addPeriodicTimeObserver不是每毫秒调用一次吗? [英] addPeriodicTimeObserver is not called every millisecond?

问题描述

我知道player.currentItem.currentTime().seconds返回正在播放的音频文件的当前时间(以秒为单位).

I know that player.currentItem.currentTime().seconds returns the current time in seconds of the audio file that is being played.

我可以在player上添加一个回调函数，以每毫秒调用一次吗?
例如对于第二个1，此callBack函数应被调用1000次.

Can I add a callback function on player to be called every millisecond?
For example for second 1, this callBack function should be called 1000 times.

问题是使用addPeriodicTimeObserver的callBack函数每秒仅被调用1次，而不是每秒被调用1000次.

The problem is that using addPeriodicTimeObserver the callBack function is called only 1 time per second, rather than 1000 times per second.

我为什么需要这个?

1.
我正在播放音频文件时，通过在UI中点击一个按钮来手动提取Salsa歌曲的节拍计数，并将其记录为[Int:Int]// milisecondButtonTapped:beatCount.

1.
I am extracting the beat count of a Salsa song manually by tapping on a button in the UI while the audio file is being played and I record it as [Int:Int] // milisecondButtonTapped: beatCount.

我的数组看起来像
var beatCounts = [982: 1, 2051: 2, 3006: 3, 5027: 5, 6011: 6, 7028: 7]

My array is going to look like
var beatCounts = [982: 1, 2051: 2, 3006: 3, 5027: 5, 6011: 6, 7028: 7]

音频播放完毕后，我将得到一个包含BeatCounts的数组，该数组对应于player.currentItem.currentTime()的某些毫秒

After the audio finishes playing I will end up with an array containing the beatCounts corresponding to certain milliseconds of player.currentItem.currentTime()

2.

现在，我要再次播放歌曲，并检查播放器的currentTime(以毫秒为单位)是否等于var beatCounts

Now, I want to play the song again and check if player currentTime in milliseconds is == to one of the values in var beatCounts

func checkCurrentTime(playerTimeMilliseconds: Int) {

  for (millisecond, beatCount) in beatCounts {
    if  playerTimeMilliseconds == millisecond {
       //show beatCount in label on UI 
     }
 }
}





func playSound(url: URL) {

    let playerItem: AVPlayerItem = AVPlayerItem(url: url)
    player = AVPlayer(playerItem: playerItem)


    try! AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback)
    try! AVAudioSession.sharedInstance().setActive(true)
    player?.play()

    player?.addPeriodicTimeObserver(forInterval: CMTimeMakeWithSeconds(1, 1000), queue: DispatchQueue.main, using: { [weak self] (CMTime) in

        print("cmtime is \(CMTime)")
      CMTime.value

        if self?.player?.currentItem?.status == .readyToPlay {

        }
    })

}//end playSound

推荐答案

您只需要以不同的方式使用forInterval，而时间单位为0.001，则首选时间标度应与NSEC_PER_SEC配合使用，如下所述

You just have to use forInterval differently, whereas time unit will be 0.001 and preferred time scaled should be used with NSEC_PER_SEC as quoted below

让间隔:CMTime = CMTimeMakeWithSeconds(0.001，preferredTimescale:Int32(NSEC_PER_SEC))

player?.addPeriodicTimeObserver(forInterval: *interval*), queue:
.main) { [weak self] (CMTime) in

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