Opencv直接使用YUV视频源

OpenCV默认情况下是BGR24的方式将数据丢到Mat中，

In header file videoio.hpp:

// Generic camera output modes.
// Currently, these are supported through the libv4l interface only.
enum { CAP_MODE_BGR  = 0, // BGR24 (default)
       CAP_MODE_RGB  = 1, // RGB24
       CAP_MODE_GRAY = 2, // Y8
       CAP_MODE_YUYV = 3  // YUYV
     };

可直接设置模式：

cv::VideoCapture camera = cv::VideoCapture();
camera.open(0);
camera.set(CV_CAP_PROP_MODE, CV_CAP_MODE_YUYV);