VDR Software Decoder Plugin
Historically, VDR required an AV711x based DVB PCI card to decode Audio and Video and to render it's OSD. Since these cards are quite expensive and old-fashioned now you can alternatively install the VDR Software Decoder Plugin which is even able to decode HDTV channels, and avoids the limitations and problems of the AV711x based PCI cards.
However, this plugin is not installed by default, so you have to expect some amount of work to get a software-decoder based VDR setup running.
As far I know there have been two alternatives: the Xine-Plugin and the softdevice plugin (is this correct?).
there is no public consensus whether the word "old-fashioned" is politically correct, all texts written here are based on the purely subjective experiences of the authors, feel free to add your very own personal opinions and make this text as objective as it can get only if many authors share their experiences. See the VDR-Wiki for manuals and install instructions regarding VDR.
Sadly, no portable OpenGL-based renderer is known which would allow to build a STB with any cheap modern graphics card. (is this true, allows the xine-plugin OpenGL outputs?)