title: ffmpeg - very slow conversion
body: <p>I create web app in JavaEE which displays many video formats. I use ffmpeg solution to convert videos to formats which is supported natively by main browsers. </p>
  
  <p>According to : <a href="http://www.jwplayer.com/html5/formats/" rel="noreferrer">http://www.jwplayer.com/html5/formats/</a> 
  I convert to WEBM container (VP8/VORBIS or VP9/OPUS). But conversion is very slow, bit rate equals to ~ 200kbits/s. To convert I execute following command</p>
  
  <p><code>ffmpeg -i file.mov -c:v libvpx -preset ultrafast result.webm
  </code>
  How to speed up conversion to natively supported formats by main browsers?</p>