Couple good tips.
Hi Nishik,
Are you from Lithuania? Just curious.
Congratulations on your Onkyo HT9100THX system, it is one of the very best in that category.
#1. My best guess on your problem is that the connections from your DVD or Blu-ray player are not fully inserted into their respective jacks. Please, recheck and fully insert them, in particular the RCA jacks.
#2. Also, I would replace the speaker cables with a higher gauge, say 16AWG, and making sure that they are properly inserted into the speaker's posts.
Twist the ends (about 3/8 of an inch), by making sure no threads are touching the back panel of your receive, when you insert them and tight them up.
The speaker's cables that come with your system is approximatively 20AWG, which is a pretty cheap gauge. Just buy a roll of hundred feet of 16AWG.
And follow the instructions from your manual to how properly install them at both end of your system (receiver and speakers).
* Try these two tips, and let us know.
Cheers,
Bob