[FFmpeg-user] 'incorrect' number of extracted frames in a non-VFR video

Jon Beyer jbeyer at gmail.com
Fri Aug 13 06:35:55 EEST 2021

> A quick calculation gave me the impression that the number of decoded
frames mostly matches the expectation ((8x60+9.5)x30000/1001) - what did
you calculate?

Thanks for the reply Carl, and I apologize.  I had pasted two commands that
used slightly different files.

We had an 'original' file from the old hardware.  That video was supposedly
26:10.77, as reported by ffmpeg and VLC.  When we tried to extract jpegs
from that video, we ended up with 14,671 frames or ~ 8 minutes of video at
29.97 fps.  If we scaled the original video, we also ended up with ~ 8
minutes of video.

So I was trying to figure out how we were only getting 14,671 frames at
29.97 fps from 26 minutes of video.

I see now that the original is definitely corrupted.  If I let it play
through in VLC, there are times where the timestamp jumps a full 3 minutes

So I think this isn't an issue with ffmpeg or ffprobe, and simply a
corrupted video whose file implies there is 26 minutes of video, when there
is only 8 minutes.


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