I've a HDHomeRun (hardware, 2 tuner unit) along with Elgato EyeTV Digital TV Recorder (Software). It basically ports High Definition to my LAN, the Elgato running on my iMac pulls the signal and provides DVR functionality on the iMac. It saves files in proprietary format but does provide translation (Export --->) to multiple conventions, i.e.: MPEG, MPEG-4, HD 720p, HD 1080p, Apple TV HD, . . . . .
You get the idea.
If you can get at the HDD where your DVR files reside, copy them to another storage device, there may be tools, even free tools to convert and manipulate to your own end goals.