Boxee will play recordings from the mythtv backend. All you need to do is add the mythtv backend as a source.
Here is how:
- Navigate the menu->settings->media sources->Manually add source
Source Name: Mythtv Source Location: myth://username:password@ip_OR_hostname/
- Check on Video, Check on Private
To Playback videos:
This is an older post, you don't need to do it if you follow the instructions above. http://forum.boxee.tv/showthread.php?t=286