[LAD] Multi-Channel channel order

[David Robillard]

On Sun, 2009-08-16 at 18:55 +0200, Fons Adriaensen wrote:
> On Sun, Aug 16, 2009 at 05:34:47PM +0200, Lennart Poettering wrote:
> 
> > Look for kCAFChannelBit_xxx resp. SPEAKER_xxx.
> > 
> > The CAF wand WAVEX channel mask is identical, however they used
> > different names for the same channels. (CAF allows more flexible
> > definitions via a different chunk, too though, which enables
> > ambisonics). Given that both MS and Apple seem to follow this rule it
> > might be a good idea to follow it too.
> 
> That would be  L R C Lfe Ls Rs.
> 
> Protools uses  L C R Ls Rs Lfe, which is the 'Dolby'
> order as used in the film industry and also for AC3
> encoding.
> 
> DTS and AAC use C, L, R, Ls, Rs, Lfe.

What a mess.  In a maze of little standard, all different, I think I
will use the simple rule: "left-to-right, then front-to-back, finally
LFE", which seems to match the dolby/AC3/Protools order.

e.g. (LFE in parenthesis)

5.1:

1  2  3

4     5
  (6)


7.1:

1  2  3
4     5
6     7
  (8)


7.1 wide:

1 2 3 4 5

6       7
   (8)

etc.  Least it's logical. :)  A downside is that just taking the first
two channels doesn't get you stereo, which could suck if you have a 5.1
"multi-buffer" output and a stereo "multi-buffer" input and the buffers
are just layed out one after another, because if it was LRC you could
connect them directly...

OTOH it's impossible to define a scheme where this is doable for all
combinations, and a proper converter plugin should probably be used in
this case to avoid losing sound anyway.

-dr

P.S. "multi-buffer" is just hypothetical