XAudio.cpp

loat* SoundVoice::CalculatePanMatrix(float pan, float scale, float *matrix, int srcChannels)
{
	if (srcChannels == 1)
	{
		matrix[0] = (pan >= 0 ? ( 1.f - pan ) : 1.f) * scale; 	// Left
		matrix[1] = (pan <= 0 ? ( -pan - 1.f ) : 1.f) * scale;	// Right
	}
	else if (srcChannels == 2)
	{
		if ( -1.0f <= pan && pan <= 0.0f )
		{
		    matrix[0] = (0.5f * pan + 1.0f) * scale;	// .5 when pan is -1, 1 when pan is 0
		    matrix[1] = (0.5f * -pan) * scale;		// .5 when pan is -1, 0 when pan is 0
		    matrix[2] = 0.0f;				//  0 when pan is -1, 0 when pan is 0
		    matrix[3] = (pan + 1.0f) * scale;		//  0 when pan is -1, 1 when pan is 0
		}
		else
		{
		    matrix[0] = (-pan + 1.0f) * scale;		//  1 when pan is 0,   0 when pan is 1
		    matrix[1] = 0.0f;				//  0 when pan is 0,   0 when pan is 1
		    matrix[2] = (0.5f * pan) * scale;		//  0 when pan is 0, .5f when pan is 1
		    matrix[3] = (0.5f * -pan + 1.0f) * scale;	//  1 when pan is 0. .5f when pan is 1
		}
	}
  
  return matrix;
}

void SoundVoice::UpdateOutputMatrix(SoundSystem* system)
{
	XAUDIO2_VOICE_DETAILS details;
	memset(&details, 0, sizeof(details));
	
	_voice->GetVoiceDetails(&details);
  	int srcChannelCount = details.InputChannels;	
	system->GetMasterVoice()->GetVoiceDetails(&details);
	int dstChannelCount = details.InputChannels;
	
	// Default to zero volume on all channels.
	float panMatrix[16];
	memset(panMatrix, 0, sizeof(panMatrix));
	
	// Set the pan on the correct channels based on the reverb mix.
  	if (!(_reverbMix > 0.0f))
		_voice->SetOutputMatrix(nullptr, srcChannelCount, dstChannelCount, CalculatePanMatrix(_pan, 1.0f, panMatrix, srcChannelCount));
  	else
  	{
     		_voice->SetOutputMatrix(system->GetReverbVoice(), srcChannelCount, dstChannelCount, CalculatePanMatrix(_pan, _reverbMix, panMatrix, srcChannelCount));
     		_voice->SetOutputMatrix(system->GetMasterVoice(), srcChannelCount, dstChannelCount, CalculatePanMatrix(_pan, 1.0f - (_reverbMix > 1.0f ? 1.0f : _reverbMix), panMatrix, srcChannelCount));
  	}
}