AVFrame和cv::Mat互转

《音视频应用开发系列文章目录》

ffmpeg视频解码后得到图像经常需要一些图像处理，opencv是图像处理的神器。所以就需要两者之间互相转化，ffmpeg解码后的数据类型是AVFrame，而opencv的图像数据结构是Mat，这就需要做个转化，本文实现了avframe->mat，mat->avframe。封装成函数

cv::Mat avframe2cvmat(AVFrame *avframe, int w = 0, int h = 0);

AVFrame *cvmat2avframe(cv::Mat mat);

avframe->mat

cv::Mat avframe2cvmat(AVFrame *avframe, int w, int h) {

	if (w <= 0) w = avframe->width;
	if (h <= 0) h = avframe->height;
	struct SwsContext *sws_ctx = NULL;
	sws_ctx = sws_getContext(avframe->width, avframe->height, (enum AVPixelFormat)avframe->format,
		w, h, AV_PIX_FMT_BGR24, SWS_BICUBIC, NULL, NULL, NULL);

	cv::Mat mat;
	mat.create(cv::Size(w, h), CV_8UC3);
	AVFrame *bgr24frame = av_frame_alloc();
	bgr24frame->data[0] = (uint8_t *)mat.data;
	avpicture_fill((AVPicture *)bgr24frame, bgr24frame->data[0], AV_PIX_FMT_BGR24, w, h);
	sws_scale(sws_ctx,
		(const uint8_t* const*)avframe->data, avframe->linesize,
		0, avframe->height, // from cols=0,all rows trans
		bgr24frame->data, bgr24frame->linesize);

	av_free(bgr24frame);
	sws_freeContext(sws_ctx);
	return mat;
}

w，h可以对输入图像进行resize，默认和原图大小一致，不resize。

mat->avframe

AVFrame *cvmat2avframe(cv::Mat mat) {

	// alloc avframe
	AVFrame *avframe = av_frame_alloc();
	if (avframe && !mat.empty()) {

		avframe->format = AV_PIX_FMT_YUV420P;
		avframe->width = mat.cols;
		avframe->height = mat.rows;
		av_frame_get_buffer(avframe, 0);
		av_frame_make_writable(avframe);
		cv::Mat yuv; // convert to yuv420p first
		cv::cvtColor(mat, yuv, cv::COLOR_BGR2YUV_I420);
		// calc frame size
		int frame_size = mat.cols * mat.rows;
		unsigned char *pdata = yuv.data;
		// fill yuv420
		// yyy yyy yyy yyy
		// uuu
		// vvv
		avframe->data[0] = pdata; // fill y
		avframe->data[1] = pdata + frame_size; // fill u
		avframe->data[2] = pdata + frame_size * 5 / 4; // fill v
	}
	return avframe;
}

emmm···，注释的很清楚了！用完了别玩了释放AVFrame~~