FFmpeg在Windows上设置dshow mjpeg编码+libyuv解码显示测试代码

之前在https://blog.csdn.net/fengbingchun/article/details/103444891中介绍过在Windows上通过ffmpeg dshow设置为mjpeg编解码方式进行实时显示的测试代码。这里测试仅调用ffmpeg的mjpeg编码接口，获取到packet后，通过libyuv+libjpeg-turbo对mjpeg进行解码并实时显示的测试代码，代码如下：

#include 
#include 
#include 
#include 

#ifdef __cplusplus
extern "C" {
#endif

#include 
#include 
#include 
#include 
#include 
#include 

#ifdef __cplusplus
}
#endif

#include 
#include 
#include 

int test_ffmpeg_dshow_mjpeg_encode_libyuv_decode()
{
	avdevice_register_all();

	AVCodecID id = AV_CODEC_ID_MJPEG;
	AVCodec* encoder_id = avcodec_find_encoder(id);
	if (!encoder_id) {
		fprintf(stderr, "codec not found: %d\n", id);
		return -1;
	}

	AVFormatContext* format_context = avformat_alloc_context();
	format_context->video_codec_id = id;

	AVInputFormat* input_format = av_find_input_format("dshow");
	AVDictionary* dict = nullptr;
	if (av_dict_set(&dict, "video_size", "960x540", 0) < 0) fprintf(stderr, "fail to av_dict_set: line: %d\n", __LINE__);
	int ret = avformat_open_input(&format_context, "video=Integrated Webcam", input_format, &dict);
	if (ret != 0) {
		fprintf(stderr, "fail to avformat_open_input: %d\n", ret);
		return -1;
	}

	ret = avformat_find_stream_info(format_context, nullptr);
	if (ret < 0) {
		fprintf(stderr, "fail to get stream information: %d\n", ret);
		return -1;
	}

	int video_stream_index = -1;
	for (unsigned int i = 0; i < format_context->nb_streams; ++i) {
		const AVStream* stream = format_context->streams[i];
		if (stream->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
			video_stream_index = i;
			fprintf(stdout, "type of the encoded data: %d, dimensions of the video frame in pixels: width: %d, height: %d, pixel format: %d\n",
				stream->codecpar->codec_id, stream->codecpar->width, stream->codecpar->height, stream->codecpar->format);
		}
	}

	if (video_stream_index == -1) {
		fprintf(stderr, "no video stream\n");
		return -1;
	}

	AVCodecParameters* codecpar = format_context->streams[video_stream_index]->codecpar;
	if (codecpar->codec_id != id) {
		fprintf(stderr, "this test code only support mjpeg encode: %d\n", codecpar->codec_id);
		return -1;
	}

	AVPacket* packet = (AVPacket*)av_malloc(sizeof(AVPacket));
	if (!packet) {
		fprintf(stderr, "fail to alloc\n");
		return -1;
	}

	std::unique_ptr data(new unsigned char[codecpar->width * codecpar->height * 4]);
	cv::Mat mat(codecpar->height,codecpar->width, CV_8UC4, data.get());
	const char* winname = "dshow mjpeg encode and libyuv decode";
	cv::namedWindow(winname);
	AVFrame* frame = av_frame_alloc();

	while (1) {
		ret = av_read_frame(format_context, packet);
		if (ret >= 0 && packet->stream_index == video_stream_index && packet->size > 0) {
			int dst_width, dst_height;
			libyuv::MJPGSize(packet->data, packet->size, &dst_width, &dst_height);
			if (dst_width != codecpar->width || dst_height != codecpar->height) {
				fprintf(stderr, "width or height dismatch: (%d, %d), (%d, %d)\n",
					dst_width, dst_height, codecpar->width, codecpar->height);
				return -1;
			}

			libyuv::MJPGToARGB(packet->data, packet->size, data.get(), dst_width * 4,
				codecpar->width, codecpar->height, dst_width, dst_height);
			cv::imshow(winname, mat);

		} else if (ret < 0 || packet->size <= 0) {
			fprintf(stderr, "fail to av_read_frame: %d, packet size: %d\n", ret, packet->size);
			continue;
		}

		av_packet_unref(packet);

		int key = cv::waitKey(30);
		if (key == 27) break;
	}

	cv::destroyWindow(winname);
	av_freep(packet);
	avformat_close_input(&format_context);
	av_dict_free(&dict);

	fprintf(stdout, "test finish\n");
	return 0;
}

执行结果如下：

GitHub：https://github.com//fengbingchun/OpenCV_Test