DVD-Video players and DVD-ROM PCs. (The most common use of the term hybrid, but more accurately called an enhanced DVD)

  2. A DVD-ROM disc that runs on Windows and Mac OS computers. (More accurately called a cross-platform DVD.)

  3. A DVD-ROM or DVD-Video disc that also contains Web content for connecting to the Internet. (More accurately called a WebDVD or Web-connected DVD.)

  4. A disc that contains both DVD-Video and DVD-Audio content. (More accurately called a universal DVD.)

  5. A disc with two layers, one that can be read in DVD players and one that can be read in CD players. (More accurately called a legacy or CD-compatible disc.) There are at least three variations of this hybrid (none were commercially available as of 12/99):

    1. A 1.2mm CD substrate bonded to the back of a 0.6mm DVD substrate. One side can be read by CD players, the other side by DVD players. The resulting disc is 0.6mm thicker than a standard CD or DVD, which can cause problems in players with tight tolerances, such as portables. Sonopress, the first company to announce this type, calls it DVDPlus. It's colloquially known as a "fat" disc.

    2. A 0.6mm CD substrate bonded to the front of a semitransparent 0.6mm DVD substrate. Both layers are read from the same side, with the CD player being required to read through the semitransparent DVD layer, causing problems with some CD players.

    3. A 0.6mm CD substrate, with a special refractive coating that causes a 1.2mm focal depth, bonded to the back of a 0.6mm DVD substrate. One side can be read by CD players, the other side by DVD players.

  6. A disc with two layers, one containing pressed (DVD-ROM) data and one containing rewritable (DVD-RAM, etc.) media for recording and re-recording. (More accurately called a mixed-media or rewritable sandwich disc.)

  7. A disc with two layers on one side and one layer on the other. (More accurately called a DVD-14.)

  8. A disc with an embedded memory chip for storing custom usage data and access codes. (More accurately called a chipped DVD.)

Did I miss any?

Do all DVD-Videos use Dolby Digital (AC-3), and do they all have 5.1 channels?

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.

Will DVD replace Laser Disk?

Laser what?? Oh, I remember those.....

After DVD was released, it became clear that it had doomed laserdisc to quick obscurity. Pioneer Entertainment, the long-time champion of laserdisc, abandoned it in June of 1999. This was sooner than even Pioneer thought possible, (in September 1998, Pioneer's president Kaneo Ito said the company expected laserdisc products to be in the market for another one-and-a-half to two years).

Laserdisc is fading very quickly as an entertainment format. Existing players and discs will still be around for a very long time, and new discs are still being produced, since laserdisc has become well established over 20 years 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 level, and even then there's no reason for laserdisc player owners to stop buying or playing laserdiscs, especially rare titles that may not appear on DVD for a long while if ever. One bright point is that laserdiscs (especially used discs) can now be had at bargain prices!

How does LaserDisk compare with DVD?

  • Features: DVD has the same basic features as CLV LD (scan, pause, search) and CAV LD (freeze, slow) and adds branching, multiple camera angles, parental control, video menus, interactivity, etc., although some of these features are not available on all discs. Unlike CAV LD, DVD can't play backwards (it's technically possible, but no current players can do it).
  • Capacity: Single-layer DVD holds over 2 hours, dual-layer holds over 4 hours. CLV LD holds one hour per side, CAV holds half an hour. A CAV laserdisc can hold 104,000 still images. DVD can hold thousands of still pictures accompanied by hundreds of hours of audio and text.
  • Convenience: An entire movie fits on one side of a DVD, so there's no need to flip the disc or wait for the player to do it. DVDs are smaller and easier to handle. DVD players can be portable, similar to CD players. Discs can be easily and cheaply sent through the mail. On the other hand, laserdiscs have larger covers for better art and text.
  • Noise: Most LD players make a whirring noise that can be heard during quiet segments of a movie. Most DVD players are as quiet as CD players.
  • Audio: LD has better quality on Dolby Surround soundtracks, which are stored in uncompressed PCM format. DVD has better quality on Dolby Digital or music only. LD has 2 audio tracks: analog and digital. DVD has up to 8 audio tracks. LD uses PCM audio sampled with 16 bits at 44 kHz. DVD LPCM audio can use 16, 20, or 24 bit samples at 48 or 96 kHz (although PCM won't be used with most movies). LD has surround audio in Dolby Surround, Dolby Digital (AC-3), and DTS formats. 5.1-channel surround sound is available by using one channel of the analog track for AC-3 or both channels of the digital track for DTS. DVD uses the same Dolby Digital surround sound, usually at the same data rate (384 kbps) but can go up to 448 kbps for better quality, and can optionally include DTS (at data rates up to 1536 kbps compared to LD's 1411 kbps, but in practice DTS data rates will probably be lower on DVD than on LD). DVD players convert Dolby Digital to Dolby Surround. This conversion (downmix) process can reduce dynamic range. Combined with the effects of compression, this usually results in lower-quality sound than from LD Dolby Surround tracks.
  • Video: DVD usually has better video. LD suffers from degradation inherent in analog storage and in the composite NTSC or PAL video signal. DVD uses digital video, and even though it's heavily compressed, most professionals agree that when properly and carefully encoded it's virtually indistinguishable from studio masters. Nevertheless, this doesn't mean that the video quality of DVD, especially at first, WILL be better than LD. Only that it CAN be better. Also keep in mind that the average television is of insufficient quality to show much difference between LD and DVD. Home theater systems or HDTVs are needed to take full advantage of the improved quality. The arguments about DVD quality vs. LD quality will rage for a long time. The only final answer is to compare them side by side and form your own opinion.
  • Resolution: In numerical terms DVD has 345,600 pixels (720x480), which is 1.3 times LD's approximately 272,160 pixels (567x480). Widescreen DVD has 1.7 times the pixels of letterboxed LD (or 1.3 times anamorphic LD). As for lines of horizontal resolution, DVD ~= 500, LD ~= 425, and VHS ~= 240. In analog output signal terms, typical luma frequency response maintains full amplitude to between 5.0 and 5.5 MHz. This is below the 6.75 MHz native frequency of the MPEG-2 digital signal. Chroma frequency response is one-half that of luma. Laserdisc frequency response usually begins to fall off at 3 MHz. (All figures are for NTSC, not PAL.)
  • Legacy titles: There are thousands of movies on laserdisc that will probably never appear on DVD.
  • Availability: DVD players and discs are available for purchase and rental in thousands of outlets and on the Internet. LD players and discs are becoming hard to find.
  • Price: Low-cost DVD players are cheaper than the cheapest LD player, and the success of DVD-ROM will inevitably drive the price to the under-$100 level of CD players. Most movies on DVD cost less than on LD.
  • Restrictions: For those outside the US, regional coding is a definite drawback of DVD. For some people Macrovision copy protection is an annoyance. Laserdisc has no copy protection and does not have regional differences other than PAL vs. NTSC.

Does DVD support HDTV?

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. ATSC standard in specific. The ATSC standard includes both standard-definition (SD) and high-definition (HD) digital formats. The notation H/DTV is often used to specifically refer to high-definition digital TV.

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.

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. 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 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 fields/sec [30 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. CEA expects 10 percent of U.S. households to have HDTV in 2003, 20 percent by 2005, and 30 percent by 2006.

HDTV 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 (YCbCr) 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 for under $3000. The quality of a good DVD PC connected to a data-grade video projector beats $30,000 line-doubler systems.

Eventually the DVD-Video format will be upgraded to an "HD-DVD" format.

What's Wide Screen, and how do aspect ratios work?

Video can be stored on a DVD in 4:3 format (standard TV shape) or 16:9 (widescreen). The width-to-height ratio of standard televisions is 4 to 3; in other words, 1.33 times wider than high. New widescreen televisions, specifically those designed for HDTV, have a ratio of 16 to 9; that is, 1.78 times wider than high.

DVD is specially designed to support widescreen displays. Widescreen 16:9 video, such as from a 16:9 video camera, can be stored on the disc in anamorphic form, meaning the picture is squeezed horizontally to fit the standard 4:3 rectangle, then unsqueezed during playback.

Things get more complicated when film is transferred to video, since most movies today have an aspect ratio of 1.66, 1.85 ("flat"), or 2.40 ("scope"). Since these don't match 1.33 or 1.78 TV shapes, two processes are employed to make various movie pegs fit TV holes:

Letterbox (often abbreviated to LBX) means the video is presented in its theatrical aspect ratio, which is wider than standard or widescreen TV. Black bars, called mattes, are used to cover the gaps at the top and bottom. A 1.85 movie that has been letterboxed for 1.33 display has thinner mattes than a 2.4 movie letterboxed to 1.33 (28% of display height vs. 44%), although the former are about the same thickness as those of a 2.4 movie letterboxed to 1.78 (26% of display height). The mattes used to letterbox a 1.85 movie for 1.78 display are so thin (2%) that they're hidden by the overscan of most widescreen TVs. Some movies, especially animated features and European films, have an aspect ratio of 1.66, which can be letterboxed for 1.33 display or sideboxed for 1.78 display.

Pan & scan means the thinner TV "window" is panned and zoomed across the wider movie picture, chopping off the sides. However, most movies today are shot soft matte, which means a full 1.33 aspect film frame is used. (The cinematographer has two sets of frame marks in her viewfinder, one for 1.33 and one for 1.85, so she can allow for both formats.) The top and bottom are masked off in the theater, but when the film is transferred to video the full 1.33 frame can be used in the pan & scan process. Pan & scan is primarily used for 1.33 formatting, not for 1.78 formatting, since widescreen fans prefer that letterboxing be used to preserve the theatrical effect.

Once the video is formatted to full-frame or widescreen form, it's encoded and stored on DVD discs. DVD players have four playback modes, one for 4:3 video and three for 16:9 video:

  • full frame (4:3 video for 4:3 display)

  • auto letterbox (16:9 video for 4:3 display)

  • auto pan & scan (16:9 video for 4:3 display)

  • widescreen (16:9 video for 16:9 display)

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 with letterboxing or pan & scan before being transferred to DVD. All formatting done to the video prior to it being stored on the disc is transparent to the player. It merely reproduces it as a standard 4:3 TV picture. Video that is letterboxed before being encoded can be flagged so that the player will tell a widescreen TV to automatically expand the picture. Unfortunately, some discs (such as Fargo) do not flag the video properly. And worse, some players ignore the flags.

The beauty of anamorphosis is that less of the picture is wasted on letterbox mattes. DVD has a frame size designed for 1.33 display, so the video still has to be made to fit, but because it's only squeezed horizontally, 33% more pixels (25% of the total pixels in a video frame) are used to store active picture instead of black. Anamorphic video is best displayed on widescreen equipment, which stretches the video back out to its original width. Alternatively, many new 4:3 TV's can reduce the vertical scan area to restore the proper aspect ratio without losing resolution (an automatic trigger signal is sent to European TVs on SCART pin 8). Even though almost all computers have 4:3 monitors, they have higher resolution than TVs so they can display the full widescreen picture in a window (854x480 pixels or bigger for NTSC; 1024x576 or bigger for PAL).

Anamorphic video can be converted by the player for display on standard 4:3 TVs in letterbox or pan & scan form. 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. The setup options of DVD players allow the viewer to indicate whether they have a 16:9 or 4:3 TV. In the case of a 4:3 TV, a second option lets the viewer indicate a preference for how the player will reformat anamorphic video. The two options are detailed below.

For automatic letterbox mode, the player generates 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 (1.78:1). In order to fit this shorter rectangle, the anamorphic picture is squeezed vertically using a letterbox filter that combines every 4 lines into 3, reducing the vertical resolution from 480 scan lines to 360. (If the video was already letterboxed to fit the 1.78 aspect, then the mattes generated by the player will extend the mattes in the video.) The vertical squeezing exactly compensates for the original horizontal squeezing so that the movie is shown in its full width. Some players have better letterbox filters than others, using weighted averaging to combine lines (scaling 4 lines into 3 or merging the boundary lines) rather than simply dropping one out of every four lines. Widescreen video can be letterboxed to 4:3 on expensive studio equipment before it's stored on the disc, or it can be stored in anamorphic form and letterboxed to 4:3 in the player. If you compare the two, the letterbox mattes will be identical but the picture quality of the studio version may be slightly better.

For automatic pan & scan mode, the anamorphic video is unsqueezed to 16:9 and the sides are cropped off so that 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. Auto pan & scan has three strikes against it: 1) it doesn't provide the same artistic control as studio pan & scan, 2) there is a loss of detail when the picture is scaled up, and 3) equipment for recording picture shift information is not widely available. Therefore, no anamorphic 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 can be used in both widescreen and 4:3 mode. In order to present a quality full-screen picture to the vast majority of TV viewers, yet still provide the best experience for widescreen owners, some DVD producers choose to put two versions on a single disc: 4:3 studio pan & scan and 16:9 anamorphic.

Playback of widescreen material can be restricted by the producer of the disc.
Programs can be marked for the following display modes:
- 4:3 full frame
- 4:3 LB (for sending letterbox expand signal to 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)

You can usually tell if a disc contains anamorphic video if the packaging says "enhanced for 16:9 widescreen" or something similar. If all it says is "widescreen," it may be letterboxed to 4:3, not 16:9.

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). 

How do a DVD's interactive features work?

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 on of three types: 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).

Can I play DVD Videos on my computer?

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. You don't need special drivers for Windows, since the existing CD-ROM drivers work fine with DVD-ROM drives. 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. Good-quality software-only playback requires a 350-MHz Pentium II or a Mac G4. Less than 10% of new computers with DVD-ROM drives include decoder hardware, since software decoding is now possible on even the cheapest new models. Hardware upgrade kits can be purchased for existing computers (usually minimum 133 MHz Pentium or G3).

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. All modern graphics cards also provide hardware colorspace conversion (YCbCr to RGB) and videoport overlay.

Microsoft Windows 98 and Windows 2000 includes DirectShow, which provides standardized support for DVD-Video and MPEG-2 playback. DirectShow can also be installed in Windows 95 (it's available for download). DirectShow creates a framework for DVD applications, but a third-party hardware or software decoder is required (see below). Windows NT 4.0 supports DVD-ROM drives for data, but has very little support for playing DVD-Video discs. Margi DVD-To-Go, Sigma Designs Hollywood Plus, and the related Creative Labs Dxr3 are among the few hardware decoders that work in NT 4.0. InterVideo WinDVD software works in NT 4.0 (Mediamatics DVD Express and MGI SoftDVD Max also work in NT 4.0, but they aren't available retail.) Windows 2000 uses essentially the same WDM drivers and DirectShow software as Windows 98, so it fully supports movie playback and DVD applications, including WebDVD. Internet Explorer 5.0 includes version 6.1 of Windows Media Player that enables scriptable DVD playback 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.

Apple QuickTime 4 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.

Note: The QuickTime MPEG Extension for Mac OS 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 need at least a 350 MHz Pentium II and a DVD-ROM drive with bus mastering DMA to play without dropped frames. Anything slower than a 400 MHz Pentium III will benefit quite a bit from hardware decode acceleration in the graphics card. An AGP graphics card (rather than PCI) also improves the performance of software decoders.

All but the Sigma Designs decoder (including Creative Dxr3) have WDM drivers for DirectShow. The Sigma Designs decoder card is used in hardware upgrade kits from Hitachi, Panasonic, Phillips, Sony, Toshiba, and VideoLogic. 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. The Chromatic Mpact2 chip does 3-field analysis to produce exceptional progressive-scan video from DVDs (unfortunately, Chromatic was bought by ATI and the chip is no longer supported) Hardware decoders use video overlay to insert the video into the computer display. Some use analog overlay, which takes the analog VGA signal output from the graphics card and keys in the video, while others use video port extension (VPE), a direct digital connection to the graphics adapter via a cable inside the computer. Analog overlay may degrade the quality of the VGA signal.

Macintosh G4's and some iMacs come standard with DVD-ROM or DVD-RAM drives. They use the Velocity Engine (AltiVec) portion of the PowerPC chip for video and audio decoding. Unfortunately, there are numerous problems with Apple's software decoding. Apple released five software updates in the first four months.  A few models of the iMac, PowerBook, and G3 lines can be ordered with DVD-ROM drives and hardware decoders. 

Computers have the potential to produce better video than set-top DVD-Video players by using progressive display and higher scan rates, but 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). Video quality is much better with 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. The RGB output of the VGA card in computers is at a different frequency than standard component RGB video, so it can't be directly connected to most RGB video monitors. If the decoder card or the sound card has Dolby Digital or DTS output, you can connect to your A/V receiver to get multichannel audio.

A DVD PC connected to a progressive-scan monitor or video projector, instead of a standard TV, usually looks much better than a consumer player.

What are the features and speeds of DVD-ROM drives?

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. 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 physical spin rate is about 3 times faster than CD (that is, 1x DVD spin ~ 3x CD spin), but most DVD-ROM drives increase motor speed when reading CD-ROMs, achieving 12x or faster performance.  A drive listed as "16x/40x" spins a DVD at 16 times normal, or a CD at 40 times normal. DVD-ROM drives are available in 2x, 4x, 4.8x, 5x, 6x, 8x, 10x, and 16x speeds, although they usually don't achieve sustained transfer at their full rating. The "max" in DVD and CD speed ratings means that the listed speed only applies when reading data at the outer edge of the disc, which moves faster. The average data rate is lower than the max rate. Most 1x DVD-ROM drives have a seek time of 85-200 ms and access time of 90-250 ms.

DVD drive speed Data rate Equivalent CD rate Actual CD speed
1x 11.08 Mbps (1.32 MB/s) 9x 8x-18x
2x 22.16 Mbps (2.64 MB/s) 18x 20x-24x
4x 44.32 Mbps (5.28 MB/s) 36x 24x-32x
5x 55.40 Mbps (6.60 MB/s) 45x 24x-32x
6x 66.48 Mbps (7.93 MB/s) 54x 24x-32x
8x 88.64 Mbps (10.57 MB/s) 72x 32x-40x
10x 110.80 Mbps (13.21 MB/s) 90x 32x-40x
16x 177.28 Mbps (21.13 MB/s) 144x 32x-40x

This is useful primarily for data, not video. It may reduce or eliminate the pause during layer changes, but has no effect on video quality.

In order to maintain constant linear density, typical CD-ROM and DVD-ROM drives spin the disc more slowly when reading near the outside where there is more physical surface in each track. (This is CLV, constant linear velocity.) Some faster drives keep the rotational speed constant and use a buffer to deal with the differences in data readout speed. (This is CAV, constant angular velocity.) In CAV drives, the data is read fastest at the outside of the disc, which is why specifications often list "max speed."

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.

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Much of this information was compiled with the help of Jim Taylor's DVD FAQ. Thanks Jim!

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