如何使用AVAssetExportSession在AVMutableComposition上正确导出CALayer [英] How to properly export CALayer on top of AVMutableComposition with AVAssetExportSession

问题描述

我知道此问题之前已被问过（例如此处和此处）但我可以'弄清楚我做错了什么。

I know this question was asked before (for example here and here) but I just can't figure out what I'm doing wrong.

我有一个 AVMutableComposition 我用它来组合一些视频片段一些 CALayer s在它们之上设置动画。

I have an AVMutableComposition that I use to combine some video clips with some CALayers that animate on top of them.

当我拿走<$ c $时，一切正常c> AVMutableComposition 并将其与 AVSynchronizedLayer 组合，以便在 AVPlayerLayer 内播放。视频输出正确，一切都放在应有的位置。

Everything works ok when I take my AVMutableComposition and combine it with an AVSynchronizedLayer for playback inside an AVPlayerLayer. The video comes out correctly and everything is positioned where it should.

我的问题是，当我尝试导出这个东西时，我尝试使用 AVVideoCompositionCoreAnimationTool 而不是 AVSynchronizedLayer （这是我们应该用于导出的文档）和AVAssetExportSession，但出了点问题，因为在导出的电影中每个 CALayer 让它的坐标系反转。

My problem is that when I tried to export this thing I tried using AVVideoCompositionCoreAnimationTool instead of AVSynchronizedLayer (that's what the documentation says we should use for export) and an AVAssetExportSession, but something goes wrong because in my exported movie every CALayer has it's coordinate system reversed.

因此，如果在回放期间0,0点位于顶部当我导出电影0,0点在左下角角落时屏幕的左侧一角，因此我的动画变得疯狂。

So if during playback the the 0,0 point is in the top-left corner of the screen when I export the movie the 0,0 point is in the bottom-left corner hence my animation go nuts.

我阅读了有关此内容的任何可能的文章，我还从Apple下载了AVVideoEdit样本，但我无法看到发生了什么......

I read any possible article about this and I also downloaded AVVideoEdit sample from Apple but I just can't see what is going on...

推荐答案

对于任何遇到同样问题的人，我终于找到了答案。每个 CALayer 都有一个名为 geometryFlipped 的属性，你需要设置为 YES 就在出口之前，一切都会好的。更多信息这里。

For anyone who has the same problem as I had I've finally found an answer. There is a property of every CALayer called geometryFlipped wich you need to set to YES just before exporting and everything will be ok. More information here.

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