The camera is not working

edit savecancel

I'm new and just starting to learn OpenCV. The camera is not initialized during image capture I tried different cameras, but there is no result, even a window with a black screen does not show. Below information about the video:

 Video I/O:
    DC1394:                      YES (ver 2.2.5)
    FFMPEG:                      YES
      avcodec:                   YES (ver 57.107.100)
      avformat:                  YES (ver 57.83.100)
      avutil:                    YES (ver 55.78.100)
      swscale:                   YES (ver 4.8.100)
      avresample:                YES (ver 3.7.0)
    GStreamer:                   NO
    gPhoto2:                     YES

program text:

#include <opencv2/opencv.hpp>
#include <iostream>

int main( int argc, char** argv )
{

      cv::namedWindow( "Example10", cv::WINDOW_AUTOSIZE );
      cv::VideoCapture cap;
      if (argc == 1)
         cap.open(0);

      else
         cap.open( argv[1] );

      if (!cap.isOpened())
      { 
           std::cerr << "Error." << std::endl;
           return -1;
      } 

      cv::Mat frame;

      for (;;)
      {

            cap >> frame;
            if (frame.empty()) break;
            cv::imshow( "Example10", frame );
            if (cv::waitKey(33) == 27) break;
       }

     return 0;
    }

P.S (OpenCV - 3.4.1, Linux ubuntu 18.04)