AVMutableVideoCompositionLayerInstruction转换比例旋转

Question

我正在使用AVMutableComposition合并/缝合多个录制的视频轨道并将其保存为预期的输出

..所以我循环遍历子视图,根据每个子视图大小转换每个轨道.

    var index = 0
    for subview:UIView in template.subviews {
        let scaleX = (subview.frame.width / template.frame.width) / (tracks[index].naturalSize.width /  mainComposition.renderSize.width)
        let scaleY = (subview.frame.height / template.frame.height) / (tracks[index].naturalSize.height /  mainComposition.renderSize.height)
        let x = subview.frame.origin.x
        let y = subview.frame.origin.y

        let rotate = CGAffineTransformMakeRotation(CGFloat(M_PI_2))
        let scale = CGAffineTransformMakeScale(scaleX, scaleY)
        let translate = CGAffineTransformMakeTranslation(x, y)
        let transform = CGAffineTransformConcat(scale, translate)

        let transformation = AVMutableVideoCompositionLayerInstruction(assetTrack: tracks[index])
        transformation.setTransform(CGAffineTransformConcat(rotate, transform), atTime: kCMTimeZero)
        instructions.append(transformation)
        index++
    }

问题是视频全部不在保存的视频中.但是如果没有旋转,我会得到预期的输出,如附图中的视频,但视频中的视频 - 我读到的是iPhone设备中捕获的视频总是如此(如何通过AVAssetExportSession以纵向模式导出视频资源)

我一直在玩CGAffineTransform,重新排列翻译,旋转或缩放,这是首先或最后但没有得到好结果.我也试过创建两个分离旋转和sctaletranslate但仍然相同的layerinstruction.

谢谢你的帮助