[Mesa-dev] GSoC : Video decoding state tracker for Gallium3d
emeric.grange at gmail.com
Mon Apr 4 14:36:28 PDT 2011
Working on the loop filter first is probably a good idea you are
right, I will change the roadmap. Beside as it is the last operation
to be done during the decoding and there is no dependency upon other
operations maybe more aggressive parallelization can be achieved.
I did not have time to dive into your code yet but I'm sure I will
find it very valuable, I'll keep your email and your github bookmarked
Thank you !
2011/4/4 Aaron Watry <awatry at gmail.com>:
> Hi Emeric,
> It doesn't affect your proposal too much, but I'd recommend changing
> the order of your August tasks a bit. I would suggest trying to work
> on the loop filter before the motion compensation. A few of the 720p
> and 1080p videos that I profiled during my thesis work suggested that
> the loop filter was responsible for ~50-60% of the decoding time using
> the C code paths (using cachegrind). I haven't profiled the assembly
> code recently, so you might want to do that before taking my word as
> If you check out the WebM Codec Developer mailing list archive, you
> might be able to find a little of the discussion that we had on the
> loop filter algorithm and how to make it more appropriate to a GPU.
> The loop filter is much less branchy than the motion compensation as
> well, so you might have an easier time with the loop filter.
> If you need to look at my OpenCL code, you've already got the github
> location. I also plan to push this work upstream in the future. I've
> created OpenCL kernels for motion compensation, IDCT/Dequant, and loop
> filtering. I haven't started intra-prediction, and most of the kernels
> are not launching many threads (common case is under a hundred... I
> spent too much time in my project adding the OpenCL infrastructure and
> wasn't able to optimize the algorithms as well as I had hoped).
> Also, the vpxdec utility that is included with the libvpx decoder has
> a '--md5' command line option that helped out a lot for checking for
> correctness of a decoder implementation. The WebM project has a git
> repository that includes a conformance testing script which you can
> also use. If you are continually using this conformance testing suite
> as part of your workflow, item K (debugging) will become a lot easier.
> If you have any questions, feel free to email me. I have a month of
> class to finish up before graduation, but I plan on continuing to work
> on this project in the meantime and after graduation).
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