convert CMSampleBufferRef to mat

- (void) parseBuffer:(CMSampleBufferRef) sampleBuffer
{
    CVImageBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    
    CVPixelBufferLockBaseAddress( pixelBuffer, 0 );
    
                                                          
    //Processing here
    int bufferWidth = CVPixelBufferGetWidth(pixelBuffer);
    int bufferHeight = CVPixelBufferGetHeight(pixelBuffer);
    unsigned char *pixel = (unsigned char *)CVPixelBufferGetBaseAddress(pixelBuffer);
    
    // put buffer in open cv, no memory copied
    cv::Mat mat = cv::Mat(bufferHeight,bufferWidth,CV_8UC4,pixel); 
    
    //End processing
    CVPixelBufferUnlockBaseAddress( pixelBuffer, 0 );
}

One suggestion, based on my experience using this: some iPhone device video streams have padding at the end of each pixelBuffer row, which will result in corrupted images if the Mat auto-calculates the step size. To fix it, manually set the 5th 'step' argument to cv::Mat to CVPixelBufferGetBytesPerRow(pixelBuffer). So line 14 would be:

cv::Mat mat = cv::Mat(bufferHeight,bufferWidth,CV_8UC4,pixel,CVPixelBufferGetBytesPerRow(pixelBuffer));

What encoding is this for? YUV?

@mabounassif This piece expects RGB instead of YUV.