Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!elroy.jpl.nasa.gov!lll-winken!taco!hobbes.catt.ncsu.edu!kdarling From: kdarling@hobbes.catt.ncsu.edu (Kevin Darling) Newsgroups: comp.sys.amiga.advocacy Subject: Re: CDTV vs CD-I again Message-ID: <1991Apr11.052215.143@ncsu.edu> Date: 11 Apr 91 05:22:15 GMT References: <1991Apr8.085845.24662@ncsu.edu> <1991Apr8.181613.5507@cunixf.cc.columbia.edu> <1991Apr9.170659.17365@ncsu.edu> <1089@cbmger.UUCP> Sender: news@ncsu.edu (USENET News System) Organization: North Carolina State University Lines: 64 peterk@cbmger.UUCP (Peter Kittel GERMANY) writes: >kdarling@hobbes.ncsu.edu (Kevin Darling) writes: >> >>Super-smooth titles require that close attention be paid to exactly WHERE >>on a CDROM information is stored, because CDROMs are pigs compared to HDs. >>It's almost a science unto itself to interleave sectors of the audio/video >>information. Developing/testing an interactive CDROM application requires >perfect emulation of a CDROM, in order to know how it will actually playback. >That's what CD-I developers do. You do NOT make it look like "a big HD". > >Well, yes and no. Developing takes place on a big HD. But as I remember, >the developer utilities include software that also emulates timing of a >real CDROM on such a HD. So you can well test the layout of your >application. And yes, arranging of which data you put where on the CD >is said to be very critical. But as I said, also this should be covered. Umm ... your pardon, I may not be explaining this clearly enough. It's not easy to do so the first time :-). In an interactive environment, where you are combining audio and visual data which is often coming from a relatively slow CDROM, it can be critical to arrange the data so that the flow is as uninterrupted as possible. We've both pretty much said this, and so I think we both agree. Okay... CDTV: From what I gather (corrections gladly welcomed), an author creates his programs and data on a hard disk, then sends the HD to CBM for CDROM mastering. The most control over data placement is the general location of files (for nearness). The end CDROM is more or less an exact copy of the HD. CD-I: The player decides where each incoming sector ends up: into memory, or directly through the audio section. Playing sound off disc _while_ also loading/displaying video data may be done by interleaving sectors. Example of interleaving video with simultaneous German/English audio tracks: | video | video | German | video | video | English | ... repeat... The video data goes into memory. The audio tracks are mixed by a separate audio processor and can continously play without entering the computer section. Or if wished, the audio can be vectored into memory for later play, while previously stored audio is played. In either case, what you have is crucial control during mastering on a per-sector basis as to what data is where, allowing what you might call a 'flowing multi-I/O capability'. Now, it has occurred to me that I don't know (does someone?) exactly how the CDTV player is set up in this situation. That is, does it have similar capabilities? Or does it simply play straight audio from disc while displaying previously loaded video data, and vice versa? Or ? IF CDTV uses the disc _only_ like a large HD, then you would be correct that the included utilities are sufficient for mastering discs... altho obviously the final capabilities fall short of CD-I. IF CDTV _does_ have per-sector distribution hardware, then the included utilities seem to fall very short. In either case, the upshot has been (as I said), that I have already heard rumblings from multimedia CDROM specialists that CDTV has not mastered the science of interleaving data (if used as a HD, then it will _never_ do so). Those were not "gloating" rumors, but expressions of dismay that interactive TV might get a black eye from lack of flow smoothness under CDTV. That dismays me also, as I've been excited at the possibilities of interactive TV for many years now... and wish it well regardless of brandname (hmmm... except that an MSDOS-based I-TV unit might make me cringe ;-). best regards - kevin PS: My work is suffering . I may bow out for a while. Thx.