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• Add Meta-Data to OpenCV VideoWriter as it records

  29 avril 2016, par Kells1986

  I have some simple code that records video at 3 frames per second using openCV 2.4. The code is running on a Raspberry Pi, which is going to be powered by a battery for about 5 minutes before it will die.

  Because the Raspberry Pi dies the video recording does not terminate gracefully, and it seems that the meta-data isn’t written to the file properly.

  mplayer is capable of playing the file back, but what I would like to do is post-process the video in some existing software. In order to be able to do that the software needs to extract the number of frames in the video from the meta-data, which it cannot do at present.

  Is there anyway of forcing openCV to write the meta-data as it records ? Or can I get mplayer / ffmpeg to fill in the gaps later ?

  Here is the code that records the video :

      VideoCapture cap(0); // open the default camera
  
      cap.set(CV_CAP_PROP_FPS, fps);
  
      cap.set(CV_CAP_PROP_FRAME_WIDTH, 1280);
  
      cap.set(CV_CAP_PROP_FRAME_HEIGHT, 720);
  
      if(!cap.isOpened())  // check if we succeeded
  
          return -1;
  
  
  
      Mat testFrame;
  
      cap >> testFrame;
  
      cap >> testFrame;
  
      cap >> testFrame;
  
  
  
      Size outSize = Size(testFrame.cols, testFrame.rows);
  
      VideoWriter writer(filename, CV_FOURCC('M','J','P','G'), fps, outSize, true);
  
  
  
      int count = 0;
  
      for(; ;)
  
      {
  
          Mat frame;
  
          cap >> frame; // get a new frame from camera
  
          writer.write(frame);    
  
      }
  

• ffmpeg : Continiously encode and append base64 data chunks into output file

  11 février 2021, par O.O

  I have a .mov file thats being written into by my iphone cam saved as input.mov and I have a script that's reading the currently updating file and I am trying to encode the video and audio codec into a .mkv container.

  


  I have little knowledge of this tool, but looking at similar Q/A's around ffmpeg usage I have found little on using base64 as input. But it is documented by ffmpeg for images, so I assume it is possible and I have also used data:video/mp4 since these file types are very similar.

  


  I have :

  


  const ifRecordingStream = await fs.readStream('input.mov', 'base64', 4095);
ifRecordingStream.open();

ifRecordingStream.onData((chunk) => 
    execute(`ffmpeg -f concat -i "data:video/mp4;base64,${chunk} -c:v h264 -c:a aac output.mkv")
);


  


  onData() currently throws Line {}: unknown keyword {}

  


  Is my command wrong ?

  


  ffmpeg -f concat -i "data:video/mp4;base64,${chunk}" -c:v h264 -c:a aac output.mkv

  


  Any help at all is welcomed.

  


• fftools/ffmpeg_demux : add demuxing thread private data

  5 janvier 2024, par Anton Khirnov

  fftools/ffmpeg_demux : add demuxing thread private data
  To be used for data that never needs to be visible outside of the
  
  demuxer thread, similarly as was previously done for other components.
  

  • [DH] fftools/ffmpeg_demux.c