Most modern games are capable of delivering discrete 5.1 or 7.1 surround sound to the listener's receiver without the need for any post processing.
Also referred to as Dolby Surround, Dolby Pro Logic II-compatible, Dolby Stereo, or 4-channel surround sound (not to be confused with 4.0 quadraphonic sound). This was first used in theaters in the 1970s, and was introduced to the home alongside VHS and Betamax in 1982, predating discrete surround sound. It was used in many venues and mediums until discrete surround sound became viable. One notable benefit of surround-compatible stereo is that it can be played back on any stereo speakers and still sound normal.
Content mixed in surround-compatible stereo will have a surround effect when listened to over earphones or headphones.
This requires a Dolby TrueHD capable sound card, a Dolby Atmos capable receiver and speaker setup (with at least 2 in-ceiling or upward-firing speakers), as well as Windows v1703 or later and the Dolby Access app.
HRTF (Head Related Transfer Functions) refers to the way that the curvature of one's ears are used to localize sound in 3D space. Algorithms exist that can simulate this action, allowing for full 3D surround sound with just a normal pair of earphones or headphones. The resulting audio is refered to as binaural. While some games, such as CS:GO and Quake Champions include built-in HRTF options, many other games do not; requires external wrappers to enable. As such, it is not recommended for online usage. Listed are methods for adding HRTF using various APIs.
A pre-configured version of DSOAL that includes compiled HRTF tables can be found here. Note that while listed as being for Fallout New Vegas, it can work with most DirectSound3D games.
HRTF data (2)
makehrtf.exe -r RATE -d sphere -i YOURDEF -o YOURMHR
makehrtf.exe -m -r=RATE -d=sphere -i=YOURDEF -o=YOURMHR
X3DAudio HRTF is a third-party injector for games using X3DAudio that converts the original spatial sound of the game into binaural sound instead. The tool works for Arma 3, Skyrim, and Fallout 4, but should also potentially work for other titles, including ones based on Unreal Engine 4 or developed using the Unreal Development Kit (such as The Vanishing of Ethan Carter).
Some games do not support true binaural audio mixing. For these games, it may be beneficial to use a virtual surround sound solution.
See DirectSound 3D restoration software.