Mr.T said:
You will find the definitions of UPconverting and DOWNconverting an HD signal here:
http://www.wishtv.com/Global/story.asp?S=1052725
Geez, those definitions are pretty simplistic, and not exactly accurate.
Many new receivers offer up and down conversion as it is a by-product of what they need to do to use on-screen menus for component video. They are using chips inside that can output over composite, s-video, and component. So, they spend five bucks more and allow the video to be converted (up/down) to match one of those formats.
Now, I am not sure about HD down converting to 480i, but you do get simpler cabling, if you want it, by up converting and just using a component connection to your display. I have never heard anyone complain about added noise or distortion from running their s-video/composite equipment through a receiver and having it processed. Most display devices process the video signal anyway.
Bottom line is that people have been paying thousands of dollars for years to Faroudja and other companies to get good video processing. It used to be $10,000.00 for a cheap doubler, now it is 'standard' to have some sort of processor in most $1,000.00 receivers. How good the processing is, definitely could be put to a test, but I would expect that if you are using it with SDTV, VCR, and a video camera then you won't be complaining at all.