There are a few scenarios where previews will fail to show:
- The person accessing the file could be using an old browser which doesn't support media playback for example; older versions of Internet Explorer. To ensure they have at least the ability to download files we display a basic version of the download page that won't show previews.
- For more modern browsers that don't natively support media playback we require Adobe Flash to enable previews. If the user doesn't have this installed they will see a placeholder requesting that they install support for this.
- If the downloader accesses the files before our system generates previews they will see a placeholder with the text "Generating previews".