使用avplayer / avaudioplayer预加载流媒体

Question

我遇到了avplayer / avaudioplayer的问题。我使用这些类来传输aac或pls音频内容（无线电）。

我想预先加载指定时间内容并播放延迟播放，例如20秒。当我打开时，例如飞机模式和网络丢失，玩家应该在此时刻停止播放20秒。

我在网络上使用此代码用于mp4，它似乎有效，但是当我为aac / pls流式更改时...它正在加载并且一切似乎都有效但是当我打开飞行模式时，它会停止immidiately ...

是否可以保留缓冲区内容并通过流式播放延迟播放？

我的代码：

@interface AVFViewController ()
{
    AVPlayer *player;
    PlayerView *playerView;
    id t

imeObserver;
    NSInteger _playing;
}
@end

@implementation AVFViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self playURL:[NSURL URLWithString:@"http://nba.cdn.turner.com/nba/big/channels/top_plays/2012/02/03/20120203_top10.nba_nba_ipad.mp4"]];
    //http://acdn.smcloud.net/t042-1_mp3.pls
    //http://nba.cdn.turner.com/nba/big/channels/top_plays/2012/02/03/20120203_top10.nba_nba_ipad.mp4
}

- (void)playURL:(NSURL *)videoURL
{
    if (!player) {
        player = [[AVPlayer alloc] init];
        playerView = [[PlayerView alloc] init];
        [playerView setPlayer:player];
        playerView.frame = CGRectInset(self.view.bounds, 20, 20);
        playerView.backgroundColor = [UIColor greenColor];
        playerView.alpha = 1;
        [self.view addSubview:playerView];

        [player addObserver:self forKeyPath:@"currentItem.loadedTimeRanges"    options:NSKeyValueObservingOptionNew context:kTimeRangesKVO];

    }
    [player replaceCurrentItemWithPlayerItem:[[AVPlayerItem alloc] initWithURL:videoURL]];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context 
{
    if (kTimeRangesKVO == context) {
        NSArray *timeRanges = (NSArray *)[change objectForKey:NSKeyValueChangeNewKey];
        if (timeRanges && [timeRanges count]) {
        NSArray *loadedTimeRanges = [[player currentItem] loadedTimeRanges];
        CMTimeRange timeRange = [[loadedTimeRanges objectAtIndex:0] CMTimeRangeValue];
        float startSeconds = CMTimeGetSeconds(timeRange.start);
        float durationSeconds = CMTimeGetSeconds(timeRange.duration);
        NSTimeInterval result = startSeconds + durationSeconds;
        NSLog(@"duration is %f",result);

            if (!_playing && result > 20) {
                [player.currentItem seekToTime:CMTimeMakeWithSeconds(0, 1)];
                [player play];
                _playing = 1;
            }
        }
    }
}

@end