News Releases


DVD Forum Reports on Status of Industry Standard DVD-RAM Drives


Sep 15, 1997 00:00 AM

The DVD Forum today demonstrated interchangeability of media recorded on DVD-RAM drives from three different manufacturers. At a press briefing today, the DVD Forum, comprised of ten leading electronics and media companies, presented a report on the status of DVD-RAM Format Version 1.0, including the results of extensive compatibility testing, the status of international standardization activity, and the roadmap for development of DVD-RAM and DVD-ROM drive and media technologies.

The DVD Forum is comprised of 10 member companies: Hitachi, Ltd., Matsushita Electric Industrial Co., Ltd., Mitsubishi Electric Corp., Victor Company of Japan, Pioneer Electronics Corp., Sony Corp., Toshiba Corp., Philips Electronics N.V., THOMSON Multimedia, and Time Warner, Inc. Initially known as the DVD Consortium, the Forum was instrumental in establishing the standards that have made the launch of DVD-Video and DVD-ROM players successful. The DVD Forum is now in the process of proposing the DVD-RAM format to international standards organizations.

At today’s briefing, held in the Fairmont Hotel (San Jose), members of the DVD Forum reviewed key features of DVD-RAM Format Version 1.0 and clarified issues regarding compatibility with DVD-ROM drives. Establishing a standard to assure this compatibility was one of the primary objectives of the DVD Forum. As a result of the group’s efforts, playback of DVD-RAM discs on DVD-ROM drives requires a simple, low-cost circuit modification. Manufacturers will be able to produce drives that can read DVD-ROM discs, as well as 2.6 Gigabyte (GB) capacity, single-sided DVD-RAM discs.

During the briefing, representatives of three DVD Forum member companies, Hitachi. Ltd., Matsushita Electric Industrial Co., Ltd. (Panasonic), and Toshiba Corp. demonstrated DVD-RAM drives. The DVD Forum also presented its roadmap for development of future DVD-RAM and DVD-ROM products. In addition to DVD-ROM drives capable of reading DVD-RAM standard media, this roadmap includes future DVD-RAM media with 4.7 GB per side capacity, equal to a single-side/single-layer DVD-ROM disc.

The DVD-RAM Format Version 1.0 was made final by the DVD Forum in July 1997, following a three-month evaluation of drive and media compatibility with other DVD disc formats. More than 20 personal computer and storage media manufacturers from around the world took part in this evaluation. At the end of the evaluation process, the DVD Forum published its Format Book, and embarked on a worldwide series of meetings to review the new standard. Key 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 5.2 GB 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 drives laser transforms from a crystalline to a morphous state. The signal is read as the difference in the laser reflection rate between the two states.

4. At the disc manufacturing stage, the discs positioning accuracy is enhanced by including position data (an 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. Different disc cartridges will be provided, with single-sided discs and double-sided discs. Double-sided discs must be used in the cartridge, single-sided discs can be removed from the cartridge and played on DVD-ROM drives and DVD players.