DVD: Frequently Asked Questions

What is the difference between standard and high definition video?
What are the differences among DVD formats like HD DVD, Blu-ray, WMV HD, and UMD?
What makes DVDs so much better than VHS videocassettes?
What's the difference between Dolby Surround, Dolby Digital 5.1, and DTS?
What is Dolby Digital 6.1?
What does "THX certified" mean?
What is region encoding?
What is Regional Code Enhancement (RCE)?
Why are some DVDs released in other countries months before they are released in the U.S.?
What is a dual-layered DVD?
What's the difference between widescreen and anamorphic?
What about the pan-and-scan and full-frame (or full-screen) formats?
What's the difference between "close-captioned" and "subtitled"?
Why do some DVDs require flipping from one side to the other?
What is a Slipsleeve?
What is keepcase/snapcase?
What's the difference between PAL and NTSC?
Can I play imported DVDs on my player?
What is progressive-scan technology?
How can a DVD offer parental control or parental locking of potentially offensive material?
Can I play DVD-ROM materials on my DVD player?
What's a "fully loaded DVD"?
What is "Infinifilm"?
What is "Superbit"?
What are test discs?
What are "Easter eggs"?

The answer is video resolution. Standard definition video DVDs have at most 480 lines of visible detail. High definition video has as many as 1,080 lines of detail. Essentially, 480 lines or below is standard definition, 780 lines or above is considered high definition. To fully enjoy the quality of high resolution video, an HDTV is required (for more information, see our HDTV Buying Guide). The vast majority of DVDs currently on the market (and probably in your collection) are standard definition. As of January 2006, there are two competing high definition formats emerging into the marketplace: HD DVD and Blu-ray. For more information on these and other DVD formats, see below.

HD DVD (high-definition digital versatile disc) is a high-capacity format for DVD capable of storing and playing high-definition images. Using advanced technology, an HD DVD is densely layered and read by a thinner laser than conventional standard DVDs. This means that an HD DVD can store up to five times the amount of data that a standard DVD can.

Similar to HD DVDs, Blu-ray discs are also a high capacity format capable of storing and playing high-definition images. Both HD and Blu-ray use blue laser technology to capture the more closely packed data on their discs, but Blu-ray players utilize a shorter wavelength blue-violet laser than an HD DVD laser. This allows it to focus even more closely to read the more densely packed data on the Blu-ray disc. As a result, Blu-ray discs have even higher capacity than HD. A standard HD DVD can hold 15 gigabytes (GB) per side (30 GB on a dual-layer disc), whereas Blu-ray can hold 25 GB per side (50 GB on a dual-layer disc).

While the two formats are not compatible with each other, they both offer vastly superior audio/video quality, extra features, and a less intrusive menu system compared to standard DVDs. For more information, see our HD DVD and Blu-ray buying guides.

UMDs, or Universal Media Discs, are a compact, high capacity optical format that stores up to 1.8 GB of digital data on a 60mm disc, developed for use in the Sony Playstation Portable (PSP). UMDs are playable only in the PSP and not in DVD players. See our selection of UMDs here.

WMV HD stands for Windows Media Video High Definition. These are discs created with a series of codecs, developed by Microsoft for its Windows Media Player, that enable high resolution video and multichannel audio playback on an HD capable, Windows XP-based computer. Most standard DVDs do not contain the WMV HD codecs; these discs are not intended for play on standard DVD players, they are designed to play on your PC. However, by connecting your PC to your HDTV, you should be able to enjoy these DVDs on your high definition television. You can find WMV HD DVDs here.

Two words: data capacity. Although a DVD (short for "digital versatile disc" or "digital video disc") looks identical to a compact disc, the format uses much smaller and more compact digital "pits" in its physical structure. And compared to a CD, it is capable of storing up to 25 times as much digital information--up to 17 gigabytes of data on a double-sided, dual-layered DVD (see the following question for more on sides and layers). Most movies can easily fit onto a single-sided, single-layer DVD (which can hold 4.7 gigabytes of data), allowing ample room for additional soundtrack options, language tracks, filmmaker commentaries, and subtitles, as well as bonus features such as deleted scenes, featurettes, biographies, and interviews. And because DVD is an all-digital format, it offers superior sound clarity and picture resolution, which are enjoyable even on a modest budget but can be best appreciated with a state-of-the-art home-theater system.

Dolby Surround (also Dolby Pro Logic) is the surround-sound format most commonly found on video cassettes and laser discs (and many DVDs). It refers to a nondiscrete sound format in which four channels (left, right, center, and surround) are combined into two channels and decoded back (by Pro Logic receivers) into the original four surround channels of your home-theater speaker system.

Dolby Digital 5.1 is a discrete-channel surround-sound format consisting of five distinctly separate channels (left front, left rear, right front, right rear, and center), plus a subwoofer channel (the .1 in 5.1) to provide deeper, fuller bass. And while not all DVD movies offer a Dolby Digital 5.1 soundtrack, an increasing number of them do, and you will definitely notice and appreciate the difference. (Side note: Dolby Digital AC-3, a sound process introduced in the laser disc format, translates original two-channel stereo sources into simulated 5.1-channel output. It is less frequently used on DVD.)

DTS (Digital Theater Systems) is an impressive digital surround-sound system first introduced in theaters with the release of Jurassic Park in 1993. DVDs encoded with a DTS soundtrack require a DVD player and stereo receiver equipped with DTS-processing capability. Preferred by avid videophiles, DTS demands more data space on a DVD (often sacrificing bonus features), but many believe the audio quality to be superior to that of Dolby Digital 5.1-channel surround sound.

Dolby Digital 6.1 enhances the Dolby 5.1 surround-sound configuration by adding a third rear channel, giving the listener 3 channels in the front, 3 in the back, and the subwoofer (the .1). With the advent of high-definition DVDs, expect to see more releases featuring Dolby Digital 6.1 and DTS audio capabilities.

Many people mistakenly believe that THX is an audio format, but it's not. Rather, THX is a patented quality-control program created by Lucasfilm to ensure consistently high quality in acoustics and sound systems approved for theatrical and home-theater use. If you see the THX logo on a DVD, it means that the audio tracks on the disc have been subjected to stringent THX standards throughout the mastering process and will perform best on home-theater systems using THX-certified equipment. If your home theater does not include THX-certified equipment (amplifier, speakers, etc.), the high standard of THX cannot be fully appreciated.

Because DVD is subject to the same issues of piracy and market sharing that govern the entire video industry, region encoding was introduced to set geopolitical boundaries for compatibility of DVDs and players. For instance, a DVD encoded for Region 1 can be played only on a Region 1 (U.S. and Canada) DVD player.

There are six land-based global DVD regions, and two other non-geographical regions (one for "reserved" purposes and one for international venues like airplanes and cruise ships). DVD manufacturers can encode their product to play in any combination of regions. The vast majority of DVDs are Region 1 or 2 compatible, and many DVDs are "all region"--suitable for playback on any player, anywhere. (For a complete chart of international DVD regions, see our DVD Region Encoding page.)

While numerous methods have emerged to illegally bypass region encoding with "hacked" DVD players capable of playing DVDs from any region, movie studios have also increased their efforts to protect their regional copyrights with advanced DVD security coding.

Regional Code Enhancement (RCE) is different from region encoding. Introduced by several major studios in 2000, RCE is digital code added to Region 1 DVDs (for use in the U.S. and Canada) to prevent them from being played on a "region-free" DVD player. (This was primarily intended to curtail the use of region-free players in Region 1.) A disc with RCE will automatically check a DVD player's region code setting, and if the disc detects a region-free player, it will refuse to play (typically accompanied by an onscreen warning). In the interest of copyright protection and market-share equity, RCE was introduced to ensure that DVDs released in each region will play only on DVD players sold in the same designated region.

You may have noticed that your favorite TV show or a hit movie has already been released in Europe months before it's scheduled to come out in the U.S. This reasons for this can vary, but what it generally boils down to is that each studio releases their titles according to what they feel is the best schedule for that particular marketplace, based on demand. One other reason may be that TV syndication rights aren't as lucrative abroad as they are in the U.S., so there is more financial incentive to get TV shows out on DVD quicker in foreign countries.

A DVD can hold digital information on both sides of the disc and in two sandwiched layers on each side. A dual-layered disc can, for example, offer a movie in both widescreen and full-screen (or pan-and-scan) formats, and your DVD player can switch from one layer to another with a barely perceptible interruption in playback. Dual-layered DVDs are also useful for holding longer films (such as Titanic and Saving Private Ryan ) or video games that exceed the capacity of a single layer.

Most DVDs will be properly labeled to indicate if they are dual-layered. (You can also identify a dual-layered DVD by its golden-colored data side, as opposed to the shiny silver of a single-layered disc.) There are two types of dual-layered DVDs--PTP and OTP (also known as RSDL). The PTP (or "parallel track path") configuration allows a DVD player's laser to switch easily from layer to layer to access features like multiple menus, pop-up information, and other special effects. The OTP (for "opposite track path") configuration is more commonly referred to as RSDL (for "reverse spiral dual layer"), meaning that the DVD laser reads the first (top) layer outward from the center of the disc, then switches to the second (bottom) layer and continues to read the disc inward from the outer edge. On most DVD players, viewers will experience a slight pause as the player's laser switches from the top to bottom layer. In most cases, this pause is very brief and should not compromise the viewing experience.

These terms are often confused, but they're not interchangeable. On a standard widescreen DVD, the disc is encoded with both the widescreen movie and the black bars (at the top and bottom of the picture) that are necessary to properly fit the movie onto a standard 4:3 ratio TV screen. (In other words, precious data storage is required to generate the black bars.) On an anamorphic DVD, the widescreen movie is compressed to fit a standard 4:3 TV screen, then decompressed by your player, which generates the black bars at top and bottom to accommodate the widescreen image. Anamorphic widescreen is best appreciated by those who own widescreen (16:9) video monitors, because this allows the entire anamorphic image to fill the screen at full resolution, with no black bars. (Consequently, the issue of widescreen vs. anamorphic will become less important as widescreen video monitors become the accepted norm.)

The pan-and-scan technique is used to fit widescreen movies onto a standard 4:3 TV screen, so named because the image is often cropped (sacrificing picture detail from the edges) and then "panned" across to reveal actors or details that don't fit into the narrower frame. Fortunately, this method has grown less common as DVD has offered more widescreen viewing options. The full-frame format is used for films (often but not exclusively older films) that were shot in the 4:3 screen ratio (or, more accurately, the 1.33:1 aspect ratio most common in Hollywood's golden age). On home video and DVD, these films actually include some frame detail that would normally be masked off in theatrical exhibition, but you're seeing essentially the same image shown in theaters. Full-frame can also refer to a film (for example, Stuart Little ) that has been reformatted (often but not always with panning and scanning) from its theatrical format (typically 1.85:1) to fill a standard TV screen.

Simply put, closed captions consist of onscreen text specifically intended for hearing-impaired viewers, and they provide scene- and character-specific references to sound (e.g. "phone rings" or "crowd laughing") and music, in addition to dialogue. In contrast, subtitles are just as you would see on a foreign-language film, i.e., direct transcriptions or translations of spoken dialogue only. On most DVDs, subtitles are seen only when they are selected as options from a specified onscreen menu. Closed captions, however, are usually controlled by display settings on your TV set.

"Flippers" are DVDs that divide their content over both sides of the disc, resulting in actual interruption of playback. They are relatively rare, but they still exist (the first DVD release of GoodFellas is a regrettable example). Although dual-layered DVDs are capable of holding four hours of material on each side, some DVDs favor two-sided configuration (allowing less data compression) over one-sided, dual-layered formatting. Fortunately, data compression has improved, and one-movie "flippers" are now exceedingly rare. (Other discs, such as the four-disc set of the original Outer Limits TV series, maximize their capacity with dual-layering on both sides, but none of the content is compromised or interrupted by this configuration, hence they are not, strictly speaking, "flippers.")

A slipsleeve, also known as O-ring, is a form of packaging that slips a decorative sleeve over the cover of the box or case containing the DVDs. These are most often used for special editions and boxed sets.

A keepcase is a specific type of packaging consisting of a plastic, book-shaped shell that holds the DVD on a small spindle in the center. This is probably the most common form of DVD packaging. A snapcase, most commonly used by Warner Home Video, is a predominantly cardboard case with a plastic snaplock to hold it closed..

There are two television display systems in commercial use: PAL (common in Europe and parts of Asia) delivers a scanning/frame rate of 25 frames per second, while NTSC (used in the U.S. and Canada) delivers a scanning/frame rate of 29.97 frames per second. Currently there are no DVD players that convert from PAL to NTSC or vice versa. However, many PAL DVD players are able to display NTSC video on televisions that support what is known as the 60-Hz PAL system. For all DVD players in the U.S. and Canada, NTSC is the exclusive system in use. (For more information, see our video and DVD formats page.)

The short answer is, probably not. The vast majority of DVD users in North America own Region 1 DVD players that will not play imported DVDs. Imported DVDs (i.e. DVDs with different region coding than the region you're living in) will play only on a "region-free" DVD player, or a player that has been set (or switched) to play DVDs from that specific region. Region-free DVD players are not sold through traditional U.S. retail markets. Region-free players are more common in Europe.

For use with HDTV-enabled televisions, a progressive-scan DVD player provides a superior, filmlike picture by creating its images differently than conventional televisions, which use "interlaced scanning." The conventional process creates its picture by drawing around 400 horizontal lines twice per frame: once for the even-numbered lines and once for the odd-numbered lines, interlacing about 30 times per second. Progressive-scan DVD players scan from top to bottom in one fluid pass, making it harder to discern a picture's individual scan lines, which increases resolution while minimizing distortion and flickering.

DVDs encoded with the parental lock feature can be edited to skip over offensive or adult-oriented material during playback--sort of like turning an R-rated movie into a PG-13, and so on. If a DVD is encoded with this capability (check the packaging to make sure), your DVD player's internal rating system can be set to different levels of parental control, typically accessed via the player's set-up menu. (For example, the parental lock feature on the Galaxy Quest DVD can be used to automatically edit out brief use of mature language and a violent scene involving frightening aliens.)

Probably not. Most DVD players are not able to access DVD-ROM materials, which are coded differently for use (in most cases) on a personal computer. (This is most often because DVD-ROM features include materials accessible only on the Internet.) As DVD players, computers, and TV monitors continue to become compatible or hybrid components, the ability to access DVD-ROM content will become more flexible from platform to platform.

Fully loaded is simply a phrase coined by Amazon.com (and adopted elsewhere) to indicate that a DVD contains an abundance of bonus features and supplemental materials. There are different varieties of fully loaded DVDs, but they all offer the same added value of additional content to enhance the main feature (i.e. a movie, documentary, etc.). See Amazon.com's Fully Loaded DVD Store.

Infinifilm DVDs were introduced in 2001 by New Line Home Video to promote its most feature-enhanced titles. Infinifilm is a trademarked name for New Line DVDs with such advanced features as pop-ups that direct the viewer to bonus features and supplemental materials, readily accessed during playback of a movie. Essentially, Infinifilm DVDs use their uniquely presented capabilities to exploit the versatility of the DVD format. The pop-up option is now used by other studios to access DVD extras. See a list of Infinifilm DVDs available at Amazon.com.

Superbit DVDs were first offered by Columbia Home Video in 2001, and Superbit is an exclusive Columbia trademark. Essentially, Superbit DVDs reserve all of their data storage capacity for movies that have been digitally mastered at a higher bit-sampling rate, thus requiring less compression of the data. Bonus features, animated menus, and other supplemental materials are sacrificed in favor of best-available quality of picture and sound. Additional language tracks are also sacrificed in favor of one DTS audio track. The subtle advantages of Superbit DVDs are best enjoyed on high-end home theater systems with DTS capability and progressive-scan monitors (which further enhance picture quality). See a list of Superbit DVDs available at Amazon.com.

Test discs are DVDs specifically designed to optimize the audio and video performance of your home-theater system. These discs adhere to the stringent standards of the audio and video industries, providing test materials (color bars, sound checks, contrast charts, etc.) and detailed instructions, guiding home-theater enthusiasts to adjust their systems, according to exacting industry tests, to achieve their maximum potential with the DVD format. Examples of these highly specialized (and typically higher-priced) DVDs include Digital Video Essentials: Optimize Your Home Entertaiment System (NTSC Component), Sound & Vision Home Theater Tune-Up, and The AVIA Guide to Home Theater.

As their name implies, Easter eggs are hidden surprises, frequently disguised as mysterious logos, symbols, or unlabeled buttons on a DVD content menu. An Easter egg can be any kind of bonus feature or supplemental material that is not specifically listed in a DVD's table of contents. Because they are not identified in any obvious way, they must be discovered by using the DVD remote to jump around on menus where they might be hidden. These eggs can include something as trivial as an outtake or as essential as a completely different version of the film. The only way to find them is to thoroughly locate and select all of the functional buttons--labeled or not--on a DVD's menus.

Jeff Shannon is a Seattle-based freelance writer focusing primarily on films and filmmakers.