For visualization to work with these TV cards I believe PCI passthrough is needed. The new Xen 4.0 might help here.

Xen PCI Passthrough

Xen version 3.0 released in 2005 was the first version to support PCI passthrough. You can use PCI passthru to assign a PCI device (NIC, disk controller, HBA, USB controller, firewire controller, soundcard, etc) to a virtual machine guest, giving it full and direct access to the PCI device.

The guest (domU) needs to have a driver for the actual PCI device, just like on baremetal without Xen. Paravirtual (PV) guests also need to have a generic Xen PCI frontend driver.

Dom0 also needs to have the Xen pciback driver for the PCI passthru to work.