Ios 设置AVSynchonizedLayer

我一直在尝试制作一个将视频与动画对象连接起来的概念证明（本质上，我是在特定位置将用户选择的位图“旋转”到一个罐装视频上）。在观看了所有关于核心动画（WWDC10等）和AVSync..Layer（苹果WWDC10示例代码、doc示例代码）的可用苹果材料后，根本没有足够清晰的独立代码示例来推导如何正确实现此播放模式

使用CA，我有一个加载到CALayer的视频资源和一个附加到位图的动画，然后连接到另一个CALayer。我创建了一个AVSynchronizedLayer，并将这两个对象添加为子层

当这棵树被添加到UIView的层属性时，我希望动画的播放与视频同步。相反，我只看到视频播放，动画从不执行——以下是我的相关代码片段，它们都位于单个视图控制器（称为ViewDidLoad）中

Video101.m4v=简单的m4v视频， gerald.png=位图

NSURL *fileURL = [[NSBundle mainBundle] URLForResource:@"Video101" withExtension:@"m4v"];
AVURLAsset *asset = [AVURLAsset URLAssetWithURL:fileURL options:nil];
AVPlayerItem *playerItem = [AVPlayerItem playerItemWithAsset:asset];

AVPlayer *player = [[AVPlayer playerWithPlayerItem:playerItem]retain];
AVPlayerLayer *playerLayer = [AVPlayerLayer playerLayerWithPlayer:player];
playerLayer.frame = CGRectMake(0, 0, 1024, 768);
playerLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;

CALayer *gerald = [CALayer layer];
gerald.frame = CGRectMake(0, 0, 120, 120);
gerald.contents = (id) [UIImage imageNamed:@"gerald.png"].CGImage;

[self.view.layer addSublayer:playerLayer];
[self.view.layer insertSublayer:gerald above:playerLayer];


CAKeyframeAnimation *anim = [CAKeyframeAnimation animationWithKeyPath:@"position"];
anim.duration = 18.0;

anim.values = [NSArray arrayWithObjects:
               [NSValue valueWithCGPoint:CGPointMake(320.0, 406.0)],
               [NSValue valueWithCGPoint:CGPointMake(310.0, 400.0)],
               [NSValue valueWithCGPoint:CGPointMake(320.0, 406.0)],
               [NSValue valueWithCGPoint:CGPointMake(310.0, 400.0)],
               [NSValue valueWithCGPoint:CGPointMake(320.0, 406.0)],
               [NSValue valueWithCGPoint:CGPointMake(310.0, 400.0)],
               [NSValue valueWithCGPoint:CGPointMake(480.0, 206.0)],
               [NSValue valueWithCGPoint:CGPointMake(310.0, 400.0)],
               [NSValue valueWithCGPoint:CGPointMake(320.0, 406.0)],
               [NSValue valueWithCGPoint:CGPointMake(320.0, 406.0)],
               [NSValue valueWithCGPoint:CGPointMake(310.0, 400.0)],
               [NSValue valueWithCGPoint:CGPointMake(320.0, 406.0)],
               [NSValue valueWithCGPoint:CGPointMake(10.0, 760.0)],
               [NSValue valueWithCGPoint:CGPointMake(320.0, 406.0)],
               [NSValue valueWithCGPoint:CGPointMake(310.0, 400.0)],
               [NSValue valueWithCGPoint:CGPointMake(320.0, 406.0)],
               [NSValue valueWithCGPoint:CGPointMake(310.0, 400.0)], nil];


anim.keyTimes = [NSArray arrayWithObjects:
                 [NSNumber numberWithFloat:0.02],
                 [NSNumber numberWithFloat:0.06],
                 [NSNumber numberWithFloat:0.09],
                 [NSNumber numberWithFloat:0.1], 
                 [NSNumber numberWithFloat:0.12],
                 [NSNumber numberWithFloat:0.2],
                 [NSNumber numberWithFloat:0.25],
                 [NSNumber numberWithFloat:0.32], 
                 [NSNumber numberWithFloat:0.38],
                 [NSNumber numberWithFloat:0.49],
                 [NSNumber numberWithFloat:0.53],
                 [NSNumber numberWithFloat:0.59], 
                 [NSNumber numberWithFloat:0.63],
                 [NSNumber numberWithFloat:0.69],
                 [NSNumber numberWithFloat:0.78],
                 [NSNumber numberWithFloat:0.81], 
                 [NSNumber numberWithFloat:0.91], 
                 [NSNumber numberWithFloat:1.0], nil];


AVSynchronizedLayer *syncLayer = [AVSynchronizedLayer synchronizedLayerWithPlayerItem:playerItem];
[syncLayer addSublayer:gerald];
[gerald addAnimation:anim forKey:@"transform.position"];

[self.view.layer addSublayer:syncLayer];

[player play];

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实现AVSynchronizedLayer以使动画和视频同时播放的正确格式或方式是什么？

您已正确设置了

CAKeyframeAnimation

，除了一位： 根据WWDC“利用AV基金会编辑媒体”讲座，您需要将动画的

beginTime

属性设置为非零值

零开始时间自动转换为CACurrentMediaTime（）。使用一个小的非零数字：例如1e-100或-1e-100（AVCoreAnimationBeginTimetZero）

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我认为如果您添加

anim.beginTime=avcoreanimationbegintimezero您会发现动画在视频开始播放时就开始了。
我是否可以通过以下操作为动画添加延迟：avcoreAnimationBeginTimesZero+1或caccurrentMediaTime（）+1