[FFmpeg-devel] idct/fdct optimizations on arm

Måns Rullgård mans
Tue Mar 9 03:13:10 CET 2010

Pavel Pavlov <pavel at summit-tech.ca> writes:

> I read doc/optimization.txt and I have a question.
> I'm using h263 video encoder and swscaler to stretch images and I'm
> kind of low on CPU power (windows mobile, arm11 cpu). I have some
> custom code to use hardware acceleration for idct/fdct. I see there
> are optimized version for arm in libavcodec/arm/, so I just wanted to
> ask 1) if I can get noticeable improvements in video encoder with more
> optimized idct code and 2) if it's easy to do (to hook up custom
> functions for that) :)

In encoding more time is usually spent in motion search than in
(i)dct, but optimising the transforms is still worthwhile.

What hardware do you have with accelerated dct?

> Also, it seems that my code suffers the most from swscale (I timed
> execution times and, surprisingly, stretching an image takes more time
> than h263 encoding) and there is no optimized version for arm in
> swscale

I'm not at all surprised by that.  Scaling is very CPU intensive.

M?ns Rullg?rd
mans at mansr.com

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