title: FFmpeg Windows directshow filter
body: <p>I'm trying to open a directshow video source (webcam/push source) using the ffmpeg api however I'm not having any luck. 
  I've tried using </p>
  
  <pre><code>av_open_input_file()
  </code></pre>
  
  <p>however I don't think this is the right way... Does anyone have any pointers?</p>
  
  <p>I'm using visual studio and c++ on a windows system</p>