that Original HD programming should always be shot at 1080,it goes through post-production at 1080 & is delivered at 1080....After that broadcasters then may choose to downconvert & broadcast at 720. Add on the fact that this 720 broadcast is heavily compressed as well & you end up with something that is far away from the original resolution.
Progressive Segmented Frame is a method of showing a progressive picture on an interlaced monitor.So when shooting HD its always advisable to shoot PSF instead of interlaced apart from Sports where interlaced is advised....