Passing Sunday drivers. (nonstandard CD-ROMs) (New Media) (Column)

Passing Sunday drivers

Ready to live dangerously? For a limited time only, it might be worth breaking the rules and making nonstandard CD-ROMs.

The motive for this crime is simple - most interactive CD-ROM-based applications are limited by the response time and transfer speed of the drive. Digital video applications are particularly demanding, but even animation-based presentations with audio are prone to electronic stuttering.

Suppose we could boost the data rate from the disc and the rate at which the drive can hop from one sector to another. If so, we could make these disc-bound applications run better.

In fact, we might have the means, even if we keep our current CD-ROM hardware. All we have to do is change the format, maybe switch a ROM chip or two, and write some special drivers.

The details of CD-ROM formatting are fairly technical, so I won't go into the calculations here. But like most disk formats, the original specification was probably more conservative than we need with more recent technology. It's possible, especially if you're reading image or sound data where you can tolerate the chance of an occasional error, to squeeze more data into the same space - just like the way Apple used Steve Wozniak's clever encoding to squeeze extra data on the Mac's 800-Kbyte disks.

A streaming mode that gave up individual disc sectors within a block (which we wouldn't need with write-once audio or video clips that we're always going to play from the start) would do even better. And if we could get the raw bits from the disc before error correction, we could boost the rate even higher.