Weird DTS problem

Hello everybody, I'm new here, I hope I'm asking this question in the right place. As the title claims, I have a weird problem with DTS sound. This is the thing (and sorry if I make this too long, I tend to over-explain things): I bought my computer a few months ago, a little less than a year. I have it connected via SPDIF to a SONY audio receiver that can play both Dolby Digital and DTS sound in 5.1. I went through all the trouble that is configuring the sound. Once done, I managed to make everything work as it should (apparently). Inside the properties of my sound device, under the "Compatible formats" tab, I check the Dolby Digital box and test it. In my audio receiver the display shows the title "Dolby Digital 3/2.1" and I listen to a short sound from each speaker at a time, as it should be. Then I check the DTS Audio box and the audio receiver display shows the title "DTS 3/2.1" and I listen the same short sounds from each speaker at a time, as it should be! So far, so good. I play videogames and they are in 5.1, just as I want them, I listen to music in Winamp, everything works as expected. I watch movies in dolby digital sound format, everything is perfect. BUT! When I play a video file with DTS sound... I listen 5.1 just as I should, but the audio receiver doesn't display the DTS title. The display keeps showing the DD logo instead. So here's my question: Am I actually listening to DTS audio? Is this the way it's supposed to work? If not... How am I listening to everything just fine? Is my PC converting the DTS to Dolby Digital before sending the audio signal to the Audio receiver? I use KMPlayer but I tried the same video files with another sofware (Classic Media Player) and the result is the same. I also made sure the video file has DTS format and not Dolby Digital. It's not crucial, but I would like to know if I can solve this anyway. Of course you can ask for any specifications. Thanks in advance. Here go the frequent specs:

OS: Windows 10
CPU: AMD Ryzen 7 2700
Motherboard: A320M-S2H-CF
RAM: DDR4 8GB
Audio card: ASUS Xonar DX audio device

I this case it is important that you configure your media player to do Dolby/DTS passthrough. I don't know KMPlayer unfortunately. In VLC player you would set the audio output option "HDMI/SPDIF audio passthrough to either "enabled" or "enabled AC3/DTS only".

Perhaps you can find out if KMPlayer has a similar option.

Firstly, thanks to Ben Hastings for the help, it was actually half of the solution, and apologize for not replying for this long. I decided to publish the solution just in case anybody with the same problem stumbles uopn this thread. As Ben explained, I had to configure my media player (in my cas KMPlayer). It wasn't easy, because everything isn't too clear, but after trial and error I did manage to understand how to configure it right. But as stated before, this was only half the solution. As it turns out, I wasn't using my ASUS Xonar DX soundcard, but the onboard soundcard. The way I understand it is that the onboard soundcard encodes EVERYTHING into Dolby Digital 5.1. When I tested the sound in the device properties, as I was testing from the ASUS Xonar soundcard the home theatre received DTS indeed, but only that. When I changed the configurations to make the "S/PDIF Pass-through Device (Asus Xonar DX Audio device)" default, I finally got to enjoy true DTS sound in my movies. I still have to change the configuration when playing games, because apparently the ASUS Xonar DX soundcard does enconde Dolby Digital but not 5.1 in games. So, problem solved. Ben Hastings, thanks again. Bye!