AudioUnit基础概念

1、描述音频单元

AudioComponentDescription desc;

desc.componentType = kAudioUnitType_Output;

desc.componentSubType = kAudioUnitSubType_RemoteIO;

desc.componentFlags = 0;

desc.componentFlagsMask = 0;

desc.componentManufacturer = kAudioUnitManufacturer_Apple;

2、查找音频单元

AudioComponent inputComponent = AudioComponentFindNext(NULL, &desc);

3、获取音频单元实例

status = AudioComponentInstanceNew(inputComponent, &audioUnit);

4、启用录制功能、启用播放功能

UInt32 flag = 1;

status = AudioUnitSetProperty(audioUnit,

kAudioOutputUnitProperty_EnableIO,

kAudioUnitScope_Input,

kInputBus,

&flag,

sizeof(flag));

status = AudioUnitSetProperty(audioUnit,

kAudioOutputUnitProperty_EnableIO,

kAudioUnitScope_Output,

kOutputBus,

&flag,

sizeof(flag));

5、音频流描述

AudioStreamBasicDescription audioFormat;

audioFormat.mSampleRate

= 44100.00;

audioFormat.mFormatID

= kAudioFormatLinearPCM;

audioFormat.mFormatFlags

= kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;

audioFormat.mFramesPerPacket

= 1;

audioFormat.mChannelsPerFrame

= 1;

audioFormat.mBitsPerChannel

= 16;

audioFormat.mBytesPerPacket

= 2;

audioFormat.mBytesPerFrame

= 2;

6、应用录制和播放的音频流描述

status = AudioUnitSetProperty(audioUnit,

kAudioUnitProperty_StreamFormat,

kAudioUnitScope_Output,

kInputBus,

&audioFormat,

sizeof(audioFormat));

status = AudioUnitSetProperty(audioUnit,

kAudioUnitProperty_StreamFormat,

kAudioUnitScope_Input,

kOutputBus,

&audioFormat,

sizeof(audioFormat));

7、设置回调

AURenderCallbackStruct callbackStruct;

callbackStruct.inputProc = recordingCallback;

callbackStruct.inputProcRefCon = self;

status = AudioUnitSetProperty(audioUnit,

kAudioOutputUnitProperty_SetInputCallback,

kAudioUnitScope_Global,

kInputBus,

&callbackStruct,

sizeof(callbackStruct));

callbackStruct.inputProc = playbackCallback;

callbackStruct.inputProcRefCon = self;

status = AudioUnitSetProperty(audioUnit,

kAudioUnitProperty_SetRenderCallback,

kAudioUnitScope_Global,

kOutputBus,

&callbackStruct,

sizeof(callbackStruct));

8、回调方法

static OSStatus recordingCallback(void *inRefCon,

AudioUnitRenderActionFlags *ioActionFlags,

const AudioTimeStamp *inTimeStamp,

UInt32 inBusNumber,

UInt32 inNumberFrames,

AudioBufferList *ioData) {

AudioBufferList *bufferList;

OSStatus status = AudioUnitRender([(shockmanViewController *)inRefCon audioUnit],

ioActionFlags,

inTimeStamp,

inBusNumber,

inNumberFrames,

bufferList);

return noErr;

}

static OSStatus playbackCallback(void *inRefCon,

AudioUnitRenderActionFlags *ioActionFlags,

const AudioTimeStamp *inTimeStamp,

UInt32 inBusNumber,

UInt32 inNumberFrames,

AudioBufferList *ioData) {

return noErr;

}