[FFmpeg-user] Stream specifier ':a' in filtergraph Error

[Nicolas George]

andrei ka (12020-11-11):
> ffmpeg would be enuf, ffmpeg would list all the tracks in input files
> before starting transco, on failure dude should just check his first
> 20lines of log to see if mp4 have snd tracks...

Bad advice. The log output of ffmpeg is not meant to be parsed by an
application. The fact that it goes to stderr should be a hint. In
particular, there are no promises that the syntax of the list of streams
will be kept constant.

ffprobe is the right tool for this, because the output is guaranteed to
be stable.

Regards,

-- 
  Nicolas George
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