播放期间如何更改音高? (快速4)

问题描述

我希望使用Xcode，Swift 4中的滑块或变量(即在播放声音时)实时更改某些音频的音调和播放速度.

I'm looking to change the pitch and playback speed of some audio in real time with a slider, or a variable (i.e. while the sound is playing) in Xcode, Swift 4.

当前，我正在使用AVAudioEngine，它允许我在播放开始之前设置这些值，但是在实际播放音频时无法更改它们.

Currently, I'm using AVAudioEngine, which allows me to set these values before playback starts, but I can't change them while I the audio is actually playing.

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()

}

使用AVAudioEngine甚至有可能吗?

Is this even possible with AVAudioEngine?

如果AVAudioEngine无法做到这一点，还有哪些其他可能的解决方案?

If this is not possible with AVAudioEngine, what are other possible solutions?

推荐答案

实际上，我从reddit那里得到了答案.我要做的就是在Play()函数之外声明pitch和speed变量，以及pitch.pitch = speedIncrement * (-500)和speed.rate = speedIncrement表达式.我知道我缺少一些简单的东西...

Actually, I got the answer from reddit. All I had to do was to declare the pitch and speed variables outside of the Play() function, along with the pitch.pitch = speedIncrement * (-500) and speed.rate = speedIncrement expressions. I knew I was missing something simple...

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