Re: Eric's OpenAL presentation

On 9/1/11, [email protected] <[email protected]> wrote:
>> My monster 2 hour presentation is finally posted on YouTube.
>> http://www.youtube.com/watch?v=6QQAzhwalPI
>>
>
> Thanks for posting that, I'm not a iOS user but it was a good
> introduction/explanation of how the 3D modelling works.
>
> Does anyone have examples/experience with listeners with more that 2 (L/R)
> channels?
>
> Simon.
>

I might be misunderstanding the question, but the question that is
missing in the middle of the video seems similar. Canonical OpenAL
only spatializes mono sounds. It is the responsibility of the
application programmer to specify the 3D positions of sources. But it
is the responsibility of the OpenAL implementation, driver, and
hardware to play the sound in the correct way so it sounds like it
comes out at the correct position.

So in a theoretical world where you had a speaker system that
surrounded you in 360 degrees, the ideal OpenAL implementation would
render sounds at the correct points in your speaker so you hear things
as you would expect.

A little less theoretical, if you have 4 speakers: two front corners,
two back corners, for a sound that is supposed to play directly behind
you, the OpenAL implementation, driver, and hardware, might try to
coordinate so that the sound plays equally in the two back speakers to
make it seem like the sound is coming directly behind you.

I have seen some fancy sound card driver setups (on Windows) where you
could specify the number of speakers you had connected, and I think
you could also specify their positional arrangements, presumably so
the driver could do the necessary balancing/offsets.

But the ultimate point is that as an OpenAL programmer/user, you don't
worry about channels yourself for 3D spatialization. That is the job
of OpenAL.

-Eric
-- 
Beginning iPhone Games Development
http://playcontrol.net/iphonegamebook/
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