使用不同的起点条目快速混合两个音频文件答案

【问题标题】：Mix two audio files in swift with different start point entry使用不同的起点条目快速混合两个音频文件
【发布时间】：2018-11-16 15:48:52
【问题描述】：

我正在尝试在 swift AVFoundations 中混合两个音频文件。我有一个混合两个音频并同时播放它们的解决方案。我真正想要的是在一段时间后开始第二个音频。例如，音频 1 播放，然后第二个音频在 10（给定时间）秒后开始播放。任何帮助表示赞赏。提前致谢。

private var audioFiles: Array<String>
private var audioEngine: AVAudioEngine = AVAudioEngine()
private var mixer: AVAudioMixerNode = AVAudioMixerNode()

func Play() {
    // do work in a background thread
    DispatchQueue.global(qos: .background).async {
      self.audioEngine.attach(self.mixer)
      self.audioEngine.connect(self.mixer, to: self.audioEngine.outputNode, format: nil)
      // !important - start the engine *before* setting up the player nodes
      try! self.audioEngine.start()

      let fileManager = FileManager.default
      for audioFile in self.audioFiles {
        // Create and attach the audioPlayer node for this file
        let audioPlayer = AVAudioPlayerNode()
        self.audioEngine.attach(audioPlayer)
        // Notice the output is the mixer in this case
        self.audioEngine.connect(audioPlayer, to: self.mixer, format: nil)
        let fileUrl = NSURL.init(fileURLWithPath: fileName.removingPercentEncoding!)
        var file : AVAudioFile

        // We should probably check if the file exists here ¯\_(ツ)_/¯
        try! AVAudioFile.init(forReading: fileUrl.absoluteURL!)

        audioPlayer.scheduleFile(file, at: nil, completionHandler: nil)
        audioPlayer.play(at: nil)
      }
    }
  }

【问题讨论】：

标签： ios swift cocoa cocoa-touch avfoundation

【解决方案1】：

你应该使用scheduleSegment。

func scheduleWithOffset(_ offset: TimeInterval) {

    let samplerate1 = file1.processingFormat.sampleRate
    player1.scheduleSegment(file1,
                            startingFrame: 0,
                            frameCount: AVAudioFrameCount(file1.length),
                            at: AVAudioTime(sampleTime: 0, atRate: samplerate1))

    let samplerate2 = file2.processingFormat.sampleRate
    player2.scheduleSegment(file2,
                            startingFrame: 0,
                            frameCount: AVAudioFrameCount(file2.length),
                            at: AVAudioTime(sampleTime: AVAudioFramePosition(offset * samplerate2), atRate: samplerate2))

    //This can take an indeterminate amount of time, so both files should be prepared before either starts.
    player1.prepare(withFrameCount: 8192)
    player2.prepare(withFrameCount: 8192)

    // Start the files at common time slightly in the future to ensure a synchronous start.
    let hostTimeNow = mach_absolute_time()
    let hostTimeFuture = hostTimeNow + AVAudioTime.hostTime(forSeconds: 0.2);
    let startTime = AVAudioTime(hostTime: hostTimeFuture)

    player1.play(at: startTime)
    player2.play(at: startTime)
}

【讨论】：

【解决方案2】：

我个人没有使用AVAudioEngine 或AVAudioMixerNode 的经验，但是，您可以使用Timer 来做到这一点。

您当前拥有audioPlayer.play(at: nil)，但是，它始终会在建立此播放器后立即播放。我会做或尝试做的是为此应用某种计时器。

var timeAfter = 10
var timer = NSTimer.scheduledTimerWithInterval(timeAfter, target: self, selector: #selector(playAudio), userInfo: audioPlayer, repeats: false)

将取代

audioPlayer.play(at: nil)

然后你会添加定时器的功能来播放音频。

func playAudio(timer:NSTimer){
  var audioPlayer = timer.userInfo as AVAudioPlayerNode
  audioPlayer.play()
}

【讨论】：

【解决方案3】：

你可以添加另一个 playerNode 到混音器，然后像这样延迟播放：

    let audioPlayer2 = AVAudioPlayerNode()
    self.audioEngine.attach(audioPlayer2)
    self.audioEngine.connect(audioPlayer2, to: self.mixer, format: nil)
    var file2 : AVAudioFile = try! AVAudioFile.init(forReading: fileUrl2!)
    func delayTime(_ delayTime : TimeInterval) -> AVAudioTime{
        let  outputFormat = audioPlayer2.outputFormat(forBus: 0)
        let  startSampleTime = (audioPlayer2.lastRenderTime ?? AVAudioTime()).sampleTime +  Int64(Double(delayTime) * outputFormat.sampleRate);
        return  AVAudioTime(sampleTime: startSampleTime, atRate: outputFormat.sampleRate)
    }
    audioPlayer2.scheduleFile(file2, at: nil, completionHandler: nil)
    audioPlayer2.play(at: delayTime(3.0))

您还可以在 node2 和混音器之间挂钩 sampleDelay AU。这让事情变得更容易，无需手动编程。

【讨论】：