Vfrdtyky

I'm trying to mix two audio files in swift AVFoundations. I have a solution that mixes two audio and plays them simultaneously. What I really want is to start the second audio after some time. For example audio 1 plays then second audio starts playing after 10(given time) seconds. Any help is appreciated. Thanks in advance.

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)

      }

    }

  }

You should use 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)

}

I don't personally have experience with AVAudioEngine or AVAudioMixerNode, however, you can do this with Timer.

You currently have audioPlayer.play(at: nil), however, this will always play immediately after establishing this player. What I would do, or try to do, is apply some kind of timer to this.

var timeAfter = 10

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

which would replace

audioPlayer.play(at: nil)

Then you would add the function of the timer to play the audio.

func playAudio(timer:NSTimer){

  var audioPlayer = timer.userInfo as AVAudioPlayerNode

  audioPlayer.play()

}

You may add another playerNode to the mixer and then play it after delay like this :

    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))

You can also hook a sampleDelay AU between node2 and mixer. That makes things easier without programming manually.