[Openal] Question about Motu 828mkIII hardware

[Jason Daly]

Serge Lages wrote:
> On Thu, Apr 2, 2009 at 5:28 PM, Jason Daly <jdaly at ist.ucf.edu 
> <mailto:jdaly at ist.ucf.edu>> wrote:
>
>     Serge Lages wrote:
>
>         Hi Dan and Jason,
>
>         Thanks for your replies. I am a real newbie about sound
>         development so please excuse me if my questions are a little
>         dumb... :/
>
>         If I understand it well, having a single 12.2 system managed
>         with 2 cards will be difficult (but possible).
>
>
>     Just to clarify, you'll have to edit the OpenAL implementation
>     (the library) itself to do this.  Since you're a self-described
>     newbie, it might not be the best solution for you (no offense
>     intended ;-) ).
>
>
> Don't worry, there's no offense here, I am a real newbie ! :)
>  
>
>
>     If you do want to give it a try, Chris Robinson's OpenAL-Soft
>     implementation would be the best starting point.  You can get it at:
>
>      http://kcat.strangesoft.net/openal.html
>
>
>
>         And what about having a single application managing two 6.1
>         systems ? Or even two applications, one for each card, then I
>         can make them communicate to know where to play the sounds.
>
>
>     You can certainly open two devices and contexts in OpenAL.  The
>     problem is that the implementation will assume a typical 6.1
>     speaker layout (a la Dolby Surround EX) for both contexts, and
>     there is no way (that I know of) to tell it where your speakers
>     are.  There will always be sound coming from at least one speaker,
>     even if all of your speakers are on the left or right side of the
>     room.
>
>     You're not the first person with a non-standard hardware
>     configuration like this, but unfortunately, I don't remember
>     anyone contributing an implementation for your kind of use case,
>     even though the OpenAL API would be the perfect interface for it.
>
>
> And is it possible to select independently which speaker to send the 
> sound on ? It would be a good starting point for me, even if the best 
> would be a real spacialization.

One feature of OpenAL is that it does not spatialize multi-channel 
sounds (only mono sounds).  If you give OpenAL, for example, a 
5.1-channel buffer to render, it will render it on the left, center, 
right, surround left, surround right, and LFE channels, just like it 
would be rendered without OpenAL in the loop. 

In this way, you could in theory do your own spatialization by creating 
a multi-channel sound stream on the fly and passing it to OpenAL for 
rendering.  This is really the long way around, though.

I just noticed that OpenAL-Soft 1.7 has support for configuring the 
speaker layout.  You might want to wait for Chris Robinson to comment on 
this before you get going.  He may have some other ideas that would make 
this easier for you.

--"J"

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