Xref: utzoo comp.graphics:14427 comp.sys.next:9695 Path: utzoo!attcan!uunet!zaphod.mps.ohio-state.edu!swrinde!ucsd!ucbvax!agate!shelby!helens!baroque!jim From: jim@baroque.Stanford.EDU (James Helman) Newsgroups: comp.graphics,comp.sys.next Subject: Re: Next machine as animation platform Message-ID: Date: 14 Nov 90 19:10:15 GMT References: <85866@tut.cis.ohio-state.edu> <2463@dover.sps.mot.com> Sender: news@helens.Stanford.EDU Organization: Stanford University Lines: 39 In-reply-to: talent@spanky.sps.mot.com's message of 14 Nov 90 06:15:26 GMT I have the same brochure. But the wording, "lets you take live video, compress it, and store it on a hard disk," isn't totally explicit about the frame rate or resolution of the images. If it means 30 full NTSC resolution frames per second, that's good. talent@spanky.sps.mot.com writes: I think the sales rep. stated a compression range of 50X to 200X. It seems that image degradation for animation would be less noticible that for still images. Someone from C-Cube gave a talk here last year. I think 50:1 to 200:1 might be pushing it a little bit. I remember approximately 20:1 compression of an NTSC frame without perceptible degradataion. That could probably be pushed up to 50:1 without it looking too bad. 200:1 is the absolute max I've heard. The higher compression ratios were claimed to be most useful on print images, e.g. mostly white with some black. Of course, JPEG is a *still image* compression technique (it doesn't use any of the correlations between frames). CCITT/ISO is supposed to (soon?) announce the MPEG (motion video compression) standard. Once this gets into silicon, compression ratios should jump substantially. I'd like to hear more numbers: the storage per frame required, sustainable data rates to and from disk, as well as compression ratios. One concern I have is trying to do a quasi-realtime (i.e. 30Hz) operation on a Unix (ok, really Mach underneath) machine. Is there enough headroom so that as long as system is pretty quiescent you don't need to kill all the daemons or reboot in single user mode? The same issue applies to disk access. Do you need to use a raw partition in order to get (barring bad block/cylinder forwarding) contiguous storage? Or is there enough headroom so that the normal filesystem is usually adequate? Jim Helman