[FFmpeg-user] Audio channel mapping of stereo channel without re-encode
Carl Eugen Hoyos
cehoyos at ag.or.at
Fri Aug 22 10:36:06 CEST 2014
Claudiu Rad-Lohanel <jazzman <at> misalpina.net> writes:
> >> From the source audio I would like to take
> >> either only the left or the right channel
> >> into my outputs. While only transcoding the
> >> video and copy the audio.
> > This cannot work.
> Indeed, you are right. But from what I know so
> far, this is because the level of data access
> that we have now is either at the stream level
> (audio, video, subtitles, etc) after demuxing,
> either somehow at the uncompressed frame level
> after decoding.
If this were true, the relevant filters might
even work as suggested by you: After all, we
usually aim to be as fast as possible.
But the problem is that stereo (in real codecs,
I am of course not speaking about pcm audio) is
encoded in a way that makes it impossible to
extract one channel without decoding.
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