Macbook pro to Panasonic Viera GT30 TV?

I have a brand new 15 inch Macbook pro with a high res antiglare screen. I connected it to my brand new Panasonic Viera GT30 plasma TV via an HDMI cable and a Moshi minidisplay port to HDMI adapter. The computer is in mirror mode and the resultion automatically goes to 1080p. The desktop does appear on the television, however the problem is that the picture that appers ont the TV does not fit the whole screen. the top and bottom is cut off slightly and the right and left have blak bars on them. Why is this? Is there anyway to fix this?

Every video i watch of people hooking up their new macs to their tv's shows the desktop or video they r playing filling the whole tv screen. I would like to do the same. Thx!