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• 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.

• How to convert an ffmpeg texture to Open GL texture without copying to CPU memory

  19 avril, par PPP

  This ffmpeg example demonstrates how to do hardware decoding : https://github.com/FFmpeg/FFmpeg/blob/release/4.2/doc/examples/hw_decode.c

  



  At line 109 it does this :

  



  /* retrieve data from GPU to CPU */
            if ((ret = av_hwframe_transfer_data(sw_frame, frame, 0)) < 0) {


  



  I want to avoid this because it takes time. Therefore, I need a way to reuse that decoded video, which is in GPU memory, to redo color conversion.

  



  How to transform the decoded texture in GPU memory to texture in Open GL without getting it back to CPU memory like in the code above ?

  



  If the above is not possible, how to do color conversion in the decoded video using open gl ? I heard that ffmpeg supports passing opengl shaders as input, so I guess it's possible.

  


• How do I make ffmpeg not open a window when used in Python (Discord Bot Youtube Audio Player Pytube)

  20 juin 2019, par Brandalf

  I am using pytube to create a Discord bot that gets audio from a YouTube video and plays it in the voice channel using the code below. The code works perfectly fine and does what I want which is playing audio from YouTube with a link. The issue is that it uses ffmpeg and when it does, it opens the ffmpeg.exe window. Having a window constantly pop up on my screen is kind of annoying but what’s worse is that if I am playing a game in full screen, when ffmpeg is run, it will tab out of my game. So I’m wondering if there is a way to prevent ffmpeg from opening the window or if there is an alternative to playing youtube audio in Discord with a bot that doesn’t use ffmpeg.

  user=ctx.message.author
  
  voice_channel=user.voice.voice_channel
  
  vc = await client.join_voice_channel(voice_channel)
  
  player = await vc.create_ytdl_player(videoLink)
  
  video = pafy.new(videoLink) #runs ffmpeg
  
  player.start()