[Openal] Split wav channel

[Daniel PEACOCK]

Hi,

Stereo wave files have interleaved data i.e a Left Channel Sample followed
by a Right Channel Sample followed by Left, Right etc ...  If you want to
split the file into two monos then you would do something like this
(assuming 16bit samples and that the pointers are all valid and point to
enough storage space, etc ...)

ALvoid SplitStereo(ALshort *pStereoData, ALshort *pLeft, ALshort *pRight,
ALuint uiNumSamples)
{
      ALuint i;

      for (i = 0; i < uiNumSamples; i++)
      {
            pLeft[ i ] = pStereoData[i*2];
            pRight[ i ] = pStereoData[i*2+1];
      }
}

If you just want to create a single mono stream from a stereo file, then
you need to mix the Left and Right samples together (and watch out for
overflows).

ALvoid StereoToMono(ALshort *pStereoData, ALshort *pMonoData, ALuint
uiNumSamples)
{
      ALuint i;
      ALint result;

      for (i = 0; i< uiNumSamples; i++)
      {
            result = (ALint)pStereoData[i*2] + (ALint)pStereoData[i*2+1];
            if (result > 32767)
                  result = 32767;
            else if (result < -32768)
                  result = -32768;
            pMonoData[i] = (ALshort)result;
      }
}

NOTE :  uiNumSamples is the number of 'blocks' or 'frames' and not the
count of all the samples in all the channels. e.g. For 16bit stereo data,
uiNumSamples = DataSizeInBytes / 4.  (divide by 2 because it is 16bit
shorts, and divide by 2 again because there are 2 channels).

If you intend to play both mono parts of the stereo file then you should
use the vector play call (alSourcePlayv)  to keep the parts in sync
otherwise you might hear some strange artifacts.

Dan
Creative Labs (UK) Ltd.

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             Andrea Mannarà                                                
             <andrea.mannara at t                                             
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             07/28/2009 02:00                                              
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Hello,
I'm new user of OpenAl and i need to make spatial a wave with stereo
channel.
I thought I can split it in two separated sources and make these spatial.
But How can I split the 2 channel?

Thanks, Huvber

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