[FFmpeg-devel] Fw: [foms] Paper submissions to LCA

[Michael Niedermayer]

On Fri, Jul 17, 2009 at 12:50:14AM -0700, Jason Garrett-Glaser wrote:
> 2009/7/17 M?ns Rullg?rd <mans at mansr.com>:
> > Jason Garrett-Glaser <darkshikari at gmail.com> writes:
> >
> >>>> Interleave entropy decoding and MC/idct.  This means, for example,
> >>>> decoding an MV, and immediately performing motion compensation with
> >>>> that MV.
> >>>
> >>> This is unfortunately the opposite of what is needed to do part of the
> >>> decoding on a DSP or other coprocessor.
> >>
> >> We have CONFIG_SMALL for that.  This isn't an issue.
> >
> > I wasn't talking about code size.  To share work with a DSP, you have
> > to parse lots of syntax elements and hand them over to the DSP in
> > bulk.  Passing messages to the DSP for every macroblock would totally
> > kill performance.
> 
> That doesn't work in current ffmpeg either, as macroblocks are decoded
> in-sequence and the deblocking done immediately after decoding of each
> macroblock.
> 
> You could separate it out, or even keep two versions of the codebase
> for that reason.  But in non-DSP situations, the interleaved method is
> better, especially on chips with small cache.

this is not neccessarily true, a chip with a small code cache could
very well end up being faster with them seperated
IMHO it would be interresting to see actual benchmarks with them seperated
on various CPUs ...

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Concerning the gods, I have no means of knowing whether they exist or not
or of what sort they may be, because of the obscurity of the subject, and
the brevity of human life -- Protagoras
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