ios - AVSynchronizedLayer 动画适用于本地文件但在流式传输时效果不佳

Question

我有一个动画，使用 AVSynchronizedLayer 可以很好地处理本地视频文件。现在，当我用(同一文件的)流链接替换本地文件时，动画完全停止工作。我不知道是什么原因造成的，已经尝试了多次，它在本地文件上工作得很好，但在流式传输时却不行。有什么想法吗？

编辑:

- (void)observeValueForKeyPath:(NSString*) path
                  ofObject:(id)object
                    change:(NSDictionary*)change
                   context:(void*)context{
/* AVPlayerItem "status" property value observer. */
if (context == AVPlayerDemoPlaybackViewControllerStatusObservationContext)
{
    [self syncPlayPauseButtons];

    AVPlayerStatus status = [[change objectForKey:NSKeyValueChangeNewKey] integerValue];
    switch (status)
    {
            /* Indicates that the status of the player is not yet known because
             it has not tried to load new media resources for playback */
        case AVPlayerStatusUnknown:
        {
            [self removePlayerTimeObserver];
            [self syncScrubber];

            [self disableScrubber];
            [self disablePlayerButtons];
        }
            break;

        case AVPlayerStatusReadyToPlay:
        {
            /* Once the AVPlayerItem becomes ready to play, i.e.
             [playerItem status] == AVPlayerItemStatusReadyToPlay,
             its duration can be fetched from the item. */

            [self initScrubberTimer];

            [self enableScrubber];
            [self enablePlayerButtons];
        }
            break;

        case AVPlayerStatusFailed:
        {
            AVPlayerItem *playerItem = (AVPlayerItem *)object;
            [self assetFailedToPrepareForPlayback:playerItem.error];
        }
            break;
    }
}
/* AVPlayer "rate" property value observer. */
else if (context == AVPlayerDemoPlaybackViewControllerRateObservationContext)
{
    [self syncPlayPauseButtons];
}
/* AVPlayer "currentItem" property observer.
 Called when the AVPlayer replaceCurrentItemWithPlayerItem:
 replacement will/did occur. */
else if (context == AVPlayerDemoPlaybackViewControllerCurrentItemObservationContext)
{
    AVPlayerItem *newPlayerItem = [change objectForKey:NSKeyValueChangeNewKey];

    /* Is the new player item null? */
    if (newPlayerItem == (id)[NSNull null])
    {
        [self disablePlayerButtons];
        [self disableScrubber];
    }
    else /* Replacement of player currentItem has occurred */
    {
        /* Set the AVPlayer for which the player layer displays visual output. */
        [self.playbackView setPlayer:_player];

        /* Specifies that the player should preserve the video’s aspect ratio and
         fit the video within the layer’s bounds. */
        [self.playbackView setVideoFillMode:AVLayerVideoGravityResizeAspect];

        [self syncPlayPauseButtons];
    }
}
else if( context == AVPlayerDemoPlaybackViewControllerCurrentItemObservationContextForDisplay)
{
    AVPlayerLayer *layer = (AVPlayerLayer*) object;
    if (layer.readyForDisplay){
        [layer removeObserver:self forKeyPath:kReadyForAdDisplayKeyT];

        AVPlayerItem *item = _player.currentItem;
        AVSynchronizedLayer *syncedLayer = [AVSynchronizedLayer synchronizedLayerWithPlayerItem:item];
        syncedLayer.frame = CGRectMake(0, 0, 568, 320);
        syncedLayer.backgroundColor = [[UIColor clearColor] CGColor];
        //ADDING THE SYNCHRONIZED LAYER TO MY VIEW
        [self.madnessView addSyncedLayer:syncedLayer player:[self.playbackView player] withGravity:layer.videoGravity];
    }
}
else
{
    [super observeValueForKeyPath:path ofObject:object change:change context:context];
}}

这是我将 AVSynchronized 层添加到播放动画的自定义 View 的地方。动画代码是:

CAKeyframeAnimation *anim = [CAKeyframeAnimation animationWithKeyPath:@"transform"];
anim.beginTime = AVCoreAnimationBeginTimeAtZero;
anim.duration = self.videoDuration;
anim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
anim.removedOnCompletion = NO;
anim.fillMode = kCAFillModeForwards;
anim.values = [self.transforms objectAtIndex:adNumber];
UIImageView* imageView = [self.adViews objectAtIndex:adNumber];
[imageView.layer addAnimation:anim forKey:@"transformAnimation"];
imageView.hidden = NO;

Answer 1

检查 self.videoDuration 值，我在流式传输视频时遇到了同样的问题 - 持续时间始终为 0。希望这对您有所帮助。