AVFrame 转 Mat

IYUV(I420)格式

y = width * height
u(v) = width / 2 * height * 2 

伪代码

    ...   
    AVFrame *p_frame;//AV_PIX_FMT_YUV420P AV_PIX_FMT_YUVJ420P
    ...

    Mat rgbMat;
    Mat yuv_I420;
    yuv_I420.create(p_frame->height * 3 / 2, p_frame->width, CV_8UC1);

    uint8_t* p_data = yuv_I420.data;
	for (int j = 0; j < p_frame->height; j++)
	{
		memcpy(p_data
				, p_frame->data[0] + j * p_frame->linesize[0], p_frame->width);
		p_data += p_frame->width;
	}

	for (int j = 0; j < p_frame->height / 2; j++)
	{
		memcpy(p_data
				, p_frame->data[1] + j * p_frame->linesize[1], p_frame->width / 2);
		p_data += p_frame->width / 2;

	}

	for (int j = 0; j < p_frame->height / 2; j++)
	{
		memcpy(p_data
				, p_frame->data[2] + j * p_frame->linesize[2], p_frame->width / 2);
		p_data += p_frame->width / 2;
	}
	cvtColor(yuv_I420, rgbMat, COLOR_YUV2BGR_I420);