title: Main content starts playing before preroll in video.js when using videojs-contrib-ads
body: <p>When using videojs-contrib-ads to create an ad plugin in video.js, the main programme often starts playing before the ads start playing.  It seems that video.js connects to the CDN of the main content initially and then contrib-ads checks if it needs to play prerolls.  A few seconds of the main content is sometimes played before this happens and only then does it start to play the adverts.</p>
  
  <p>This was seen mostly on iOS on live feeds.</p>
  
  <p>Does anyone know why it works like this and is there a way to stop it?</p>