[FFmpeg-user] Help needed to work around incorrect DTS when capturing H264 from a Logitech C920

Carl Eugen Hoyos cehoyos at ag.or.at
Tue Dec 16 10:57:50 CET 2014

Peter Rabbitson <rabbit+list <at> rabbit.us> writes:

> On 12/16/2014 10:44 AM, Peter Rabbitson wrote:
> > On 12/16/2014 10:33 AM, Carl Eugen Hoyos wrote:
> >> Peter Rabbitson <rabbit+list <at> rabbit.us> writes:
> >>
> >>> a playback of the stream via `ffplay -i stdin.h264`
> >>> seems to run faster.
> >>
> >> You can now use the input option "-r 30" to remux
> >> this stream with "correct" timestamps.
> >> (I am not sure if they will really be correct but
> >> playback works fine here.)
> Which command are you using exactly?

$ ffmpeg -r 30 -i input -vcodec copy out.mkv

> Adding -r 30 on the input seems to 
> make 0 difference with the h264 capture for me.

Different values for -r make a difference here.

> That is - the result is frame by frame identical 
> with or without r 30

Of course: Remuxing should not change the content 
of individual frames.
(You reported that it "runs too fast" iirc, this 
can be fixed with "-r 30".)

Carl Eugen

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