I don't know a damned thing about the technology by which old TV shows are reproduced, but I would like to make a comment.
I am one of the group Gothick so delightfully refers to as the "Ancient Blood"....the kids who ran home after school to watch the original show. I remember the terrible anguish of getting home late and missing even the fewest of minutes of that day's show. Once we missed it, it was gone....no way to get it back. The idea of it being re-run at some later date was unimagined. We just got over it, and made damn sure we ran faster the next day.
The fact that DS, in any of its incarnations, is available to us, in a succession of formats, is a miracle, pure and simple. Yes, it would be nice to have it all, in a perfect and pristine and original state....... but it seems to me to be more than a bit ungrateful to keep bemoaning the lack of perfection, when we could be discussing the show entirely from our ever more faulty memories....and nothing else.