如何将MTLTexture转换为CVpixelBuffer以写入AVAssetWriter？

Question

我要求在直播视频上应用过滤器，并尝试在Metal中进行过滤。

但是在将过滤器编码为目标过滤器后，我遇到了将MTLTexture转换为CVPixelBuffer的问题。参考（https://github.com/oklyc/MetalCameraSample-master-2）

这是我的代码。

if let pixelBuffer = pixelBuffer {
                CVPixelBufferLockBaseAddress(pixelBuffer, CVPixelBufferLockFlags.init(rawValue: 0))             
                let region = MTLRegionMake2D(0, 0, Int(currentDrawable.layer.drawableSize.width), Int(currentDrawable.layer.drawableSize.height))                    
                let bytesPerPixel = 4;
                let bytesPerRow = CGFloat(bytesPerPixel) * currentDrawable.layer.drawableSize.width

                let tempBuffer = CVPixelBufferGetBaseAddress(pixelBuffer)
                destinationTexture.getBytes(tempBuffer!, bytesPerRow: Int(bytesPerRow), from: region1, mipmapLevel: 0)

                let image = self.imageFromCVPixelBuffer(buffer: pixelBuffer)
                CVPixelBufferUnlockBaseAddress(pixelBuffer, CVPixelBufferLockFlags.init(rawValue: 0))

            }

imageFromCVPixelBuffer方法看起来像这样。

func imageFromCVPixelBuffer(buffer: CVPixelBuffer) -> UIImage {

    let ciimage = CIImage(cvPixelBuffer: buffer)
    let context = CIContext(options: nil)
    let cgimgage = context.createCGImage(ciimage, from: CGRect(x: 0, y: 0, width: CVPixelBufferGetWidth(buffer), height: CVPixelBufferGetHeight(buffer)))

    let uiimage = UIImage(cgImage: cgimgage!)

    return uiimage
}

以下是通过金属进行图像渲染的屏幕截图

以下是将MTLTexture转换为CVPixelBuffer的同一图像的截屏。

将MTLtexture转换为CVPixelBuffer需要写入AVAssetWriter，然后将其保存到库中。

Answer 1

不要那样自己计算bytesPerRow。它被传递给Metal以让Metal知道如何排列行。您希望Metal以CVPixelBuffer期望的方式排列它们。因此，您应该使用CVPixelBufferGetBytesPerRow()来确定值。