[FFmpeg-devel] [RFC] Channel layouts

[Andreas Öman]

Ian Caulfield wrote:
> 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...

Of course, stereo/mono downmix is perfectly supported today, the
question is more if anyone will ever write codec-internal
rematrixing for other combinations. But as Ben said, this can
be added later.