AUDIO: ScummVM engaging Windows Surround Sound plugins

[Purplemoustache]

ScummVM 2.1.1a (Feb 3 2020 21:46:14)

Using following sound settings:
Preferred Device MT-32 Emulator (with roms at the base installation directory)
AdLib emulator set to OPL3LPT

GM device set to Microsoft GS Wavetable Synth [Windows MIDI]
Using the latest version of the FatBoy MIDI soundfont (housed in the ScummVM extras folder)

I am a surround sound enthusast without the space, money or time to actually...have a surround sound setup. As a result, I use the system level windows virtual surround plugins, Windows Sonic, Dolby Atmos for Headphones, and DTS:X. I have all 3, but mostly use DTS:X, and occasionally Dolby Atmos. The way these plugins work is, if engaged, will pass through stereo and mono audio as Stereo/Mono and not turn on, but if a 5.1 or 7.1 (and presumably quad, tri, etc) signals are sent by an application it will switch on and down mix those signals to a stereo signal built for headphones. Bonus points if the application was built with DTS:X or Dolby Atmos For Headphones in mind, as a special version of the plugin will kick in based on object based 3D audio.

ScummVM engages this for all games, mono, stereo, old, new, etc. You can tell when it's "on" as opposed to passing through a stereo/mono signal by clicking the windows volume slider icon on the dock, a small message that says "[Insert plugin name here] is in use" just below the volume slider. The audio... does sound like it's being processed, forcing output to two channels to the front of the user. Considering (AFAIK) no games in ScummVM output true surround sound, this is an oddity.

[lotharsm]

I can't test this on my own since I don't have a surround sound setup here.

Can you please check if this also happens with other SDL2 applications so we can rule out a general SDL2 issue here?

[Purplemoustache]

I just ran ResidualVM's implementation of Grim Fandango and The Longest Journey. My understanding is as of 0.3.0 they are SDL2 based. The surround sound plugins do not activate using ResidualVM.

A surround sound setup is not required to test this, as Windows Sonic, Dolby Atmos for Headphones and DTS:X are implementations of surround sound down-mixing for headphones. As part of the Xbox division's drive for 3D audio, these plugins are baked into the Windows audio system. Windows Sonic is free, while Atmos and DTS:X are paid.

[sev-]

This is an SDL issue, not ScummVM. Most probably you have to set up some settings there. We are just providing a stereo stream to SDL.