Why is it that when I watch (in KMPlayer for the sake of discussion, but it doesn't get any better on most other players I've tried either) a dvdrip movie (ac3, x264) the sound of people's voices is very faint, but the background sound is very loud.

This is relatively new ... since in the "old days" the movies played ok. So it must be something with the encoding, or with the used player ?

I'm playing it on windows xp on a cheap (i guess) laptop sound card. Nothing special.