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

Michael Niedermayer michaelni
Fri Jul 17 11:44:51 CEST 2009

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
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20090717/eb0d3c19/attachment.pgp>

More information about the ffmpeg-devel mailing list