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

Derk-Jan Hartman hartman at videolan.org
Wed Jun 9 23:18:34 CEST 2004

For AUHAL also look

And check the archives of the CoreAudio-dev list from apple for the 
replies to this email message.]


Jean-Alexis Montignies wrote:
> 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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