[Openal] Question about Motu 828mkIII hardware

[Chris Robinson]

On Thursday 02 April 2009 5:00:15 am Serge Lages wrote:
> Do you thing OpenAL is well suited to manage sound outputs on a setup like
> the following : 1 computer with 2 MOTU 828mkIII sound cards (
> http://www.motu.com/products/motuaudio/828mk3/body.html) with 12 speakers
> and 2 subwoofers
>
> The idea is to be able to spatialize the sound between all the speakers.
> Thanks in advance for your help.

Hi Serge.

If the two sound cards can be seen by apps as a single 12.2 device, it should 
be theoretically possible, given an implementation that can handle that kind 
of output. There's a few issues, though:

1) As mentioned, I don't believe there's an implementation that /can/ handle 
12.2 output. In theory, I could make OpenAL Soft do up to 12.2, but 
DirectSound (which OpenAL Soft uses for output on Windows) doesn't seem to 
have a method for handling multiple LFE channels.

2) I would need to know what position the speakers are (eg. front-left, front-
right, side-left, etc). I'd also need to know the order the data is expected 
in.. eg. stereo data is left,right,left,right,etc, and quad is front-
left,front-right,back-left,back-right,etc. Given the positions, the order 
would be defined for Windows, though Linux and OSX could be different, and I'd 
be hesitant to add it without being reasonably sure it can work on all three 
platforms.

3) It may or may not add a negligible amount of processing time for multi-
channel sources, given the code used to properly re-channel them.

If you can, I'd probably try to see if you can use the two cards as a single 
7.1 output device, which OpenAL Soft 1.7 can handle without a problem. This 
shouldn't degrade the quality all much. Though I can see about trying to add 
12.2 support to OpenAL Soft if you do want it.

- Chris