[FFmpeg-trac] #6264(avcodec:new): Strange performance results

[FFmpeg]

#6264: Strange performance results
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             Reporter:  zezinho  |                     Type:  enhancement
               Status:  new      |                 Priority:  normal
            Component:  avcodec  |                  Version:  3.2.1
             Keywords:           |               Blocked By:
             Blocking:           |  Reproduced by developer:  0
Analyzed by developer:  0        |
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 Summary of the bug:
 Encoding with VAAPI is much slower if sound is converted. Launching
 another ffmpeg dedicated to the sound conversion gives much better
 results.

 The test was done with  9th generation Intel HD500 in a Celeron N3350 and
 a 1080p at 24 and 18Mb/s file.

 With the example below, I get 60fps so it is 2.42x speed. Removing the
 acodec copy option, it is converted to vorbis, speed drops to 42fps
 (1.41x).

 The strange point is that launching another simultaneous ffmpeg to drops
 the video and converts to vorbis, I get normal speed  for this CPU : 5.5x
 and the other ffmpeg keeps at 2.42x.

 So it seems using VAAPI along with Vorbis slows down both codecs.

 How to reproduce:
 {{{
 % ffmpeg \
   -hwaccel vaapi \
   -vaapi_device /dev/dri/renderD128 \
   -i input.mkv \
   -vf 'format=nv12,hwupload,scale_vaapi=w=1366:h=768' \
   -vcodec h264_vaapi \
   -acodec copy \
   -qp 23 \
   output.mkv
 ffmpeg version 3.2.4
 built on gcc 5.4.0 (Mageia 6 package)
 }}}

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Ticket URL: <https://trac.ffmpeg.org/ticket/6264>
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