func: static void update_video_pts(VideoState *is, double pts, int64_t pos, int serial) {
  
      double time = av_gettime() / 1000000.0;
  
      /* update current video pts */
  
      is->video_current_pts = pts;
  
      is->video_current_pts_drift = is->video_current_pts - time;
  
      is->video_current_pos = pos;
  
      is->frame_last_pts = pts;
  
      check_external_clock_sync(is, is->video_current_pts);
  
  }
  