Swift:断开AVAudioUnit播放AVAudioEngine的连接

Question

在某一时刻，我正在播放一个具有某些效果的音频文件。代码如下：

 engine = AVAudioEngine()
    playerB = AVAudioPlayerNode()

    playerB.volume = 0.5

    let path = Bundle.main.path(forResource: "ukulele", ofType: "wav")!
    let url = NSURL.fileURL(withPath: path)

    let file = try? AVAudioFile(forReading: url)
    buffer = AVAudioPCMBuffer(pcmFormat: file!.processingFormat, frameCapacity: AVAudioFrameCount(file!.length))!
    try! file!.read(into: buffer)

    reverb.loadFactoryPreset(AVAudioUnitReverbPreset.cathedral)
    reverb.wetDryMix = 50

    distortion.loadFactoryPreset(AVAudioUnitDistortionPreset.speechRadioTower)
    distortion.wetDryMix = 25

    let delay = AVAudioUnitDistortion()
    delay.loadFactoryPreset(AVAudioUnitDistortionPreset.speechAlienChatter)
    delay.wetDryMix = 25


    engine.attach(playerB)
    engine.attach(reverb)
    engine.attach(distortion)
    engine.attach(delay)
    engine.attach(pitch)
    engine.attach(speedControl)

    engine.connect(playerB, to: pitch, format: nil)

    engine.connect(pitch, to: speedControl, format: nil)
    engine.connect(speedControl, to: reverb, format: nil)

    engine.connect(reverb, to: distortion, format: nil)
    engine.connect(distortion, to: engine.mainMixerNode, format: buffer.format)

    playerB.scheduleBuffer(buffer, at: nil, options: AVAudioPlayerNodeBufferOptions.loops, completionHandler: nil)



    engine.prepare()
    try! engine.start()

我想要的是在发生特定操作时断开其中一个AVAudioUnit。但是，在移除AVAudioUnit之后，播放器完全处于静默状态。

例如，如果我想删除reverb，代码是：engine.disconnectNodeOutput(reverb)，但是在这一行运行之后，播放器是静默的。

我做错了什么？我只想删除已经添加的一个效果。

Answer 1

这是一条链子，你弄断了其中的一个链环。下面是你的代码：

engine.connect(pitch, to: speedControl, format: nil)
engine.connect(speedControl, to: reverb, format: nil)
engine.connect(reverb, to: distortion, format: nil)
engine.connect(distortion, to: engine.mainMixerNode, format: buffer.format)

如果移除混响节点，现在速度控制和失真之间会有一个空洞。没有任何东西可以穿过那个洞。您需要将它们连接起来。