how can I convert ivdr video on a disk from a hitachi ivdr-s

Hi all, I have a friend whose old hitachi tv is dying so they copied a number of videos they care about to an ivdr disk using the built in ivdr recorder.

We are sourcing the usb adapter but I am fairly certain there will be some kind of proprietary copy protection in use preventing playback/conversion.

I can’t find any real info on this in English – does anyone have any pointers on how this might be worked around? Links in Japanese are fine (they can read though I can’t).

Thank you!