ios - AVPlayer 停止播放并且不再恢复

Question

在我的应用程序中，我必须播放存储在 Web 服务器上的音频文件。我正在使用AVPlayer它。我有所有播放/暂停控件以及所有代表和观察者，它们工作得非常好。在播放小音频文件时，一切都很好。

播放长音频文件时，它也开始正常播放，但几秒钟后AVPlayer暂停播放（很可能是为了缓冲它）。问题是它不会再次自行恢复。它保持暂停状态，如果我再次手动按下播放按钮，它会再次流畅播放。

我想知道为什么AVPlayer不自动恢复以及如何在不用户再次按下播放按钮的情况下再次恢复音频？谢谢。

Answer 1

是的，它停止是因为缓冲区是空的，所以它必须等待加载更多视频。之后，您必须手动要求重新开始。为了解决这个问题，我按照以下步骤操作：

1) 检测：为了检测播放器何时停止，我使用 KVO 和值的 rate 属性：

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if ([keyPath isEqualToString:@"rate"] )
    {

        if (self.player.rate == 0 && CMTimeGetSeconds(self.playerItem.duration) != CMTimeGetSeconds(self.playerItem.currentTime) && self.videoPlaying)
        {
            [self continuePlaying];
        }
      }
    }

这个条件：CMTimeGetSeconds(self.playerItem.duration) != CMTimeGetSeconds(self.playerItem.currentTime)就是检测到达视频结尾和中间停的区别

2) 等待视频加载 - 如果您继续直接播放，您将没有足够的缓冲区继续播放而不会中断。要知道何时开始，您必须观察playbackLikelytoKeepUpplayerItem 的值（这里我使用库来观察块，但我认为这很重要）：

-(void)continuePlaying
 {

if (!self.playerItem.playbackLikelyToKeepUp)
{
    self.loadingView.hidden = NO;
    __weak typeof(self) wSelf = self;
    self.playbackLikelyToKeepUpKVOToken = [self.playerItem addObserverForKeyPath:@keypath(_playerItem.playbackLikelyToKeepUp) block:^(id obj, NSDictionary *change) {
        __strong typeof(self) sSelf = wSelf;
        if(sSelf)
        {
            if (sSelf.playerItem.playbackLikelyToKeepUp)
            {
                [sSelf.playerItem removeObserverForKeyPath:@keypath(_playerItem.playbackLikelyToKeepUp) token:self.playbackLikelyToKeepUpKVOToken];
                sSelf.playbackLikelyToKeepUpKVOToken = nil;
                [sSelf continuePlaying];
            }
                    }
    }];
}

就是这样！问题解决了

编辑：顺便说一下，使用的库是 libextobjc

Answer 2

我正在处理视频文件，所以我的代码比你需要的要多，但是下面的解决方案应该在播放器挂起时暂停播放器，然后每 0.5 秒检查一次，看看我们是否有足够的缓冲来跟上。如果是这样，它会重新启动播放器。如果播放器挂起超过 10 秒没有重新启动，我们会停止播放器并向用户道歉。这意味着您需要合适的观察者。下面的代码对我来说工作得很好。

在 .h 文件或其他地方定义/初始化的属性：

AVPlayer *player;  
int playerTryCount = -1; // this should get set to 0 when the AVPlayer starts playing
NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];

部分.m：

- (AVPlayer *)initializePlayerFromURL:(NSURL *)movieURL {
  // create AVPlayer
  AVPlayerItem *videoItem = [AVPlayerItem playerItemWithURL:movieURL];
  AVPlayer *videoPlayer = [AVPlayer playerWithPlayerItem:videoItem];

  // add Observers
  [videoItem addObserver:self forKeyPath:@"playbackLikelyToKeepUp" options:NSKeyValueObservingOptionInitial | NSKeyValueObservingOptionNew context:nil];
  [self startNotificationObservers]; // see method below
  // I observe a bunch of other stuff, but this is all you need for this to work

  return videoPlayer;
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
  // check that all conditions for a stuck player have been met
  if ([keyPath isEqualToString:@"playbackLikelyToKeepUp"]) {
      if (self.player.currentItem.playbackLikelyToKeepUp == NO &&
          CMTIME_COMPARE_INLINE(self.player.currentTime, >, kCMTimeZero) && 
          CMTIME_COMPARE_INLINE(self.player.currentTime, !=, self.player.currentItem.duration)) {

              // if so, post the playerHanging notification
              [self.notificationCenter postNotificationName:PlayerHangingNotification object:self.videoPlayer];
      }
  }
}

- (void)startNotificationObservers {
    [self.notificationCenter addObserver:self 
                                selector:@selector(playerContinue)
                                   name:PlayerContinueNotification
                                 object:nil];    

    [self.notificationCenter addObserver:self 
                                selector:@selector(playerHanging)
                                   name:PlayerHangingNotification
                                 object:nil];    
}

// playerHanging simply decides whether to wait 0.5 seconds or not
// if so, it pauses the player and sends a playerContinue notification
// if not, it puts us out of our misery
- (void)playerHanging {
    if (playerTryCount <= 10) {

      playerTryCount += 1;
      [self.player pause];
      // start an activity indicator / busy view
      [self.notificationCenter postNotificationName:PlayerContinueNotification object:self.player];

    } else { // this code shouldn't actually execute, but I include it as dummyproofing

      [self stopPlaying]; // a method where I clean up the AVPlayer,
                          // which is already paused

      // Here's where I'd put up an alertController or alertView
      // to say we're sorry but we just can't go on like this anymore
    }
}

// playerContinue does the actual waiting and restarting
- (void)playerContinue {
    if (CMTIME_COMPARE_INLINE(self.player.currentTime, ==, self.player.currentItem.duration)) { // we've reached the end

      [self stopPlaying];

    } else if (playerTryCount  > 10) // stop trying

      [self stopPlaying];
      // put up "sorry" alert

    } else if (playerTryCount == 0) {

      return; // protects against a race condition

    } else if (self.player.currentItem.playbackLikelyToKeepUp == YES) {

      // Here I stop/remove the activity indicator I put up in playerHanging
      playerTryCount = 0;
      [self.player play]; // continue from where we left off

    } else { // still hanging, not at end

        // create a 0.5-second delay to see if buffering catches up
        // then post another playerContinue notification to call this method again
        // in a manner that attempts to avoid any recursion or threading nightmares 
        playerTryCount += 1;
        double delayInSeconds = 0.5;
        dispatch_time_t executeTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
        dispatch_after(executeTime, dispatch_get_main_queue(), ^{

          // test playerTryCount again to protect against changes that might have happened during the 0.5 second delay
          if (playerTryCount > 0) {
              if (playerTryCount <= 10) {
                [self.notificationCenter postNotificationName:PlayerContinueNotification object:self.videoPlayer];
              } else {
                [self stopPlaying];
                // put up "sorry" alert
              }
          }
        });
}

希望能帮助到你！

Answer 3

接受的答案为问题提供了可能的解决方案，但缺乏灵活性，也难以阅读。这是更灵活的解决方案。

添加观察者：

//_player is instance of AVPlayer
[_player.currentItem addObserver:self forKeyPath:@"status" options:0 context:nil];
[_player addObserver:self forKeyPath:@"rate" options:0 context:nil];

处理程序：

-(void)observeValueForKeyPath:(NSString*)keyPath
                     ofObject:(id)object
                       change:(NSDictionary*)change
                      context:(void*)context {

    if ([keyPath isEqualToString:@"status"]) {
        if (_player.status == AVPlayerStatusFailed) {
            //Possibly show error message or attempt replay from tart
            //Description from the docs:
            //  Indicates that the player can no longer play AVPlayerItem instances because of an error. The error is described by
            //  the value of the player's error property.
        }
    }else if ([keyPath isEqualToString:@"rate"]) {
        if (_player.rate == 0 && //if player rate dropped to 0
                CMTIME_COMPARE_INLINE(_player.currentItem.currentTime, >, kCMTimeZero) && //if video was started
                CMTIME_COMPARE_INLINE(_player.currentItem.currentTime, <, _player.currentItem.duration) && //but not yet finished
                _isPlaying) { //instance variable to handle overall state (changed to YES when user triggers playback)
            [self handleStalled];
        }
    }
}

魔法：

-(void)handleStalled {
    NSLog(@"Handle stalled. Available: %lf", [self availableDuration]);

    if (_player.currentItem.playbackLikelyToKeepUp || //
            [self availableDuration] - CMTimeGetSeconds(_player.currentItem.currentTime) > 10.0) {
        [_player play];
    } else {
        [self performSelector:@selector(handleStalled) withObject:nil afterDelay:0.5]; //try again
    }
}

“[self availableDuration]”是可选的，但您可以根据可用视频的数量手动启动播放。您可以更改代码检查是否缓冲了足够的视频的频率。如果您决定使用可选部分，这里是方法实现：

- (NSTimeInterval) availableDuration
{
    NSArray *loadedTimeRanges = [[_player currentItem] loadedTimeRanges];
    CMTimeRange timeRange = [[loadedTimeRanges objectAtIndex:0] CMTimeRangeValue];
    Float64 startSeconds = CMTimeGetSeconds(timeRange.start);
    Float64 durationSeconds = CMTimeGetSeconds(timeRange.duration);
    NSTimeInterval result = startSeconds + durationSeconds;
    return result;
}

不要忘记清理。移除观察者：

[_player.currentItem removeObserver:self forKeyPath:@"status"];
[_player removeObserver:self forKeyPath:@"rate"];

以及处理停滞视频的可能待处理呼叫：

[UIView cancelPreviousPerformRequestsWithTarget:self selector:@selector(handleStalled) object:nil];

Answer 4

我有一个类似的问题。我有一些我想播放的本地文件，配置了 AVPlayer 并调用了 [player play]，播放器在第 0 帧处停止并且不会再播放，直到我再次手动调用 play。由于解释错误，我无法实施接受的答案，然后我只是尝试延迟播放并神奇地工作

[self performSelector:@selector(startVideo) withObject:nil afterDelay:0.2];

-(void)startVideo{
    [self.videoPlayer play];
}

对于网络视频，我也遇到了问题，我使用华莱士的答案解决了这个问题。

创建 AVPlayer 时添加一个观察者：

[self.videoItem addObserver:self forKeyPath:@"playbackLikelyToKeepUp" options:NSKeyValueObservingOptionInitial | NSKeyValueObservingOptionNew context:nil];

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
// check that all conditions for a stuck player have been met
if ([keyPath isEqualToString:@"playbackLikelyToKeepUp"]) {
    if (self.videoPlayer.currentItem.playbackLikelyToKeepUp == NO &&
        CMTIME_COMPARE_INLINE(self.videoPlayer.currentTime, >, kCMTimeZero) &&
        CMTIME_COMPARE_INLINE(self.videoPlayer.currentTime, !=, self.videoPlayer.currentItem.duration)) {
        NSLog(@"hanged");
        [self performSelector:@selector(startVideo) withObject:nil afterDelay:0.2];
    }
}

}

记得在关闭视图之前移除观察者

[self.videoItem removeObserver:self forKeyPath:@"playbackLikelyToKeepUp"]

Answer 5

我认为使用AVPlayerItemPlaybackStalledNotification 检测停滞是一种更好的方法。

Answer 6

我也遇到了这里描述的这个问题

我在下面多次测试了这个答案，到目前为止它每次都有效。

这是我为@wallace 的答案的 Swift 5 版本提出的。

1-我没有观察keyPath，而是在里面"playbackLikelyToKeepUp"使用.AVPlayerItemPlaybackStalled Notificationand检查缓冲区是否已满if !playerItem.isPlaybackLikelyToKeepUp {...}

2-而不是使用他的PlayerHangingNotification我使用一个名为的函数playerIsHanging()

3-而不是使用他的PlayerContinueNotification我使用一个名为的函数checkPlayerTryCount()

4-在里面checkPlayerTryCount()我做的一切都和他的(void)playerContinue功能一样，除非我遇到} else if playerTryCount == 0 {什么都不会发生。return为避免这种情况，我在语句上方添加了 2 行代码

5-就像@PranoyC 在@wallace 的评论下建议的那样，我将 设置playerTryCount为最大值20而不是10. 我也将它设置为类属性let playerTryCountMaxLimit = 20

您必须在评论建议的地方添加/删除您的活动指示器/微调器

代码：

NotificationCenter.default.addObserver(self, selector: #selector(self.playerItemPlaybackStalled(_:)),
                                       name: NSNotification.Name.AVPlayerItemPlaybackStalled,
                                       object: playerItem)

@objc func playerItemPlaybackStalled(_ notification: Notification) {
// The system may post this notification on a thread other than the one used to registered the observer: https://developer.apple.com/documentation/foundation/nsnotification/name/1387661-avplayeritemplaybackstalled

    guard let playerItem = notification.object as? AVPlayerItem else { return }
    
    // playerItem.isPlaybackLikelyToKeepUp == false && if the player's current time is greater than zero && the player's current time is not equal to the player's duration
    if (!playerItem.isPlaybackLikelyToKeepUp) && (CMTimeCompare(playerItem.currentTime(), .zero) == 1) && (CMTimeCompare(playerItem.currentTime(), playerItem.duration) != 0) {
        
        DispatchQueue.main.async { [weak self] in
            self?.playerIsHanging()
        }
    }
}

var playerTryCount = -1 // this should get set to 0 when the AVPlayer starts playing
let playerTryCountMaxLimit = 20

func playerIsHanging() {
    
    if playerTryCount <= playerTryCountMaxLimit {
        
        playerTryCount += 1

        // show spinner

        checkPlayerTryCount()

    } else {
        // show spinner, show alert, or possibly use player?.replaceCurrentItem(with: playerItem) to start over ***BE SURE TO RESET playerTryCount = 0 ***
        print("1.-----> PROBLEM")
    }
}

func checkPlayerTryCount() {
    
    guard let player = player, let playerItem = player.currentItem else { return }
    
    // if the player's current time is equal to the player's duration
    if CMTimeCompare(playerItem.currentTime(), playerItem.duration) == 0 {
        
        // show spinner or better yet remove spinner and show a replayButton or auto rewind to the beginning ***BE SURE TO RESET playerTryCount = 0 ***
        
    } else if playerTryCount > playerTryCountMaxLimit {
        
        // show spinner, show alert, or possibly use player?.replaceCurrentItem(with: playerItem) to start over ***BE SURE TO RESET playerTryCount = 0 ***
        print("2.-----> PROBLEM")

    } else if playerTryCount == 0 {

        // *** in his answer he has nothing but a return statement here but when it would hit this condition nothing would happen. I had to add these 2 lines of code for it to continue ***
        playerTryCount += 1
        retryCheckPlayerTryCountAgain()
        return // protects against a race condition
        
    } else if playerItem.isPlaybackLikelyToKeepUp {
        
        // remove spinner and reset playerTryCount to zero
        playerTryCount = 0
        player?.play()

    } else { // still hanging, not at end
        
        playerTryCount += 1
        
        /*
          create a 0.5-second delay using .asyncAfter to see if buffering catches up
          then call retryCheckPlayerTryCountAgain() in a manner that attempts to avoid any recursion or threading nightmares
        */

        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
            DispatchQueue.main.async { [weak self] in

                // test playerTryCount again to protect against changes that might have happened during the 0.5 second delay
                if self!.playerTryCount > 0 {
                    
                    if self!.playerTryCount <= self!.playerTryCountMaxLimit {
                        
                      self!.retryCheckPlayerTryCountAgain()
                        
                    } else {
                        
                      // show spinner, show alert, or possibly use player?.replaceCurrentItem(with: playerItem) to start over ***BE SURE TO RESET playerTryCount = 0 ***
                      print("3.-----> PROBLEM")
                    }
                }
            }
        }
    }
}

func retryCheckPlayerTryCountAgain() {
    checkPlayerTryCount()
}

Answer 7

首先我观察播放停顿

NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(playerStalled),
    name: AVPlayerItemPlaybackStalledNotification, object: videoPlayer.currentItem)

然后我强制播放继续

func playerStalled(note: NSNotification) {
  let playerItem = note.object as! AVPlayerItem
  if let player = playerItem.valueForKey("player") as? AVPlayer{
    player.play()
  }
}

这可能不是最好的方法，但我一直在使用它，直到找到更好的东西:)

Answer 8

在非常糟糕的网络中很playbackLikelyToKeepUp可能是错误的。

使用kvo观察playbackBufferEmpty更好，对是否存在可用于播放的缓冲区数据更敏感。如果值更改为true，则可以调用play方法继续播放。

Answer 9

就我而言，

• 我试图用 imagePickerController 录制视频并用 AVPlayerController 播放录制的视频。但它开始播放视频并在 1 秒后停止。不知何故，它有时间保存视频，如果你立即播放它，它就不会播放。
  所以解决方案是，

• 0.5 秒后调用播放视频（延迟）。像下面

      -(void)imagePickerController:(UIImagePickerController *)picker 
               didFinishPickingMediaWithInfo:(NSDictionary *)info {
              [self performSelector:@selector(playVideo) withObject:self 
              afterDelay:0.5];
        }
  
  
  -(void) playVideo {
  
     self.avPlayerViewController = [[AVPlayerViewController alloc] init];
        if(self.avPlayerViewController != nil)
      {
       AVPlayerItem* playerItem = [AVPlayerItem playerItemWithURL:Vpath];
       AVPlayer* player = [[AVPlayer alloc] initWithPlayerItem:playerItem];
       self.avPlayerViewController.player = player;
       self.avPlayerViewController.showsPlaybackControls = NO;
       [self.avPlayerViewController setVideoGravity:AVLayerVideoGravityResizeAspectFill];
       [self.avPlayerViewController.view setFrame:[[UIScreen mainScreen] bounds]];
       self.avPlayerViewController.view.clipsToBounds = YES;
       self.avPlayerViewController.delegate = self;
       [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(playerDidFinishPlaying) name:AVPlayerItemDidPlayToEndTimeNotification object:playerItem];
       [self.viewVideoHolder addSubview:self.avPlayerViewController.view];
       [self.avPlayerViewController.player play];
  
   }
  

  }

   -(void) playerDidFinishPlaying
    {
      [avPlayer pause];
    }
  

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