[MPlayer-users] mencoder: howto strip/separate left/right audio channel

Peter Daum gator_ml at yahoo.de
Mon Mar 17 17:09:51 CET 2008


I regularly have to deal with DVB-T recordings where 2 totally different audio
tracks (different languages, description for visually impaired people, ...) are
packed into the left/right channel of 1 stereo audio track.Since most players
don't have the option to select only one stereo channel, the result is totally
incomprehensible. What i am looking for is a way to either just drop 1 channel
and create a mono sound track or (better) transform the left/right stereo
channels into 2 separate (mono) audio tracks, preferably without re-encoding
the data.

Regarding the 1st possibility (selecting the right channel), I came up with:

mencoder in.mpg -o out.mpg -ovc copy -oac lavc -lavcopts acodec=mp2 -of mpeg \
-mpegopts format=dvd:vaspect=4/3:muxrate=9500 -af channels=2:2:1:0:1:1

which works, but wastes space by creating 2 identical channels. All attempts
to get just one mono channel didn't work or didn't play (e.g. "channels=1:1:1:0")

For the 2nd possibility, I can't even think of a way how to do this with mencoder.

Does anybody know a more sensible way how to deal with this problem?

                  Peter Daum

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