I had found that after editing a DVD the subtitles would be on by default when playing the DVD which naturally I didn't want. I then hit upon the idea of inserting the command 'sub-picture = 0 (track 0:OFF)' as the first command in the root menu. This worked fine and subtitles would now be off by default when playing (although I could then turn them on via the remote as required).

However I now see that this is a little too simplistic because when I turn subtitles on with the remote and then navigate around the DVD (say to another chapter) the subtitles are turned off again. Presumably this is because I'm navigating via the root menu which then reissues the command to turn off subtitles before taking me to the new point on the DVD. I'd like to be able to still have subtitles off by default but when I turn them on have them remain on regardless of navigation until I wish to turn them off again.

I assume this is how 'well designed' DVD's work although I'm beginning to realise that a number of 'professionally created' DVD's may not have good navigation design.