private void AllocateCoreAudioBuffers(SystemAudioInputBuffer buffer)
{
//8.10 p173 - Calculate capture buffer size
uint bufferSizeFrames = 0;
int uintSize = Marshal.SizeOf(typeof(uint));
ErrorHandler.CheckError(AudioUnitService.GetProperty(
buffer.AudioUnit.Handle,
AudioDevicePropertyID.BufferFrameSize,
AudioUnitScopeType.Global,
AudioUnitConstant.Element.OUTPUT_BUS,
out bufferSizeFrames,
ref uintSize
));
//8.11-8.12 p173-175 - Allocate AudioBuffers & RingBuffer
buffer.AllocateCoreAudioBuffers(buffer.StreamFormat.Value.ChannelsPerFrame, (int)bufferSizeFrames);
}
private AudioUnit CreateInputUnit(SystemAudioInputBuffer buffer)
{
// Create input unit - 8.4 - 8.13 - Learning Core Audio p169 - 176
//8.4 p169 - Create AudioUnit
var component = GetHALAudioComponent();
buffer.AudioUnit = component.CreateAudioUnit();
buffer.AudioUnit.Initialize();
//8.5 p169-170 - Enable IO on Input AUHAL
ErrorHandler.CheckError(buffer.AudioUnit.SetEnableIO(true, AudioUnitScopeType.Input, AudioUnitConstant.Element.INPUT_BUS));
ErrorHandler.CheckError(buffer.AudioUnit.SetEnableIO(false, AudioUnitScopeType.Output, AudioUnitConstant.Element.OUTPUT_BUS));
//8.7 p171 - Set current device on AUHAL
ErrorHandler.CheckError(buffer.AudioUnit.SetCurrentDevice((uint)buffer.Device.DeviceID, AudioUnitScopeType.Global, AudioUnitConstant.Element.OUTPUT_BUS));
//8.8 p171-172 - Get format from AUHAL input
var auHalFormat = buffer.AudioUnit.GetAudioFormat(AudioUnitScopeType.Output, AudioUnitConstant.Element.INPUT_BUS);
//8.9 p172 - Use AUHAL input sample rate
var auHalInputFormat = buffer.AudioUnit.GetAudioFormat(AudioUnitScopeType.Input, AudioUnitConstant.Element.INPUT_BUS);
AudioStreamBasicDescription requestedFormat = auHalFormat;
requestedFormat.SampleRate = auHalInputFormat.SampleRate;
buffer.StreamFormat = requestedFormat;
ErrorHandler.CheckError(buffer.AudioUnit.SetFormat(requestedFormat, AudioUnitScopeType.Output, AudioUnitConstant.Element.INPUT_BUS));
//8.10 - 8.11 - Calculate buffer size & allocate AudioBuffers
AllocateCoreAudioBuffers(buffer);
//8.13 p174 - Create Input Callback -- sets callback for the SystemAudioInputBuffer instance
ErrorHandler.CheckError(buffer.AudioUnit.SetInputCallback(buffer.InputRenderProc, AudioUnitScopeType.Global, AudioUnitConstant.Element.INPUT_BUS)); // contradicts book-- need INPUT_BUS to get trigger callback
return(buffer.AudioUnit);
}