[FFmpeg-user] really simple pan= question

Paul Miller listmail at voltar-confed.org
Tue May 8 16:22:21 CEST 2012

I think this is a basic syntax problem, but I could be missing
it.  I have a short clip from the movie Tron:Legacy in 3D ripped
from the HD 3D Blueray.  The audio appears to be 5.1(side) DTS —
though, I have reason to suspect it's really 7.1 ...

Anyway, the downmix audio is effing horrible.  I wanted to look
at each channel individually and see if I couldn't come up with a
game plan for a downmix before I switch to non-ffmpeg tools for
the job.  That's when I noticed my pan= filters were not doing

I expect I'm missing something simple.  I tried putting -ac 1
before the filter and I tried omitting it entirely.  Changing the
argument order seems to have no effect.  Removing -ac 1 causes an
output error, since (I think) mp3s can't have 6 channels.

for i in c{0..5}; do
    ffmpeg -i short.mkv -strict experimental -filter:a pan=1:c0=$i -ac 1 -y $i.mp3;

md5sum c{0..5}.mp3
> e39170046d31193a01676458798e2b69  c0.mp3
> e39170046d31193a01676458798e2b69  c1.mp3
> e39170046d31193a01676458798e2b69  c2.mp3
> e39170046d31193a01676458798e2b69  c3.mp3
> e39170046d31193a01676458798e2b69  c4.mp3
> e39170046d31193a01676458798e2b69  c5.mp3

If riding in an airplane is flying, then riding in a boat is swimming.
116 jumps, 48.6 minutes of freefall, 92.9 freefall miles.

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