About DVD

What is DVD

DVD stands for both Digital Video Disk and Digital Versatile Disk. This is because the format, although initially used as a home video medium, has a wide variety of potential applications.

A Format for Multiple Purposes:

For a long time technical pundits have predicted that the computer, television, audio equipment, etc. would converge into a common format. DVD is the fulfillment of this prediction. In addition to home video, the DVD format can be used for storing data, dramatically increasing capacity over the current CD-ROM. It will also extend the amount of music or audio stored on an Audio CD. Other uses of DVD include interactive video, games, photo, and more. DVD is truly a "versatile" format. The consumer will no longer need separate hardware to play both video and audio discs. And he can attach the DVD player to a computer to access high capacity DVD-ROM.

A Wealth of Features:

The DVD format will provide a list of features unprecedented in the history of consumer electronics. These include multiple soundtracks, subtitles, aspect formats, MPAA versions and film releases on the same disc.

Backward Compatibility to Current Formats:

.DVD also protects the consumer's current investment in Audio CD, CD-ROM CDR, etc. The DVD players will be able to play back these existing formats. Note the first run of DVD players can not play CDR, but all second generation players can.

Competitive Costs:

DVD players are expected to be priced in the $400 to $800 range, depending on features. Discs will probably be priced from $20 to $30 for feature films. The costs of replicating DVDs are significantly less than for VHS tape or laser discs. The costs of mastering, however, are much higher than for VHS tape, and somewhat more than laser discs. This skews the economics of DVD in favor of high volume, low priced DVD content. Replication of DVDs is faster than VHS Tape. Under operation, a DVD replicator can produce one disc every six seconds. Once a master has been encoded and cut, low volume production runs can be easily accommodated. In summary, the DVD format will be priced at a level very attractive to consumers.

Picture and Sound Quality:

The quality of DVD is close to source, D1, material; 720 pixels per horizontal line vs. 320 pixels for VHS Tape. HDTV versions will have even greater resolution. Because DVD is digital, the NTSC artifacts of analog formats is completely eliminated. DVD delivers outstanding picture clarity and color sharpness. The DVD format provides multiple CD quality audio with AC-3, discrete 5.1 surround sound stereo, to recreate the theater experience in your own home.

Technical Specifications

Size:

The DVD disk is 5" in diameter, the same size as a compact disk. A 3.5" disk may also be offered.

Capacity:

Currently there have been seven DVD formats, with various capacities, proposed. Those which have been announced are:

SD5 4.7 GB, play only, single sided, single layered

SD9 8.5 GB, play only, single sided, dual layered

SD10 9.4 GB, play only, dual sided, single layered (2 SD5s)

SD18 17 GB, play only, dual sided, dual layered

SD-R 7.6 GB, Write once, dual sided, single layered (WORM)

SD-RAM 5.2 GB, Read/Write, dual sided, single layered (Erasable)

SD-HDTV 20+ GB, play only using blue laser for higher disc capacity

The capacity of DVD will allow most feature films to be recorded on single sided, single layer of a disc. This eliminates the need to flip or change discs in the middle of a film. Some of the movies that do not fit on a single sided, single layer disc will require you to flip the disk over, like you do with all laser disc. As more studios are putting movies that exceed the 133 minuets on dual layer disc using RSDL (Reverse Spiral Dual Layer) technology, a movie will be able to play seamlessly without requiring to flip the disc over.

Regional Coding

The Warner Home Video DVDs contain an insert showing the breakdown of the DVD Regional Coding restrictions. In the video studios' effort to prevent exporting, discs manufactured in one region will only play on players manufactured in that same region.

Region 1: The U.S., its territories and Canada

Region 2: Europe, Japan, the Middle East, Egypt, South Africa, Greenland

Region 3: Taiwan, Korea, the Philippines, Indonesia

Region 4: Mexico, South America, Australia, New Zealand

Region 5: Russia, Eastern Europe, India, most of Africa

Region 6: China

The Region Code is specified on the back of the DVD package, either with a Regional Coding logo of a globe with the region number superimposed on it, as on the Warner and New Line DVDs, or spelled out on the MGM discs: "This disc has been encoded for region 1: The United States, U.S. territories and Canada." Some discs have no regional coding--Lumivision discs are labeled "Available worldwide," but some other studios have not specified the Region Code one way or another.

Audio Specifications:

AC-3, discrete digital 5.1 channel Surround Sound:

CD quality sound with AC-3 surround stereo has been adopted for the DVD format. Europe has adopted the AC-3 sound also. It is hoped, however, that a single format will be adopted worldwide, eliminating the need to produce two different soundtracks.

Multiple Sound Tracks:

DVD can include up to eight separate AC-3 soundtracks to accommodate different languages or other audio nuances. This allows multiple audio versions of a film to be delivered on a single disc. Although most of the movies only have one to three different language tracks, it depends on the language within the region codes, for example region 1 will have an English, French, and Spanish audio tracks. With extra room for audio tracks some studios also has put audio commentaries with the movies, this allows you to watch the movie while the director, talks about the movie. For example in contact, which has three audio commentaries, one with the director and producer, one with the special effects supervisors, and one with Jodi Foster.

Multiple Subtitles:

Up to 32 subtitle tracks can be stored on a single DVD. A viewer can choose the subtitle to be displayed or suppress subtitles altogether. Subtitles are bit-mapped so that non-ASCII characters, such as Asian languages, can be accommodated. This will also allow overlays of graphics, such as a grid or play diagrams, on the screen.

Features of Dolby AC-3 vs. Pro-Logic:

While Dolby Labs developed both formats, AC-3 sound is stored on six separate channels. This is known as discrete 5.1 sound. There are five full range channels for front (left, center and right) and rear (left and right) speakers, plus a low frequency "woofer" channel. These signals are amplified separately and sent to the speakers. The channels are never mixed.

With Dolby Pro-Logic four channels (left, center, right and rear) are matrixed into two standard stereo channels. The two rear speakers receive a monaural, limited frequency range signal, these are decoded upon playback into the four channels. With this format there are some blending of the channels, resulting in a loss of directional effects and a less dynamic recreation of the soundtrack.

Dolby AC-3 is the true state of the art in creating the audio ambiance of a movie theater in your home. Sounds can be placed and moved anywhere in relationship to the listener; providing full 360 degree audio.

Video Specifications

Aspect Ratio Support:

DVD format can contain 16x9, Letterbox, and Pan & Scan formats on the same disk. The New Line and Warner packages are very specific with their aspect ratio information; all of these discs list the aspect ratios of the Letterboxed transfers, whether 1.85:1 or 2.35:1. If the disc contains a Pan & Scan transfer, that is also specified.

Some movies contain both Widescreen and Pan & Scan versions on the same disc they have the Letterbox version on the A Side and the Pan & Scan version on the B Side. There are several exceptions, such as Goldeneye or Species--discs that features the "dual-layer" format, where two sides worth of programming can be read by the DVD player from one side of the disc. When these discs are started, the viewer is first given an on-screen option to choose the widescreen or full-screen version.

Because of the large quantities of data stored on the disc for some of the longer films, a few discs contain only one version of the film, either Letterbox or Pan & Scan. For instance, A Time to Kill is 150 minutes long, and the Letterbox transfer is spread to both sides of the disc. This disc has to be flipped over--there are no DVD players (yet) that will automatically change sides--but very few films will require using both sides; most films up to approximately 2 hours 15 minutes or more will fit on one side of a DVD. (Unlike laserdisc, which has a strict time limit per side of 30 minutes for CAV and 60 minutes for CLV, DVD discs are limited by the amount of data they can hold. On DVD, 120 minutes of fast action, spinning cameras and constantly changing visuals take up more disc space than 120 minutes of stationary cameras and very little on-screen movement.) Studios are now starting to put movies requiring two sides on one side using dual-layer discs, and that the DVD player will be able to switch from one layer to the other automatically and with little or no visible break.

Several titles have been released only in Pan & Scan format--among them, Space Jam and The Bodyguard. Although these titles are Letterboxed at 1.85:1 on laserdisc. Each DVD package states. STANDARD VERSION: This film has been modified as follows from its original version It has been formatted to fit your screen. All of these DVDs are single-sided discs; it appears that a widescreen version of each movie could have been placed on the other side of its disc. Why this was not done has not been explained.

Of course, some films, such as Wizard of Oz and A Streetcar Named Desire, were shot at 1.33:1 and do not require Letterboxing. The Streetcar disc makes no mention of aspect ratios on the packaging, but specifically refers to it as full-frame format. The Letterboxing on many MGM titles is more problematic. Their Letterboxed titles appear on-screen at the correct aspect ratios at which they were shot--but this aspect ratio does not always appear on the package. Go to my Aspect Ratio page to learn more about Widescreen and Pan & Scan.

Enhanced for 16x9 widescreen TV's

The short explanation is that DVD is the first video format (apart from a few Japanese laserdiscs) to take full advantage of 16 x 9 TV capabilities, with these "enhanced for 16 x 9" DVDs and the TV's special circuitry squeezing more "lines of resolution" onto the screen than a regular 4 x 3 TV set can.

A 4 x 3 TV set picture is made up of approximately 480 horizontal lines of resolution from the top of the screen to the bottom. A laserdisc or video tape letterboxed at 2.35:1 uses only around 270 of those lines of resolution to display the picture; the other 210 lines make up the black bars you see at the top and bottom of the screen.

On an "enhanced for 16 x 9" DVD disc (also known as an "anamorphic" DVD), that same 2.35:1 letterboxed image is stretched vertically to use all 480 lines of resolution. (If you were to look at that image without any further processing, all of the actors would appear unnaturally tall and thin.) Then, the special circuitry in the 16x9 TV set squeezes those 480 lines of picture back down to the proper size. In effect, a picture that would be made up of 270 lines of resolution on a regular 4 x 3 TV set is made up of a full 480 tightly-spaced lines on a 16 x 9 set, resulting in finer detail than regular TVs can display.

MPAA Rating Control:

A single DVD disc can contain multiple versions of a movie with different MPAA ratings. This allows a viewer to select the version of the film he or she prefers. For example, a viewer could choose the "R" or "PG-13" version of a particular film. This feature also allows parental lockout, so that a child or other person, without the correct access code, could not view film versions above a certain MPAA rating. Furthermore, this feature allows certain countries to mandate that players sold in that country be outfitted with a chip which prohibits viewing of films above a certain MPAA rating. This eliminates the need to produce different versions of a film with different MPAA ratings for countries with content restrictions. When played, certain scenes will be skipped or alternative scenes shown according to the MPAA rating chosen. This "editing" occurs seamlessly without interruption of the playback. However no studio has yet implemented this feature, but Columbia Tri-Star do offer the parental lockout on some titles.

Multiple Film Versions:

DVD allows multiple versions of a film to be recorded on a single disc. For example a disc could contain both the theatrical and "director's cut" of a movie. The user could then choose which version of the film to watch. When played, certain scenes will be skipped or alternative scenes shown according to the film version chosen. This "editing" occurs seamlessly without interruption of the playback. However there are many director’s cut titles on DVD, no title has the option of choosing one or the other.

Miscellaneous

Audio-CD and CD-ROM Compatibility:

Audio DVD standards are in development. This will produce an audio format with higher fidelity and capacity then the current audio CD format. Current audio CDs can be played on DVD players. DVD-ROM will provide a more than ten-fold increase in capacity over current CD-ROM discs. DVD players will be able to playback current CD-ROM discs. WORM (Write Once, Read Many) and DVD-RAM (Erasable) DVD formats are expected to be available in two to three years.

Costs:

DVD players are ranging from $400 to $1000 depending on the features. DVD discs prices rang from $20 to $35 for most feature films. These expected prices make DVD very competitive to other video formats.

Other DVD Uses:

DVD-Interactive will allow games to be distributed on DVD format. The higher capacity will allow better graphics and more sophisticated games to be designed. DVD-Photo will accommodate stock photographs to be distributed with greater resolution and capacity then current CD-ROM formats. This may allow the migration from film to electronic storage of photographs.