[vlc-devel] Re: [MOD] Mac OSX multichannel patch

[Jean-Alexis Montignies]

On 7 juin 04, at 11:38, Matthew Romaine wrote:

>
> On 2004/06/07, at 18:16, Matthew Romaine wrote:
>
>> Like Jean-Alexis points out, VLC-OSX apparently doesn't allow a user 
>> to change which channel-setup to use.  My patch basically chose 
>> whatever stream(s) held the most options. (actually, I was testing 
>> 5.1 and forgot to un-comment the 8ch support; sorry).  My thinking is 
>> that a simple drop-down on the pane where it currently only says 
>> "Audio Device: -1 (under 
>> preferences->modules->audio_output->coreaudio) would be a nice for 
>> now.  This would require obtaining a list of options from the 
>> coreaudio.c audio_output module.  I would be happy to create said 
>> access function, but I'm not sure if the interface between the UI and 
>> the module exists...
>
> Actually, I think I just found what to change and how to add options 
> to the interface for the module.
> I'll be back with more changes in a bit :)
>
Fine :)

I tried your code Matthew, and it didn't work as excepted.

I have a Motu 828 Mk2, the streams looks like the one of a 896. In the 
audi-device menus I had the choice between twice 'mono', twice 'stereo' 
and once for the remaining surround format.
However, whatever stream I chose, I would end up with the 5.1 surround 
output.

Your code was very helpful, I watched some DTS movies in quad by just 
commenting the 5.1 stream format in the coreaudio.c. Not an easy way to 
do that but it's what I need ;).
The quad output of liba52 seems false (two much signal at left, bad 
coefficients or wrong channel mapping).

To return to the HALOutput unit, it's really helpful to use this 
features as it takes care of channel mapping (but not downmixing) all 
you have to do is to give the output unit the channel layout, and this 
unit does the mapping and takes care of turning on/off the streams if 
necessary.
The layout is defined in the AudioMidiSetup application.

The documentation is at 
/Devloper/Documentation/CoreAudio/AudioUnits/AUHAL.rtfd

Regards,

Jean-Alexis Montignies

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