Convert/import .PVR to MP4 freely

" I got a set top box which records TV programs to USB in .PVR format. For I always use PVR to record many interesting TV Shows for reviewing anytimes. But it's trubled me that i can't watch the videos when i was travelling. I also try to import .pvr files to my ipad , but it can't play .pvr files. How can i do? " "I want to share my funny videos for PVR to Youtube, but Youtube didn't support .pvr files."