AudioUnit 用法

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;

}