Re: Does a 768p plasma look best with 720p or 1080i?
Regular DVD, I suggest outputting 480i or 480p and see what looks better.
Hi-def DVD, You'll just have to see what looks better.
Cable box, I suggest native, namely 480i for the 480i shows, 720p for the 720p shows, etc.
For 720p shows or 720p input, try decreasing the picture height (vertical size) to see if a sharp sweet spot develops (with 720 rows of pixels in use). If the same scaling process that does the final conversion to 768p also controls the VSIZE, you might luck out.
There is no choice about converting 1080i in order to get it on your screen. Very few TV's do 1080i to anything else well, but very few cable boxes even match that. Very few cable boxes do 480i to anything else well. DVD players and TV's on average do 480i to 480p about the same but individually it varies all over the map.
DVD player outputting 480i: Player does nothing. TV does 480i to 480p then 480p to 768p.
DVD player outputting 480p: Player does 480i to 480p and TV does 480p to 768p. No unusual problems.
DVD player outputting 720p: Player does 480i to 480p and 480p to 720p, TV does 720p to 768p. Here is where extra processing can half kill you.
Hi-def DVD outputting 720p: Player does 1080i to 1080p and then 1080p to 720p (Or 1080i directly to 720p). TV does 720p to 768p.
Hi-def DVD outputting 1080i: Player does nothing, TV does 1080i to 1080p and then 1080p to 720p. (Or 1080i directly to 720p)
The parenthesized processings are usually inferior. For film source disks, the player will probably do 1080i to 1080p better than the TV and might do 1080i to 720p better than the TV can do 1080i to anything.
Video hints:
http://members.aol.com/ajaynejr/viddoubl.htm