DVD-Audio is a separate format from DVD-Video. DVD-Audio discs can be designed to work in DVD-Video players, but it's possible to make a DVD-Audio disc that won't play at all in a DVD-Video player, since the DVD-Audio specification includes new formats and features, with content stored in a separate "DVD-Audio zone" on the disc (the AUDIO_TS directory) that DVD-Video players never look at. New DVD-Audio players are needed, or new "universal players" that can play both DVD-Video and DVD-Audio discs. Universal players are also called VCAPs (video-capable audio players).

Plea to producers: Universal players won't be available for some time, but you can make universal discs today. With a small amount of effort, all DVD-Audio discs can be made to work on all DVD players by including a Dolby Digital version of the audio in the DVD-Video zone.
Plea to DVD-Audio authoring system developers: Make your software do this by default or strongly recommend this option during authoring.

DVD-Audio players (and universal players) work with existing receivers. They output PCM and Dolby Digital, and some will support the optional DTS and DSD formats. However, most current receivers can't decode high-definition, multichannel PCM audio (see 3.6.1 for details), and even if they could it can't be carried on standard digital audio connections. DVD-Audio players with high-end digital-to-analog converters (DACs) can only be hooked up to receivers with 2-channel or 6-channel analog inputs, but some quality is lost if the receiver converts back to digital for processing. Future receivers with improved digital connections such as IEEE 1394 (FireWire) will be needed to use the full digital resolution of DVD-Audio.

DVD audio is copyright protected by an embedded signaling or digital watermark feature. This uses signal processing technology to apply a digital signature and optional encryption keys to the audio in the form of supposedly inaudible noise so that new equipment will recognize copied audio and refuse to play it. Audiophiles claim this degrades the audio, but tests performed by the 4C indicate that even golden-eared listeners can't detect the watermarking noise. Proposals from Aris, Blue Spike, Cognicity, IBM, and Solana were evaluated by major music companies in conjunction with the 4C Entity, comprising IBM, Intel, Matsushita, and Toshiba. Aris and Solana merged to form a new company called Verance, whose Galaxy technology was chosen for DVD-Audio in August 1999. (In November 1999, Verance watermarking was also selected for SDMI.)

Sony and Philips have developed a competing Super Audio CD format that uses DVD discs. (See 3.6.1 for details.) Sony released version 0.9 of the SACD spec in April 1998, the final version appeared in April (?) 1999. SACD technology is available to existing Sony/Philips CD licensees at no additional cost. Most initial SACD releases have been mixed in stereo, not multichannel. SACD was originally supposed to provide "legacy" discs with two layers, one that plays in existing CD players, plus a high-density layer for DVD-Audio players, but technical difficulties kept dual-format discs from being produced until the end of 2000, and only then in small quantities. Pioneer, which released the first DVD-Audio players in Japan at the end of 1999, included SACD support in their DVD-Audio players. If other manufacturers follow suit, the entire SACD vs. DVD-Audio standards debate could be moot, since DVD-Audio players would play both types of discs.

Sony released an SACD player in Japan in May 1999 at the tear-inducing price of $5,000. The player was released in limited quantities in the U.S. at the end of 1999. Philips released a $7,500 player in May 2000. Sony shipped a $750 SACD player in Japan in mid 2000. About 40 SACD titles were available at the end of 1999, from studios such as DMP, Mobile Fidelity Labs, Pioneer, Sony, and Telarc.

A drawback related to DVD-Audio and SACD players is that most audio receivers with 6 channels of analog input aren't able to do bass management. Receivers with Dolby Digital and DTS decoders handle bass management internally, but most receivers with 6-channel audio inputs simply pass them through to the amplifier. Until new audio systems with full bass management from 6-channel inputs are developed, any setup that doesn't have full-range speakers for all 5 surround channels will not properly reproduce all the bass frequencies. In the interim, you may be able to use an outboard bass managment box, such as from Outlaw Audio.

If you are interested in making the most of a DVD-Audio or SACD player, you need a receiver with 6-channel analog audio inputs. You also need 5 full-frequency speakers (that is, each speaker should be able to handle subwoofer frequencies) and a subwoofer, unless you have a receiver that can perform bass management on the analog inputs.

For more on DVD-Audio, particularly various player models, visit Digital Audio Guide.

[1.13] Which studios are supporting DVD?

All major movie studios, most major music studios.

When DVD players became available in early 1997, Warner and Polygram were the only major movie studios to release titles. Additional titles were available from small publishers. The other studios gradually joined the DVD camp (see 6.2 for a full list, see 1.6 for movie info). Dreamworks was the last significant studio to announce full DVD support. Paramount, Fox, and Dreamworks initially supported only Divx, but in summer 1998 they each announced support for open DVD.

[1.14] Can DVD record from VCR/TV/etc?

Short Answer: Not yet, but soon. Most of the major DVD player manufactureres have announced DVD home video recorders. (See 4.3.)

Long answer: Recording analog video to DVD is a very tricky process. 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. It's difficult in real time to encode the video and audio, combine them with DVD-Video info, and write the whole thing to a recordable DVD disc, especially in a form that's compatible with standard DVD-Video players. This is still extremely expensive for a home recorder, even though prices for DVD production systems have dropped over the space of three years from millions of dollars to thousands of dollars to hundreds of dollars for the simplest packages.

Other obstacles: Blank discs cost about $25 (although they will get cheaper over time). Real-time compression requires higher bit rates for decent quality, thus lowering capacity. MPEG-2 compression works much better with high-quality source, so recording from VHS or broadcast/cable may not give very good results (unless the DVD recorder has special prefilters, which increases the cost).

Don't be confused by DVD-R drives, DVD-RAM drives, or other recordable DVD drives for computers (see 4.3). These existing recorders can store data, but to create full-featured DVD-Videos requires additional hardware and software to do video encoding (MPEG), audio encoding (Dolby Digital, MPEG, or PCM), subpicture encoding (run-length-compressed bitmaps), still frame encoding (MPEG), navigation and control data generation, and multiplexing.

In spite of all the difficulties, many of the major DVD manufacturers are working on recordable DVD for the home. We will see various DVD video recorders in the year 2000. Early units, especially those that can record from analog video sources such as TV, will be expensive: probably $2,000 and up. There will also be cheaper units that can record only from a source of already-compressed digital audio and video, such as satellite, DTV, or digital cable. At some point, DVD recorder/players will be built into satellite and cable receivers. 

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. Once the encoding technology is fast and cheap enough, and blank discs are cheap enough, recordable DVD will reach the mainstream.

[1.15] What happens if I scratch the disc? Aren't discs too fragile to be rented?

Most scratches will cause minor channel data errors that are easily corrected. That is, data is stored on DVDs using powerful error correction techniques that can recover from scratches as big as 6 millimeters with no loss of data. A common misperception is that a scratch will be worse on a DVD than on a CD because of higher storage density and because video is heavily compressed. DVD data density (say that fast ten times!) is physically four times that of CD-ROM, so it's true that a scratch will affect more data. But DVD error correction is at least ten times better than CD-ROM error correction and more than makes up for the density increase. It's also important to realize that MPEG-2 and Dolby Digital compression are partly based on removal or reduction of imperceptible information, so decompression doesn't expand the data as much as might be assumed. Major scratches may cause uncorrectable errors that will produce an I/O error on a computer or show up as a momentary glitch in DVD-Video picture. Paradoxically, sometimes the smallest scratches can cause the worst errors (because of the particular orientation and refraction of the scratch). There are many schemes for concealing errors in MPEG video, which may be used in future players.

See 1.39 for information on care and cleaning of DVDs.

The DVD computer advisory group specifically requested no mandatory caddies or other protective carriers. Consider that laserdiscs, music CDs, and CD-ROMs are likewise subject to scratches, but many video stores and libraries rent them. Major chains such as Blockbuster and West Coast Entertainment rent DVDs in many locations. So far most reports of rental disc performance are positive. A nice list of DVD rental outlets is at <home.earthlink.net/~tlfordham/rental.html>.

[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, so they would like the packaging to be different. There are a number of DVD packages that are as wide as a CD jewel box (about 5-5/8") and as tall as a VHS cassette box (about 7-3/8"), as recommended by the Video Software Dealers Association (VSDA). However, no one is being forced to use a larger package size. Some companies use standard jewel cases or paper and vinyl sleeves. Divx discs came in paperboard and plastic Q-Pack cases the same size as a CD jewel case.

Most movies are packaged in the Amaray "keep case," an all-plastic clamshell with clear vinyl pockets for inserts, that's popular among consumers. Time Warner's "snapper," a paperboard case with a plastic lip, is less popular. There's also a "super jewel box," the stretch-limo version of a CD jewel case, that's common in Europe. 

[1.18] What's a dual-layer disc? Will it work in all players?

A dual-layer disc has two layers of data, one of them semi-transparent so that the laser can focus through it and read the second layer. Since both layers are read from the same side, a dual-layer disc can hold almost twice as much as a single-layer disc, typically 4 hours of video (see 3.3 for more details). Many discs use dual layers. Initially only a few replication plants could make dual-layer discs, but most plants now have the capability. The second layer can use either a PTP (parallel track path) layout where both tracks run in parallel (for independent data or special switching effects), or an OTP (opposite track path) layout where the second track runs in an opposite spiral; that is, the pickup head reads out from the center on the first track then in from the outside on the second track. The OTP layout is designed to provide continuous video across both layers. The layer change can occur anywhere in the video; it doesn't have to be at a chapter point. There's no guarantee that the switch between layers will be seamless. The layer change is invisible on some players, but it can cause the video to freeze for a fraction of a second or up to 4 seconds on other players. The "seamlessness" depends as much on the way the disc is prepared as on the design of the player. OTP is also called RSDL (reverse-spiral dual layer). The advantage of two layers is that long movies can use higher data rates for better quality than with a single layer. See 1.27 for more about layer changes.

There are various ways to recognize dual-layer discs: 1) the gold color, 2) a menu on the disc for selecting the widescreen or letterbox version, 3) two serial numbers on one side.

The DVD specification requires that players and drives read dual-layer discs. There are very few units that have problems with dual-layer discs--this is a design flaw and should be corrected for free by the manufacturer. Some discs are designed with a "seamless layer change" that technically goes beyond what the DVD spec allows. This causes problems on a few older players.

All players and drives also play double-sided discs if you flip them over. No manufacturer has announced a model that will play both sides. The added cost is hard to justify since discs can hold over 4 hours of video on one side by using two layers. (Early discs used two sides because dual-layer production was not widely supported. This is no longer a problem.) Pioneer LD/DVD players can play both sides of an LD, but not a DVD. (See 2.12 for note on reading both sides simultaneously.)

[1.19] Is DVD-Video a worldwide standard? Does it work with NTSC, PAL, and SECAM?

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 options (Dolby Digital vs. MPEG audio). (See 3.4 and 3.6 for details.) Therefore, there are two kinds of DVDs: NTSC DVDs and PAL/SECAM DVDs.

Video from film is usually encoded 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% at playback, so the audio must be adjusted accordingly before being encoded. All PAL DVD players can play Dolby Digital audio tracks, but not all 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 by SECAM TVs. Note that modern TVs in most SECAM countries can also read PAL signals, so you can use a player that only has PAL output. The only case in which you need a player with SECAM output is for older SECAM-only TVs (and you'll probably need a SECAM RF connection, see 3.1).

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 60-Hz 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 "pseudo-PAL" 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 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. (Sound is not affected by video conversion.)

Most NTSC players can't play PAL discs. A very small number of NTSC players (such as Apex and SMC) can convert 625/50 PAL to NTSC. External converter boxes are also available, such as the Emerson EVC1595 ($350). High-quality converters are available at TenLab and Snell and Wilcox.

A producer can choose to put 525/60 video on one side of the disc and 625/50 on the other. Most studios put 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.

Bottom line: NTSC discs (with Dolby Digital audio) play on over 95% of DVD installations worldwide. PAL discs play on very few players outside of PAL countries. (This is irrespective of regions -- see 1.10.)

[1.20] What about animation on DVD? Doesn't it compress poorly?

Some people claim that animation, especially hand-drawn cell animation such as cartoons and anime, does not compress well with MPEG-2 or even ends up larger than the original. Other people claim that animation is simple so it compresses better. Neither is true.

Supposedly the "jitter" between frames caused by differences in the drawings or in their alignment causes problems. An animation expert at Disney pointed out that this doesn't happen with modern animation techniques. And even if it did, the motion estimation feature of MPEG-2 would compensate for it.

Because of the way MPEG-2 breaks a picture into blocks and transforms them into frequency information it can have a problem with the sharp edges common in animation. This loss of high-frequency information can show up as "ringing" or blurry spots along edges (called the Gibbs effect). However, at the data rates commonly used for DVD this problem does not occur.

[1.21] Why do some discs require side flipping? Can't DVDs hold four hours per side?

Even though DVD's dual-layer technology (see 3.3) allows over four hours of continuous playback from a single side, some movies are split over two sides of a disc, requiring that the disc be flipped partway through. Most "flipper" discs exist because of producers who are too lazy to optimize the compression or make a dual-layer disc. Better picture quality is a cheap excuse for increasing the data rate; in many cases the video will look better if carefully encoded at a lower bit rate. Lack of dual-layer production capability is also a lame excuse; in 1997 very few DVD plants could make dual-layer discs, but this is no longer the case. No players can automatically switch sides, but it's not needed since most movies less than 4 hours long can easily fit on one dual-layer (RSDL) side.

There is a list of "flipper" discs in the Film Vault at DVD Review. Note: A flipper is not the same as a disc with a widescreen version on one side and a pan & scan version or supplements on the other. Please send additions to info@dvdreview.com. (The list has gotten too long to keep in this FAQ.)

[1.22] Why is the picture squished, making things look too skinny?

Answer: RTFM. You are watching an anamorphic picture intended for display only on a widescreen TV. (See 3.5 for technical details). You need to go into the player's setup menu and tell it you have a standard 4:3 TV, not a widescreen 16:9 TV. It will then automatically letterbox the picture so you can see the full width at the proper proportions.

In some cases you can change the aspect ratio as the disc is playing (by pressing the "aspect" button on the remote control). On most players you have to stop the disc before you can change aspect. Some discs are labeled with widescreen on one side and standard on the other. In order to watch the fullscreen version you must flip the disc over.

See 1.38 for more on letterboxing.

[1.23] Do all videos use Dolby Digital (AC-3)? 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.

See 3.6 for more audio details.

[1.24] Can DVDs have laser rot?

Laserdiscs are subject to what's commonly called laser rot: the deterioration of the aluminum layer due to oxidation or other chemical change. This often results from the use of insufficiently pure aluminum during replication, but can be exacerbated by mechanical shear stress due to bending, warping or thermal cycles (the large size of laserdiscs makes them flexible, so that movement along the bond between layers can break the seal). Deterioration of the data layer can be caused by chemical contaminants or gasses in the glue, or by moisture that penetrates the acrylic substrates.

Like laserdiscs, DVDs are made of two platters glued together, but DVDs are more rigid and use newer adhesives. DVDs are molded from polycarbonate, which absorbs about ten times less moisture than the slightly hygroscopic acrylic (PMMA) used for laserdiscs.

It's too early to know for sure, but DVDs will probably have few laser rot problems. There have been reports of a few discs going bad, possibly due to poor adhesive, chemical reactions, or oxidation of the aluminum layer. See www.mindspring.com/~yerington/.

[1.25] Which titles are pan & scan only? Why?

Some titles are available only in pan & scan because there was no letterbox or anamorphic transfer made from film. (See 3.5 for more info on pan & scan and anamorphic formats.) Since transfers cost $50,000 to $100,000, studios may not think a new transfer is justified. In some cases the original film or rights to it are no longer available for a new transfer. In the case of old movies, they were shot full frame in the 1.37 "academy" aspect ratio so there can be no widescreen version. Video shot with TV cameras, such as music concerts, is already in 4:3 format.

The list of pan & scan only titles has gotten too big to keep here. You can get a list from the Film Vault at DVD Review, or from Internet Movie Database (which also includes discs with both widescreen and pan & scan versions).

[1.26] How do I make the subtitles on my Pioneer player go away?

On the remote control, press Subtitle, then either Clear or 0 (zero). No need to use the menus.

[1.27] What is a layer change? Where is it on specific discs?

Some movies, especially those over two hours long or encoded at a high data rate, are spread across two layers on one side of the disc. When the player changes to the second layer, the video and audio may freeze for a moment. The length of the pause depends on the player and on the layout of the disc. The pause is not a defect in the player or the disc. See 1.18 for details.

There is a list of layer switch points in the Film Vault at DVD Review. Please send new times to info@dvdreview.com. (The list has gotten too long to keep in this FAQ.)

[1.28] The disc says Dolby Digital. Why do I get 2-channel surround audio?

Some discs (many from Columbia TriStar) have 2-channel Dolby Surround audio (or plain stereo) on track one and 5.1-channel audio on track two. Since some studios create separate sound mixes optimized for Dolby Surround or stereo, and they feel the default track should match the majority of sound systems in use. Unless you specifically select the 5.1-channel track (with the audio button on the remote or with the on-screen menu) the player will play the default 2-channel track. (Note: Some players such as the Sony 3000 have a feature to automatically select the first 5.1 track.)

Dolby Digital doesn't necessarily mean 5.1 channels. See 3.6.

[1.29] Why doesn't the repeat A-B feature work on some discs?

Almost all features of DVD such as search, pause, and scan can be disabled by the disc, which can prevent the operation the player needs to back up and repeat a segment. If the player uses time search to repeat a segment, then a disc with fancy non-sequential title organization may also block the repeat feature. In many cases the authors don't even realize they have prevented the use of this feature.

[1.30] What's the difference between first, second, and third generation DVD?

There is no meaningful answer to this question, since you'll get a different response from everyone you ask. The terms "2nd generation" and "3rd generation," and so on refer both to DVD-Video players and to DVD-ROM drives. In general, they simply mean newer versions of DVD playback devices. The terms haven't been used (yet) to refer to DVD products that can record, play video games, or so on.

According to some people, second-generation DVD players came out in the fall of 1997 and third-generation players are those that came out in the beginning of 1998. According to others, the second generation of DVD will be HD players (see 2.12) that won't come out until 2003 or so. There are many conflicting variations between these extremes, including the viewpoint that DTS-compatible players or Divx players or progressive-scan players or 10-bit video players or players that can play The Matrix constitute the second, third, or fourth generation.

Things are a little more clear cut on the PC side, where second generation (DVD II) usually means 2x DVD-ROM drives that can read CD-Rs, and third generation (DVD III) usually means 5x (or sometimes 2x or 4.8x or 6x) DVD-ROM drives, a few of which can read DVD-RAMs, and some of which are RPC2 format. Some people refer to RPC2 drives or 10x drives as fourth generation. See section 4.2 for more speed info. See section 1.10 for RPC2 explanation.

[1.31] What's 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 or AV 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 0.9 to 1.2 mm CD substrate bonded to the back of a 0.6 mm DVD substrate. One side can be read by CD players, the other side by DVD players. The resulting disc is 0.6 mm 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. There's a variation in which an 8-cm data area is embedded in a 12-cm substrate so that a label can be printed on the outer ring. 
    2. A 0.6 mm CD substrate bonded to a semitransparent 0.6 mm 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 0.6 mm CD substrate, with a special refractive coating that causes a 1.2 mm focal depth, bonded to the back of a 0.6 mm 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 DVD-PROMmixed-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?

[1.32] What's the deal with DTS and DVD?

Digital Theater Systems Digital Surround is an audio encoding format similar to Dolby Digital. It requires a decoder, either in the player or in an external receiver. See 3.6.2 for technical details. Some people claim that because of its lower compression level DTS sounds better than Dolby Digital. Others claim there is no meaningfully perceptible difference, especially at the typical data rate of 768 kbps, which is 60% more than Dolby Digital. Because of the many variances in production, mixing, decoding, and reference levels, it's almost impossible to accurately compare the two formats (DTS usually produces a higher volume level, causing it to sound better in casual comparisons).

DTS originally did all encoding in house, but as of October 1999 DTS encoders are available for purchase. DTS titles are generally considered to be specialty items intended for audio enthusiasts. Most DTS are also be available in a Dolby Digital-only version.

DTS is an optional format on DVD. Contrary to uninformed claims, the DVD specification has included an ID code for DTS since 1996 (before the spec was even finalized). Because DTS was slow in releasing encoders and test discs, players made before mid 1998 (and many since) ignore DTS tracks. A few demo discs were created in 1997 by embedding DTS data into a PCM track (the same technique used with CDs and laserdiscs), and these are the only DTS DVD discs that work on all players. New DTS-compatible players arrived in mid 1998, but theatrical DTS discs using the proper DTS audio stream ID did not appear until January 7, 1999 (they were originally scheduled to arrive in time for Christmas 1997). Mulan, a direct-to-video animation (not the Disney movie) with DTS soundtrack appeared in November 1998. DTS-compatible players carry an official "DTS Digital Out" logo.

Dolby Digital or PCM audio are required on 525/60 (NTSC) discs, and since both PCM and DTS together don't usually leave enough room for quality video encoding of a full-length movie, essentially every disc with a DTS soundtrack also carries a Dolby Digital soundtrack. This means that all DTS discs will work in all DVD players, but a DTS-compatible player and a DTS decoder are required to play the DTS soundtrack. DTS audio CDs work on all DVD players, since the DTS data is encapsulated into standard PCM tracks that are passed untouched to the digital audio output.

[1.33] Why is the picture black and white?

You are probably trying to play an NTSC disc in a PAL player, but your PAL TV is not able to handle the signal. If your player has a switch or on-screen setting to select the output format for NTSC discs, choosing PAL (60-Hz) may solve the problem. See section 1.19 for more information.

Or you may have connected one of the component outputs (Y, R-Y, or B-Y) of your DVD player to the composite input of your TV. See section 3.2 for hookup details. 

[1.34] Why are both sides fullscreen when one side is supposed to be widescreen?

Many DVD's are labeled as having widescreen (16:9) format video on one side and standard (4:3) on the other. If you think both sides are the same, you're probably seeing uncompressed 16:9 on the widescreen side. It seems to be 4:3 pan & scan, but if you look carefully you'll discover that the picture is horizontally compressed. The problem is that your player has been set for a widescreen TV. See 1.22 for details.

[1.35] Why are the audio and video out of sync?

There have been numerous reports of "lip sync" problems, where the audio lags slightly behind the video, and even reports of the audio coming before the video. Perception of a sync problem is highly subjective--some people are bothered by it while others can't discern it at all. Problems have been reported on a variety of players (notably the Pioneer 414 and 717 models, possibly all Pioneer models, some Sony models including the 500 series and the PS2, new Toshiba models including the 3109, and some PC decoder cards). Certain discs are also more problematic (notably Lock, Stock, and Two Smoking Barrels; Lost In Space; TRON; The Parent Trap; and Austin Powers).

The cause of the sync problem is a complex interaction of as many as four factors

  1. Improper sync in audio/video encoding or DVD-Video formatting.
  2. Poor sync during film production or editing (especially post-dubbing or looping).
  3. Loose sync tolerances in the player.
  4. Delay in the external decoder/receiver.

Factor 1 or 2 usually must be present in order for factor 3 or 4 to become apparent. Some discs with severe sync problems have been reissued after being re-encoded to fix the problem. In some cases, the sync problem in players can be fixed by pausing or stopping playback and then restarting, or by turning the player off, waiting a few seconds, then turning it back on. Pioneer has stated that altering the audio-visual synchronization of their players "to compensate for the software quality would dramatically compromise the picture performance."

Unfortunately, there is no simple answer and no simple fix. More complaints from customers will motivate manufacturers to take the problem more seriously and hopefully correct it in future players or with firmware upgrades.

[1.36] Why does the picture alternate between light and dark?

You are seeing the effects of Macrovision copy protection (see 1.11), probably because you are running your DVD player through your VCR or VCR/TV combo (see 3.2.1).

[1.37] How do I find "Easter eggs" and other hidden features?

Some DVD movies contain hidden features, often called "Easter eggs." These are extra screens or video clips hidden in the disc by the developers. For example, Dark City includes scenes from Lost in Space and the Twin Peaks movie buried in the biography pages of William Hurt and Keifer Sutherland. There's also an amusing "Shell Beach" game entwined throughout the menus. On Mallrats, perhaps indicating that DVD has already become too postmodern for its own good, there's a hidden clip of the director telling you to stop looking for Easter eggs and do something useful.

It's more fun to search for hidden features on your own, but if you need some help, the best list is at DVD Review.

[1.38] How do I get rid of the black bars at the top and bottom?

The black bars are part of the letterbox process (see 3.5), and in many cases you can't get rid of them. If you set the display option in your player to pan & scan (sometimes called fullscreen or 4:3) instead of letterbox, it won't do you much good since no DVD movies have been released with this feature enabled. If you set the player to 16:9 widescreen output it will make the bars smaller, but you will get a tall, stretched picture unless you have a widescreen TV.

In some cases, there may be both a fullscreen and a letterbox version of the movie on the same disc, with a variety of ways to get to the fullscreen version (usually only one works, so you may have to try all three):

  1. Check the other side of the disc (if it's two-sided)
  2. Look for a fullscreen choice in the main menu
  3. Use the "aspect" button on the remote control

DVD was designed to make movies look as good as possible on TV. Since most movies are wider than most TVs, letterboxing preserves the format of the theatrical presentation. (Nobody complains that the top and bottom of the picture are cut off in theaters.) DVD is ready for TVs of the future, which are widescreen. For these and other reasons, many movies on DVD are only available in widescreen format.

About two thirds of widescreen movies are filmed at 1.85 ("flat") aspect ratio or less. In this case, the actual size of the image on your TV is the same for a letterbox version and a full-frame version, unless the pan & scan technique is used to zoom in (which cuts off part of the picture). In other words, the picture is the same size, with extra areas visible at the top and bottom in the fullscreen version. In more other words, letterboxing covers over the part of the picture that was also covered in the theater, or it allows the entire widescreen picture to be visible for movies wider than 1.85, in which case the letterboxed picture is smaller and has less detail than a pan & scan version would.

For a detailed explanation of why most movie fans prefer letterboxing, see the Widescreen Cinema page and the Letterbox/Widescreen Advocacy Page. For an explanation of anamorphic widescreen and links to more information on other Web sites, see 3.5.

The best solution to this entire mess might be the FlikFX Digital Recomposition System, "the greatest advance in entertainment in 57 years."

[1.39] How should I clean and care for DVDs?

Since DVDs are read by a laser, they are resistant—to a point—to fingerprints, dust, smudges, and scratches (see 1.15 for more info). However, surface contaminants and scratches can cause data errors. On a video player, the effect of data errors ranges from minor video artifacts to frame skipping to complete unplayability. So it's a good idea to take care of your discs. In general treat them the same way as you would a CD.

Your player can't be harmed by a scratched or dirty disc, unless there are globs of nasty substances on it that might actually hit the lens. Still, it's best to keep your discs clean, which will also keep the inside of your player clean. Never attempt to play a cracked disc, as it could shatter and damage the player. It doesn't hurt to leave the disc in the player (even if it's paused and still spinning), but leaving it running unattended for days on end might not be a good idea.

In general, there's no need to clean the lens on your player, since the air moved by the rotating disc keeps it clean. However, if you commonly use a lens cleaning disc in your CD player, you may want to do the same with your DVD player. I recommend only using a cleaning disc designed for DVD players, since there are minor differences in lens positioning.

There is no need for periodic alignment of the pickup head. Sometimes the laser can drift out of alignment, especially after rough handling of the player, but this is not a regular maintenance item.

Care and feeding of DVDs

Handle only at the hub or outer edge. Don't touch the shiny surface with your popcorn-greasy fingers.

Store in a protective case when not in use. Do not bend the disc when taking it out of the case, and be careful not to scratch the disc when placing it in the case or in the player tray.

Make certain the disc is properly seated in the player tray before you close it.

Keep away from radiators/heaters, hot equipment surfaces, direct sunlight (near a window or in a car during hot weather), pets, small children, and other destructive forces. Magnetic fields have no effect on DVDs. The DVD specification recommends that discs be stored at a temperature between -20 to 50 °C (-4 to 122 °F) with less than 15 °C (27 °F) variation per hour, at relative humidity of 5% to 90%.

Coloring the outside edge of a DVD with a green marker (or any other color) makes no difference in video or audio quality. Data is read based on pit interference at 1/4 of the laser wavelength, a distance of less than 165 nanometers. A bit of dye that on average is more than 3 million times farther away is not going to affect anything.

Cleaning and repairing DVDs

If you notice problems when playing a disc, you may be able to correct them with a simple cleaning.

If you continue to have problems after cleaning the disc, you may need to attempt to repair one or more scratches. Sometimes even hairline scratches can cause errors if they just happen to cover an entire ECC block. Examine the disc, keeping in mind that the laser reads from the bottom. There are essentially two methods of repairing scratches: 1) fill or coat the scratch with an optical material; 2) polish down the scratch. There are many commercial products that do one or both of these, or you may wish to buy polishing compounds or toothpaste and do it yourself. The trick is to polish out the scratch without causing new ones. A mess of small polishing scratches can cause more damage than a big scratch. As with cleaning, polish only in the radial direction.

Libraries, rental shops, and other venues that need to clean a lot discs may want to invest in a commercial polishing machine that can restore a disc to pristine condition after an amazing amount of abuse. Keep in mind that the data layer on a DVD is only half as deep as on a CD, so a DVD can only be re-polished about half as many times.

[1.40] What's a progressive DVD player?

A progressive-scan DVD player converts the interlaced (480i) video from DVD into progressive (480p) format for connection to a progressive display (31.5 kHz or higher). Progressive players work with all standard DVD titles, but look best with film source. The result is a significant increase in perceived vertical resolution, for a more detailed and film-like picture.

There's enormous confusion about whether DVD video is progressive or interlaced. Here's the one true answer: Progressive-source video (such as from film) is usually encoded on DVD as interlaced field pairs that can be re-interleaved by a progressive player to recreate the original progressive video. See 3.8 for further explanation of interlaced and progressive scanning.

You must use a progressive-scan display in order to get the full benefit of a progressive-scan player. However, all progressive players also include interlaced outputs, so you can buy one to use with a standard TV until you upgrade to a progressive TV. (You may have to use a switch on the back of the player to set it to interlaced output.)

Toshiba developed the first progressive-scan player (SD5109, $800) in mid 1998, but didn't release it until fall of 1999 because of copy protection concerns. Panasonic also released a progressive-scan player (DVD-H1000, $3000) in fall of 1999. Many manufacturers have released progressive models since then. It's also possible to buy an external line multiplier to convert the output of a standard DVD player to progressive scanning. All DVD computers are progressive players, since the video is displayed on a progressive monitor, but quality varies a lot. (See 4.1 and 2.12.)

Converting interlaced DVD video to progressive video involves much more than putting film frames back together. There are essentially two ways to convert from interlaced to progressive:
1- Re-interleaving (also called weave). If the original video is from a progressive source, such as film, the two fields can be recombined into a single frame.
2- Line doubling (also called bob). If the original video is from an interlaced source, simply combining two fields will cause motion artifacts (the effect is reminiscent of a zipper), so each line of a single field is repeated twice to form a frame. Better line doublers use interpolation to produce new lines that are a combination of the lines above and below. The term line doubler is vague, since cheap line doublers only bob, while expensive line doublers (those that contain digital signal processors) can also weave.
(3- There's actually a third way, called field-adaptive de-interlacing, which examines individual pixels across three or more fields and selectively weaves or bobs regions of the picture as appropriate. Most systems that do this well cost $10,000 and up, so it will be a while before we see it in consumer DVD players.)
(4- And there's also a fourth way, called motion-adaptive de-interlacing, which examines MPEG-2 motion vectors or does massive image processing to identify moving objects in order to selectively weave or bob regions of the picture as appropriate. Most systems that do this well cost $50,000 and up (aside from the cool but defunct Chromatic Mpact2 chip).

There are three common kinds of de-interlacing systems:
1- Integrated. This is usually best, where the de-interlacer is integrated with the MPEG-2 decoder so that it can read MPEG-2 flags and analyze the encoded video to determine when to bob and when to weave. Most DVD computers use this method.
2- Internal. The digital video from the MPEG-2 decoder is passed to a separate deinterlacing chip. The disadvantage is that MPEG-2 flags and motion vectors may no longer available to help the de-interlacer determine the original format and cadence. (Some internal chips receive the repeat_first_field and top_field_first flags passed from the decoder, but not the progressive_scan flag.)
3- External. Analog video from the DVD player is passed to a separate de-interlacer (line multiplier) or to a display with a built-in de-interlacer. In this case, the video quality is slightly degraded from being converted to analog, back to digital, and often back again to analog. However, for high-end projection systems, a separate line multiplier (which scales the video and interpolates to a variety of scanning rates) may achieve the best results.

Most progressive DVD players use an internal Genesis gmVLX1A de-interlacing chip. The Princeton PVD-5000 uses a Sigma Designs decoder with integrated de-interlacing. The JVC XV-D723GD uses a custom decoder with integrated de-interlacing. Toshiba's "Super Digital Progressive" players and the Panasonic HD-1000 use 4:4:4 chroma oversampling, which provides a slight quality boost from DVD's native 4:2:0 format. Add-on internal de-interlacers such as the Cinematrix and MSB Progressive Plus are available to convert existing players to progressive-scan output. Faroudja and Silicon Image (DVDO) line multipliers are examples of external de-interlacers.

A progressive DVD player has to determine whether the video should be line-doubled or re-interleaved. When re-interleaving film-source video, the player also has to deal with the difference between film frame rate (24 Hz) and TV frame rate (30 Hz). Since the 2-3 pulldown trick can't be used to spread film frames across video fields, there are worse motion artifacts than with interleaved video. However, the increase in resolvable resolution more than makes up for it. Advanced progressive players such as the Princeton PVD-5000 and DVD computers can get around the problem by displaying at multiples of 24 Hz such as 72 Hz, 96 Hz, and so on.

A progressive player also has to deal with problems such as video that doesn't have clean cadence (as when it's edited after being converted to interlaced video, when bad fields are removed during encoding, when the video is speed-shifted to match the audio track, and so on). Another problem is that many DVDs are encoded with incorrect MPEG-2 flags, so the re-interleaver has to recognize and deal with pathological cases. In some instances it's practically impossible to determine if a sequence is 30-frame interlaced video or 30-frame progressive video. For example, the documentary on Apollo 13 is interlaced video encoded as if it were progressive. Other examples of improper encoding are Titanic, Austin Powers, Fargo, More Tales of the City, the Galaxy Quest theatrical trailer, and The Big Lebowski making-of featurette.

A growing problem is that many TVs with progressive input don't allow the aspect ratio to be changed. When a non-anamorphic signal is sent to these TVs, they stretch it out! Before you buy an HDTV, make sure that it allows aspect ratio adjustment on progressive input.

Just as early DVD computers did a poor job of progressive-scan display of DVDs, the first generation of progressive consumer players are also a bit disappointing. But as techniques improve, and as DVD producers become more aware of the steps they must take to ensure good progressive display, and as more progressive displays appear in homes, the experience will undoubtedly improve, bringing home theaters closer to real theaters.

For more on progressive video and DVD, see part 5 and player ratings in the excellent DVD Benchmark series at Secrets of Home Theater and High Fidelity.

[1.41] Why doesn't disc X work in player Y?

The DVD specification is complex and open to interpretation. DVD-Video title authoring is also very complex. As with any new technology, there are compatibility problems here and there. The DVD-Video standard has not changed substantially since it was finalized in 1996, but many players don't properly support it. Discs have become more complex as authoring tools improve, so recent discs often uncover engineering flaws in players. Some discs behave strangely or won't play at all in certain players. In some cases, manufacturers can fix the problem with an upgrade to the player (see 1.47). In other cases, disc producers need to re-author the title to correct an authoring problem or to work around a player defect. Problems can also occur because of damaged or defective discs or because of a defective player.

If you have problems playing a disc, try the following:

  1. Check the list below to see if it's a reported problem. Also check the list of problem discs in DVD Review's Film Vault and at InterActual's PCFriendly tech support page. Try a newsgroup search at Deja.
  2. Try playing the disc a few more times. If you don't get the exact same problem every time, then it's probably a defective or damaged disc. Make sure the disc isn't dirty or scratched (see 1.39).
  3. Try the disc in a different player. (Visit a friend or a nearby player retailer.) The problem is usually the player, not the disc. If the disc plays properly in a different player, contact the manufacturer of your player for a firmware upgrade. Or, if you bought the player recently, you may wish to return it for a different model.
  4. Try a different copy of the disc. If the problem doesn't recur, it indicates that your first copy was probably damaged or defective. If more than one copy of the disc has problems in more than one player, then it may be a misauthored disc. Contact the distributor or the studio.

For other DVD and home theater problems, try Doc DVD, or DVD Digest's Tech Support Zone. Also check the PCFriendly tech support site for info about players that have problems with some enhanced discs. If you have a Samsung 709, see the Samsung 709 FAQ. For troubleshooting DVD on computers, see 4.6. The Dell Inspiron 7000 DVD Movie List has Inspiron-specific problems.

Below are problems reported by readers of this FAQ. The FAQ author has not verified these claims and takes no responsibility for their accuracy. Please report other confirmed problems. 

Title Player Problem Solution
various Polygram titles early Toshiba and Magnavox models won't load or freezes upgrade available from Toshiba service centers
various Central Park Media (anime) titles similar problems as The Matrix
RCE titles (see 1.10) Fisher DVDS-1000,  Sanyo Model DVD5100 world map and "only plays on non-modified players" message contact tech Sanyo/Fisher support for workaround
The Abyss, SE early Toshiba models disc 2 won't load or freezes upgrade available from Toshiba service centers
many cheap players  repeats scenes player doesn't properly handle seamless branching, get upgrade from manufacturer
Apex AD-600A scenes play twice check with Apex for upgrade
American Beauty (Awards Edition) Toshiba SD-3108, Philips DVD805 won't load get upgrade from manufacturer service center (Toshiba firmware 3.30 or newer)
American Pie Philips 940 freezes at layer change (1:17:09)  
Any Given Sunday Pioneer Elite DVL90 won't load  
Arlington Road see Cruel Intentions
Armageddon Panasonic A115-U and A120-U won't load unplug player with disc inserted, plug in, turn on
Avenger's TV series (A&E) Toshiba SD-3108 locks up player upgrade available from Toshiba service centers
Philips 930, 935 won't load check with Philips for firmware upgrade
Bats Apex AD 600A wont' load check with Apex for upgrade
Big Trouble in Little China Special Edition Panasonic SC-DK3 won't load unplug player with disc inserted, plug in, turn on
The Blair Witch Project some Toshiba players doesn't play properly upgrade available from Toshiba service centers
Cruel Intentions some JVC and Yamaha error in first release messes up parental controls, causing other discs to not play reset the player or get the corrected version of the disc or set parental country code to AD with password of 8888
Deep Blue Sea similar problems as The Matrix
Dinosaur many players (JVC-XV501BK, Philips DVD781 CH, Pioneer DV-737/ DV-37/ DV-09/ DVL-919/ DV-525/ DVL-90/ KV-301C, Sony 7700, Panasonic A300, Toshiba SD-3109, RCA 5220, Denon DVD 2500, Magnavox DVD502AT Toshiba 2109/3109, JVC XV-D2000/XV-D701 Oritron DVD600/DVD100, Sylvania DVL100A, and others) won't load, ejects disc, freezes, skips, slow menus, won't pause/forward/rewind, sound cuts out authoring problem -- contact Disney for a refund/replacement (also see Disney's The Kid below)
Disney's The Kid many players (Apex 600AD, Philips 711, Pioneer DV-737, RCA, and others) skips, ejects disc, freezes, blue lines on screen authoring problem -- contact Disney for a refund/replacement; (solution on Philips player: put disc in drawer, do not close drawer, press "1" on remote to jump to chapter 1)
Dragon's Lair Toshiba SD-2109/3109 (before mid 1999) various upgrade available from Toshiba service centers
most Samsung, Aiwa various check with Samsung (800-726-7864) or Aiwa for firmware upgrade
Entrapment JVC, Sony 850 freezes check with JVC for firmware upgrade
Sigma Hollywood Plus see The World Is Not Enough
Everything, Everything (Underworld) Toshiba SD3108 and SD3109 won't load upgrade available from Toshiba service centers
Galaxy Quest most Samsung players freezes at chapter 7 check with Samsung (800-726-7864) for firmware upgrade
Girl, Interrupted Apex AD-600A jumps to Features menu, won't play movie might be same problem as Stuart Little
Gladiator Toshiba SD3108/SD3109, Wharfedale DVD 750, others won't load contact studio for new version of disc
Idle Hands see Cruel Intentions
Independence Day Toshiba SD3108 and SD3109 won't load upgrade available from Toshiba service centers
Philips DVD805 and DVD855 won't load check for upgrade from Philips
many cheap players  repeats scenes player doesn't properly handle seamless branching, get upgrade from manufacturer
The Last Broadcast GE 1105P won't load  
The Last Of the Mohicans see The World Is Not Enough
Lost In Space Sharp freezes  
Creative DXR3 freezes, audio out of sync check for updated drivers
The Man With The Golden Gun a few first-generation players, many software player garbled video after layer change might be a disc authoring error
The Matrix various players various problems details at PCFriendly tech support
(for GE 1105-P, serial number beginning with 940 or lower, get upgrade from GE; see Samsung 709 FAQ)
Mission Impossible II Toshiba SD-3108 won't load get upgrade from manufacturer service center
Mission to Mars Toshiba SD-3108 won't load get upgrade from manufacturer service center
The Mummy Philips 930, 935 won't load  
The Patriot Apex AD 600A wont' play movie check with Apex for upgrade (pressing Resume may work)
JVC XV-511BK won't load check with JVC for upgrade 
The Perfect Storm Toshiba SD-3108 won't load get upgrade from manufacturer service center
Saving Private Ryan all players distortion (smearing, flares)  in beach scene at end of ch. 4 This is a deliberate camera effect in the film. Stop returning discs.
Scary Movie Creative Encore 12x, GE 1105P crashes in FBI warning try to skip past FBI warning; check for bug fix from Creative
The Sixth Sense Sigma Hollywood Plus MMSYSTEM275 error wait for a software update from Sigma
Sleepy Hollow some Toshiba players doesn't play properly upgrade available from Toshiba service centers
Space Ace see Dragon's Lair
Stargate SE Magnavox 400AT freezes in director's commentary  
Stuart Little Apex AD-600A, Shinco 2120, Smart DVDMP3000, others won't play past menu press Resume on remote control; upgrade available for Smart
The Three Kings LG DVD-2310P won't play extras  
The World Is Not Enough Sigma Hollywood Plus MMSYSTEM275 error Wait for a software update from Sigma. Might be related to trying to play in wrong region.
The World Is Not Enough (region 2) Philips 750 stutters and freezes presumably a flaw in the player; plays region 1 version ok
Tomorrow Never Dies Sharp 600U
Bush DVD2000
locks up player
won't load
 
Universal Soldier Wharfedale 750 picture breakup after ch. 30 might be a problem with the disc
Wild Wild West Samsung DVD 709; Philips 930, 935; GE 1105P  won't load check with Samsung (800-726-7864), Philips, or GE for firmware upgrade
You've Got Mail various players various problems details at PCFriendly tech support

[1.42] How do the parental control and multi-rating features work?

DVD includes parental management features for blocking playback and for multiple versions of a movie on a single disc. Players (including software players on PCs) can be set to a specific parental level using the onscreen settings. If a disc with a rating above that level is put in the player, it won't play. In some cases, different programs on the disc have different ratings. The level setting can be protected with a password.

A disc can also be designed so that it plays a different version of the movie depending on the parental level that has been set in the player. By taking advantage of the seamless branching feature of DVD, objectionable scenes are automatically skipped over or replaced during playback. This requires that the disc be carefully authored with alternate scenes and branch points that don't cause interruptions or discontinuities in the soundtrack. There is no standard way to identify which discs have multi-rated content.

Unfortunately, very few multi-rating discs have been produced. Hollywood studios are not convinced that there is a big enough demand to justify the extra work involved (shooting extra footage, recording extra audio, editing new sequences, creating branch points, synchronizing the soundtrack across jumps, submitting new versions for MPAA rating, dealing with players that don't properly implement parental branching, having video store chains refuse to carry discs with unrated content, and much more). If this feature is important to you, let the studios know. A list of studio addresses is available at DVD File, and there's a Studio and Manufacturer Feedback area at Home Theater Forum.

Multi-ratings discs include Kalifornia, Crash, Damage, Embrace of the Vampire, Poison Ivy, Species II. Discs that use multi-story branching (not always seamless) for a director's cut or special edition version include Dark Star, Stargate SE, The Abyss, Independence Day, and Terminator 2 SE (2000 release). Also see www.multipathmovies.com.

Another option is to use a software player on a computer that can read a "play list" telling it where to skip scenes or mute the audio. Play lists can be created for the thousands of DVD movies that have been produced without parental control features. There was a shareware Cine-bit DVD Player that did this, but it has apparently been withdrawn because of legal threats from Nissim, who seem determined to stifle the very market they claim to support. A few other projects are under development.

Yet another option is TVGuardian or Curse Free TV, a device that attaches between the DVD player and the TV to filter out profanity and vulgar language. The box reads the closed caption text and automatically mutes the audio and provides substitute captions for objectionable words. (Note that current versions of these devices don't work with digital audio connections.)

[1.43] Which discs include multiple camera angles?

There's actually a euphemism in the DVD industry, where "multi-angle titles" --spoken with the right inflection-- means adult titles. However, apart from hundreds of X-rated discs, not very many DVDs have multiple angles, since it takes extra work and limits playing time (a segment with two angles uses up twice as much space on the disc).

Short Cinema Journal vol. 1 was one of the first to use camera angles, in the animated "Big Story," which is also available on the DVD Demystified sample disc. Ultimate DVD (Gold or Platinum) is another sample disc with examples of angles. King Crimson: Deja Vroom has excellent angles, allowing you to focus on any of the musicians. Other multi-angle music discs include Dave Matthews Band: Listener Supported, Metallica Cunning Stunts, Sarah McLachlan Mirrorball. Some movies, such as Detroit Rock City (KISS video), Ghostbusters SE, Mallrats, Suicide Kings, Terminator 2 SE, and Tomorrow Never Dies SE use multiple angles in supplements. Some discs, especially those from Buena Vista, use the angle feature to show credits in the selected language (usually with the angle button locked out).

You can get an incomplete list of multi-angle discs by doing an extended search at DVD File or a power search at DVD Express. To weed out the adult titles at DVD Express, select all entries in the category list (click top entry, Shift-click bottom entry) then deselect Adult (Ctrl-click).

[1.44] Is it ok to put labels or magnetic strips on DVDs?

Libraries and DVD rental outlets often want to label discs or attach magnetic strips for security. Rectangular labels and strips are a bad idea since they can unbalance the disc and cause errors, or even damage a player, especially if they peel off while the disc is spinning. It's best not to use stickers at all, but if you must, use a ring-shaped label that goes around the center of the disc. As long as the circular label doesn't interfere with the player clamping onto the hub, it should be ok. If you have to use a non-circular label, place it as close to the center as possible to minimize unbalancing. Placing a second label straight across from the center will also help. Writing with a marker in the clear (not reflective) area at the hub is better than using a sticker, although there's not much room to write. Write only in the area inside a 44 mm diameter. Writing anywhere else on the disc is risky, since the ink could possibly eat away the protective coating and damage the data layer underneath.

In most cases a better alternative is a security case that can only be opened with special equipment at the register or checkout counter. Barcodes, stickers, and security strips can be placed on the case without endangering discs (or players). This is especially good for double-sided discs, which have no space for