FFMPEG-based video pull stream and pass it to OPENCV for display

Dependency file decompression

Unzip ffmpeg-master-latest-win64-gpl-shared and get the folder shown below:

Copy the .dll file in the bin directory to the C:\Windows\System32 directory.

Code writing

The streaming code based on FFMPEG is as follows, just modify and add the streaming address.

#include <iostream>
#include <opencv2/opencv.hpp>
extern "C"   //ffmpeg是采用c语言实现的 c++工程种 导入c语言
{
    
    
    //avcodec:编解码(最重要的库)
    #include <libavcodec/avcodec.h>
    //avformat:封装格式处理
    #include <libavformat/avformat.h>
    //swscale:视频像素数据格式转换
    #include <libswscale/swscale.h>
    //avdevice:各种设备的输入输出
    #include <libavdevice/avdevice.h>
    //avutil:工具库（大部分库都需要这个库的支持）
    #include <libavutil/avutil.h>

    #include <libavutil/imgutils.h>

}


int main() {
    
    
    // Initialize FFmpeg
    //av_register_all();//在新版本4.0以后，不需要调用该方法，可以直接使用所有模块。
    avformat_network_init();
    std::cout << "start work" << std::endl;

    // Open RTSP stream
    AVFormatContext* formatContext = nullptr;
    if (avformat_open_input(&formatContext, "rtsp://xxx", nullptr, nullptr) != 0) {
    
    //拉流地址
        std::cerr << "Failed to open RTSP stream." << std::endl;
        return -1;
    }

    // Find stream info
    if (avformat_find_stream_info(formatContext, nullptr) < 0) {
    
    
        std::cerr << "Failed to find stream info." << std::endl;
        return -1;
    }

    // Find video stream index
    int videoStreamIndex = -1;
    for (unsigned int i = 0; i < formatContext->nb_streams; ++i) {
    
    
        if (formatContext->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
    
    
            videoStreamIndex = i;
            break;
        }
    }

    if (videoStreamIndex == -1) {
    
    
        std::cerr << "Failed to find video stream." << std::endl;
        return -1;
    }

    // Get codec parameters for the video stream
    AVCodecParameters* codecParameters = formatContext->streams[videoStreamIndex]->codecpar;

    // Find video decoder
    const AVCodec* codec = avcodec_find_decoder(codecParameters->codec_id);
    if (codec == nullptr) {
    
    
        std::cerr << "Failed to find video decoder." << std::endl;
        return -1;
    }

    // Allocate codec context
    AVCodecContext* codecContext = avcodec_alloc_context3(codec);
    if (avcodec_parameters_to_context(codecContext, codecParameters) < 0) {
    
    
        std::cerr << "Failed to allocate codec context." << std::endl;
        return -1;
    }

    // Open codec
    if (avcodec_open2(codecContext, codec, nullptr) < 0) {
    
    
        std::cerr << "Failed to open codec." << std::endl;
        return -1;
    }
  
    // Prepare image conversion context
    //SwsContext* swsContext = sws_getContext(codecContext->width, codecContext->height,
    //    codecContext->pix_fmt,
    //    codecContext->width, codecContext->height,
    //    //AV_PIX_FMT_RGB24, SWS_BILINEAR, nullptr, nullptr, nullptr);
    //    AV_PIX_FMT_YUV420P, SWS_BILINEAR, nullptr, nullptr, nullptr);


    // Create OpenCV window for displaying frames
    cv::namedWindow("RTSP Stream", cv::WINDOW_NORMAL);

    AVPacket packet;
    cv::Mat frame;

    frame = cv::Mat(codecContext->height, codecContext->width, CV_8UC3);

    AVFrame* pFrameRGB = av_frame_alloc();
    uint8_t* buffer = (uint8_t*)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_RGB24, codecContext->width, codecContext->height, 1));
    av_image_fill_arrays(pFrameRGB->data, pFrameRGB->linesize, buffer, AV_PIX_FMT_RGB24, codecContext->width, codecContext->height, 1);

    struct SwsContext* sws_ctx = sws_getContext(codecContext->width, codecContext->height, codecContext->pix_fmt,
        codecContext->width, codecContext->height, AV_PIX_FMT_RGB24,
        SWS_BILINEAR, nullptr, nullptr, nullptr);

    while (av_read_frame(formatContext, &packet) >= 0) {
    
    
        if (packet.stream_index == videoStreamIndex) {
    
    
            // Decode video frame
            avcodec_send_packet(codecContext, &packet);
            AVFrame* avFrame = av_frame_alloc();
            int ret = avcodec_receive_frame(codecContext, avFrame);

            if (ret == 0) {
    
    
                // Convert frame to RGB
                sws_scale(sws_ctx, avFrame->data, avFrame->linesize, 0, codecContext->height, pFrameRGB->data, pFrameRGB->linesize);
                frame.data = pFrameRGB->data[0];
                // Display frame
                cv::imshow("RTSP Stream", frame);
                cv::waitKey(1);
            }

            av_frame_free(&avFrame);
        }

        av_packet_unref(&packet);
    }

    // Clean up
    avformat_close_input(&formatContext);
    avformat_network_deinit();
    avcodec_free_context(&codecContext);
    sws_freeContext(sws_ctx);

    return 0;
}

Depend on configuration

The dependencies of opencv will not be described here

1. Open the project's property manager and add the decompressed include and lib paths of ffmpeg to the "Include Directory" and "Library Directory", as shown below:
   

My include directory path is: E:\ffmpeg-master-latest-win64-gpl-shared\ffmpeg-master-latest-win64-gpl-shared\include The path to the library directory is: E:\ffmpeg-master-
latest- win64-gpl-shared\ffmpeg-master-latest-win64-gpl-shared\lib
2. Add the library in the additional dependencies in the input section of the linker on the property page.

Just add the following library:

avcodec.lib
avdevice.lib
avfilter.lib
avformat.lib
avutil.lib
postproc.lib
swresample.lib
swscale.lib

Compile and run

Set it as a startup project, compile and run, and an opencv pop-up window will appear.