That's possible.
cv::Mat picYV12 = cv::Mat(nHeight * 3/2, nWidth, CV_8UC1, yv12DataBuffer);
cv::Mat picBGR;
cv::cvtColor(picYV12, picBGR, CV_YUV2BGR_YV12);
cv::imwrite("test.bmp", picBGR); //only for test
The height is multiplied by 3/2 because there are 4 Y samples, and 1 U and 1 V sample stored for every 2x2 square of pixels. This results in a byte sample to pixel ratio of 3/2
4*1+1+1 samples per 2*2 pixels = 6/4 = 3/2
Correction: In the last version of OpenCV (i use oldest 2.4.13 version) is color conversion code changed to COLOR_YUV2BGR_YV12
cv::cvtColor(picYV12, picBGR, COLOR_YUV2BGR_YV12);