[FFmpeg-user] ffmpeg ignores duration and skips concat images

Moritz Barsnick barsnick at gmx.net
Mon Jun 16 00:19:08 CEST 2014

On Sun, Jun 15, 2014 at 20:37:47 +0000, Carl Eugen Hoyos wrote:
> Spencer Graves <spencer.graves <at> prodsyse.com> writes:
> > ffmpeg -y -r 1 -i restrictSecrecy3.mp2^
> >            -f concat -i framesFiles.txt^
> Did you intend to set an input framerate of 1 
> for the audio file or for the images?

Was this the implicit explanation for the described behavior, or just a

Because if not the former, I can provide another observation. ;-)

> Input #0, mp3, from 'restrictSecrecy3.mp2':
>   Duration: 00:00:59.13, start: 0.000000, bitrate: 159 kb/s
>     Stream #0:0: Audio: mp2, 44100 Hz, stereo, s16p, 159 kb/s
> Input #1, concat, from 'framesFiles.txt':
>   Duration: 00:01:00.00, start: 0.000000, bitrate: 8 kb/s
>     Stream #1:0: Video: png, rgb24, 842x842, 25 tbr, 25 tbn, 25 tbc

The intention seems to have been to provide 1500 frames for about one
minute of video plus audio. At 25 fps, that would have been
appropriate. By reducing the frame rate to 1 fps, only about 60 frames
are required, which matches Spencer's observation.

On the other hand, this would mean that "-shortest" is implicitly
applied here. (Creation of the output ends when the audio track ends,
even though the input video is sufficient for another 1440 seconds.) I
though that needed to be stated explicitly? (I'm not sure, but that's
what I read from the documentation.)


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