audio unit 混音

 

ios audio unit 提供了強大的混音功能， 這就就不介紹audioUnit 的基本邏輯和使用方法了，直接開始介紹介紹
要實現混音必須使用 audioGraph 
 

1 ： 第一步 初始化兩個unit ( 一個misUnit 一個 ioUnit )

 

 

 

// augraph
    CheckError(NewAUGraph(&auGraph), "NewAUGraph error");
    CheckError(AUGraphOpen(auGraph), "open graph fail");
    // output audio unit
    AudioComponentDescription outputAudioDesc;
    outputAudioDesc.componentType = kAudioUnitType_Output;//audioUnit類型（一共有四種）
    outputAudioDesc.componentSubType = kAudioUnitSubType_VoiceProcessingIO;//子類型
//    outputAudioDesc.componentSubType = kAudioUnitSubType_RemoteIO;;//子類型
   
    outputAudioDesc.componentManufacturer = kAudioUnitManufacturer_Apple;
    outputAudioDesc.componentFlags = 0;
    outputAudioDesc.componentFlagsMask = 0;
//  AUNode outputNode;
    CheckError(AUGraphAddNode(auGraph, &outputAudioDesc, &outputNode), "add node fail");
    CheckError(AUGraphNodeInfo(auGraph, outputNode, NULL, &outputUnit), "get audio unit fail");
    
    
    // mix audio unit
    AudioComponentDescription mixAudioDesc;
    mixAudioDesc.componentType = kAudioUnitType_Mixer;
    mixAudioDesc.componentSubType = kAudioUnitSubType_MultiChannelMixer;
    mixAudioDesc.componentManufacturer = kAudioUnitManufacturer_Apple;
    mixAudioDesc.componentFlags = 0;
    mixAudioDesc.componentFlagsMask = 0;
//  AUNode mixNode;
    CheckError(AUGraphAddNode(auGraph, &mixAudioDesc, &mixNode), "add node fail");
    CheckError(AUGraphNodeInfo(auGraph, mixNode, NULL, &mixUnit), "get audio unit fail");

 

2 鏈接連個unit

// connect augraph 鏈接 auNode
    CheckError(AUGraphConnectNodeInput(auGraph,
                                       mixNode,
                                       MIX_UNIT_OUTPUT_BUS,//0
                                       outputNode,
                                       REMOTE_IO_UNIT_OUTPUT_BUS), "connect fail");

 

 

3 設置回調 

UInt32 busCount = 2;
    CheckError(AudioUnitSetProperty(mixUnit,
                                    kAudioUnitProperty_ElementCount,
                                    kAudioUnitScope_Input,
                                    MIX_UNIT_INPUT_BUS0,//0
                                    &busCount,
                                    sizeof(UInt32)), "set property fail");
    
    

    
    AURenderCallbackStruct callback0;
    callback0.inputProc = mixCallback0;
    callback0.inputProcRefCon = (__bridge void *)self;


    
    CheckError(AudioUnitSetProperty(mixUnit,
                                    kAudioUnitProperty_SetRenderCallback,
                                    kAudioUnitScope_Input,
                                    MIX_UNIT_INPUT_BUS0,
                                    &callback0, sizeof(AURenderCallbackStruct)), "add mix callback fail");
    
    CheckError(AudioUnitSetProperty(mixUnit,
                                    kAudioUnitProperty_StreamFormat,
                                    kAudioUnitScope_Input,
                                    MIX_UNIT_INPUT_BUS0,
                                    &audioFormat, sizeof(AudioStreamBasicDescription)), "set mix format(input 0) fail");
    
    
    AURenderCallbackStruct callback1;
    callback1.inputProc = mixCallback1;
    callback1.inputProcRefCon = (__bridge void *)self;
    
    
    CheckError(AudioUnitSetProperty(mixUnit,
                                    kAudioUnitProperty_SetRenderCallback,
                                    kAudioUnitScope_Input,
                                    MIX_UNIT_INPUT_BUS1,
                                    &callback1, sizeof(AURenderCallbackStruct)), "add mix callback fail");
    
    CheckError(AudioUnitSetProperty(mixUnit,
                                    kAudioUnitProperty_StreamFormat,
                                    kAudioUnitScope_Input,
                                    MIX_UNIT_INPUT_BUS1,
                                    &audioFormat, sizeof(AudioStreamBasicDescription)), "set mix format(input 1) fail");
    
    
    
    _mixStreamFmt = *([[AVAudioFormat alloc] initWithCommonFormat:AVAudioPCMFormatInt16
                                                       sampleRate:audioFormat.mSampleRate
                                                         channels:audioFormat.mChannelsPerFrame
                                                      interleaved:YES].streamDescription);
    
    CheckError(AudioUnitSetProperty(mixUnit,
                                  kAudioUnitProperty_StreamFormat,
                                  kAudioUnitScope_Output,
                                  0,
                                  &_mixStreamFmt,
                                  sizeof(AudioStreamBasicDescription)), "add mix format(output) fail");

 

4 播放 因爲把兩個Unit鏈接， 只要把取數據的回調設置好系統就可以播放了