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• palettegen : Fill with last color, not black

  16 janvier 2019, par Tomas Härdin

  palettegen : Fill with last color, not black
  If we fill with black then the generated palette will have one color more
  
  than what the user requested. This also resulted in unwanted black specks in
  
  the output of paletteuse, especially when generating small palettes.
  

  • [DH] libavfilter/vf_palettegen.c
  • [DH] tests/ref/fate/filter-palettegen-2

• Got black screen when recording screen by x11grab device

  5 août 2019, par shawmzhu

  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 decoding MP4 to Open GL texture black screen

  5 septembre 2019, par Dakiaiu

  I decoded a MP4 video and want to display the AVFrame via glTexImage2D and glTexSubImage2D but all I get is a blank GL Window.

  I’ve tried looking at the various examples in the ffmpeg github examples tree. https://github.com/FFmpeg/FFmpeg/tree/master/doc/examples and different posts from the past and recently on this site learning slowly from them but I could not find anything I am doing wrong.

  while(av_read_frame(format_context,packet) >= 0){
  
  
  
          if(packet->stream_index == video_stream_index){
  
  
  
              av_frame = decode(codec_context,av_frame,packet);
  
  
  
              sws_context = sws_getContext(codec_context->width,codec_context->height,codec_context->pix_fmt,codec_context->width,codec_context->height,
  
                      AV_PIX_FMT_RGB24, SWS_BICUBIC,nullptr,nullptr,nullptr);
  
  
  
              sws_scale(sws_context,
  
                      av_frame->data,
  
                      av_frame->linesize,
  
                      0,
  
                      codec_context->height,
  
                      gl_frame->data,
  
                      gl_frame->linesize);
  
  
  
              sws_freeContext(sws_context);
  
  
  
              if(first_use == true) {
  
  
  
                  glTexImage2D(GL_TEXTURE_2D,
  
                               0,
  
                               GL_RGB,
  
                               codec_context->width,
  
                               codec_context->height,
  
                               0,
  
                               GL_RGB,
  
                               GL_UNSIGNED_BYTE,
  
                               gl_frame->data[0]);
  
  
  
                  first_use = false;
  
  
  
              }else{
  
  
  
                  glTexSubImage2D(GL_TEXTURE_2D,
  
                          0,
  
                          0,
  
                          0,
  
                          codec_context->width,
  
                          codec_context->height,
  
                          GL_RGB,
  
                          GL_UNSIGNED_BYTE,
  
                          gl_frame->data[0]);
  
  
  
              }
  
  
  
          }
  
  
  
  
  
      }
  
  
  
  
  
      while( glfwGetKey(window, GLFW_KEY_ESCAPE ) != GLFW_PRESS &&
  
             glfwWindowShouldClose(window) == 0 );
  
  
  
  }

  The frames decode successfully but I cannot see anything. It has to be something with the above gl code that I have done wrong. I can show the ffmpeg code above if necessary.