[FFmpeg-user] Rescuing inconsistent frame rate screen capture file?

[Simon Roberts]

Hi all, I have some video files (video only, no audio) that were
recorded using ffmpeg to capture a computer screen. Unfortunately, it
seems that the frame rate is somehow inconsistent. When I stretch it
(almost four minutes overall!) to synchronize over the 38 minutes of
the audio file which was captured simultaneously, but on a different
machine, the middle part goes way out of sync, drifting ahead and
behind at different points. We're not talking a few frames here
either, but tens of seconds.

So, I suppose I have two questions, the more important is whether
there might be a way to have ffmpeg recreate a fixed frame rate,
building in the necessary duplicate frames, or dropping frames, based
on the *timestamps* on frames? I will say that I tried simply
transcoding from the x264/mp4 original file to a prores_ks/mov file,
but the inconsistency was not fixed.

The secondary question is what might cause this (it's an x11grab input
through libx264, and was using about 2.5 of the 4 cores the machine
has.) and how might I know that it's failing while the recording is
taking place?

TIA,
Simon
-- 
Simon Roberts
(303) 249 3613