Audio routing for playing live music in videogame worlds

❦ Published

Summary: Routing audio from Logic Pro DAW on a Mac to an Open Broadcaster Studio (OBS) livestream on a PC to perform live music in videogame worlds that are sometimes published on YouTube and Spotify as finished improvisational tracks.

Jotted down over the course of lots of trial-and-error to help me remember which thing does what in a tangled mess of real and digital cables while avoiding earsplitting audio feedback, and to help you, dear visitor, to do the same without excess cursing.

(=todo: ¶ Make a diagram and add screenshots, you damned fool! ¶ Figure out how to bring in other human instrument players remotely with tools like Jack Trip, Sonobus, and Jamulus (or just meet them in game : )

Hardware

I have a Scarlett 18i16 audio interface connected to a Mac running Logic Pro, with audio routed to a PC called Interwebs Communotron 2023 with the following cable connections, hereforth represented by an equals sign =

  • Guitar = TRS line cable = Input 1 (on the Scarlett).
  • Hydrasynth Explorer = TRS = Input 2, and MIDI OUT cable = Scarlett’s MIDI IN, to control DAW software instruments (change this around depending on what effects on what instruments we want to combine, and whether we want many instruments simultaneously, or the full-stereo width of the Hydrasynth with two line ins).
  • Numa Compact X SE = TRS = Input 3 (using effects in Logic Pro in addition to its own sound banks; change to use two line inputs for stereo width as with the Hydra above).
  • SM58 mic = TRS = Input 4 (Nota bene: The SM58 is for music vocals. The livestream voice is via a Rode NT-1 connected via USB-C to the PC, described further below).
  • Ambient 0 = Y-split cable (3.5mm-to-two-TRS) = Inputs 7+8.
  • Speakers (audio monitors) = TRS cables = Outputs 1+2 (also heard through the headphone outputs of the Scarlett).
  • PC Line In (blue hole) = 3.5mm female-to-male Ground Loop Isolator (to help prevent line noise) = Y-split = Outputs 3+4 to send the Logic-processed instruments to the PC.
  • PC Line Out (green hole) = Inputs 5+6 via Y-split (to let me listen to, or monitor, the videogame sounds from the PC).

Mac software settings

Focusrite Control settings

Mixer

  • Mix A on the Mac has all Analogue and Playback faders up at normal, except for faders for Analogue 5,6,7,8 cranked up, and Playback 9-10 all the way down for some reason I forget, or maybe that was the default.
  • Mix B on the Mac has faders up, except for Analogue 5 and 6 which are all the way down, muted.
  • Playback faders are all down, except for 3-4 which are up (see Logic Pro section).

Routing

  • Monitor groups > Main Output 1-2 Source set to Mix A to be monitored from headphones (or speakers, though watch out for feedback if using speakers and mics simultaneously)
  • Analogue outputs > Output 3-4 Source set to Mix B
  • Digital outputs > Loopback set to Playback 1-2

Logic Pro settings

I’ve dedicated an output pair in Logic by changing the main stereo output away from the default Playback 1-2 with the following settings:

  1. Logic Pro > Settings > Audio > I/O Assignments
  2. Stereo Output: Output 3/4

By default, the Mac’s system sound (YouTube, Spotify, etc.) will still use Playback 1-2. By moving Logic’s Stereo Out to 3-4, We’ve separated its signal.

Mix B, which routes to PC/OBS (Outputs 3+4), now consists of:

  1. The direct analogue and digital inputs from the instruments (1, 2, 3, 4, 7+8).
  2. The processed Logic output (via Playback 3-4).

Then, we update Mix B (which goes to PC Line In/Outputs 3+4) by adjusting it thus:

  1. Select Mix B in Focusrite Control.
  2. Mute Playback 1-2 faders. This is what carries the Spotify/YouTube audio.
  3. Raise Playback 3-4 faders. This is now only receiving the signal from Logic Pro.
  4. Keep instrument inputs (1, 2, 3, 4, 7+8) up at the desired level.

This way, if we’re listening to music or other sounds on the Mac (which uses Playback 1-2), these will be excluded from Mix B that routes audio to the PC running the OBS livestream.

Mix A (Speakers/Outputs 1+2) can remain as is, with Playback 1-2 raised, so we hear everything as normal. We don’t have to change anything when switching between practicing and listening to music.

To make music played on Mac be heard on PC (for Just Chatting streams that are not published, for example), raise the Playback 1-2 fader on Focusrite Control Mix B.

Our Logic session (all tracks, effects, the whole processed mix) is now being sent digitally to the Scarlett’s Playback 3-4 channels, and the Mac’s general system audio (Spotify, YouTube, etc) is still automatically being sent to the Scarlett’s Playback 1-2 channels, because we didn’t change the Mac’s system sound settings.

PC software and sound settings

On the PC, there’s a Rode NT-1 mic plugged in via USB-C, and we get its audio united with the Line In input with the Scarlett/Mac/Logic instrument sounds (so others can hear me speak and play instruments in video game worlds) by using Voicemeeter Banana with the following settings:

Voicemeeter

  • Stereo Input 1: Rode Mic with only B2 selected.
  • Stereo Input 2: Line In Realtek Audio (the Line In from Mac) with only B2 selected.
  • Virtual Input 1 (the left one): Only B2 selected.
  • Settings: Save settings as hypertexthero on docs folder, and have Load Voicemeeter and Load Settings On Startup set.

Sound settings

  • Right-click the little speaker icon on the taskbar and go to Sound Settings.
  • Sound Output for listening: Speakers Realtek Audio (default).
  • Sound Input for speaking or recording: Voicemeeter Out B2 (which unites the Rode mic and the Line Input instruments from the Mac.)

OBS

  • Settings > Audio:
  • Desktop: Speakers
  • Mic/Aux: Mic (Rode)
  • Mic/Aux 2: Instruments (Line In from Mac)

Disable the rest.

Videogames

With the above setup, we can now play live, and hopefully, good, music for others to hear in multiplayer online videogame worlds like Arc Raiders or Arma Reforger, by pressing the push-to-talk or hold-to-talk keys found in the control settings for the game we’re playing, and play our instruments.

In games like Elite with built-in VOIP voice chat upon connection our instruments will also be processed by the in-game voice filters, sounding like they come from within the digital “holodeck” world.

And we can also improvise alone, playing for the void of the Cosmos, in single-player worlds like Exanima.

Many instruments at once

A setup with everything connected (potentially with another ADAT “optical door” expansion like a Scarlett OctoPre for even more instruments) seems excessive, but means we can have a band of people playing in the same physical room while transmitting and recording each part to a track simultaneously.

This is a sort of dream-come-true here, an always on studio where “mistakes” can be captured, and we can pick up the instrument that feels most attractive in the moment.

Years ago I had a Jimi Hendrix poster with an illustration of a lot of wires coming out of his head, and with all the wires here, I’m beginning to understand more about the technical aspects of the creativity in his sound.

2nd audio interface?

Eventually we may replace the loopback cables running to the PC’s motherboard and the Voicemeeter audio routing software with a 2nd audio interface connected to the PC via USB, so the signal chain between the two computers is fully digital.

There would likely be pros and cons to doing this, but I think overall it would help to eliminate line noise and make gain staging easier.

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