How to play sound only in one ear i.e. left or right at a time using AudioUnit

Question

AudioComponentDescription defaultOutputDescription;
defaultOutputDescription.componentType = kAudioUnitType_Output;
defaultOutputDescription.componentSubType = kAudioUnitSubType_RemoteIO;
defaultOutputDescription.componentManufacturer = kAudioUnitManufacturer_Apple;
defaultOutputDescription.componentFlags = 0;
defaultOutputDescription.componentFlagsMask = 0;

// Get the default playback output unit
AudioComponent defaultOutput = AudioComponentFindNext(NULL, &defaultOutputDescription);
NSAssert(defaultOutput, @"Can't find default output");

// Create a new unit based on this that we'll use for output
OSErr err = AudioComponentInstanceNew(defaultOutput, &toneUnit);
NSAssert1(toneUnit, @"Error creating unit: %hd", err);


// Set our tone rendering function on the unit
AURenderCallbackStruct input;
input.inputProc = RenderTone;
input.inputProcRefCon = self;
err = AudioUnitSetProperty(toneUnit, 
    kAudioUnitProperty_SetRenderCallback, 
    kAudioUnitScope_Input,
    0, 
    &input, 
    sizeof(input));

NSAssert1(err == noErr, @"Error setting callback: %hd", err);

// Set the format to 32 bit, single channel, floating point, linear PCM
const int four_bytes_per_float = 4;
const int eight_bits_per_byte = 8;
AudioStreamBasicDescription streamFormat;
streamFormat.mSampleRate = sampleRate;
streamFormat.mFormatID = kAudioFormatLinearPCM;
streamFormat.mFormatFlags =
    kAudioFormatFlagsNativeFloatPacked | kAudioFormatFlagIsNonInterleaved;
streamFormat.mBytesPerPacket = four_bytes_per_float;
streamFormat.mFramesPerPacket = 1;  
streamFormat.mBytesPerFrame = four_bytes_per_float;     
streamFormat.mChannelsPerFrame = 1; 
streamFormat.mBitsPerChannel = four_bytes_per_float * eight_bits_per_byte;

err = AudioUnitSetProperty (toneUnit,
      kAudioUnitProperty_StreamFormat,
      kAudioUnitScope_Input,
      0,
      &streamFormat,
      sizeof(AudioStreamBasicDescription));

Now I am using AudioUnit callback function to create a sound at different frquencies and amplitude, now I want the sound to move between ears like we do using pan property of AVAudioPlayer.For this I tried using the kMultiChannelMixerParam_Pan property using AudioUnitSetParameter ( toneUnit, kMultiChannelMixerParam_Pan, kAudioUnitScope_Output, 0, sender.value, 0 ) But it's not working for me.

it's very hard to read your code and you give little explanation as to what is going wrong or what you need yo accomplish (nil actually to be precise), but personally i wouldn't use a mono channel. i would use a stereo output and silence either the left or right as needed. — MDB983, Jun 11 '15 at 13:30

Gene De Lisa · Answer 1 · 2015-06-11T20:27:46.870

0

Setting the pan value on a mixer unit doesn't do it? kMultiChannelMixerParam_Pan There is also a kAudioUnitType_Panner you can add.

edited Jun 11 '15 at 20:27

answered Jun 11 '15 at 20:22

Gene De Lisa

3,628
1
21
36

I have already tried this change, but its not having any effect on that. Here is what exactly I am doing. I have a slider with range from -1 to 1 for pan and I am sliding its value and doing this. - (IBAction)panChanged:(UISlider *)sender { OSStatus result = AudioUnitSetParameter ( toneUnit, kAudioUnitType_Panner, kAudioUnitScope_Output, 0, sender.value, 0 ); } – Rahul Narang Jun 12 '15 at 05:37
What is `toneUnit`? If it's a mixer, then the parameter you're setting needs to be `kMultiChannelMixerParam_Pan` – Gene De Lisa Jun 12 '15 at 13:36

score 0 · Answer 2 · answered Jun 15 '15 at 10:05

I used the following code.

 AudioUnitSetParameter(<mixerUnit>,
                          kMultiChannelMixerParam_Pan,
                          kAudioUnitScope_Input,
                          0,
                          <panValue>,
                          0);

Audio unit type : kAudioUnitType_Mixer

Subtype :kAudioUnitSubType_MultiChannelMixer

score 0 · Answer 3 · answered Jun 07 '16 at 22:42

0

I've found that setting the pan on bus 0 does not work until after the mixer audio unit has been initialized. Setting volume on bus 0 works before this, and setting pan on bus 1 works before this. I do not know why. I am on iOS if that matters

answered Jun 07 '16 at 22:42

robotcoder

75
1
5

How to play sound only in one ear i.e. left or right at a time using AudioUnit

3 Answers3