Recherche avancée

Sur d’autres sites (4627)

• 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.

• ffmpeg generate first non black frame

  17 octobre 2019, par Milousel

  I get via readstream video from AWS server. I modify it into different format and save it back into server. After that I want to create non black image from first frame of this video. So I need to check if first frame is black or not.

  ffmpeg(stream)
  
          .size('1320x438')
  
          .videoCodec('libx264')
  
          .toFormat('avi')
  
          .output(fileName)
  
          .on('end', function() {
  
            console.log('Finished processing video');
  
            const params = {
  
              Body: fs.createReadStream(fileName),
  
              Bucket: videoBucket,
  
              Key: 'test/modification/' + fileName,
  
            };
  
            s3.putObject(params, (err, data) => {
  
              if (err) {
  
                console.log(err);
  
              }
  
            });
  
          })
  
          .output(screensName + '.jpg')
  
          .outputOptions(
  
            '-frames',
  
            '1', // Capture just one frame of the video
  
          )
  
          .on('end', function() {
  
            console.log('Finished processing screenshot');
  
            const params = {
  
              Body: fs.createReadStream(screensName + '.jpg'),
  
              Bucket: videoBucket,
  
              Key: 'test/shots/' + screensName + '.jpg',
  
            };
  
            s3.putObject(params, (err, data) => {
  
              if (err) {
  
                console.log(err);
  
              }
  
            });
  
          })
  
          .run();