[vdr] multiple DVB cards sharing a CAM??

Hi - idiot question....

Is there any config changes needed when I add a second DVB card to my system? Can the 2 cards share a single CI/CAM?

My first card is a budget TT1500-C with CAM (all channels are encrypted). I just tried adding a TT-2300-C FF card with no CAM (sharing the TT-1500-C CAM) but I can't get any picture on the DVB video-out? /var/log/messages looks like it's decoding ok, but no picture.

(Don't know if this is causing any additional problems, but I have no TV to test with so am using tvtime to monitor /dev/video0)

Thanks

Simon