Overview

Whether you’re starting a radio podcast, a youtube channel, or delivering presentations online, chances are that you’ve found a situation where you wanted your audience to be able to hear what you hear on your computer. Taking control of the multiple audio streams available in our machine is indispensable nowadays. In this article we introduce the concept of Audio Loopback, the problems it can solve, and the type of implementations and solutions one can explore.

The Problem

In order to better understand What is Audio Loopback, it is helpful to first think of a couple of scenarios that might motivate you to search for it. Say you want to:

• Make a podcast where you want to record both your microphone as well your online guest and mix in some music in the background.
• Stream your gameplay where you want to include both the game’s sound, your voice, and some funny audio clips.
• Deliver a presentation over video conferencing with multiple audio examples to share from different sources.

Some might suggest that you’ll need to record everything separately, and then bring it all together on an editing software. However, not all applications have a recording capability built-in. Besides, if you need to do it live (as in a live podcast, live streaming, or live presentation) that is simply not an option. So, what do you do?

The Idea

Photo by Drew Patrick Miller on Unsplash

Picture yourself for a moment as a live show radio host at a radio station: managing different streams of audio seems to be only a matter of bringing up a fader. Want to play a track to your listeners? Just raise this fader. Time to make an announcement? Raise that other fader. Every possible audio stream is just there, at your fingertips, all laid out as equally available inputs. Regardless of whether you want to become a live show radio host or not, you actually don’t need to have access to a radio station or a music studio and a whole mixing board in order to take control of your audio streams. When working with your computer all you really need is to make sure that all the audio streams that you want to work with are available as audio inputs. But, you might ask, when the audio source is an application running on the same computer — say a music file on the computer, a youtube video on the browser, or a guest on a video call -, how do you turn it into input? This is where Audio Loopback comes in: turning outputs into available inputs by creating a loop!

Approaches

If you look at your current computer’s available inputs, chances are that you’ll see the built-in microphone as the only available input device. If you have an audio interface, that would add another option (for both inputs and outputs), and depending on its model the number of input channels that the device provides will change. On the software applications that you are using on your computer, you might be able to choose which device to hear the playback from — computer speakers, headphones, audio interface, Bluetooth speaker, etc. In order to explore ways to re-route the audio of those applications to be sent to the inputs of the computer (i.e. to create an Audio Loopback) there are 3 different types of approaches: analog, electric, and virtual. The first one would consist in capturing the sound of the speaker with a microphone, as explored in the historical sound art piece, by Alvim Lucier [1]. The second approach requires hardwiring the outputs of an audio interface back into the input channels with audio cables, which would get rid of any ambient noise captured by a microphone. The third type of approach requires patching these loop wires virtually! This is arguably the best avenue to pursue since it has an even more improved quality (no conversion between digital and analog), and significantly reduced costs. These loops are created by using the so-called virtual devices that show up in the computer as available output channels and corresponding input channels that are virtually patched together. When an application selects that virtual output device for playback, its audio stream will be available on the corresponding virtual input device.

Solutions

Implementing Audio Loopback virtually is possible to achieve using both hardware and software solutions. Besides allowing you to manually patch audio cables, some audio interface models like the Audient EVO 4 [2] or the RME Babyface [3] can also create loopback connections internally. These are usually created using the audio interface’s software control panel. Software solutions also come in different shapes and sizes. GingerAudio offers 2 software that can both create Audio Loopback and easily integrate it into live or studio practice. GroundControl CASTER LIVE [4] allows you to mix and manage all the audio sources in your computer in one simple-to-use interface — be it individual applications audio, microphones, audio interfaces, and even built-in audio samples. You can use your mix in other applications by choosing the CASTER stream mix device, or create individual virtual devices for each application or audio source. The second software solution offered by GingerAudio, aimed at professionals, is GroundControl ROOM [5]. This software allows you to route any audio source and calibrate all your monitoring devices with improved audio quality. Whether you choose one solution or another, once you set up Audio Loopback, you’ll be able to use your new inputs in your next live show, or even during the production of your next artistic or research endeavors that requires you to perform digital sampling of an audio stream in your computer.

GroundControl CASTER LIVE interface

GroundControl ROOM interface

Conclusion

Audio Loopback is a very powerful technique that allows users to take control of the multiple audio streams in the computer. In its essence, it consists of rerouting an output to become an available input, creating a loopback connection. This is helpful for podcasting, streaming, presentations, and some offline work too. Various solutions are available, both hardware and software-based.