title: How to use FFMPEG to capture a browser's tab content
body: <p>I'm working on a project where I need to record HTML5 animations that are going to play in different browser's tabs. </p>
  
  <p>So I've been reading a bit, and apparently it could be done using FFMPEG, maybe using the gdigrab device: 
  <a href="https://www.ffmpeg.org/ffmpeg-devices.html#gdigrab" rel="noreferrer">https://www.ffmpeg.org/ffmpeg-devices.html#gdigrab</a></p>
  
  <p>Where you can even grab from a specific window (<em>like record calc.exe using title=Calculator</em>)</p>
  
  <p>I want to use this logic to capture each of the multiple browser tabs contents. (<em>or at least one</em>) But I don't know the Firefox/Chrome tabs "title" or if they even work as windows.</p>
  
  <p>I'd also need to record audio, so I would need to either mix the computer's output device with the video from the tab.</p>
  
  <p>If anyone has more information on how I could do this, I would greatly appreciate it.</p>
  
  <p>Thanks,</p>