What is the model number of your DVRs? Are they from DirecTV?
I have heard that output from these DVRs is usually limited to SVHS quality, that is you can plug an svhs cable in and record to a DVD Recorder or SVHS VCR.
Also you may not be able to copy some content, such as HBO movies or Series, or you may have to do the DVD-R VR mode (which allows only one copy).