swift - 如何在播放期间更改音频音高？ ( swift 4)

Question

我希望在 Xcode、Swift 4 中使用 slider 或变量(即在播放声音时)实时更改某些音频的音高和播放速度。

目前，我正在使用 AVAudioEngine，它允许我在播放开始之前设置这些值，但在实际播放音频时我无法更改它们。

这是有问题的代码:

func Play() {
    engine = AVAudioEngine()
    audioPlayer = AVAudioPlayerNode()
    audioPlayer.volume = 1.0

    let path = Bundle.main.path(forResource: "filename", ofType: "mp3")!
    let url = NSURL.fileURL(withPath: path)

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

    let pitch = AVAudioUnitTimePitch()
    let speed = AVAudioUnitVarispeed()

    pitch.pitch = speedIncrement * (-500)
    speed.rate = speedIncrement

    engine.attach(audioPlayer)

    engine.attach(pitch)

    engine.attach(speed)

    engine.connect(audioPlayer, to: speed, format: buffer?.format)

    engine.connect(speed, to: pitch, format: buffer?.format)

    engine.connect(pitch, to: engine.mainMixerNode, format: buffer?.format)

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

    engine.prepare()
    do {
        try engine.start()
    } catch _ {
    }

    audioPlayer.play()

}

这甚至可以使用 AVAudioEngine 吗？

如果 AVAudioEngine 无法做到这一点，还有哪些其他可能的解决方案？

Answer 1

实际上，我从reddit得到了答案。我所要做的就是声明 pitch和 speed Play() 之外的变量函数，以及 pitch.pitch = speedIncrement * (-500)和 speed.rate = speedIncrement表达式。我知道我错过了一些简单的东西......