[Bug 97075] VCE encoding slow when GPU is not stressed (HD 7970M)

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Mon Jul 25 14:27:51 UTC 2016


https://bugs.freedesktop.org/show_bug.cgi?id=97075

            Bug ID: 97075
           Summary: VCE encoding slow when GPU is not stressed (HD 7970M)
           Product: DRI
           Version: unspecified
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Radeon
          Assignee: dri-devel at lists.freedesktop.org
          Reporter: haagch at frickel.club

This is on an intel + radeon laptop, so I need to run encoding with gstreamer
with DRI_PRIME=1.

Here is an example video:
http://www.sample-videos.com/video/mp4/720/big_buck_bunny_720p_1mb.mp4

DRI_PRIME is doing a good job of waking up the GPU from runpm when needed for
encoding via VAAPI and OMX, but for comparison I'll run glxgears both times.

I'm encoding the mentioned example video with VAAPI with this exact command:
$ time DRI_PRIME=1 LIBVA_DRIVER_NAME=radeonsi gst-launch-1.0 -e filesrc
location=big_buck_bunny_720p_1mb.mp4 ! qtdemux ! h264parse ! avdec_h264 ! queue
! videoconvert ! queue ! video/x-raw,format=NV12 ! vaapih264enc ! h264parse !
matroskamux ! filesink location=output.mkv

For low GPU stress I run the gst pipeline while glxgears with vsync is running:
$ DRI_PRIME=1 glxgears
Result: 0.75s user 0.33s system 2% cpu 52.779 total

For higher GPU stress I run the gst pipeline while glxgears without vsync is
running:
$ DRI_PRIME=1 vblank_mode=0 glxgears
Result: 0.99s user 0.28s system 43% cpu 2.928 total



I also tried a very similar pipeline with OMX:
$ time DRI_PRIME=1 gst-launch-1.0 -e filesrc
location=big_buck_bunny_720p_1mb.mp4 ! qtdemux ! h264parse ! avdec_h264 ! queue
! videoconvert ! queue ! video/x-raw,format=NV12 ! omxh264enc ! h264parse !
matroskamux ! filesink location=output.mkv

Low GPU stress: 0.96s user 0.24s system 19% cpu 6.298 total
High GPU stress: 1.10s user 0.24s system 141% cpu 0.949 total

Overall OMX encoding does a lot better, but it's still a large difference and
still below "real time" for the 5 second video.

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