使用Swift的AVAudioEngine实时变桨

我正在使用Swift在OSX上开发一个音频效果应用程序，我对集成音高变换效果感兴趣

我想在实时，改变音调向上或向下的八度。目前我只收到一个干燥信号

我不确定这是否可能，我想知道这是否可能，或者任何人可能有任何帮助或建议

与问题相关的当前代码如下：

import Cocoa
import AVFoundation


class ViewController: NSViewController {
       var engine = AVAudioEngine()
       var timePitch = AVAudioUnitTimePitch()


    override func viewDidLoad() {
         timePitch.pitch = 1200

        // Setup engine and node instances
        var mixer = engine.mainMixerNode
        var input = engine.inputNode
        var output = engine.outputNode
        var format = input.inputFormatForBus(0)
        var error:NSError?

       engine.attachNode(timePitch)

       engine.connect(input, to: timePitch, format: format)
       engine.connect(timePitch, to: output, format: format)

      engine.startAndReturnError(&error)

        super.viewDidLoad()
    }

   override var representedObject: AnyObject? {
        didSet {
        // Update the view, if already loaded.
        }
    }


}

检查。更多信息，请参阅教程中的示例

Swift 2.0的示例：

import UIKit
import AVFoundation

class ViewController: UIViewController {

    var engine: AVAudioEngine!
    var player: AVAudioPlayerNode!

    var file = AVAudioFile()

    override func viewDidLoad() {
        super.viewDidLoad()

        engine = AVAudioEngine()
        player = AVAudioPlayerNode()
        player.volume = 1.0

        let path = NSBundle.mainBundle().pathForResource("in", ofType: "caf")!
        let url = NSURL.fileURLWithPath(path)

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

        let pitch = AVAudioUnitTimePitch()

        //
        pitch.pitch = -500 //Distortion
        pitch.rate = 1.5 //Voice speed
        //

        engine.attachNode(player)

        engine.attachNode(pitch)

        engine.connect(player, to: pitch, format: buffer.format)

        engine.connect(pitch, to: engine.mainMixerNode, format: buffer.format)
        player.scheduleBuffer(buffer, atTime: nil, options: AVAudioPlayerNodeBufferOptions.Loops, completionHandler: nil)

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

        player.play()

    }
}

---

虽然这段代码可以回答这个问题，但提供关于它如何和/或为什么解决这个问题的附加上下文将提高答案的长期价值。谢谢您的建议@Donald duck。下次我会记住这一点，非常感谢分享。当我改变音高时，质量会改变。当费率发生变化时，有没有办法保持相同的质量

import UIKit
import AVFoundation

class ViewController: UIViewController {

    var engine: AVAudioEngine!
    var player: AVAudioPlayerNode!

    var file = AVAudioFile()

    override func viewDidLoad() {
        super.viewDidLoad()

        engine = AVAudioEngine()
        player = AVAudioPlayerNode()
        player.volume = 1.0

        let path = NSBundle.mainBundle().pathForResource("in", ofType: "caf")!
        let url = NSURL.fileURLWithPath(path)

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

        let pitch = AVAudioUnitTimePitch()

        //
        pitch.pitch = -500 //Distortion
        pitch.rate = 1.5 //Voice speed
        //

        engine.attachNode(player)

        engine.attachNode(pitch)

        engine.connect(player, to: pitch, format: buffer.format)

        engine.connect(pitch, to: engine.mainMixerNode, format: buffer.format)
        player.scheduleBuffer(buffer, atTime: nil, options: AVAudioPlayerNodeBufferOptions.Loops, completionHandler: nil)

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

        player.play()

    }
}

timePitch.pitch = 1000 //Filtered Voice
timePitch.rate = 1 //Normal rate