当我使用 AVPlayerLayer 时放大镜以错误的方式出现

Question

我正在使用 AVPlayerLayer 在我的 UIViewController 实例的后台播放视频。当我在 iPhone 上启动我的应用程序时，我注意到放大镜的显示方式有误。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）在我的放大镜内绘制。

- (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发生？

Answer 1

我想出的唯一解决办法是：

将 UIImageView 放在 container 视图下方：

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];

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];
}];

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;
        });
    });
}

属性 imageGenerator 的类型是 AVAssetImageGenerator:

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

N.B。快照在后台更新，因此帧滞后于视频。但这聊胜于无。

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