In case anybody is interested: i have written a little PMS plugin for the VDR.
What it does:
It queries the VDR via Streamdev Plugin for its channels and adds the TV channels as direct TS links to PMS (= streaming is done directly from the VDR to the renderer), so that PMS is not bothered with re-encoding or even buffering.
The Radio channels are added as normal web audio links to the ES streams of the VDR/Streamdev (because they need to be re-encoded for the PS3).
I am using with my PS3 and it works quite OK. If there is enough interest i will post the binary and/or post the source on github.
[Edit 3. Dec. 11]
Here is the latest code: :teddibaer/ps3mediaserver-vdr.git
Attached is the latest version, compiled for 1.50 (remember that you may have to rename it to .jar after downloading it).