Hi Core Audio/Au community,
I have hit a roadbloc during development. My current AUGraph is set up as 2 Mono streams->Mixer unit->remoteIO unit on an iOS platform. I am using the mixer to mix two mono stream into stereo interleaved. However, the need is that mono streams neednt be mixed at all times while being played out in stereo i.e the interleaved stereo output should be composed of: the 1st mono stream in the left ear and the 2nd mono stream in the right ear. I am able to accomplish this using the kAudioUnitProperty_MatrixLevels property on the Multichannel mixer.
//Left out //right out
matrixVolumes[0][0]=1; matrixVolumes[0][1]=0.001;
matrixVolumes[1][0]=0.001; matrixVolumes[1][1]=0.001;
result = AudioUnitSetProperty(mAumixer, kAudioUnitProperty_MatrixLevels, kAudioUnitScope_Input, 0,matrixVolumes , matrixPropSize);
if (result) {
printf("Error while setting kAudioUnitProperty_MatrixLevels from mixer on bus 0 %ld %08X %4.4s\n", result, (unsigned int)result, (char*)&result);
return -1;
}
printf("setting matrix levels kAudioUnitProperty_MatrixLevels on bus 1 \n");
//Left out //right out
matrixVolumes[0][0]=0.001; matrixVolumes[0][1]=1;
matrixVolumes[1][0]=0.001; matrixVolumes[1][1]=0.001;
result = AudioUnitSetProperty(mAumixer, kAudioUnitProperty_MatrixLevels, kAudioUnitScope_Input, 1,matrixVolumes , matrixPropSize);
if (result) {
printf("Error while setting kAudioUnitProperty_MatrixLevels from mixer on bus 1 %ld %08X %4.4s\n", result, (unsigned int)result, (char*)&result);
return -1;
}
As shown above I am using the volume controls to control the streams playing as unmixed stereo interleaved separately. This works fine when I am using a wired headset to play the audio; the 1st mono stream plays on the left ear and the second mono stream plays on the right ear. But when I am switching to a bluetooth headset the audio output is a mix of both the mono streams playing on both the left and right channel. So, the matrix levels do not seem to work there. The formats used for the i/p and o/p of the mixer are as follows:
printf("create Input ASBD\n");
// client format audio goes into the mixer
obj->mInputFormat.mFormatID = kAudioFormatLinearPCM;
int sampleSize = ((UInt32)sizeof(AudioSampleType));
obj->mInputFormat.mFormatFlags = kAudioFormatFlagsCanonical;
obj->mInputFormat.mBitsPerChannel = 8 * sampleSize;
obj->mInputFormat.mChannelsPerFrame = 1; //mono
obj->mInputFormat.mFramesPerPacket = 1;
obj->mInputFormat.mBytesPerPacket = obj->mInputFormat.mBytesPerFrame = sampleSize;
obj->mInputFormat.mFormatFlags |= kAudioFormatFlagIsNonInterleaved;
// obj->mInputFormat.mSampleRate = obj->mGlobalSampleRate;(// set later while initializing audioStreamer or from the client app)
printf("create output ASBD\n");
// output format for the mixer unit output bus
obj->mOutputFormat.mFormatID = kAudioFormatLinearPCM;
obj->mOutputFormat.mFormatFlags = kAudioFormatFlagsCanonical | (kAudioUnitSampleFractionBits << kLinearPCMFormatFlagsSampleFractionShift);
obj->mOutputFormat.mChannelsPerFrame = 2;//stereo
obj->mOutputFormat.mFramesPerPacket = 1;
obj->mOutputFormat.mBitsPerChannel = 8 * ((UInt32)sizeof(AudioUnitSampleType));
obj->mOutputFormat.mBytesPerPacket = obj->mOutputFormat.mBytesPerFrame = 2 * ((UInt32)sizeof(AudioUnitSampleType));
// obj->mOutputFormat.mSampleRate = obj->mGlobalSampleRate; (// set later while initializing)
N.B : I am setting the sample rates separately from the application.The i/p and o/p sample rate of the mixer is same as sample rate of the mono audio files.
Thanks in advance for taking a look at the issue...:)
