Thanks for the info.
Using Nero I can select, Progressive, or bottom layer first, or top layer first.
There is also a selection for "automatic", will selecting "automatic" do the job properly to achieve best quality ?
PS - just noticed in the same selections with Nero, you can choose 16:9 and 4:3 etc.
If I am workng with 16:9 files and choose to have them at 4:3 will Nero degrade the quality ?, I think I have read before Nero doesn't do a proper job of this ?