Michael Nadeau and Bram Vermeer
A significant limitation of current CD-ROM standards is their inability to allow more than 70 minutes of compressed VHS-quality video on a disc. Several CD-ROM companies are preparing new video formats that, when combined with compression, will let you put over 2 hours of full-screen, full-motion video with 16-bit audio on a disc. However, it could take more than a year before consumer-level products are available that conform to a proposed New High-Density CD System that's being developed by Philips and Sony.
Toshiba, Time Warner, and CD-ROM drive manufacturer JVC are also working on new formats. All three formats use similar techniques, such as an increase in pit density and reliance on the MPEG 2 video-compression standard. But drive vendors and medium produ
cers have traditionally looked to Philips and Sony to set the standard.
The proposed standard's smaller track pitch (see the figure) presents a problem for the infrared laser used in CD-ROM drives today. Because the laser beams used in current CD-ROM drives are not narrow enough to read the smaller high-density CD-ROM pits in the new discs, existing players will not be able to read a New High-Density CD-ROM. However, Philips says CD-ROM players built for the new standard will read older discs.
Another area of concern is that of CD-ROM production. Philips officials say today's technology is capable of pressing higher-density discs, but mastering the discs is another matter. Philips says the blue lasers used for mastering might not be able to handle the new discs: It might be necessary to use narrower ultraviolet lasers.
Philips is negotiating with members of the CD-ROM, film, publishing, and game industries to reach consensus on the New High-Density standard. The company expected to have a
proposal completed by the end of the summer.
Illustration: The read-only New High-Density CD System will require a major increase in pit density, which it will accomplish by halving the track pitch from 1.6 micrometers to 0.8 micrometer. This will reduce the pit width by a similar ratio and effectively quadruple capacity to 2.7 GB. Further improvements in error correction and the mechanical specifications will give the disc a capacity of about 3 GB. The proposed standard will supplement changes to the track pitch and pit density with MPEG 2 compression to give the disc a capacity of more than 2 hours of video with standard TV resolution.
Coming ``Soon'': 3-GB CD-ROMs
