使用 Swift 通过 iPhone 扬声器强制播放音频文件

Question

我有一个可以录制然后播放音频文件的应用程序。目前正在通过听筒扬声器播放音频。有人能告诉我 Swift 将如何处理编码以强制将音频从扬声器中输出吗？

下面是我用来播放音频文件的一个实例：

@IBAction func playAudioVader(sender: UIButton) {
    playAudioWithVariablePitch(-1000)
    }

    func playAudioWithVariablePitch(pitch: Float){
    audioPlayer.stop()
    audioEngine.stop()
    audioEngine.reset()

        var audioPlayerNode = AVAudioPlayerNode()
        audioEngine.attachNode(audioPlayerNode)

        var changePitchEffect = AVAudioUnitTimePitch()
        changePitchEffect.pitch = pitch
        audioEngine.attachNode(changePitchEffect)

        audioEngine.connect(audioPlayerNode, to: changePitchEffect, format: nil)
        audioEngine.connect(changePitchEffect, to: audioEngine.outputNode, format: nil)

        audioPlayerNode.scheduleFile(audioFile, atTime: nil, completionHandler: nil)
        audioEngine.startAndReturnError(nil)

        audioPlayerNode.play()

}

   override func viewDidLoad() {

    super.viewDidLoad()

    audioPlayer = AVAudioPlayer(contentsOfURL:receivedAudio.filePathURL, error: nil)
    audioPlayer.enableRate = true
    audioEngine = AVAudioEngine()
    audioFile = AVAudioFile(forReading:receivedAudio.filePathURL, error: nil)


}

Answer 1

2017 年 7 月编辑：请参阅 Husam 对 Swift 2.0 解决方案的回答。

从 Swift 1.2 开始，您使用 overrideOutputAudioPort 和 AVAudioSessionPortOverride。它可以通过执行以下操作来实现：

if !session.overrideOutputAudioPort(AVAudioSessionPortOverride.Speaker, error:&error) {
   println("could not set output to speaker")
   if let e = error {
      println(e.localizedDescription)
   }
}

我正在开发一个使用它的应用程序，并且我有一个名为 setSessionPlayandRecord 的函数，它看起来像：

func setSessionPlayAndRecord() {
    let session:AVAudioSession = AVAudioSession.sharedInstance()
    var error: NSError?
    if !session.setCategory(AVAudioSessionCategoryPlayAndRecord, error:&error) {
        println("could not set session category")
        if let e = error {
            println(e.localizedDescription)
        }
    }
    if !session.overrideOutputAudioPort(AVAudioSessionPortOverride.Speaker, error:&error) {
        println("could not set output to speaker")
        if let e = error {
            println(e.localizedDescription)
        }
    }
    if !session.setActive(true, error: &error) {
        println("could not make session active")
        if let e = error {
            println(e.localizedDescription)
        }
    }
}

Answer 2

Swift 2.0代码

func setSessionPlayerOn()
{
    do {
        try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayAndRecord)
    } catch _ {
    }
    do {
        try AVAudioSession.sharedInstance().setActive(true)
    } catch _ {
    }
    do {
        try AVAudioSession.sharedInstance().overrideOutputAudioPort(AVAudioSessionPortOverride.Speaker)
    } catch _ {
    }
}
func setSessionPlayerOff()
{
    do {
        try AVAudioSession.sharedInstance().setActive(false)
    } catch _ {
    }
}