[FFmpeg-devel] [PATCH 3/3] avdevice: use av_gettime_relative() for timestamps

[Kieran Kunhya]

On Sun, 7 Feb 2021, 17:29 Nicolas George, <george at nsup.org> wrote:

> Kieran Kunhya (12021-02-07):
> > You do care because different sources generated either by a PC or
> different
> > physical cameras will drift. E.g at 25fps after one hour you might get
> > 90000 frames from one and 90002 or whatever frames from another etc. And
> of
> > course the timestamps will drift slowly. Unfortunately you seem to share
> > the same fundamental misunderstandings as the kernel developers.
>
> Your reasoning is backwards: different time bases is precisely the
> reason we need the option of timestamps with a common reference frame.
>
> With the situation you describe, the application that captures the two
> cameras can detect that one is faster than the other and duplicate or
> skip frames as necessary. Without a common timestamp, it is not
> possible.
>

Yes and thus you need a monotonic clock as a starting point for proper
filtering. Ffmpeg has neither.

Kieran


> --
>   Nicolas George
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".