问使用AVFoundation和Swift访问多个音频硬件输出/通道

EN

func setupAudioPath(){
    //print("setupAudioPath")

    // get output hardware format
    let output = engine.outputNode
    outputHWFormat = output.outputFormat(forBus: 0)

    //print("outputHWFormat = \(outputHWFormat)")
    //print("outputHWFormat.channelCount = \(outputHWFormat.channelCount)")

    // connect mixer to output
    mixer = engine.mainMixerNode

    //then work on the player end by first attaching the player to the engine
    engine.attach(player)

    engine.connect(mixer, to: output, format: outputHWFormat)

    var channelMap: [sint32] = []
    //UInt32 numOfChannels = fileFormat.NumberChannels();
    let numOfChannels: UInt32 = UInt32(numberOfStreams) * UInt32(2);    // Number of output device channels
    let mapSize: UInt32 = numOfChannels * UInt32(MemoryLayout<sint32>.size);
    for _ in 0...(numOfChannels-1) {
        channelMap.append(-1)
    }
    //channelMap[desiredInputChannel] = deviceOutputChannel;
    channelMap[leftChannel - 1] = 0;
    channelMap[leftChannel]     = 1;


    //print(channelMap)
    //print("number of channels in my map: \(channelMap.count)")

    let code: OSStatus = AudioUnitSetProperty((engine.outputNode.audioUnit)!,
                                              kAudioOutputUnitProperty_ChannelMap,
                                              kAudioUnitScope_Global,
                                              1,
                                              channelMap,
                                              mapSize);


    print("osstatus = \(code)")
}

let engine = AVAudioEngine()
let player = AVAudioPlayerNode()

func testCode(){

    // get output hardware format
    let output = engine.outputNode
    let outputHWFormat = output.outputFormatForBus(0)
    // connect mixer to output
    let mixer = engine.mainMixerNode
    engine.connect(mixer, to: output, format: outputHWFormat)


    //then work on the player end by first attaching the player to the engine
    engine.attachNode(player)


    //find the audiofile
    guard let audioFileURL = NSBundle.mainBundle().URLForResource("tones", withExtension: "wav") else {
        fatalError("audio file is not in bundle.")
    }


    var songFile:AVAudioFile?
    do {
        songFile = try AVAudioFile(forReading: audioFileURL)
        print(songFile!.processingFormat)

        // connect player to mixer
        engine.connect(player, to: mixer, format: songFile!.processingFormat)

    } catch {
        fatalError("canot create AVAudioFile \(error)")
    }



    let channelMap: [Int32] = [0, 1] //left out left, right out right
    //let channelMap: [Int32] = [1, 0] //right out left, left out right


    let propSize: UInt32 = UInt32(channelMap.count) * UInt32(sizeof(sint32))

    let code: OSStatus = AudioUnitSetProperty((engine.inputNode?.audioUnit)!,
                                              kAudioOutputUnitProperty_ChannelMap,
                                              kAudioUnitScope_Global,
                                              1,
                                              channelMap,
                                              propSize);

    print(code)


    do {
        try engine.start()
    } catch {
        fatalError("Could not start engine. error: \(error).")
    }

    player.scheduleFile(songFile!, atTime: nil) {
        print("done")
        self.player.play()
    }

    player.play()



}