Re: [mpeg2-dev] [RFC] [PATCH] ARM Advanced SIMD motion compensation

[Rémi Denis-C. <re...@vi...>]

On Tue, 15 Sep 2009 22:18:22 +0100, Måns Rullgård <ma...@ma...> wrote:
>> Attached is an intial patch against libmpeg2 trunk to use NEON for
>> motion compensation. This is preliminary. There are a bunch of known
>> CPU stalls. Those could probably be fixed using plain assembly and
>> interleaving subsequent loads. Also, iDCT is not optimized.
> 
> Why don't you steal the functions from FFmpeg instead?  They are much
> better optimised than this patch.

FFmpeg-based MPEG2 decoding was so slow on the target, that I did not even
consider the possibility that it might have been optimized. For whatever
reason, it is (eye-)noticeably slower than current libmpeg2 with the
non-SIMD ARM optimizations. Why is this so? I do not know. There could be
something wrong with VLC, but then again the FFmpeg h.264 decoding is
accelerated fine. Or it could be a build problem, or it could be that I did
not test properly, or it could be a FFmpeg problem in other part.

-- 
Rémi Denis-Courmont