[Openal] Using stereo sounds

[Chris Robinson]

On Monday 28 May 2007 05:08:32 pm Kieran Hayes wrote:
>  Sound files that are stereo will not respond correctly when applying
> orientation and position.  All mono files work perfectly, and I suppose
> this is because the stereo files have multiple channels and work against
> what OpenAL is trying to do with them, but it seems as though this
> limitation should not be there.

Non-mono sources aren't affected by 3D spatialization. According to the spec:
"Buffers containing audio data with more than one channel will be played 
without 3D spatialization features – these formats are normally used for 
background music."

Panning multi-channel sources is a bit ambiguous (do the channels blend to one 
side? do the other channels just go quiet?), so I guess they didn't want to 
worry about such implementation details.

> Should I write a converter myself so that 
> any sound files that are used are converted to mono, or is there a special
> way of loading or playing stereo WAVEs?  Thanks for the help.

Something you could try to do is just supply the stereo data, specify a 
single-channel format and double the reported frequency. Though I suppose 
converting stereo data to mono would be a safer choice. It's not really hard:

for(i = 0;i < num_frames;++i)
    data[i] = (int)(data[i*2]+data[i*2+1])/2;

Where num_frames is the number of left-right sample pairs, and 'data' is the 
correct pointer type (short* for 16-bit, unsigned char* for 8-bit).