AVQueuePlayer frustrations (buffer underrun handling)

问题

I am having a hell of a time with AVQueuePlayer. Very simply, I am making it on an array of AVPlayerItems built with playerItemWithURL: and pointing to video assets on a server out on the Net.

If I try to run this thing in the stimulator (sic) it plays through the first asset, begins playing the second and just dies. Sometimes it doesn't even get through the first asset.

Now, I understand that the sim behaves differently than the device, so I tried it on the device as well, with the same problem.

When I log the various status changes on the item, I see that the buffer runs out, and the player just dies. This seems a bit silly to me for a construct that is playing a queue of items... of course the buffer may underrun, but why would it just die?

Am I doing something wrong, or is this how it is supposed to behave?

I have gotten around this problem by observing the loadedTimeRanges property and when it changes sending PLAY to the player. But this results in stuttering playback, which sucks too.

Here is my code. Can someone please tell me how to do this without the playback being complete crap?

- (void)viewDidLoad {
    [super viewDidLoad];

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handlePlayerItemReachedEnd:) name:AVPlayerItemDidPlayToEndTimeNotification object:self.queuePlayer];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handlePlayerStalled:) name:AVPlayerItemPlaybackStalledNotification object:self.queuePlayer];

    NSString *baseURL = @"http://www.aDomain.com/assets/";
    NSMutableArray *vidItemArray = [[NSMutableArray alloc] initWithCapacity:5];

    for (int i = 1; i <= 5; i++) {
        AVPlayerItem *vid = [AVPlayerItem playerItemWithURL:[NSURL URLWithString:[baseURL stringByAppendingFormat:@"%d.mov", i]]];
        [vid addObserver:self forKeyPath:@"status" options:0 context:nil];
        [vid addObserver:self forKeyPath:@"playbackBufferEmpty" options:0 context:nil];
        [vid addObserver:self forKeyPath:@"loadedTimeRanges" options:0 context:nil];
        [vidItemArray addObject:vid];
    }

    self.queuePlayer = [AVQueuePlayer queuePlayerWithItems:vidItemArray];
    [self.mPlaybackView setPlayer:self.queuePlayer];
}

- (void)handlePlayerItemReachedEnd:(NSNotification *)notification {
    NSLog(@"Clip #%d finished playing", [self.queuePlayer.items indexOfObject:self.queuePlayer.currentItem]);
}

- (void)handlePlayerStalled:(NSNotification *)notification {
    NSLog(@"CLIP STALLED...");
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
    if ([object isKindOfClass:[AVPlayerItem class]]) {
        AVPlayerItem *item = (AVPlayerItem *)object;

        if ([keyPath isEqualToString:@"status"]) {
            switch (item.status) {
                case AVPlayerItemStatusFailed:
                    NSLog(@"player item status failed");
                break;
                case AVPlayerItemStatusReadyToPlay:
                    NSLog(@"player item status is ready to play");
                [self.queuePlayer play];
                break;
                case AVPlayerItemStatusUnknown:
                    NSLog(@"player item status is unknown");
                break;
            }
        }
        else if ([keyPath isEqualToString:@"playbackBufferEmpty"]) {
            if (item.playbackBufferEmpty) {
                NSLog(@"player item playback buffer is empty");
            }
        }
        else if ([keyPath isEqualToString:@"loadedTimeRanges"]) {
            NSLog(@"Loaded time range = %@", item.loadedTimeRanges);
            self.queuePlayer play];
        }
    }
}

回答1:

You should not add many AVPlayerItem to AVQueuePlayer initially because they will begin buffering at the same time, at discretion of the framework.

Attempt to load one file and then on KVO currentItem changed queue the next one, it might solve your problem. I'm using this to achieve gapless playback.

来源：https://stackoverflow.com/questions/14247306/avqueueplayer-frustrations-buffer-underrun-handling

标签

ios6

buffer

avplayer

avqueueplayer