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Re: Advice on a iBook ... [OT - TiBook recommendation because you asked for it]

On  15 Oct, this message from Derrik Pates echoed through cyberspace:
> On 16 Oct 2001, Michel Dänzer wrote:
>> Even with Linux, the choice isn't so hard, with a growing amount of
>> software supporting Altivec. In particular, watching DVDs is certainly
>> much more of a pleasure on a TiBook now than it will probably ever be on
>> a G3 Notebook.
> Are there any asm optimizations that can be done for speeding up MPEG-2
> decoding on a G3? Or is Altivec (and therefore a G4 PowerBook) the only
> answer?

The single best thing to do on a G3 is using whatever hardware decoding
support that is available in the graphics chipset. How muuch can be
gained by using hand-tuned asm depends on the compiler quality
(scheduling multiply-add instructions from 'simpler' C code) and on the
know-how of the asm coder. But in my opinion you need a _lot_ of
experience and know-how to write optimized asm.

> Where's the big performance optimization on MacOS for DVD
> playback? Is it using the ATI chips' hardware iDCT capability, or asm
> optimization, or something else?

It's using the ATI chip for IDCT, MotionCompensation and colorspace
conversion. When doing it entirely in software, the G4/400 is about the
minimum processor level you need to decode full framerate, but still
using the ATI's colorspace conversion to do YUV -> RGB in hardware
(which we know how to do in XFree 4).



Michel Lanners                 |  " Read Philosophy.  Study Art.
23, Rue Paul Henkes            |    Ask Questions.  Make Mistakes.
L-1710 Luxembourg              |
email   mlan@cpu.lu            |
http://www.cpu.lu/~mlan        |                     Learn Always. "

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