DVD Forum

August 18, 1997--- The DVD Forum (comprising Hitachi, Matsushita, Mitsubishi, Victor Company of Japan, Pioneer, Sony, Toshiba, Philips, Thomson Multimedia, and Time Warner) today proposed the format of a DVD-RAM disc (rewritable DVD) which has a storage capacity of 2.6GB on a single side to the European Computer Manufacturers' Association (ECMA), an international standardization organization.

In line with this move, at the ECMA meeting to be held in Kobe from August 20, the DVD Forum will demonstrate the compatibility between the various DVD disc formats, using drives manufactured by the members of the Forum. Also, the DVD Forum will vigorously propose the DVD-RAM format to other international standardization organizations.

The DVD-RAM format version 1.0 was agreed by the ten companies in the DVD Forum at the end of July, and the Forum started issuing the Format Book earlier this month.

Following the announcement of the format version 0.9 in April, the DVD-RAM working group evaluated the compatibility of the DVD-RAM disc with other DVD disc formats. More than 20 personal computer and media manufacturers from around the world took part in this evaluation. As a result, compatibility with other DVD disc formats, reliability and expandability for the next generation were verified. Accordingly, the DVD Forum reached an agreement on the final format version 1.0.

In finalizing the format, the Forum sought to satisfy, as much as possible, the desires of computer manufacturers and a wide range of other users as well as numerous media manufacturers and drive manufacturers, and to ensure expandability to the next-generation 4.7GB discs. The DVD-RAM format has superior expandability, economy, reliability and compatibility as follows:
(1) Playback of DVD-RAM discs on existing DVD-ROM drives is possible simply by modifying the LSIs, thereby avoiding any substantial increase in cost.
(2) Data reliability is ensured due to the use of a dedicated cartridge and, for compatibility with DVD-ROM drives, it is also possible to take the disc out of the cartridge.

Establishment of the DVD-RAM disc format clears the way for commercialization not only of DVD-RAM drives, but also of DVD-ROM drives which can play back DVD-RAM discs.

The main features of the DVD-RAM format are as follows:

1. The wobble land groove recording method* is adopted, realizing a rewritable optical disc medium with storage capacity of 2.6GB on a single side and 5.2GB for a double-sided disc.

   * With the land groove method, signals are recorded on both the lands, which are the areas between grooves, and on the grooves formed on a disc. Clock data are formed on the meanders during disc manufacturing.

2. Modulation and error correction systems are the same as for DVD-Video and DVD-ROM, assuring compatibility with other DVD formats.

3. The phase-change recording method* is adopted, realizing excellent reading output by a simple configuration of optical systems.

   * With this method, signals are recorded to a film which the DVD-RAM drive's laser transforms from a crystalline to an amorphous state. The signal is read as the difference in the laser reflection rate between the two states.

4. At the disc manufacturing stage, the disc's positioning accuracy is enhanced by including position data (address signal) in the pits formed on the lands and grooves, by laying down the tracks so that they meander slightly right and left of true, and by including clock data in the meanders.

5. Two types of disc cartridges, one for single-sided discs and the other for double-sided discs, will be provided. Double-sided discs must be used in the cartridge, but, for ensuring compatibility with DVD-ROM drives and DVD players, single-sided discs can be taken out from the cartridge.

Outline of DVD-RAM specifications

For further information, please contact DVD Forum: +81-3-5444-9580