[Openal] Play mono as "stereo"

[Carlo VOGELSANG]

Hi Andrew;

When creating the stereo buffer, you actually need to interleave the data
(i.e. L R L R L R instead of the LLLLLLLLL RRRRRRRRRR that you are doing
now):

if (eFormat == AL_FORMAT_MONO8)
{
    char* c = new char[file.GetDataSize()*2];
    for (int i=0; i < file.GetDataSize(); i++)
    {
      c[i*2]=file.GetData()[i]; // left chan
      c[I*2+1]=file.GetData()[i]; // right chan
    }
    alBufferData(m_uiBuffer, AL_FORMAT_STEREO8, c, file.GetDataSize()*2,
file.GetFrequency()/2);
    delete[] c;
}

you could also try setting the mono source to head relative that way it'll
come out of all speakers and won't move when the listener moves.

alSourcei(sid, AL_SOURCE_RELATIVE, TRUE);
alSource3f(sid, AL_POSITION, 0.0f, 0.0f, 0.0f);

-Carlo
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             "Andrew Kerkel"                                               
             <andrew.kerkel at b-                                             
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                                                                   Subject 
                                       [Openal] Play mono as "stereo"      
             10/19/2007 09:50                                              
             AM                                                            
                                                                           
                                                                           
                                                                           
                                                                           




Hi,
According to the programming guide the number of channels in buffer > 1 is
valid but it won't be positioned when played. That's ok so far but in a
special (inverse) case (exactly: speech - which is mono in our project) I
need to use a mono sound as a non 3D sound so it should behave as a stereo
(2D) sound.
I didn't find any possibility to accomplish this so I tried this blunt
trick:

("file" is a wrapper for a wave file)

if (eFormat == AL_FORMAT_MONO8)
{
    char* c = new char[file.GetDataSize()*2];
    memcpy(c, file.GetData(), file.GetDataSize()); // left chan
    memcpy(c+file.GetDataSize(), file.GetData(), file.GetDataSize()); //
right chan
    alBufferData(m_uiBuffer, AL_FORMAT_STEREO8, c, file.GetDataSize()*2,
file.GetFrequency()/2);
    delete[] c;
}

Indeed - it works but this is obviously to easy because the problem is -
while playing there are bad noises.
But where do they come from?

Has anyone any hint for me (I'm still new to OpenAL ;) )?

In DirectSound I have to create a 3D sound buffer to declare the sound as a
3D sound - if I do not - even mono sounds are treated as 2D sounds.

Thanks
- Andrew

(and no, I don't have the possiblity to replace the mono sounds to stereo
sounds because it's for an already shipped project)
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