AudioUnit 用法

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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) {    // This is a mono tone generator so we only need the first buffer    UInt16 *buffer = (SAMPLE *)ioData->mBuffers[0].mData;    // Generate the samples    for (UInt32 frame = 0; frame < inNumberFrames; frame++)    {        if(THIS->isPlaying) {　　　　// 通过修改buffer数组的值，输出自己的音频数据            buffer[frame] = audioProtocol.getEncode()[THIS->qIndex++];                        if(THIS->qIndex >= THIS->qSize) {                //[THIS stopToPlay];                [THIS performSelectorOnMainThread:@selector(stopToPlay) withObject:nil waitUntilDone:NO];                break;            }        }    }    return noErr;}

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