[libav-tools] Repeating one input constantly in an avconv mix

Camil Staps info at camilstaps.nl
Wed Sep 10 22:44:36 CEST 2014


Hello all,

I'm using avconv with the  <https://libav.org/libavfilter.html#amix> amix
function to add a watermark to an MP3 file:

avconv -i audio.mp3 -i wmark.mp3 -filter_complex amix=duration=first
output.mp3

(Here, audio.mp3 is the file I want to watermark, and wmark.mp3 is the
watermark itself. It contains a very low-volume watermark audible for a
computer, but inaudible noise to the human ear.)

However, it would be great if I could make the watermark very short. Not to
limit disk usage, but so that I can recognise the watermark even when I just
have a short part of the output file, later. Is it possible to make avconv
repeat one input stream until the other is finished?

For example, if IN1=abcdef and IN2=ab, the output would be the mix of abcdef
and ababab. Is that possible?

Thank you very much in advance.

Kind regards,

 

Camil Staps 

 

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