CODEWITHSUNDEEP
iosswiftrateavaudioengine
Nona Shah
Nona Shah

Reputation: 79

How to use the rate in AVAudioEngine

How do we use rate in AVAudioEngine?

Here's my complete code:

import UIKit
import AVFoundation

class ViewController: UIViewController {

var audioEngine = AVAudioEngine()
var myPlayer = AVAudioPlayerNode()

override func viewDidLoad() {
    super.viewDidLoad()
    if var filePath = NSBundle.mainBundle().pathForResource("music", ofType: "wav"){

        var filePathURL = NSURL.fileURLWithPath(filePath)
        audioEngine.attachNode(myPlayer)
        var audioFile = AVAudioFile(forReading: filePathURL, error: nil)
        var audioError:NSError?

        audioEngine.connect(myPlayer, to: audioEngine.mainMixerNode, format: audioFile.processingFormat)

        myPlayer.scheduleFile(audioFile, atTime: nil, completionHandler: nil)
        audioEngine.startAndReturnError(&audioError)

    }else {
        println("url not found")

    }

}


@IBAction func playSound(sender: UIButton) {

    myPlayer.rate = 0.5
    myPlayer.play()

}

So while I play the sound its not using the rate at at all. Furthermore, how do I reset the position once I am done playing the audio. AVAudioPlayer had currentTime to use to reset the bar.

Edit1: This is rather confusing cause if AVAudioPlayerNode doesn't have a class to maintain why does it allow me to use rate at all? Sorry completely noob to programming.

Edit2: Got it working with help from Matt's example code. I missed the audio output line:

        var audioEngine = AVAudioEngine()
        var myPlayer = AVAudioPlayerNode()
        audioEngine.attachNode(myPlayer)
        var changeAudioUnitTime = AVAudioUnitTimePitch()

        changeAudioUnitTime.rate = audioChangeNumber
        audioEngine.attachNode(changeAudioUnitTime)
        audioEngine.connect(myPlayer, to: changeAudioUnitTime, format: nil)
        audioEngine.connect(changeAudioUnitTime, to: audioEngine.outputNode, format: nil)
        audioPlayerNode.scheduleFile(audioFile, atTime: nil, completionHandler: nil)
        audioEngine.startAndReturnError(nil)
        audioPlayerNode.play()

Thanks everyone for the help.

Upvotes: 1

Views: 2185

Answers (1)

matt
matt

Reputation: 534924

To change the rate with AVAudioEngine, you have two choices:

  • Do 3D mixing with an AVAudioEnvironmentNode. Only the AVAudioEnvironmentNode has a meaningful AVAudio3DMixing protocol rate property.

  • Pass the file output through an AVAudioUnitTimePitch node and adjust its rate.

Upvotes: 2

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