[FFmpeg-trac] #11126(avcodec:new): Filter "setpts=PTS-STARTPTS" in 2-pass VP9 may cause abnormal bitrate allocation

[FFmpeg]

#11126: Filter "setpts=PTS-STARTPTS" in 2-pass VP9 may cause abnormal bitrate
allocation
-------------------------------------+-------------------------------------
             Reporter:  Saul Baker   |                    Owner:  (none)
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:  avcodec
              Version:  git-master   |               Resolution:
             Keywords:  regression   |               Blocked By:
  libvpx-vp9                         |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
Changes (by Saul Baker):

 * keywords:  regression 2-pass => regression libvpx-vp9
 * component:  ffmpeg => avcodec

Comment:

 In terms of minimal reproduction, this:

 {{{

 ffmpeg -y -i "source.mp4" -filter_complex "[0:v]setpts=PTS-STARTPTS[outv]"
 -map [outv] -pass 1 -passlogfile pass.log  -c:v libvpx-vp9 -b:v 3271553
 -an -sn -f null nul
 ffmpeg -y -i "source.mp4" -filter_complex "[0:v]setpts=PTS-STARTPTS[outv]"
 -map [outv] -pass 2 -passlogfile pass.log  -c:v libvpx-vp9 -b:v 3271553
 -an -sn dest_2pass_setpts.webm


 ffmpeg -y -i "source.mp4" -filter_complex "[0:v]null[outv]" -map [outv]
 -pass 1 -passlogfile pass.log  -c:v libvpx-vp9 -b:v 3271553 -an -sn -f
 null nul
 ffmpeg -y -i "source.mp4" -filter_complex "[0:v]null[outv]" -map [outv]
 -pass 2 -passlogfile pass.log  -c:v libvpx-vp9 -b:v 3271553 -an -sn
 dest_2pass_nofilter.webm

 }}}

 Seems to display the same behaviour:

 {{{
 Input #0, matroska,webm, from 'dest_2pass_setpts.webm':
 Duration: 00:00:41.57, start: 0.000000, bitrate: 65 kb/s

 Input #0, matroska,webm, from 'dest_2pass_nofilter.webm':
 Duration: 00:00:41.60, start: 0.000000, bitrate: 3275 kb/s
 }}}
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/11126#comment:5>
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