maybe incorrect parameters such as bit_rate, rate, width or height

ffmpeg -y -f rawvideo -vcodec rawvideo -s 560x320 -pix_fmt bgr24 -i - -r 30 -b:v 22710k -bufsize 22710k -an -sn -vcodec mpeg4 D:\\vc\\images\\small_new.mp4

    // 先读取视频基本信息：帧率，宽，高
    VideoCapture capture(videofile);
    framerate   = capture.get(CAP_PROP_FPS);
    framewidth  = capture.get(CAP_PROP_FRAME_WIDTH);
    frameheight = capture.get(CAP_PROP_FRAME_HEIGHT);
    bitrate     = capture.get(cv::CAP_PROP_BITRATE);    //22709，单位是kbits
    capture.release();
    
    stringstream cmdString2;
    cmdString2 << "ffmpeg -y -f rawvideo -vcodec rawvideo -s " << 
    framewidth << "x" << frameheight << " -pix_fmt bgr24 -i - -r " << 
    framerate << " -b:v "<< bitrate << "k -an -sn -vcodec mpeg4 " << videofileout;