最近學(xué)習(xí)了AudioUnit的官方指南讥巡，按照官方文檔簡(jiǎn)單實(shí)現(xiàn)錄音和耳返的功能。
1舔哪、首先配置AudioSession欢顷，代碼如下：

  self.graphSampleRate = 44100.0;
    self.ioBufferDuration = 0.005;
    NSError *error = nil;
    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    [audioSession setPreferredHardwareSampleRate:self.graphSampleRate error:&error];
    
    if (error) {
        NSLog(@"=====error===%@",error);
        exit(-1);
        return;
    }
    [audioSession setCategory:AVAudioSessionCategoryPlayAndRecord error:&error];
    if (error) {
        NSLog(@"=====error===%@",error);
        exit(-1);
        return;
    }
    [audioSession setActive:YES error:&error];
    if (error) {
        NSLog(@"=====error===%@",error);
        exit(-1);
        return;
    }
    //    音頻會(huì)話激活后，根據(jù)系統(tǒng)提供的實(shí)際采樣率更新您自己的采樣率變量捉蚤。
    self.graphSampleRate = [audioSession currentHardwareSampleRate];
    
    //    還有一個(gè)其他硬件特性可能需要配置：音頻硬件I / O緩沖區(qū)持續(xù)時(shí)間抬驴。44.1 kHz采樣率的默認(rèn)持續(xù)時(shí)間約為23 ms，相當(dāng)于1,024個(gè)采樣的切片大小缆巧。如果I / O延遲對(duì)您的應(yīng)用程序至關(guān)重要布持，則可以請(qǐng)求較短的持續(xù)時(shí)間，下降到大約0.005 ms（相當(dāng)于256個(gè)采樣）陕悬，如下所示：
    [audioSession setPreferredIOBufferDuration:self.ioBufferDuration error:&error];
    if (error) {
        NSLog(@"=====error===%@",error);
        exit(-1);
        return;
    }

2题暖、創(chuàng)建一個(gè)AudioUnit對(duì)象
2.1:構(gòu)建AudioComponentDescription,主要需要設(shè)置componentType和componentSubType。由于我們這里是需要錄音然后輸出耳機(jī),設(shè)置如下:

 //1.創(chuàng)建AudioUnit
    AudioComponentDescription ioUnitDes;
    ioUnitDes.componentType = kAudioUnitType_Output;
    ioUnitDes.componentSubType = kAudioUnitSubType_RemoteIO;
    ioUnitDes.componentManufacturer = kAudioUnitManufacturer_Apple;
    ioUnitDes.componentFlags = 0;
    ioUnitDes.componentFlagsMask = 0;

不同的的componentType和componentSubType組成有不能的作用捉超，下圖為常用不同組合的作用

391523962280_.pic_hd.jpg

2.2 創(chuàng)建AudioUnit,AudioUnit的創(chuàng)建方式有兩種胧卤，這里使用官方推薦的方式AUGraph來(lái)創(chuàng)建,

  //1.創(chuàng)建一個(gè)圖
   OSStatus status;
    status = NewAUGraph(&processingGraph);
    CheckStatus(status, @"不能構(gòu)造圖", YES);
//2.創(chuàng)建一個(gè)結(jié)點(diǎn)。
    AUNode ioNode;
    status = AUGraphAddNode(processingGraph, &ioUnitDes, &ioNode);
    CheckStatus(status, @"添加節(jié)點(diǎn)失敗", YES);
    
    //3狂秦、打開(kāi)圖灌侣，相當(dāng)于間接創(chuàng)建了音頻處理單元
    status = AUGraphOpen(processingGraph);
    CheckStatus(status, @"打開(kāi)圖失敗", YES);
    //4推捐、獲取ioUnit
    status = AUGraphNodeInfo(processingGraph, ioNode, NULL, &_ioUnit);
    CheckStatus(status, @"不能獲取 node info", YES);

上面代碼中CheckStatus為檢測(cè)是否成功的函數(shù)

static void CheckStatus(OSStatus status, NSString *message, BOOL fatal)
{
    if(status != noErr)
    {
        char fourCC[16];
        *(UInt32 *)fourCC = CFSwapInt32HostToBig(status);
        fourCC[4] = '\0';
        
        if(isprint(fourCC[0]) && isprint(fourCC[1]) && isprint(fourCC[2]) && isprint(fourCC[3]))
            NSLog(@"%@: %s", message, fourCC);
        else
            NSLog(@"%@: %d", message, (int)status);
        
        if(fatal)
            exit(-1);
    }
}

2.3 設(shè)置AudioUnit的屬性

  //2.1設(shè)置
    UInt32 flag = 1;
    status =  AudioUnitSetProperty(_ioUnit,kAudioOutputUnitProperty_EnableIO , kAudioUnitScope_Input,1, &flag, sizeof(flag));
    CheckStatus(status, @"設(shè)置輸入scope 失敗", YES);
    status =  AudioUnitSetProperty(_ioUnit,kAudioOutputUnitProperty_EnableIO , kAudioUnitScope_Output,0, &flag, sizeof(flag));
    CheckStatus(status, @"設(shè)置輸出scope 失敗", YES);

上面的1表示Element1為和錄音的麥克風(fēng)相連裂问，0表示Element0和輸出硬件相連。
2.4 設(shè)置流的格式AudioStreamBasicDescription

 size_t bytesPerSample = sizeof(AudioUnitSampleType);
    AudioStreamBasicDescription asbd = {0};
    asbd.mFormatID = kAudioFormatLinearPCM;
    asbd.mFormatFlags = kAudioFormatFlagsAudioUnitCanonical;
    asbd.mBytesPerFrame = bytesPerSample;
    asbd.mBytesPerPacket = bytesPerSample;
    asbd.mBitsPerChannel = 8*bytesPerSample;
    asbd.mFramesPerPacket = 1;
    asbd.mChannelsPerFrame = 2;
    asbd.mSampleRate = self.graphSampleRate;
    
    status = AudioUnitSetProperty(_ioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &asbd, sizeof(AudioStreamBasicDescription));
    CheckStatus(status, @"設(shè)置輸入流格式失敗", YES);
    status = AudioUnitSetProperty(_ioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, &asbd, sizeof(AudioStreamBasicDescription));
    CheckStatus(status, @"設(shè)置輸出流格式失敗", YES);

下面的圖片為不同用途的AudioUnit的設(shè)置格式

401524022790_.pic_hd.jpg

411524022810_.pic_hd.jpg

421524022825_.pic_hd.jpg

431524022849_.pic_hd.jpg

    //3椭更、設(shè)置播放回調(diào)函數(shù)
    AURenderCallbackStruct playCallBack;
    playCallBack.inputProc = playCallBackFuc;
    playCallBack.inputProcRefCon = (__bridge void*)self;
    
    
   status =  AudioUnitSetProperty(_ioUnit, kAudioUnitProperty_SetRenderCallback, kAudioUnitScope_Output, 0, &playCallBack, sizeof(playCallBack));
    CheckStatus(status, @"set renderCallBackError", YES);

  // 設(shè)置錄音回調(diào)函數(shù)
    AURenderCallbackStruct recordCallback;
    recordCallback.inputProc = RecordCallbackFuc;
    recordCallback.inputProcRefCon = (__bridge void *)self;
    AudioUnitSetProperty(_ioUnit,
                         kAudioOutputUnitProperty_SetInputCallback,
                         kAudioUnitScope_Input,
                         1,
                         &recordCallback,
                         sizeof(recordCallback));

錄音回調(diào)函數(shù)如下：

static OSStatus RecordCallbackFuc(    void *          inRefCon,
                                AudioUnitRenderActionFlags *    ioActionFlags,
                                const AudioTimeStamp *            inTimeStamp,
                                UInt32                            inBusNumber,
                                UInt32                            inNumberFrames,
                                AudioBufferList * __nullable    ioData){
    
    
    
    ViewController *viewC = (__bridge ViewController*)inRefCon;
     NSLog(@"錄音");
    if (ioData) {
        NSLog(@"size2 = %d", ioData->mBuffers[0].mDataByteSize);
        //    memcpy(ioData->mBuffers[0].mData, buffList->mBuffers[0].mData, ioData->mBuffers[0].mDataByteSize);
        AudioUnitRender(viewC.ioUnit, ioActionFlags, inTimeStamp, 1, inNumberFrames, ioData);
    }
    return noErr; 
}

播放回調(diào)函數(shù)

 static OSStatus playCallBackFuc(    void *          inRefCon,
                    AudioUnitRenderActionFlags *    ioActionFlags,
                    const AudioTimeStamp *            inTimeStamp,
                    UInt32                            inBusNumber,
                    UInt32                            inNumberFrames,
                             AudioBufferList * __nullable    ioData){
    
    ViewController *viewC = (__bridge ViewController*)inRefCon;
    NSLog(@"size2 = %d", ioData->mBuffers[0].mDataByteSize);
//    memcpy(ioData->mBuffers[0].mData, buffList->mBuffers[0].mData, ioData->mBuffers[0].mDataByteSize);
    AudioUnitRender(viewC.ioUnit, ioActionFlags, inTimeStamp, 1, inNumberFrames, ioData);
    NSLog(@"播放");
    return noErr;
}

3.2 使用AUGraph來(lái)設(shè)置（缺點(diǎn)只能是指播放回調(diào)函數(shù)，優(yōu)點(diǎn)線程安全）

   //3蛾魄、設(shè)置回調(diào)函數(shù)
    AURenderCallbackStruct playCallBack;
    playCallBack.inputProc = playCallBackFuc;
    playCallBack.inputProcRefCon = (__bridge void*)self;
    
    //該方法是線程安全的(但是只能設(shè)置renderCallBack)
    AUGraphSetNodeInputCallback(processingGraph, ioNode, 0, &playCallBack);

4 初始化AUGraph

  //4初始化啟動(dòng)一個(gè)音頻處理圖
    OSStatus result = AUGraphInitialize(processingGraph);
    
    CheckStatus(result, @"初始化失敗", YES);

5 開(kāi)啟AUGraph

 OSStatus status =  AUGraphStart(processingGraph);
    CheckStatus(status, @"啟動(dòng)圖失敗", YES);