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

Jason Garrett-Glaser darkshikari
Fri Jul 17 09:50:14 CEST 2009

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

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.

Dark Shikari

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