Here's a dumb question. If I have Atmos enabled in Windows, do I enable or disable it in-game, like Overwatch?
For best results, you enable Atmos in Overwatch, and turn on Dolby Access. This will decode Atmos, and give you the surround HRTF.
For games where there is a pre-mixed Atmos for headphone audio option in the game’s settings (of which Overwatch is one AFAIK), no Dolby Access licence is required. Where the user also already has a Dolby Access licence, it should be one on and one off, not both on.
Broadly speaking there are two types of Atmos for headphones: ad hoc and pre-mixed.
Ad hoc
Ad hoc is where the Atmos for headphone algorithm is applied by the host system (Xbox or PC) to convert a true Atmos surround audio feed into Atmos for headphone or a standard 5.1/7.1 Dolby surround or PCM surround feed into what is essentially the latest iteration of Dolby headphone virtual surround. (As for a 5.1/7.1 DTS surround feed, can’t remember. I think probably, but if not, then DTS Sound Unbound would work anyway).
In the case of the former, my experience is that games and other media content with true Atmos soundtracks offer fairly convincing height effects/cues when converted into Atmos for headphones.
In the latter case of application to a conventional surround mix, my experience is that Atmos for headphone has better depth projection than traditional Dolby headphone but the supposed upmixing to create virtual height cues and 360 3D effects is slight if there at all (after all, there would be no such cues/effects in the original mix). YMMV here as some users such as MLE report little perceived benefit from applying Atmos for headphone to conventional surround mixes so it will depend on your own HRTF.
In any case, the ad hoc method is done via the Dolby Access app. There is a free 14 or 30 day trial before you have to pay for a lifetime licence which is good for upto 10 registered devices. Just download it and follow the setup guide process. As the multichannel conversion happens at source (the Xbox or PC), whatever dac/amp you use would not need to decode or be able to decode multichannel as it is simply receiving a pre-Dolby-Atmos’d VSS stereo feed. If the game you are playing has multichannel speaker configuration options in its audio settings then you should set it to the highest channel configuration possible. Once done, or if the game has no such audio settings like Shadow of the Tomb Raider (which just means the game engine is looking to the Windows/Xbox system settings for multichannel configuration), then just activate Atmos for headphone in your system’s audio settings and you are good to go.
Pre-mixed
This is where Atmos for Headphone is available as a pre-converted / pre-mixed audio option in the game itself’s audio settings, meaning it’s been pre-mixed into the game’s audio engine by the devs themselves. In this case, you
don’t need the Dolby Access app / licence. You just select Atmos for headphone from the game’s audio settings and ensure that all other VSS processing algorithms are turned
off in your system settings and on any external dac/amp devices.
AFAIK, Overwatch Atmos for headphones is an example of pre-mixed. If you have a Dolby Access licence, you want to ensure that Atmos for headphones is
turned off for games like Overwatch otherwise you will be double-binauralising and distorting / exaggerating cue placement. Alternatively, you could have Atmos for headphone turned on in your system audio settings but the in-game pre-mixed Atmos for headphones de-selected and replaced with a true atmos speaker config setting instead and see which implementation works better for you. Either way, for accuracy, it should be one on and the other off,
not both on.