What happens to DVD encoding with simultaneous HD versions being released?

When they encode DVD's nowadays, are they using a new method since the simultaneous release of a high def Disc transfer? Are they taking shortcuts, perhaps using a codec to encode a perviously used master done in another codec? Are they being encoded without any influence by a high def transfer, even if this means that they have been given less (compute time, etc) priority? Sorry if this has already been answered.

The master tape is already digital so they are using that in a separate process for each transfer then. The movie I had in question was MI3. I read that a few were saying it was not perfect on HD so it must be something to do with the original. I had imagined that if it had looked this bad on DVD perhaps it looked even worse on HD but this may not be the case then. I didn't see any real complaints about it, but for me, it was almost unbearable to watch. That is why I asked.