On Sat, 1 Oct 2016 17:37:50 +0200 u-h...@aetey.se wrote: > Hello, > > Would someone familiar with the mmx assembler parts of ffmpeg > look over and check that the fp-state is restored as needed? > > This is crucial with musl libc which uses floating point in its > malloc() implementation. > > My troubleshooting strongly suggests that it is the mmx code which is > the culprit of ffmpeg misbehavior (the same issue has been recently > fixed in libtheora). > > Ffmpeg built against musl behaves erratically on certain combinations of > inputs and outputs, which may also depend on other settings. > Most often ffmpeg hangs forever quite early while beginning the conversion > (at "frame= 0 fps...." or even before showing this) but sometimes it > segfaults at that point or while being manually interrupted. > > At least the internal theora decoder is affected but there may be other > misbehaving decoders or encoders. I think I observed similar breakage with > other file types than ogg/theora but did not document all the tested > combinations. > > Affected ffmpeg versions: tested 2.8.8, 3.0.2, 3.1.3, same behaviour, > also when building with various gcc versions (4.x, 5.x, 6.x). > > Disabling assembler in ffmpeg gets rid of the problem. > > Given patches/fixes I will be glad to test them and report here. > > Regards, > Rune > P.S. an attempt to report via trac did not succeed, that's why posting > to the list
AFAIK most MMX code in FFmpeg does not run emms (i.e. keeps the FPU state trashed) until returning to the API user. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
