#9377: QSV MPEG2 => H264 transcode PSNR dropped by 32%
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Reporter: eero-t | Owner: (none)
Type: defect | Status: new
Priority: normal | 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):
According FFmpeg documentation, default for "-vsync" is "auto" which
selects either "cfr" or "vfr". Because I specified bitrate, not FPS, I
assume FFmpeg to have selected VFR, which seems to drop timestamp only if
consecutive frames would have duplicate timestamp.
Are you saying that this is MediaSDK timestamp handling bug exposed by the
FFmpeg change (to actually tell MediaSDK that there was no timestamp on
some frame), one that can be only fixed on MediaSDK side? (will you file
bug?)
As PSNR / SSIM calculations do frame-by-frame comparison, any change in
frame timestamps during transcoding would make things go wrong as it
affect frame content => should I '''always''' use "-vsync passtrough" (and
"-an") on transcode operation intended for PSNR / SSIM calculations? And
for performance comparisons?
PS. Is the cause for my other (more recent) PSNR bug similar:
https://trac.ffmpeg.org/ticket/9481 ?
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Ticket URL: <https://trac.ffmpeg.org/ticket/9377#comment:9>
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