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。我有所有播放/暂停控件和所有代表和观察员在那里工作得非常好。在播放小音频文件时，一切都很棒。
当播放长音频文件时，它也会开始播放正常但几秒后AVPlayer暂停播放（最有可能是缓冲它）。问题是它不能再自行恢复。它保持暂停状态，如果我再次手动按下播放按钮，它将再次流畅播放。
我想知道为什么AVPlayer无法自动恢复，如何在没有用户再次按下播放按钮的情况下再次恢复音频？感谢。
答案 0 :(得分：16)
是的，它会因为缓冲区为空而停止，因此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：要检测播放器何时停止，我使用具有该值的rate属性的KVO：
-(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)是检测到达视频结尾或停在中间的区别
2）等待视频加载 - 如果继续直接播放，则没有足够的缓冲区来继续播放而不会中断。要知道何时开始，你必须从playerItem中观察值playbackLikelytoKeepUp（这里我使用库来观察块，但我认为这是重点）：
-(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，库使用的是libextobjc
答案 1 :(得分：7)
我正在处理视频文件，因此我的代码比您需要的更多，但以下解决方案应该在播放器挂起时暂停，然后每0.5秒检查一次，看看我们是否已经缓冲足以跟上。如果是这样，它会重新启动播放器。如果播放器在没有重新启动的情况下挂起超过10秒，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员。下面的代码对我来说非常好。
在.h文件或其他地方定义的属性/ init＆＃d;
AVPlayer *player;
int playerTryCount = -1; // this should get set to 0 when the AVPlayer starts playing
NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];
partial .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
}
}
});
}
希望它有所帮助！
答案 2 :(得分：6)
我有类似的问题。 我有一些我想播放的本地文件，配置AVPlayer并调用[播放器播放]，播放器在第0帧停止并且不再播放，直到我再次手动调用播放。 由于错误的解释，我不可能实现接受的答案，然后我只是试图推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];
}
}
}
请记住在取消视图之前删除观察者
[self.videoItem removeObserver:self forKeyPath:@"playbackLikelyToKeepUp"]
答案 3 :(得分：5)
我认为使用AVPlayerItemPlaybackStalledNotification检测停滞是更好的方法。
答案 4 :(得分：5)
接受的答案为问题提供了可能的解决方案，但它缺乏灵活性，也难以阅读。这是一个更灵活的解决方案。
添加观察员：
//_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];
}
}
}
魔术：
-(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
}
}
＆＃34; [self availableDuration]＆＃34;是可选的，但您可以根据可用的视频量手动启动播放。您可以更改代码检查是否有足够的视频缓冲的频率。如果您决定使用可选部分，请参阅方法实现：
- (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;
}
别忘了清理。删除观察员：
[_player.currentItem removeObserver:self forKeyPath:@"status"];
[_player removeObserver:self forKeyPath:@"rate"];
可能有待处理停顿视频的待处理电话：
[UIView cancelPreviousPerformRequestsWithTarget:self selector:@selector(handleStalled) object:nil];
答案 5 :(得分：2)
首先我观察播放停止
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(playerStalled),
name: AVPlayerItemPlaybackStalledNotification, object: videoPlayer.currentItem)
然后我强制继续播放
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：）
答案 6 :(得分：1)
在非常糟糕的网络中playbackLikelyToKeepUp最有可能是假的。
使用kvo观察playbackBufferEmpty更好，对现有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。
答案 7 :(得分：1)
我也遇到了described here
这个问题我多次对此答案进行了测试，并且到目前为止每次都有效。
这是我为@wallace's answer的Swift 5版本想到的。
1-不是观察keyPath "playbackLikelyToKeepUp"，而是使用.AVPlayerItemPlaybackStalled Notification，并在其中检查通过if !playerItem.isPlaybackLikelyToKeepUp {...}的缓冲区是否已满
2-我使用名为PlayerHangingNotification
playerIsHanging()
3-我不是使用他的PlayerContinueNotification，而是使用了一个名为checkPlayerTryCount()的函数
4-和在checkPlayerTryCount()内，我执行与他的(void)playerContinue函数相同的所有操作，除了遇到} else if playerTryCount == 0 {时没有其他反应。为避免这种情况，我在return语句上方添加了两行代码
5-像@PranoyC在@wallace的注释下建议的那样，我将playerTryCount设置为最大20而不是10。我还将其设置为类属性let playerTryCountMaxLimit = 20
您必须在注释建议的位置添加/删除活动指示器/旋转器
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()
}
答案 8 :(得分：0)
就我而言，
在0.5秒（延迟）后呼叫播放视频。像下面一样
-(void)imagePickerController:(UIImagePickerController *)picker
didFinishPickingMediaWithInfo:(NSDictionary *)info {
[self performSelector:@selector(playVideo) withObject:self
afterDelay:0.5];
}
-（无效）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];
}