On Wed, Aug 17, 2016 at 4:41 PM, Andy Furniss <adf.li...@gmail.com> wrote:
> Mark Thompson wrote: > >> 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? >> > > Only tested with AMD UVD, but unless you use -pix_fmt nv12 you will also > get cpu load from ffmpeg doing nv12 -> yuv420p conversion. I tried ffmpeg -c:v h264_qsv -async_depth 4 -i test.h264 -pix_fmt nv12 -f null /dev/null I couldn't tell any difference. > > > >> 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 - >> > > Oh nice, I always wondered if there was a way to bench without copy back. > > > >> 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 > _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
