From: Måns R. <ma...@ma...> - 2009-09-16 10:16:40
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Rémi Denis-Courmont <re...@vi...> writes: > 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 Even if the FFmpeg mpeg2 decoder is slow, the NEON MC and IDCT functions should be fast. > 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. Can you reproduce the difference with ffmpeg and mpeg2dec called directly, not from vlc? Could you do a quick oprofile run? -- Måns Rullgård ma...@ma... |