I have a couple of questions about Freeview's DVB-T spec related to 50Hz and 60Hz transmission. I assume right now that NZ broadcasters use 50Hz for all HD 1080i/720p transmissions to be consistent with the PAL SD stream (please someone correct me if this isn't true). But since most shows from the USA are broadcast in that country in either 1080i/30 or 720p/60, could NZ simply transmit these in their 'original' form without conversion to 50Hz, if they wanted to?

The way I see it the probable answer is no, that would be difficult, since running TV shows sourced from the USA at their 'proper' 60Hz fieldrate will result in a 4% time disparity between the HD broadcast and the SD/PAL broadcasts at 50Hz. Suggests to me that (unfortunately) the PAL speedup issues will remain indefinitely.

Though, that being said, my questions are:

1. Does the Freeview DVB-T specification allow a broadcaster to dynamically switch between 1080i 60Hz and 1080i 50Hz on the fly? From what I understand most HD TVs sold around the world must support both fieldrates so it's more of a question of whether the broadcast spec allows dynamic switching. In effect, if a broadcaster did want to, could they use 60Hz for the duration of one programme?

2. Can a broadcaster switch between 720p and 1080i on the fly, such as 720p/50 for a sport feature and back to 1080i/25 for everything else? I wonder, for example, with TV3's choice of 1080i that they'll miss out on the benefit of fluid 720p/50 for any live sport they broadcast.