AVPlayer项缓冲区为空 [英] AVPlayer item buffer empty

问题描述

我使用播放流内容的AVPlayer。我想知道缓冲区为空的时间和准备播放的时间。但观察者playbackBufferEmpty和playbackLikelyToKeepUp在每次需要时都不起作用。他们有时工作，但往往不工作。我在OSX 10.7.5下只使用iPad模拟器iOS 6.1。
以下是我设置和收听观察者的方式：

I use AVPlayer that plays stream content. I want to know the time when buffer is empty and the time when it is ready to play. But the observers "playbackBufferEmpty" and "playbackLikelyToKeepUp" do not work every time as it needed. They sometimes work but often do not work. I use only iPad simulator iOS 6.1 under OSX 10.7.5. Here is how i set and listen observers:

- (void)playAudioStream:(NSURL *)audioStreamURL
{
 if(_audioPlayer && _audioPlayer.currentItem)
 {
     [_audioPlayer removeObserver:self forKeyPath:StatusKey];
     [_audioPlayer.currentItem removeObserver:self forKeyPath:@"playbackBufferEmpty"];
     [_audioPlayer.currentItem removeObserver:self forKeyPath:@"playbackLikelyToKeepUp"];
 }

 AVPlayerItem *playerItem = [AVPlayerItem playerItemWithURL:audioStreamURL];

 [playerItem addObserver:self forKeyPath:@"playbackBufferEmpty" options:NSKeyValueObservingOptionNew context:nil];
 [playerItem addObserver:self forKeyPath:@"playbackLikelyToKeepUp" options:NSKeyValueObservingOptionNew context:nil];

 _audioPlayer = [AVPlayer playerWithPlayerItem:playerItem];

 [_audioPlayer addObserver:self forKeyPath:StatusKey options:NSKeyValueObservingOptionNew context:nil];

 //[_audioPlayer replaceCurrentItemWithPlayerItem:playerItem];
 //_audioPlayer.actionAtItemEnd = AVPlayerActionAtItemEndNone;
 [_audioPlayer play];
}
...

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
 if ([keyPath isEqualToString:@"playbackBufferEmpty"] )
 {
    if (_audioPlayer.currentItem.playbackBufferEmpty)
    {
       ...
    }

 }

 if ([keyPath isEqualToString:@"playbackLikelyToKeepUp"])
 {
    if (_audioPlayer.currentItem.playbackLikelyToKeepUp)
    {
        ...
    }
 }
}

请帮助我找到缓冲区空和缓冲区就绪事件的正确方法（例如，当Internet连接断开时）。谢谢！

Please help me with the correct way to get "buffer empty" and "buffer ready" events(For example, when the Internet connection is broken). Thank you!

推荐答案

添加观察者时需要使用上下文。以下是您的示例代码。

You need to use context when adding observer. Here is sample code for you.

初始化上下文

static void *playbackLikelyToKeepUpKVOToken = &playbackLikelyToKeepUpKVOToken;
static void *playbackBufferEmpty = &playbackBufferEmpty;
static void *playbackBufferFull = &playbackBufferFull;

添加观察者

[self.playerItem removeObserver:self forKeyPath:@"playbackBufferEmpty" context:playbackBufferEmpty];
[self.playerItem removeObserver:self forKeyPath:@"playbackLikelyToKeepUp" context:playbackLikelyToKeepUpKVOToken];
[self.playerItem removeObserver:self forKeyPath:@"playbackBufferFull" context:playbackBufferFull];

句柄

if (context == playbackLikelyToKeepUpKVOToken)
{
    if (self.playerItem.playbackLikelyToKeepUp)
    {
        NSLog(@"recieve playbackLikelyToKeepUp");
    }

}
else if (context == playbackBufferEmpty)
{
    if (self.playerItem.playbackBufferEmpty)
    {
        NSLog(@"recieve playbackBufferEmpty");
    }
}
else if(context == playbackBufferFull)
{
    NSLog(@"recieve playbackBufferFull");
}
else
{
    [super observeValueForKeyPath:path ofObject:object change:change context:context];
}

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