[FFmpeg-devel] [RFC] Channel layouts

[Ian Caulfield]

2008/8/29 Andreas ?man <andreas at lonelycoder.com>:
> Dominik 'Rathann' Mierzejewski wrote:
>> What if you have 4 speakers but in a different layout than the
>> encoded one? With the two layouts above (C+L+R+S encoded and L+R+SL+SR
>> speakers) I'd expect the sound to come out of the front speakers only,
>> with C+S channels mixed equally with L and R. This could be done by the
>> codec or an audio filter if the codec isn't capable.
>
> This belongs to the audio layer of a mediaplayer IMHO.
> Most AV Amplifiers support stuff like:
>
> * Phantom Center         (Mix C to L+R)
> * Phantom LFE            (Mix LFE to L+R)
> * Small Front speakers   (in 2ch mode, mix L+R to LFE)
> etc...
>
> certainly it should stay out of the codecs.

...unless the codec specifically supports it. E.g., TrueHD and MLP can
embed a two-channel downmix into the stream - if stereo is requested,
then it's not necessary to decode any other channels...

Ian