[MEncoder-users] Dolby downmix

[Reimar Döffinger]

On Mon, Dec 27, 2010 at 06:49:46PM -0600, Rolf Ernst wrote:
> Can someone clarify this for me, please?
> 
> I am trying to do a Dolby Surround downmix from an AC3 5.1 a/v file. I 
> have found many different comments from many different sources with many 
> different observations and comments.
> 
> Can someone clarify this for me?
> 
> This is the command line I have seen that supposedly dumps the audio via 
> filter as Dolby surround into a wav file. Is this true?
> 
> mplayer inputfile -channels 6 -af channels=2 -vc null -vo null -ao 
> pcm:fast:file=audio.wav

With all the FFmpeg discussion (yes, suggesting it is ok, but please try
to keep the discussion a bit separate, hopping between programs makes it
a pain to follow the discussion) I haven't managed to actually
understand what the goal is.
Do you just want downmixing to two channels? Just use -channels 2
instead of -channels 6.
If you want to have a very specific downmixing matrix (instead of
something that should produce a reasonable 2-channel representation
from all 6 channels), use -channels 6 and -af pan with the precise
matrix coefficients.