Path: utzoo!utgpu!watserv1!watmath!att!att!pacbell.com!ucsd!ucbvax!iwarp.intel.com!pweiss From: pweiss@iwarp.intel.com (Paul Weiss (pweiss@iwarp.intel.com)) Newsgroups: comp.ivideodisc Subject: Re: How much on a CD? Keywords: CD-I DVI Message-ID: <1990Nov28.220134.25186@iwarp.intel.com> Date: 28 Nov 90 22:01:34 GMT References: <3931@mindlink.UUCP> Sender: pweiss@iwarp.intel.com Distribution: na Organization: Intel iWarp, Beaverton, Oregon, USA Lines: 77 Hi. "How much {picture,sound} time can ya fit on a CD?" is a deceptively complicated question. CD-I and DVI use the same underlying medium (as do CD-DA and CD-ROM, fundamentally) but make different choices about how to use the bandwidth. The disc can hold about 640Kb of "stuff", in any case. As far as video goes, DVI uses fancy (and very proprietary) compression/ decompression to allow sustained full-screen, full-motion pictures. I think the compression factor varies in some way with the material, from a low of 10:1 to a high of about 100:1. (Can anybody do a better job on that? Please followup!) Although decompression can be done in real time, with Intel's 2-chip set, compression is a mainframe mega-cycles kind of proposition, with supercomputer-class machines ideal. CD-I doesn't specify any video compression, so is unable to support full-screen, full-motion rates: there just ain't enough raw bits flowing off the disc to get it. You can have full-motion partial screen video (to a max of about 1/3 of the screen), or "slow-scan" styled jerky full-screen video - about 8 or 10 frames/sec, if I remember correctly. (I'm dipping 'way back on this stuff. I worked on a CD-I authoring system about 2 1/2 years ago while I was in the Advanced Development / New Media Workstation group at Sun; the work was done under contract for Philips, who, along with Sony, is the source of all the CD-xx standards. The stuff I'm saying may be wrong based on revs to the Green Book which I don't know about. Of course, it may also be bogus because - in my mom's words - "I'm up to the 'z' in Altzheimer's!") CD-I does a much better job on audio. It supports 4 or 5 different encodings, ranging from CD-DA tracks on a CD-I disc, to an encoding which uses half that space and bandwidth, giving twice the time, all the way to a "voice-grade mono" encoding which would allow 20 hours of sound. Most listeners can't tell the difference between the CD-DA and the half-rate encoding. Although the sound quality of the most efficient encoding is noticibly tinny for music, it's just fine for voice information. The other encodings I haven't identified lie between those extremes, and can be used to juggle time-space and audio quality in situations where the listener's attention is more-or-less taken up with visual data. CD-I's audio encoding doesn't have nearly the compute-time requirements as DVI's video encoding, and has been done successfully on PC-class authoring stations. For slide-show styled titles, using a combination of still video images, computer-generated box-and-arrow markup, cartoon graphics animation, and voice-over, CD-I will be a terrific medium. For things which want a lot of whizzy full-motion video, DVI will probably do a better job. Both of them will do a better job than the current platform-dependent CD-ROMs will. (There is another flavor of Sony-Philips disc which adds CD-I audio encoding to the CD-ROM standard, but the thing is still highly platform-dependent.) DVI shares the same platform-dependence as CD-ROM, at least in theory, but the new 2-chip set should make the appearence of dedicated DVI players economically possible. CD-I was designed from the start as mass-market consumer technology. The question will, I bet, finally work out to a question of time-to-market and title production. Both media are usable, neither is perfect. Both benefit from the economies of scale generated by the success of consumer CD-DA technology, which has not been available to the "big-disk" videodisk marketplace. By the way, I would very much appreciate pointers to companies and organizations working in computer-based new media in the Portland, OR, area. I miss working with this stuff, and would like to find out what's going on around here. Tanx. Paul ------------------------------------------------------------------------------- Paul Weiss <- Mangler, systems software, Intel/CMU iWarp project pweiss@iWarp.intel.com <- I wouldn't even try the "reply" key, were I you. (503)629-6371 <- ... as in "webby feets" Standard disclaimer: Yep. <- Strange powers speak through me, but Intel doesn't ------------------------------------------------------------------------------- -- ------------------------------------------------------------------------------- Paul Weiss <- Mangler, systems software, Intel/CMU iWarp project pweiss@iWarp.intel.com <- I wouldn't even try the "reply" key, were I you. (503)629-6371 <- ... as in "webby feets"