[FFmpeg-user] minterpolate PTS v frame count weirdness

Mark Filipak (ffmpeg) markfilipak at bog.us
Fri Jan 29 11:17:52 EET 2021

I've put 2 videos and a log here:
https://www.dropbox.com/t/KaFx0DljtY33Qo4p = '24p-original (480 frames).mkv'
https://www.dropbox.com/t/Pl7y7sYQsh5MZ1Uu = '60p-minterpolate (1195 frames).mkv'
https://www.dropbox.com/t/WM81XL5Xc2ZbX6AO = '60p-minterpolate.mkv.log'

The source is '24p-original (480 frames).mkv'.
The target is '60p-minterpolate (1195 frames).mkv'.

A 60p video should have 1200 frames. By visual comparison, the dropped frames in '60p-minterpolate 
(1195 frames).mkv' are NOT at the beginning. It is at this point that things get weird.

The running time for both videos is indicated to be 0:20.105 (source: MPV). But '60p-minterpolate 
(1195 frames).mkv' never reaches its full 0:20.105 running time. Its last frame is at 
PTS=0:19.920000, instead (source: MPV).


For '24p-original (480 frames).mkv':
1st PTS: 'frames.frame.0.best_effort_timestamp_time="0:00:00.000000"' (source: ffprobe)
last PTS: 'frames.frame.479.best_effort_timestamp_time="0:00:19.978000"' (source: ffprobe)
(479 frames)/(19.978000 seconds) = 23.976374011412553809190109120032 FPS. Good!
Delta-PTS = 19.978000/479 = 0.04171 s/frame. Good!

For '60p-minterpolate (1195 frames).mkv':
1st PTS: 'frames.frame.0.best_effort_timestamp_time="0:00:00.000000"'
last PTS: 'frames.frame.1194.best_effort_timestamp_time="0:00:19.920000"' (source: ffprobe)
(1194 frames)/(19.920000 seconds) = 59.939759036144578313253012048193 FPS. Good!
Delta-PTS = 19.920000/1194 = 0.01668 s/frame. Good!

All good so far.

The problem is that '60p-minterpolate (1195 frames).mkv's last time stamp means there are actually 
10 frames missing, i.e. (20.105-19.920)/0.01668 - 1 = 10.

Are there really 5 frames missing or 10 frames missing?

Can anyone answer that? Or have I made a faux pas?


Someone's sneaking in and turning up the range so that my food burns.
I'm sure of it.
And the older I get, the more sure of it I become.

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