How are HD broadcasts produced?

are all HD programs filmed in HD, or are some older shows which were originally shot in SD just upscaled by the networks and then just broadcasted in HD? just curious because i guess that would explain why some HD shows look much better then others. Is that why DiscoveryHD looks so better then other HD channels?

Also, is SD considered 480i or 480p?

I think its 480i, but is it possible that some SD channels like HBO (not HBO HD) are broadcasted in 480p?

Everything on DiscoveryHD was shot in HD. That's not true of all HD channels - TNT-HD runs endless Law & Order re-runs, most of which were shot before HD was around.

SD television programs are going to be in 480i.

thanks for the info gonk