swift - 如何使用 AVPlayer 同时播放多个音频文件？

Question

我正在尝试使用 2 个 AVPlayer 实例播放多个音频文件，但其中一个播放器停止了几分之一秒，而不是同时播放所有音频文件。程序逻辑如下:

var player: AVPlayer? 将从我的数据库流式传输音频文件。自己玩的很完美。

fileprivate var countPlayer: AVPlayer? 播放 var player 正在播放的当前项目的计数。计数是 1 到 8 的序列，对于每个数字，我在本地存储/sandobxing 一个 .wav 文件，例如 1.wav、2.wav...8.wav。

当var player的当前时间在某个时间时，countPlayer被触发，播放本地文件1.wav，2.wav..等之一.

问题是当 var countPlayer 开始播放时，它会导致背景 AVPlayer，即 var player 停止几分之一秒，类似于所描述的在此评论中:

Play multiple Audio Files with AVPlayer

   var player: AVPlayer? //plays the song
   fileprivate var countPlayer: AVPlayer?  // plays the count number of song



   private func addBoundaryTimeObserver(tableIndexPath: IndexPath) {


    let mediaItem = mediaArray[tableIndexPath.row]

    guard let url = URL(string: mediaItem.mediaAudioUrlStringRepresentation ?? "") else {return}
    let playerItem = AVPlayerItem(url: url)
    player = AVPlayer(playerItem: playerItem)

    var timesToTransverse = [NSValue]()

    //convert string representation of times elements to array
    let timesRecorded: [String] = mediaItem.timesRecorded.components(separatedBy: ",")

    // Build boundary times from arrayOfBeats keys
    let timeDoubles: [Double] = timesRecorded.compactMap {timeString in
        if let second = Double("\(timeString)") {
            return second
        }
        return nil
    }

    guard timeDoubles.count > 0 else {return} //unexpected

     timesToTransverse = timeDoubles.map { second in
        let cmtime = CMTime(seconds: second, preferredTimescale: CMTimeScale(NSEC_PER_SEC))
        return NSValue(time: cmtime)
    }

    guard timesToTransverse.count != 0 else {return}

        guard let playerCell = tableView.cellForRow(at: IndexPath(row: 0, section: 0)) as? PlayerCell else {return}

       startTime = Date().timeIntervalSinceReferenceDate

    timeIndex = 0
    player?.play()
    player?.rate = Float(initialPlaybackRate)



    // find the index of time
    //reset timeObserverToken
    // call a function with the new times sorted


    // Queue on which to invoke the callback
    let mainQueue = DispatchQueue.main
    // Add time observer
    timeObserverToken =
        player?.addBoundaryTimeObserver(forTimes: timesToTransverse, queue: mainQueue) {
            [weak self] in


            //because there are no time signature changes, we can simply increment  timeIndex with + 1 every time `addBoundaryTimeObserver` completion handler is called and subscript timesToTransverse with timeIndex in order to get the subsequent timeInSeconds
            guard let strongSelf = self, strongSelf.timeIndex < timesToTransverse.count else {return}

            let timeElement = timesToTransverse[strongSelf.timeIndex]
            strongSelf.timeInSeconds = CMTimeGetSeconds(timeElement.timeValue)

                //show progress in progressView
                let duration = CMTimeGetSeconds(playerItem.duration)
                let cmtimeSeconds = CMTime(seconds: strongSelf.timeInSeconds, preferredTimescale: CMTimeScale(NSEC_PER_SEC))

            //Total time since timer started, in seconds
            strongSelf.timeInSeconds = Date().timeIntervalSinceReferenceDate - strongSelf.startTime

            let timeString = String(format: "%.2f", strongSelf.timeInSeconds)
            strongSelf.timeString = timeString


            //use reminder operator to determine the beat count
            let beat = (strongSelf.timeIndex + 1) % 8 == 0 ? 8 : ((strongSelf.timeIndex + 1) % 8)


            //play the beat count : 1, 2, ...8
          self.preapareToPlayAudio(beatCount: beat) 

            /*
             0: (0 + 1) % 8 = 1
             1: (1 + 1) % 8 = 2
             6: (6 + 1) % 8 = 7
             7: (7 + 1) % 8 = 0
             */

            strongSelf.timeIndex += 1
    }
}//end addBoundaryTimeObserver


 //prepare determine what wav file to play 
   private func preapareToPlayAudio(beatCount: Int) {

  switch beatCount {  
    case 1:
        guard let url = Bundle.main.url(forResource: "1", withExtension: "wav") else {return}
        playWith(beatCountURL: url)

        //7 more cases go here .....
    default: print("unexpected case here")
    }   
}//end play(beatCount: Int)



     private func playWith(beatCountURL: URL) {

        let playerItem = AVPlayerItem(url: beatCountURL)
        countPlayer = AVPlayer(playerItem: playerItem)
        countPlayer?.play()
      }

Answer 1

你最好使用 AVAudioPlayerNode、AVAudioMixerNode、AVAudioEngine。使用这些类(class)，您不会遇到像现在这样的问题。设置起来也不难。

您可以查看我的要点，为了在您的 Playgrounds 中播放声音，您需要将音频文件放入 Project Navigator 的 Resources 文件夹中: https://gist.github.com/standinga/24342d23acfe70dc08cbcc994895f32b

当顶部声音被触发时，代码在不停止背景音频的情况下工作。

这也是相同的代码:

import AVFoundation
import PlaygroundSupport

PlaygroundPage.current.needsIndefiniteExecution = true

class AudioPlayer {
var backgroundAudioFile:AVAudioFile
var topAudioFiles: [AVAudioFile] = []
var engine:AVAudioEngine
var backgroundAudioNode: AVAudioPlayerNode
var topAudioAudioNodes = [AVAudioPlayerNode]()
var mixer: AVAudioMixerNode
var timer: Timer!
var urls: [URL] = []

init (_ url: URL, urls: [URL] = []) {
    backgroundAudioFile = try! AVAudioFile(forReading: url)
    topAudioFiles = urls.map { try! AVAudioFile(forReading: $0) }

    engine = AVAudioEngine()
    mixer = AVAudioMixerNode()

    engine.attach(mixer)
    engine.connect(mixer, to: engine.outputNode, format: nil)
    self.urls = urls
    backgroundAudioNode = AVAudioPlayerNode()
    for _ in topAudioFiles {
        topAudioAudioNodes += [AVAudioPlayerNode()]
    }
}

func start() {
    engine.attach(backgroundAudioNode)
    engine.connect(backgroundAudioNode, to: mixer, format: nil)
    backgroundAudioNode.scheduleFile(backgroundAudioFile, at: nil, completionHandler: nil)

    try! engine.start()
    backgroundAudioNode.play()

    for node in topAudioAudioNodes {
        engine.attach(node)
        engine.connect(node, to: mixer, format: nil)
        try! engine.start()
    }
// simulate rescheduling files played on top of background audio
    DispatchQueue.global().async { [unowned self] in
        for i in 0..<1000 {
        sleep(2)
        let index = i % self.topAudioAudioNodes.count
        let node = self.topAudioAudioNodes[index]
        node.scheduleFile(self.topAudioFiles[index], at: nil, completionHandler: nil)
        node.play()
        }
    }
    }
}

let bundle = Bundle.main
let beepLow = bundle.url(forResource: "beeplow", withExtension: "wav")!
let beepMid = bundle.url(forResource: "beepmid", withExtension: "wav")!
let backgroundAudio = bundle.url(forResource: "backgroundAudio", withExtension: "wav")!
let audioPlayer = AudioPlayer(backgroundAudio, urls: [beepLow, beepMid])
audioPlayer.start()