This is just FYI, to anyone who might experience the same problem as me. Also it is not directly related to XBMC, but it is related to Revo and HDMI sound routing.
I have a setup of a Linux Revo, hooked up via HDMI to an LCD TV, a Thomson 46", 46E91NF32. The TV has a coaxial audio output. I use this output to route digital audio to my
non-HDMI surround sound decoder (a plain old Creative DDTS-100), which supports both Dolby Digital and DTS.
I had the following problem: Passthrough audio worked
only for Dolby Digital AC3 files,
NOT FOR DTS!
This had me baffling for weeks until just a few moments earlier where I found the solution / workaround.
It appears that the TV (or my decoder) has a "bug", when switching from something else to DTS, the DTS signal is not detected. The workaround is to switch input on the TV to a different one, and then back to the Revo HDMI input, and
voila, DTS sound can be heard.
I'm not sure which device is to blame here, but, hopefully this will help other people with similar hardware like mine.
Other TV codes of Thomson which might have the same problem (for search feature): 37E90NF32, 40E90NH22, 40E91NF32, 40E93NF32, 42E90NF32, 46E90NF32, 46E91NF32, 46E93NF32.