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• Got black screen when recording screen by x11grab device

  30 janvier 2014, par shawnzhu

  I'm trying to record video from a firefox run by xvfb-run but it always output nothing in the video file except black screen.

  Here's what I did :

  start a firefox, open google.com :

  $ xvfb-run firefox https://google.com

  Then it will use the default display server number 99. I can see the display information by command xdpyinfo -display :99.

  A screenshot works very well by command :

  $ xwd -root -silent -display :99.0 | xwdtopnm |pnmtojpeg > screen.jpg

  Start using ffmpeg to record a video :

  $ ffmpeg -f x11grab -i :99.0 out.mpg

  When I play the video file out.mpg, there's black screen all the time.

  Is there any parameter I missed ?

• Ffmpeg to OpenGL texture black screen

  23 janvier 2014, par user3177342

  I am trying to make textures from ffmpeg source, but I get the black screen.

  here is the code

  avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished,
  
              &packet);
  
  
  
          // Did we get a video frame?
  
          if(frameFinished)
  
          {
  
           f++;
  
  
  
                  pFrameRGB=avcodec_alloc_frame();
  
                  struct SwsContext* swsContext = sws_getContext(pCodecCtx->width, pCodecCtx->height,
  
                          pCodecCtx->pix_fmt,
  
                          pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_RGB24, SWS_BICUBIC,
  
                          NULL, NULL, NULL);
  
                  if (swsContext == NULL) {
  
                   fprintf(stderr, "Cannot initialize the conversion context!\n");
  
                    exit(1);
  
                    };
  
  
  
  
  
                  sws_scale(swsContext, pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);
  
                  glGenTextures(1, &VideoTexture);
  
                  glBindTexture(GL_TEXTURE_2D, VideoTexture);
  
                  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  
                  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  
                  glTexImage2D(GL_TEXTURE_2D, 0, 3, pCodecCtx->width, pCodecCtx->height, 0, GL_RGB, GL_UNSIGNED_BYTE, pFrameRGB->data[0]);
  
   }
  
  }
  
  
  
  // Free the packet that was allocated by av_read_frame
  
  av_free_packet(&packet);
  
  if (f>1) break;

  Strangerly when I draw i get black screen, my video is not black.

  if (VideoTexture != 0)
  
      {
  
          glEnable(GL_TEXTURE_2D);
  
          glPushMatrix();
  
          glBindTexture(GL_TEXTURE_2D, VideoTexture);
  
          glBegin(GL_QUADS);
  
          glTexCoord2i(0, 0); glVertex2i(0, 0);
  
          glTexCoord2i(1, 0); glVertex2i(Width, 0);
  
          glTexCoord2i(1, 1); glVertex2i(Width, Height);
  
          glTexCoord2i(0, 1); glVertex2i(0, Height);
  
          glEnd();
  
          glPopMatrix();
  
          glDisable(GL_TEXTURE_2D);
  
      }

• Ubuntu 14 FFMPEG & Black and White Conversion

  3 septembre 2015, par Jesse James Richard

  As the HUE option doesn’t exist in FFMPEG on Ubuntu because it’s AVCONC, can it just be assumed that it’s nearly impossible to convert a video to black and white since FFMPEG is effectively incomplete ?