[FFmpeg-trac] #8342(undetermined:new): FFmpeg kills machine with infinitely increasing memory usage at end of PSNR calculation

[FFmpeg]

#8342: FFmpeg kills machine with infinitely increasing memory usage at end of PSNR
calculation
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             Reporter:  eero-t       |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  important    |                Component:
                                     |  undetermined
              Version:  git-master   |               Resolution:
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by eero-t):

 Replying to [comment:4 eero-t]:
 > How?  And why FFmpeg would change the timebase for output from what's
 used in the input?   Only difference between them is the selected codec
 (AVC vs. HEVC), doesn't HEVC support all timebases that AVC does?
 >
 > Btw. I just noticed that PSNR calculation complained about "-frames"
 option, and if I use "-vframes" option instead, then FFmpeg behaves just
 fine. Resident memory usage keeps within 0.6GB, instead of going to 8GB
 and beyond.  WTF?

 That warning was:
 {{{Applying unspecific -frames to non video streams, maybe you meant
 -vframes ?}}}

 Note that:
 * "-frames" option isn't ignored by FFmpeg, if I make it smaller, FFmpeg
 goes haywire earlier
 * using "-an" option instead of "-vframes" in metrics calculation will
 also make it behave sanely

 So the problem seems to be related to redundant processing of audio.  This
 is weird because AFAIK PSNR filter handles only video data (at least it
 outputs values only for YUV channels, not audio), and because
 "output.h265" file doesn't have any audio track (same issue happens if
 "-an" is applied only to transcoding).

 Questions:
 * Does "-vframes" imply "-an"?  And if yes, why it's not documented?
 * How audio handling can affect video frame quality calculation, and why
 it explodes FFmpeg?

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Ticket URL: <https://trac.ffmpeg.org/ticket/8342#comment:5>
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