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• How do I generate a lossless video file with chrome.tabCapture.capture ?

  10 juin 2019, par Black-Hole

  Problem Description :

  chrome.tabCapture.capture will generate a stream, I use MediaRecorder to operate.
  But MediaRecorder only supports webm video format.
  Webm video format will compress my recorded video

  If I recorded the tab page, nothing changed for 10 seconds (including no mouse movement, no sound), the entire web page is still. Then the final webm video file will have only one frame, not even one second.

  Is there any way to solve this problem ? Because I don’t want compressed video

  Core Code :

  let mediaRecorder = '';
  
  
  
  chrome.tabCapture.capture(captureConfig, stream => {
  
    if (stream === null) {
  
      chrome.tabs.sendMessage(id, {
  
        error: chrome.runtime.lastError
  
      });
  
      return false;
  
    }
  
  
  
    const recordedBlobs: BlobPart[] = [];
  
    mediaRecorder = new MediaRecorder(stream, {
  
      videoBitsPerSecond: 2500000,
  
      mimeType: 'video/webm;codecs=vp9'
  
    });
  
  
  
    mediaRecorder.ondataavailable = event => {
  
      if (event.data && event.data.size > 0) {
  
        recordedBlobs.push(event.data);
  
      }
  
    };
  
  
  
    mediaRecorder.onstop = () => {
  
      const superBuffer = new Blob(recordedBlobs, {
  
        type: 'video/webm'
  
      });
  
  
  
      const link = document.createElement('a');
  
      link.href = URL.createObjectURL(superBuffer);
  
      link.setAttribute('download', `${filename}.webm`);
  
      link.click();
  
    };
  
  
  
    mediaRecorder.start();
  
  });
  
  
  
  const stop = () => {
  
    mediaRecorder.stop();
  
    mediaRecorder.stream.getTracks().forEach(track => {
  
      track.stop();
  
    });
  
  }

  I am using chromium, can be replaced by chrome, as long as it can solve this problem.
  I also tried ffmpeg, but still can’t, those lost frames seem to be unable to recover.

• Progress with rtc.io

  12 août 2014, par silvia

  At the end of July, I gave a presentation about WebRTC and rtc.io at the WDCNZ Web Dev Conference in beautiful Wellington, NZ.

  

  Putting that talk together reminded me about how far we have come in the last year both with the progress of WebRTC, its standards and browser implementations, as well as with our own small team at NICTA and our rtc.io WebRTC toolbox.

  

  One of the most exciting opportunities is still under-exploited : the data channel. When I talked about the above slide and pointed out Bananabread, PeerCDN, Copay, PubNub and also later WebTorrent, that’s where I really started to get Web Developers excited about WebRTC. They can totally see the shift in paradigm to peer-to-peer applications away from the Server-based architecture of the current Web.

  Many were also excited to learn more about rtc.io, our own npm nodules based approach to a JavaScript API for WebRTC.

  

  We believe that the World of JavaScript has reached a critical stage where we can no longer code by copy-and-paste of JavaScript snippets from all over the Web universe. We need a more structured module reuse approach to JavaScript. Node with JavaScript on the back end really only motivated this development. However, we’ve needed it for a long time on the front end, too. One big library (jquery anyone ?) that does everything that anyone could ever need on the front-end isn’t going to work any longer with the amount of functionality that we now expect Web applications to support. Just look at the insane growth of npm compared to other module collections :

  

  For those that – like myself – found it difficult to understand how to tap into the sheer power of npm modules as a font end developer, simply use browserify. npm modules are prepared following the CommonJS module definition spec. Browserify works natively with that and “compiles” all the dependencies of a npm modules into a single bundle.js file that you can use on the front end through a script tag as you would in plain HTML. You can learn more about browserify and module definitions and how to use browserify.

  For those of you not quite ready to dive in with browserify we have prepared prepared the rtc module, which exposes the most commonly used packages of rtc.io through an “RTC” object from a browserified JavaScript file. You can also directly download the JavaScript file from GitHub.

  

  So, I hope you enjoy rtc.io and I hope you enjoy my slides and large collection of interesting links inside the deck, and of course : enjoy WebRTC ! Thanks to Damon, JEeff, Cathy, Pete and Nathan – you’re an awesome team !

  On a side note, I was really excited to meet the author of browserify, James Halliday (@substack) at WDCNZ, whose talk on “building your own tools” seemed to take me back to the times where everything was done on the command-line. I think James is using Node and the Web in a way that would appeal to a Linux Kernel developer. Fascinating !!

• how to copy mp4 file generated by FFMPEG spawn using another FFMPEG spawn

  2 mai 2021, par Abadi

  I am using the following code that records screen on Linux and the output is an mp4 file.

  


  const transcodeStreamToOutput = spawn('ffmpeg',[
'-hide_banner',
'-loglevel', 'error',
// disable interaction via stdin
'-nostdin',
// screen image size
'-s', `${BROWSER_SCREEN_WIDTH}x${BROWSER_SCREEN_HEIGHT}`,
// video frame rate
'-r', `${VIDEO_FRAMERATE}`,
// hides the mouse cursor from the resulting video
'-draw_mouse', '0',
// grab the x11 display as video input
'-f', 'x11grab',
    '-i', `${DISPLAY}`,
// grab pulse as audio input
'-f', 'pulse',
    '-ac', '2',
    '-i', 'default',
// codec video with libx264
'-c:v', 'libx264',
    '-pix_fmt', 'yuv420p',
    '-profile:v', 'main',
    '-preset', 'veryfast',
    '-x264opts', 'nal-hrd=cbr:no-scenecut',
    '-minrate', `${VIDEO_BITRATE}`,
    '-maxrate', `${VIDEO_BITRATE}`,
    '-g', `${VIDEO_GOP}`,
// apply a fixed delay to the audio stream in order to synchronize it with the video stream
'-filter_complex', 'adelay=delays=1000|1000',
// codec audio with aac
'-c:a', 'aac',
    '-b:a', `${AUDIO_BITRATE}`,
    '-ac', `${AUDIO_CHANNELS}`,
    '-ar', `${AUDIO_SAMPLERATE}`,
// adjust fragmentation to prevent seeking(resolve issue: muxer does not support non seekable output)
'-movflags', 'frag_keyframe+empty_moov',
// set output format to mp4 and output file to stdout
'-f', 'mp4', '-'
]


  


  ) ;

  


  I need to run ffmpeg -i captured.mp4 -c copy new.mp4 using another spawn process on the output.
I tried the following :

  


  const newStdOut =  spawn('ffmpeg',[

    '-i', `${transcodeStreamToOutput.stdout}`, 
    '-codec:v', 'copy', 
    '-codec:a', 'copy', 
    '-f', 'mp4', '-'
    ]
);


  


  But it is not working. I would appreciate any help.