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• ffmpeg fails to connect a second camera when run using python thread

  1er juin 2023, par LemonJumps

  I'm starting ffmpeg dshow -> rawvideo over pipe in python thread, see code below

  


      def run(self):
        proc = subprocess.Popen(
            [FFMPEG_DIR + "ffmpeg", "-hide_banner", "-f", "dshow", 
                "-video_size", str(self.resolution[0]) + "x" + str(self.resolution[1]), # select resolution
                "-framerate", str(self.framerate), # select framerate
                "-i", "video=" + self.device, # select device
                "-f", "rawvideo", "-pix_fmt", "bgr24", "pipe:"], # output to pipe
            stdout = subprocess.PIPE)
        
        buf = b''
        
        while True:
            outs = proc.stdout.read(self.resolution[0] * self.resolution[1] *3)
            buf += outs
            
            if len(buf) >= (self.resolution[0] * self.resolution[1] *3):
                with self.lock:
                    self.frame = buf[0:self.resolution[0] * self.resolution[1] *3] 
                    self.cnt += 1
                    
                buf = b''
                
            if self.endEvent.isSet():
                proc.kill()
                return


  


  I am using alternative name as camera name, both cameras are the same model.
both devices name and alternative name :

  


  ('ACR010 USB Webcam', '@device_pnp_\\\\?\\usb#vid_0c45&pid_636a&mi_00#8&83c432e&0&0000#{65e8773d-8f56-11d0-a3b9-00a0c9223196}\\global')

  


  ('ACR010 USB Webcam', '@device_pnp_\\\\?\\usb#vid_0c45&pid_636a&mi_00#8&34de11d9&0&0000#{65e8773d-8f56-11d0-a3b9-00a0c9223196}\\global')

  


  when I run this code for each camera individually it works flawlessly.
But when I run this for both cameras at the same time, the code results this error :


  


  The "Could not run graph" sounds like ffmpeg can't open multiple devices, or isn't allowed by windows, or maybe there's a token that gets reused because it's all within a single process ?

  


  What could be really causing this error and how can I mitigate it ?

  


• Ip camera using ffmpeg drawing on screen

  6 mars 2014, par user3177342

  I'm using ffmpeg 1.2 to take video from ip camera.I make it draw on the screen, so I wonder if there is some event mechanism to to know if it is time to call av_read_frame ?
  If I read frame not so frequent as the camera gives frames i get segmentation fault = on some malloc functions inside ffmpeg routines(video_get_buffer)

  I also get segmentation fault just when drawing on screen.

  In Render function call every 0 miliseconds

  void BasicGLPane::DrawNextFrame()
  
  {
  
  int f=1;
  
  while(av_read_frame(pFormatCtx, &packet)>=0)
  
      {
  
          // Is this a packet from the video stream?
  
          if(packet.stream_index==videoStream)
  
          {
  
  
  
  
  
              // Decode video frame
  
              avcodec_decode_video2(pCodecCtx, pFrame, &FrameFinished,
  
                                    &packet);
  
  
  
              // Did we get a video frame?
  
              if(FrameFinished)
  
              {
  
                  f++;
  
                  this->fram->Clear();
  
                 // if (pFrame->pict_type == AV_PICTURE_TYPE_I) wxMessageBox("I cadr");
  
                  if (pFrame->pict_type != AV_PICTURE_TYPE_I)
  
                  printMVMatrix(f, pFrame, pCodecCtx);
  
                  pFrameRGB->linesize[0]= pCodecCtx->width*3; // in case of rgb4  one plane
  
  
  
                  sws_scale(swsContext, pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);
  
                  //glGenTextures(1, &VideoTexture);
  
                  if ((*current_Vtex)==VideoTexture) current_Vtex = &VideoTexture2;else current_Vtex = &VideoTexture;
  
                  glBindTexture(GL_TEXTURE_2D, (*current_Vtex));
  
                  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
  
                  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
  
                  glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
  
                  glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, pCodecCtx->width, pCodecCtx->height, GL_RGB, GL_UNSIGNED_BYTE, pFrameRGB->data[0]);
  
                  //glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, pCodecCtx->width, pCodecCtx->height, 0, GL_RGB, GL_UNSIGNED_BYTE, pFrameRGB->data[0]);
  
                  //glDeleteTextures(1, &VideoTexture);
  
                  GLenum err;
  
                  while ((err = glGetError()) != GL_NO_ERROR)
  
                  {
  
                      cerr << "OpenGL error: " << err << endl;
  
                  }
  
                //  av_free(buffer);
  
              }
  
          }
  
  
  
          // Free the packet that was allocated by av_read_frame
  
          av_free_packet(&packet);
  
          if (f>1) break;
  
      }
  
  
  
  //av_free(pFrameRGB);
  
  }

  The picture I get on the screen is strange (green quads and red lines are motion vectors of those quads)

  http://i.stack.imgur.com/9HJ9t.png

• H.264 video file size from camera is much bigger than x264 output

  10 août 2020, par Lawrence song

  I have a UVC camera which supports h264 protocol. we can see the h264 listed below when we list all formats supported.

  


  msm8909:/data # ./ffmpeg -f v4l2 -list_formats all -i /dev/video1
ffmpeg version N-53546-g5eb4405fc5-static https://johnvansickle.com/ffmpeg/  Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 6.3.0 (Debian 6.3.0-18+deb9u1) 20170516
  configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gmp --enable-libgme --enable-gray --enable-libfribidi --enable-libass --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libvorbis --enable-libopus --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvpx --enable-libwebp --enable-libx264 --enable-libxml2 --enable-libxvid --enable-libzimg
  libavutil      56. 56.100 / 56. 56.100
  libavcodec     58. 97.100 / 58. 97.100
  libavformat    58. 49.100 / 58. 49.100
  libavdevice    58. 11.101 / 58. 11.101
  libavfilter     7. 87.100 /  7. 87.100
  libswscale      5.  8.100 /  5.  8.100
  libswresample   3.  8.100 /  3.  8.100
  libpostproc    55.  8.100 / 55.  8.100
[video4linux2,v4l2 @ 0x4649140] Compressed:        h264 :                H.264 : 1920x1080 1280x720 640x480 320x240
[video4linux2,v4l2 @ 0x4649140] Compressed:       mjpeg :                MJPEG : 1920x1080 1280x720 640x480 320x240


  


  I am running the ffmpeg cmd to record UVC camera video to local device.

  


  ffmpeg -f v4l2 -input_format h264 -framerate 30 -video_size 1280*720 -i /dev/video1 -c copy /sdcard/Movies/output.mkv


  


  The video size is way bigger than running the command below :

  


  ffmpeg -f v4l2 -input_format mjpeg -framerate 30 -video_size 1280*720 -i /dev/video1 -c:v libx264 -vf format=yuv420p /sdcard/Movies/output.mp4


  


  I assume the camera already supports h264 protocol. Thus I don't need to re-encode to 264 formats. However, the video size does not look like an H264 encoded video.