[mythtvnz] Video output resolution question

[Paulgir]

I've been making progress with my mythbuntu installation/set up.
I have it tuning all the freeview channels on both tuners and have been
Playing around with the controls to get familiar with the software.
I have enabled VDPAU.I have the audio and video goind to the TV via
the HDMI port on the GT430 card,
Here's the question: My TV displays the resolution for the inputs as
you select them.The resolution for the myth signal is always 720P.
even if the same channel via the TV's digital tuner indicates that it is
1080i.
How do I correct this?
Have I missed something in the set up?