Sorry for my poor English!
I had the similar problem, here is an assembly:
Toshiba L850-18Z -> HDMI -> AVR70 (H / K) -> TV (Panasonic - plasma)
Video card is: AMD Radeon HD 7670M and all drivers are successfully installed, but no DTS over HDMI from AVR?!
I tried everything but no DTS sound via AVR, just out of the TV ...
was the simplest!
1. Connection: laptop – hdmi - AVR (in my case HDMI port 2) - TV,
2. Extended desktop, to recognize TV
3. With remote control the AVR choose "TV", then „Setup” and with arrows „↑ ↓” reach „HDMI SET”, choose the HDMI AMP! Then go out with „back-exit” and get back to HDMI port 2 and with "digital" choose "H"!
Good luck to all!