Question

我需要创建CVPixelBufferRef的副本，以便能够使用副本中的值以逐位方式操作原始像素缓冲区。我似乎无法通过CVPixelBufferCreate或CVPixelBufferCreateWithBytes实现这一目标。

根据this question，也可以使用memcpy（）完成。但是，没有解释如何实现这一目标，无论如何都需要调用哪些核心视频库。

Answer 1

这似乎有效：

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {

    CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);

    // Get pixel buffer info
    const int kBytesPerPixel = 4;
    CVPixelBufferLockBaseAddress(pixelBuffer, 0);
    int bufferWidth = (int)CVPixelBufferGetWidth(pixelBuffer);
    int bufferHeight = (int)CVPixelBufferGetHeight(pixelBuffer);
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(pixelBuffer); 
    uint8_t *baseAddress = CVPixelBufferGetBaseAddress(pixelBuffer);

    // Copy the pixel buffer
    CVPixelBufferRef pixelBufferCopy = NULL;
    CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, bufferWidth, bufferHeight, kCVPixelFormatType_32BGRA, NULL, &pixelBufferCopy);
    CVPixelBufferLockBaseAddress(pixelBufferCopy, 0);
    uint8_t *copyBaseAddress = CVPixelBufferGetBaseAddress(pixelBufferCopy);
    memcpy(copyBaseAddress, baseAddress, bufferHeight * bytesPerRow);

    // Do what needs to be done with the 2 pixel buffers

}

Answer 2

ooOlly的代码在所有情况下都不适用于YUV像素缓冲区（底部的绿线和memcpy中的sig陷阱），因此对于来自相机的YUV像素缓冲区来说，它可以迅速工作：

var copyOut: CVPixelBuffer?
let status = CVPixelBufferCreate(kCFAllocatorDefault, CVPixelBufferGetWidth(pixelBuffer), CVPixelBufferGetHeight(pixelBuffer), CVPixelBufferGetPixelFormatType(pixelBuffer), nil, &copyOut)
let copy = copyOut!

CVPixelBufferLockBaseAddress(copy, [])
CVPixelBufferLockBaseAddress(pixelBuffer, [])

let ydestPlane = CVPixelBufferGetBaseAddressOfPlane(copy, 0)
let ysrcPlane = CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0)
memcpy(ydestPlane, ysrcPlane, CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 0) * CVPixelBufferGetHeightOfPlane(pixelBuffer, 0))

let uvdestPlane = CVPixelBufferGetBaseAddressOfPlane(copy, 1)
let uvsrcPlane = CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 1)
memcpy(uvdestPlane, uvsrcPlane, CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 1) * CVPixelBufferGetHeightOfPlane(pixelBuffer, 1))

CVPixelBufferUnlockBaseAddress(copy, [])
CVPixelBufferUnlockBaseAddress(pixelBuffer, [])

强烈建议比强制展开更好的错误处理。

Answer 3

Maxi Mus的代码仅适用于RGB / BGR缓冲区。因此对于YUV缓冲区，下面的代码应该可以使用。

// Copy the pixel buffer
    CVPixelBufferRef pixelBufferCopy = NULL;
    CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, bufferWidth, bufferHeight, pixelFormat, NULL, &pixelBufferCopy);
    CVPixelBufferLockBaseAddress(pixelBufferCopy, 0);
    //BGR
//    uint8_t *copyBaseAddress = CVPixelBufferGetBaseAddress(pixelBufferCopy);
//    memcpy(copyBaseAddress, baseAddress, bufferHeight * bytesPerRow);
    uint8_t *yDestPlane = CVPixelBufferGetBaseAddressOfPlane(pixelBufferCopy, 0);
    //YUV
    uint8_t *yPlane = CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0);
    memcpy(yDestPlane, yPlane, bufferWidth * bufferHeight);
    uint8_t *uvDestPlane = CVPixelBufferGetBaseAddressOfPlane(pixelBufferCopy, 1);
    uint8_t *uvPlane = CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 1);
    memcpy(uvDestPlane, uvPlane, bufferWidth * bufferHeight/2);
    CVPixelBufferUnlockBaseAddress(pixelBufferCopy, 0);

使用CVPixelBufferCreate

3 个答案: