ios - 使用 AVPlayerLayer 时放大镜出现错误

Question

我正在使用 AVPlayerLayer 在我的 UIViewController 实例的背景中播放视频。当我在 iPhone 上启动我的应用程序时，我注意到放大镜以错误的方式出现。视频规格：H.264、AAC、640x360、MOV。

没有我的视频子图层的放大镜绘图内的背景。只有子视图（按钮、文本字段等）在我的放大镜中绘制。

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor yellowColor];

    NSURL *videoURL = [[NSBundle mainBundle] URLForResource:@"bf4" withExtension:@"mov"];
    AVAsset *asset = [AVAsset assetWithURL:videoURL];
    AVPlayerItem *item = [AVPlayerItem playerItemWithAsset:asset];
    AVPlayer *player = [AVPlayer playerWithPlayerItem:item];
    player.actionAtItemEnd = AVPlayerActionAtItemEndNone;

    UIView *container = [[UIView alloc] initWithFrame:self.view.bounds];
    container.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
    [self.view addSubview:container];

    AVPlayerLayer *layer = [AVPlayerLayer playerLayerWithPlayer:player];
    [container.layer addSublayer:layer];
    layer.frame = container.bounds;
    layer.videoGravity = AVLayerVideoGravityResizeAspectFill;

    [self.view bringSubviewToFront:self.textField];        
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0f * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        [player play];
    });
}

有谁知道如何防止这种情况？

Answer 1

我想出的唯一一种解决方案是：

1. 放在UIImageView下面的container视图：

   self.containerThumbnail = [[UIImageView alloc] initWithFrame:self.view.bounds];
   self.containerThumbnail.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
   self.containerThumbnail.backgroundColor = [UIColor clearColor];
   [self.view insertSubview:self.containerThumbnail belowSubview:container];
   

2. 成为媒体播放器的时间观察者：

    CMTime bgInterval = CMTimeMake(1, 10);
   __weak __typeof(self)weakSelf = self;
   [player addPeriodicTimeObserverForInterval:bgInterval 
                                        queue:dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0)
                                   usingBlock:^(CMTime time)
   {
       [weakSelf locateThumbnail:time];
   }];
   

3. 将快照放入您的UIImageView：

   - (void)locateThumbnail:(CMTime)time
   {
       __weak __typeof(self)weakSelf = self;
       dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^(void) {
           CGImageRef imageRef = [weakSelf.imageGenerator copyCGImageAtTime:time actualTime:NULL error:NULL];
           UIImage *image = [UIImage imageWithCGImage:imageRef];
           CGImageRelease(imageRef);
           __strong __typeof(weakSelf)strongSelf = weakSelf;
           dispatch_async(dispatch_get_main_queue(), ^(void) {
               strongSelf.containerThumbnail.image = image;
           });
       });
   }
   

该属性imageGenerator的类型为AVAssetImageGenerator：

imageGenerator = [[AVAssetImageGenerator alloc] initWithAsset:asset];
imageGenerator.appliesPreferredTrackTransform = YES;

NB 快照在后台更新，因此帧滞后于视频。但这总比没有好。