Re: mpeg

[nathan@cco.caltech.edu (Nathan Mates)]

In article <1995Jan4.175533.5083@chemabs.uucp>,  <lvirden@cas.org> wrote:
>MPEG doesnt seem to require special hardware on PCs or SPARCs.

   It does for really good quality. Basically, if a processor that
can process 50-100x the info can manage maybe 10 frames per second
on a decent-sized MPeg movie, what do you think the GS will be able
to do?

   The other processors are faster for not just clock speed, bus
speed, and processor bit width; there are some other factors that make
GS graphics really slow: no floating pt in hardware, and 16 colors per
line resolution. Jpeg & Mpeg get their great compression thru a cosine
transform of the data, so decompression requires a lot of math. With
the processor having to do lots of math, doing cosines in software (as
opposed to the processor) is _much_ slower. Also, displaying things on
the GS look pretty crappy unless you properly cut it down to 16 colors
per line.

   PCs (and workstations) greatly benefit from specialized hardware to
do all the math (and work) for them. The only way a MPeg decompressor
would make any sense on the GS would be for it to decompress files
to a series of 32K pictures, then take those pictures and convert to
a GS format like PaintWorks animation. Only by doing that would we
have a chance at semi-realtime playback.

Nathan Mates
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