[FFmpeg-trac] #7690(undetermined:new): FFmpeg QSV decode + VPP performance is just a fraction of what one gets with VA-API and MediaSDK

[FFmpeg]

#7690: FFmpeg QSV decode + VPP performance is just a fraction of what one gets
with VA-API and MediaSDK
-------------------------------------+-------------------------------------
             Reporter:  eero-t       |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:  git-
  undetermined                       |  master
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:  Running 10-bit HEVC decode + downscale + upload with
 QSV backend is only 20-30% of the performance with the VA-API backend
 performance, or of the performance with the Intel MediaSDK sample
 application.

 Setup:
 * Distro: Ubuntu 18.04
 * FFmpeg: latest compiled from Git
 * MediaSDK & its deps: latest compiled from Git
 * HW: tested on KBL GT2, KBL GT3e and CFL GT2

 Steps to reproduce:
 1. Encoding 1080p 10-bit HEVC test input video with libx265:
 {{{
 $ ffmpeg -i 4k_uhd_hevc_10bit_60fps.mkv -frames 4800 -s 1920x1080 -pix_fmt
 yuv420p10le -x265-params level=5.2 1920x1080_10bit_60fps.h265
 }}}
 2. export LIBVA_DRIVER_NAME=iHD
 3. Decode + VPP with QSV for that video:
 {{{
 ffmpeg -hwaccel qsv -qsv_device /dev/dri/renderD128 -c:v hevc_qsv -i
 1920x1080_10bit_60fps.h265 -vf
 scale_qsv=w=300:h=300,hwdownload,format=p010 -f null -
 }}}
 4. Decode + VPP with VA-API:
 {{{
 $ ffmpeg -hwaccel vaapi -vaapi_device /dev/dri/renderD128
 -hwaccel_output_format vaapi -i 1920x1080_10bit_60fps.h265 -vf
 scale_vaapi=w=300:h=300,hwdownload,format=p010 -f null -
 }}}
 5. Decode + VPP with MediaSDK sample app:
 {{{
 $ sample_decode -hw h265 -w 300 -h 300 -p010 -i 1920x1080_10bit_60fps.h265
 -o /dev/null
 }}}

 Expected output:
 * Similar performance for all 3 cases

 Actual outcome:
 * MediaSDK and VA-API cases performance is within few percent of each
 other
 * QSV performance is only a fraction of MediaSDK and VA-API performance,
 at best ~30%

 When looking at the GPU information:
 * GPU runs at minimum freq with QSV, but at max with others
 * despite this, video engine is only half utilized with QSV, fully
 utilized with others

 As QSV uses less CPU than the other two cases (CPU utilization percentage
 is nearly same, but according to RAPL, CPU core power usage is much
 smaller with QSV), issue could be some extra synchronization between CPU &
 GPU with FFmpeg QSV backend.


 QSV outputs following errors at beginning:
 {{{
 Stream mapping:
   Stream #0:0 -> #0:0 (hevc (hevc_qsv) -> wrapped_avframe (native))
 Press [q] to stop, [?] for help
 [NULL @ 0x556f79e64840] missing picture in access unit with size 1
     Last message repeated 1 times
 [hevc_qsv @ 0x556f79e75dc0] A decode call did not consume any data: expect
 more data at input (-10)
 [NULL @ 0x556f79e64840] missing picture in access unit with size 1
 [hevc_qsv @ 0x556f79e75dc0] A decode call did not consume any data: expect
 more data at input (-10)
 [NULL @ 0x556f79e64840] missing picture in access unit with size 1
 [hevc_qsv @ 0x556f79e75dc0] A decode call did not consume any data: expect
 more data at input (-10)
 [NULL @ 0x556f79e64840] missing picture in access unit with size 1
     Last message repeated 2 times
 Output #0, null, to 'pipe:':
 }}}

 And a huge amount of following warnings during rest of the pipeline:
 {{{
 [NULL @ 0x556f79e64840] missing picture in access unit with size
 1peed=7.51x
     Last message repeated 224 times
 [NULL @ 0x556f79e64840] missing picture in access unit with size
 1peed=7.49x
     Last message repeated 262 times
 }}}

--
Ticket URL: <https://trac.ffmpeg.org/ticket/7690>
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