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我想知道在 iOS 上在定义的持续时间内循环音频的最佳解决方案是什么。我目前正在玩

  • AVAudioPlayer（我可以定义重复计数但不能定义结束时间）
  • AVPlayer（我可以定义一个forwardPlaybackEndTime机器人而不是循环计数）
  • AVPlayerLooper（我还没有完全理解）

所以我需要定义重复某个声音文件的持续时间。Fe 我有一个 8 秒的 mp3，想播放 fe 一分钟。

如果我可以在重新开始时交叉淡入淡出，那也很棒。

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1 回答 1

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您使用AVPlayerLooper走在正确的轨道上。

这就是你设置的方式AVPlayerLooper

var playerLooper: AVPlayerLooper!
var player: AVQueuePlayer!

func play(_ url: URL) {
    let asset = AVAsset(url: url)
    let playerItem = AVPlayerItem(asset: asset)

    player = AVQueuePlayer(playerItem: playerItem)
    playerLooper = AVPlayerLooper(player: player, templateItem: playerItem)

    player.play()
}

要在设定的时间后停止循环，您可以使用addBoundaryTimeObserver(forTimes:queue:using:) 例如：

let assetDuration = CMTimeGetSeconds(asset.duration)
let maxDuration = 60.0 // Define max duration
let maxLoops = floor(maxDuration / assetDuration)
let lastLoopDuration = maxDuration - (assetDuration * maxLoops)
let boundaryTime = CMTimeMakeWithSeconds(lastLoopDuration, preferredTimescale: 1)
let boundaryTimeValue = NSValue(time: boundaryTime)

player.addBoundaryTimeObserver(forTimes: [boundaryTimeValue], queue: DispatchQueue.main) { [weak self] in
    if self?.playerLooper.loopCount == Int(maxLoops) {
        self?.player.pause()
    }
}

对于淡入/淡出，您必须在使用它之前将audioMix属性设置为您的AVPlayerItem实例。

let introRange = CMTimeRangeMake(start: CMTimeMakeWithSeconds(0, preferredTimescale: 1), duration: CMTimeMakeWithSeconds(1, preferredTimescale: 1))
let endingSecond = CMTimeRangeMake(start: CMTimeMakeWithSeconds(assetDuration - 1, preferredTimescale: 1), duration: CMTimeMakeWithSeconds(1, preferredTimescale: 1))

let inputParams = AVMutableAudioMixInputParameters(track: asset.tracks.first! as AVAssetTrack)
inputParams.setVolumeRamp(fromStartVolume: 0, toEndVolume: 1, timeRange: introRange)
inputParams.setVolumeRamp(fromStartVolume: 1, toEndVolume: 0, timeRange: endingSecond)

let audioMix = AVMutableAudioMix()
audioMix.inputParameters = [inputParams]
playerItem.audioMix = audioMix

功能齐全：

func play(_ url: URL) {
    let asset = AVAsset(url: url)
    let playerItem = AVPlayerItem(asset: asset)

    let assetDuration = CMTimeGetSeconds(asset.duration)

    let introRange = CMTimeRangeMake(start: CMTimeMakeWithSeconds(0, preferredTimescale: 1), duration: CMTimeMakeWithSeconds(1, preferredTimescale: 1))
    let endingSecond = CMTimeRangeMake(start: CMTimeMakeWithSeconds(assetDuration - 1, preferredTimescale: 1), duration: CMTimeMakeWithSeconds(1, preferredTimescale: 1))

    let inputParams = AVMutableAudioMixInputParameters(track: asset.tracks.first! as AVAssetTrack)
    inputParams.setVolumeRamp(fromStartVolume: 0, toEndVolume: 1, timeRange: introRange)
    inputParams.setVolumeRamp(fromStartVolume: 1, toEndVolume: 0, timeRange: endingSecond)

    let audioMix = AVMutableAudioMix()
    audioMix.inputParameters = [inputParams]
    playerItem.audioMix = audioMix

    player = AVQueuePlayer(playerItem: playerItem)
    playerLooper = AVPlayerLooper(player: player, templateItem: playerItem)
    player.play()

    let maxDuration = 60.0 // Define max duration
    let maxLoops = floor(maxDuration / assetDuration)
    let lastLoopDuration = maxDuration - (assetDuration * maxLoops)
    let boundaryTime = CMTimeMakeWithSeconds(lastLoopDuration, preferredTimescale: 1)
    let boundaryTimeValue = NSValue(time: boundaryTime)

    player.addBoundaryTimeObserver(forTimes: [boundaryTimeValue], queue: DispatchQueue.main) { [weak self] in
        if self?.playerLooper.loopCount == Int(maxLoops) {
            self?.player.pause()
        }
    }
}
于 2018-10-19T13:12:50.510 回答