Programmergeek, I'll try to help here. I can't tell if you are looking for a brief explanation or something more technical so I guess I will give you my very brief understanding in hopes that it might help.
480i is simply the signal which is displayed from a non-progressive scan dvd player. Progressive scan dvd players can send the 480p signal. My understanding is that progressive scan is sent at a higher frequency 31.5Khz (480p) as opposed to 15.7Khz (480I). The 480p signal looks better because higher scanning rate. 480p is also what is output from line doublers.
My suggestion to you is to search through this board and find some users who are happy with their particular 480p player. I don't have one simply because I have a htpc.
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