之前在https://blog.csdn.net/fengbingchun/article/details/103444891中介紹過在Windows上通過ffmpeg dshow設置為mjpeg編解碼方式進行實時顯示的測試代碼。這里測試僅調用ffmpeg的mjpeg編碼接口，獲取到packet后，通過libyuv+libjpeg-turbo對mjpeg進行解碼并實時顯示的測試代碼，代碼如下：

#include <stdio.h>
#include <string.h>
#include <iostream>
#include <memory>#ifdef __cplusplus
extern "C" {
#endif#include <libavdevice/avdevice.h>
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libswscale/swscale.h>
#include <libavutil/mem.h>
#include <libavutil/imgutils.h>#ifdef __cplusplus
}
#endif#include <opencv2/opencv.hpp>
#include <libyuv/convert_argb.h>
#include <libyuv/convert.h>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<unsigned char[]> 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;
}

執行結果如下：

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

總結

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