Video input on Mac OS X

Available video input devices for OSX

Currently the following video input devices are supported on OSX:

DV camcorders and DV video converters (drivers are built into the system)
FireWire and USB webcams supported by the IOXperts driver
The XLR8 Interview USB video input device
The Televio PCI TV card from Meilenstein
Certain professional PCI video capture cards such as the Kona
 
Built in video input
Some Macs have built-in video input ports. Unfortunately these do not work on OSX because Apple (nor anyone else) has not provided any OSX driver software for them.
 
TV cards on OSX

The Televio PCI TV card from Meilenstein is a PAL/NTSC compatible TV card that works in OS X.

Also, there is a driver for TV cards on OSX being developed by Andreas Thiede here. It is still in development, but if development goes to plan in the future this driver will work with BTV and allow viewing and capture from any TV card on OSX.
 
Is OSX driver software required?
Yes. BTV (or any other video software) cannot use a video input device unless it has driver software.