DVD General Information
*The "Overview of DVD" paper is a proprietary document authored by Disc Manufacturing, Inc. (DMI).
When CD-ROM was developed over 10 years ago, it had the ability to store over 650MB worth of data or music. At the time, this capacity seemed almost unlimited. Most users never dreamed they would require over 650MB. Ten years later, the industry and consumers are pushing the 650MB barrier. Many of today's applications call for well over 650MB of storage. Currently, the only options available to address these needs are compression schemes or the use of multiple discs. Each one of these solutions has its drawbacks. Therefore, a second generation disc technology is needed to address today's high data requirements for video, multimedia, database, etc. The new technology is DVD.
Early in 1995, two major groups were competing to develop the next generation of high density compact disc. Philips and Sony partnered and were developing one format and a group led by Toshiba and Time Warner were developing another format. At one point, it looked like the two groups would each bring to market separate high density compact disc solutions. This would have been analogous to the battle of Beta versus VHS in the home videotape recorder industry. Another battle of this type would not be good for the industry or the consumer. Fortunately, in September of 1995, the two camps agreed to develop a single standard for a high density compact disc.
The most talked about application for the new standard disc is digital video. The goal of the entertainment and compact disc industries is to put a full length (over 2 hours) MPEG-2 compressed motion picture onto one side of a single CD-ROM. The current density or capacity of today's CD-ROMs does not allow for this. Currently, only approximately 75 minutes of MPEG-1 compressed full-motion video fit onto one "regular" CD.
In December 1995, the two groups agreed on the official name and most of the parameters governing the new high density compact disc. The name that was agreed upon for the new high density disc was DVD. DVD stands for just DVD. However many people refer to DVD as the Digital Versatile Disc or Digital Video Disc. It should be noted that discs for the new DVD movie players are being referred to as DVD; whereas the discs for the computer drives are being referred to as DVD-ROM.
The agreement takes parts from both Sony/Philips' and Toshiba/Time Warner's former separate proposals and combines them into one. The "best practices" compromise includes Sony/Philips' EFM-plus data storage scheme as well as backward compatibility with current CDs. In other words, the new DVD and DVD-ROM players must be able to play today's current CDs.
From the Toshiba/Time Warner side, the new DVD standard adopts their format of using two half-thickness (0.6mm) discs bonded together for a double sided disc. The new standard also allows for 3M's dual layer "2P" technology to be used.
The following is a summary of the most common DVD capacities:
4.7 GB (Single Layer Single Side) DVD 5
8.5 GB (Dual Layer Single Side) DVD 9
9.4 GB (Single Layer Double Side) DVD 10
14.1 GB (DVD 9 on one side, DVD 5 on the other) DVD 14
17.0 GB (Dual Layer Double Side) DVD 18
Therefore, the new DVD discs can store from 4.7 GB (single sided, single layer) up to 17.0 GB (double sided, dual layer per side for a total of 4 layers of information). Each layer of data on a DVD disc will allow up to 133 minutes of full motion MPEG-2 video. This amount of playing time will allow 95% of all movies to be contained on one side of a disc. This new disc will also support a variable bit data rate which will increase the quality of digital video playback thanks to a substantial buffer memory. The new DVD movie players are also capable of seamless switching between the two layers of information on each side of the disc.
DLT (Digital Linear Tape) is used as "source" to send in the large quantity of data to be mastered into DVD. DLT tape cartridges are slightly larger than 8mm tape cartridges but smaller than VHS cartridges. There are different densities of DLT tape with the highest capacities holding up to 20GB per tape (uncompressed). Other types of tapes and transfer media are under development to support DVD.
Cutting a full 4.7GB single layer of a DVD disc today at the fastest encoding speeds available takes over 90 minutes. As the mastering software and hardware are improved, this time will decrease. Remember, a full DVD disc could contain up to four mastered layers of information. A mastering cut must be done for each layer of information put onto a DVD disc. Therefore, as the number of layers of information increases, so will the mastering cost and time.
Some of the problems that threaten to delay the quick acceptance of DVD in the marketplace are the following:
The movie industry will not allow movies to be distributed on DVD until there is a way to ensure that the content on the discs are relatively protected. The industry mainly wants to ensure that the DVD disc is protected from digital to digital transfers and from digital to analog transfers (DVD to VHS for example). Fortunately the major players agreed in October 1996 on the basics for copy protection. To protect from the straight digital to digital transfers the industry has chosen to encrypt the DVD movie data. Special decryption technology must be used to be able to successfully play back the DVD movie information.
To protect against digital to analog transfers of DVD movie information the industry will use similar technology that is in use today to prevent VHS tape to tape copying. This technology allows the video information to be viewed, however when this same information is copied to a tape it is degraded to a non viewable level in most cases.
The movie industry is also planning on using special regional codes on the DVD movie discs to control distribution. These codes which will be in the discs will allow the industry to control when and where movies will be released. Six separate regional codes are currently being considered.
There are still some issues to be worked out by all the major parties concerning licensing. Most people in the industry were hoping that a one stop licensing scheme could be worked out to simplify the licensing process. However at this date it looks like some of the players are thinking of licensing their technology separately. This could add to the cost of the overall DVD players and discs.
*Today’s CD-Rs Might Not Play on DVD Drives
Due to the change in wavelength on the playback laser for DVD players today’s CD-Rs might not play on some DVD drives. This could be a serious problem for the quick acceptance of DVD in the marketplace. Changing the reflectivity on newly manufactured CD-Rs would solve this problem. However this would still leave many thousands or millions of unplayable CD-Rs in the market. Some manufacturers are planning on putting two laser optical pickups on their new DVD drives. One would be at the old wavelength and would be able to play today’s CD-Rs. The other would be at the new wavelength and would play DVDs. This would of course add cost to the drive however it would completely solve this backward compatibility issue.
The file structure on a DVD will be Micro UDF (Universal Disk Format) initially combined with ISO 9660. Eventually Micro UDF will become the standard file format used for DVD. The Micro UDF file format will extend and modify what is currently possible with ISO 9660.
The decision to standardize on a single high density digital (video) disc (which has the potential to be a$50 billion a year market) is very good news for computer, consumer electronics, and entertainment companies. Until the compromise was reached, DVD projections were for a slow, limited roll-out, with the new format not really taking hold until the end of the decade. Now, post-convergence sales projections are more optimistic.
DVD discs and players (DVD and DVD-ROM) became available in the 4th quarter 1996. The first players appeared in Japan. The cost of the DVD movie players are between $500 and $1000. The cost of the DVD-ROM drives are between $300 and $600. Widespread availability of the DVD movie and ROM players will happen in early 1997.
Disc Manufacturing, Inc. has already successfully mastered and manufactured DVD discs based on the specification information available to date. DMI has developed a prototype line that is available to manufacture DVD and DVD-ROM discs in quantity.
After the appearance of DVD and DVD-ROM players, the industry's next creation will be DVD-R (Recordable) discs and DVD-RAM (Rewritable) discs. DVD-R discs are projected to hold up to 3.8 GB/layer and have up to two layers. DVD-RAM discs are projected to be two sided and have up to 2.6 GB/side.
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