On 17/08/16 20:47, Chao Liu wrote: > Hi there, > I compared h264_qsv decoder from ffmpeg to intel media sdk sample_decode. > There is pretty big speed gap. I wonder whether I did sth. wrong or there > are really some problems with ffmpeg's implementation.. > > The test video was captured from a 3MP(2048x1536) camera. The commands I > used: > - ffmpeg -c:v h264_qsv -async_depth 10 -i test.h264 -c:v rawvideo -f null > /dev/null > - sample_decode h264 -i test.h264 > Both uses 100% cpu (a full core). ffmpeg got 170FPS. sample_decode got > 370FPS. > > I haven't got time debugging into this. Sending this out to see whether you > guys might have sth. in mind..
I think in both cases your speed bound must be on something other than the decode, because the hardware goes a lot faster than either of those for me. Perhaps you are downloading the all of the output frames to normal memory in order to write them to a null device output, and one of the cases is doing that less efficiently somehow? Using vaapi on a low-power Haswell mobile chip (i.e. the same Quick Sync hardware that libmfx uses) decodes a single 2048x1536 stream at around 800fps with less than 50% CPU for me. - Mark (My command to compare is: ./ffmpeg_g -vaapi_device /dev/dri/renderD128 -hwaccel vaapi -hwaccel_output_format vaapi -i input.mp4 -an -vf 'format=nv12|vaapi,hwupload' -f null - The nasty filtering there is contrived to do nothing, even with the inconvenient stream reinitialisation. I think libmfx might also work somehow with "-c:v h264_qsv -hwaccel qsv", but I'm not sure and I don't have anything to try it on right now.) _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
