Some DVDs I have won't let me switch audio (like between commentary tracks)
without going back to main menu and then clicking audio options, etc.

Some with no problem, just hit the audio button on DVD remote?

Alien Quadrilogy is an example?

Why would companies do this?

I really hate this too. Why do they do it? I guess because it forces you to go through their shitty animated and time consuming menus. I swear, with most DVDs released in the last couple of year practically half of your DVD player's remote buttons are freakin' disabled. It's really stupid.

I've never encountered this before. How stupid of an idea.

Doesn't seamless branching often cause the disabling of on-the-fly audio switching?

Universal are notorious for it.

I've encountered that problem with subtitles.

subtitles and close captioning are another can of worms for me - two things that are inconsistent and troubling for the hard of hearing/deaf community who watch movies at home.

Often when I choose DTS audio on a DVD, it gives me a warning about having equipment capable of handling DTS. I always assumed that discs that disabled audio switching was supposed to protect non-DTS stereo systems from being damaged by the digital blitzkrieg they would be unable handle if a user switched into DTS. That said, some discs will let you switch to DTS on the fly.

It's called crummy dvd layout and programming...

I believe going to DTS on a system that doesn't support it simply outputs silence. At worst it'd probably be no worse than sticking a data CDROM in a very old CD player and hearing clicks and noise (if I'm wrong, maybe somebody could point out some information on it).

I have a few DVDs that only allow you to view subtitles through the setup menu, NOT from the remote control while watching the movie.

"Scrubs" Season sets piss me off with this. You can't easily get to the commentary track on the 1 or 2 episodes they have it on. Irks me to no end.
But, if you select the commentary track prior to watching ep, then you can toggle in and out while watching. weird freggin systems.

That noise is what could damage their speakers. Some players may do silence but others may not.

I believe that sometimes branching is what causes this to be disabled, since selecting a track isn't registered in memory the way it is when selecting from the menu. If a title has branching but you switched tracks on the fly, when it gets to the next branching point it will go back to the default audio track.

I thought this mainly was the case for older releases, pre 2000 titles. Is this still happening with new stuff? Not only could you not change the audio on the fly with the older releases, but alot of them defaulted to 2.0.