There were a few causes. One was that on some models, surround only works from some sources. The other reason is that most video files I find are simple stereo.
My Samsung LCD is connected by digital optical cable to DVD/HomeCinema (combined) system for sound (and HDMI for video). And when I play DVD's everything is great. But when I try to play movies from USB on TV, I don't have surround sound - just get the usual stereo.
I would apreaciate any help.
DVD/Home-Cinema is Sony's DAV-DZ330