[FFmpeg-user] aevalsrc stereo auto-converted to mono?

Nicolas George nicolas.george at normalesup.org
Wed Feb 8 12:34:32 CET 2012

Le nonidi 19 pluviôse, an CCXX, Thierry Foucu a écrit :
> Thanks Nicolas, now, this command works
> ./ffmpeg -f lavfi -i
> aevalsrc="sin(440*2*PI*t):sin(880*2*PI*t)::d",aconvert=s16:stereo:packed
> -y /tmp/test.ts
> I have a correct stereo stream.

Nice to hear it.

> i think the problem is that without the aconvert, the code is auto
> inserting a aconvert filter, see output log
> [abuffersink @ 0x2e42040] auto-inserting filter 'auto-inserted aconvert 0'
> between the filter 'Parsed_aevalsrc_0' and the filter 'out'
> the auto insertion is used because aevalsrc is outputting dbl and lavfi
> seems to want to output s16.
> [aconvert @ 0x2e48e60] fmt:dbl cl:stereo planar:1 -> fmt:s16 cl:mono
> planar:0


> But i think there could be a bug here.
> The auto inserting filter should not change the number of channels. It
> should keep the same number of channels as the aevalsrc
> and just convert the fmt from dbl to s16

This is clearly a misfeature that needs fixing. I do not know if someone is
working on it; that is in my TODO queue but not at the top. Patches welcome.


  Nicolas George
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