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Lesson Plan 2

Time required: Approximately 40 minutes

Refresher on remote audio workflows

In the last lesson we explored the historical background of remote recording and collaboration workflows, looked more closely at current technologies and introduced the concepts of networks and routers and packet loss.

In this lesson we will discuss remote etiquette for collaborating long-distance, and get into the details of the very-important concept of “mix minus”, a particular way of creating your DAW session to eliminate feedback and ensure you are recording each distinct signal.

Lecture: Remote etiquette

When we are all in the same room together, we communicate a lot of information without actually speaking, such as “I am going to record now” because you can see someone move to press a record button. When we are working remotely over the Internet, even if we have a really good video stream there is a lot of information we don’t have, so we need to verbalise a lot more. This means saying things like, “I am going to record” and “I am going to leave the room” or “I am going to make changes to my audio routing, you may not hear me for a moment” and using text chat as a backup when you cannot talk to each other. The better you can communicate with your colleagues remotely, the more fun and easy it will be to collaborate.

Lecture: Learn about mix minus setups

A mix minus is a common monitoring setup for remote audio connection: the basic reason for a mix-minus setup is that you want to record and monitor a remote signal without feeding that same signal back to the person or your monitors so you avoid feedback. To understand the mix minus it is first easiest to review simpler monitoring setups often used. The simplest of all is one where there is only one monitor mix. In this setup the engineer or control room hears the same mix as the booth or talent. Items that might be included in this single mix include talkback, backgrounds, live record, playback, and the talent low latency monitor. The monitoring of the talent by the talent needs to specifically be as low latency as possible. Many factors affect this latency and are beyond the scope of this document but they may include the recording systems and computers being used. Suffice to say with almost any monitoring setup involving a talent or musician, the latter need to hear themselves in real time with virtually no latency as they perform/speak in order to have a good natural sense of how they sound, without the performance hindering effect and distraction of latency. With a simple setup like this all is good. However things get more complex when there is a remote connection involved because inherently a lot of latency is introduced into the system. For a more complex yet still simple setup lets assume the engineer and talent are no longer in the same location and instead some sort of long distance connection is used such as phone patch, ISDN, Source-Connect, etc. In this case because of the nature of the long distance connection, it is no longer possible for the engineer to feed a low latency monitor of the talent to the talent and so this part of the monitoring system must be directly accomplished locally at the talent’s side of the connection. We will discuss the talent side setup later. For the engineer/record side however there are still a few things the engineer will need to send to the talent. These items include talkback, backgrounds and playback. Notice specifically there is no live record or talent monitor in that list. This is where the “minus” in “mix minus” comes from. If the engineer was to send the live record or talent to the talent through the long distance connection it would result in an “echo” being heard by the talent and depending on the setup at the talent side this could result in a repeating infinite loop echo. To avoid this echoing use a mix minus or in other words send everything you want the talent to hear but do not send the live input/record of the talent back to themselves.

Lecture: Audio routing

Audio routing is the process that was usually done with actual physical cables in the old days. In that paradigm you needed to attach inputs or sources to outputs or a destination, or send multiple inputs/sources to one or more outputs/destinations. Since the beginning of the DAW era, this is traditionally done with software, and audio routing is done inside the DAW itself. The basic elements of routing are the hardware interface i/o’s, the internal busses, and the sends, aux inputs and other elements that can be assigned to these internal busses or hardware i/o.

Interface/Audio I/O: This is the direct input (mic, line or digital) and output device used by a track in a DAW. If a track is for example, a track where you want to record the input and at the same time have the recording outputted by your monitors/headphones in real time for monitoring, you would set the input of the i/o to the corresponding mic and the output to eg. monitors. There is no complex internal routing there, the signal comes from the input, is recorded in the DAW (and thus passes from its audio processing buffer), and subsequently it is outputted from the output; with a minimal acoustic latency that corresponds to the audio processing buffer size of the DAW. We say minimal, because the actual latency in time for this process is approximately 20 ms for a buffer of 1024 samples in a 48 kHz session.

Bus: A bus helps you send signal from one track to another. All DAWs come with a predefined set of busses (eg 32, 64) so that you have flexibility in your routing. Let’s explain this with an example. Let’s say that you want to record the signal that you receive from the remote end with Source-Connect. Supposing that you have the Source-Connect Link plugin instantiated on an aux track in your DAW, then the output of the said track, which corresponds to what the remote user is sending you, is outputted from the output of that very track. If your i/o selection is eg. monitors, then you are not able to record this signal; in fact since this is an aux track, you are not able to record the signal anyway; should it be an audio track, if you were to record the signal, it would naturally record the input signal. So how do you solve this? Easy, you use a bus, eg bus 1, to route the signal to another audio track. So, you create an additional audio track, then set the output of the Source-Connect Link track to bus 1 and the input of the new audio track to bus 1 as well. Now, this new audio track has as an input the desired signal (the receive signal from Source-Connect) and becomes your remote record track. So, busses are pretty useful. You can route more than one signal to the same bus, thus mixing signals in real time on a specific track (eg if you have 4 tracks with output set to bus 1 and one track with input set to bus 1, the latter audio track will contain a live mix of all the other four tracks).

Send: The Send is kind of similar to a bus, with the difference that you do not need to set anything as an input with respect to where the Send actually sends the signal to. Sends are instantiated on a track as a method of sending the signal to a secondary output (or more) or a secondary bus (or more). If you specify for example the send of the track to be bus 1, then the audio contents of the track will be sent to bus 1 (and subsequently to any track that has bus 1 as input), without having to select the input as the send itself in any place. Sends are very useful for multi-routing purposes.

In summary, audio routing is the procedure of manipulating the sources and destinations of the mics, headphones, monitors, virtual instruments, pre-existing audio content etc. that you have in your session. You have in your disposition your i/o’s for the inputting/outputting of the sound itself and then the busses and sends to route, mix, send that signal to any track, that allows for all kinds of (simultaneous) processing of the audio.

Action: Using Pro Tools to implement a mix minus set up

Now that we have explained the difference between local audio monitoring and remote acoustic feedback (that creates the need to implement the mix-minus setup) we can demonstrate how this setup can be implemented with a popular DAW, Pro Tools. A mix minus is typically set up using an aux send. We will explain the setup in Pro Tools but the concept is the same for other workstation software titles and even a hardware mixer.

  • A Source-Connect Link plugin is placed on an aux input track, let’s call this track SCLink. The input and outputs of the Link plugins, correspond to the input and output of Source-Connect. Using busses and sends for the routing the mix minus setup in this case would be:
Local signals:
Talkback (aux input) and playback tracks can be sent to a bus called ToSCLink

Input: BusToSCLink / Output: BusFromSCLink1

Remote Record Track 1 (from Source-Connect):
Input: BusFromSCLink1 / Output: Main Out

Now let us examine how this mix minus setup is used when multiple simultaneous connections are made with Source-Connect Pro and its multi-connect setup alongside a local talent as well. Things are a bit different, because the connection is not a mesh-type now, and one end, usually in a three-sided connection the recording end that may or may not have a local talent (we’ll consider that it has one) acts as the main node of the connection, taking care of sending the signal to the two remote ends, meaning that it also sends the voice from one remote talent to the other and vice versa (without sending the voice of one back to oneself). For the remote talents nothing changes. They just use their Source-Connect as normal, avoiding feeding their input to the output.

The studio with talent (let’s call this local, since this is the interesting part that we would be called to take and actually solve this with the mix-minus routing setup) has two Source-Connect Pro applications launched, and each one connects to one remote end. Each Source-Connect is linked to its own Link plugin, ie Link 1 and Link 2. Each Link plugin is placed on an aux input track, let’s call those tracks SCLink1 and SCLink2. As always, we only care about the inputs and outputs of those Link plugins, as they are the actual image of Source-Connect in Pro Tools (or other DAW). Using busses and sends for the routing the mix minus setup in this case would be:

Local Mic Track:
Input: Local Mic / Output: Main Out / Sends: BusToSCLink1, BusToSCLink2

Input: BusToSCLink1 / Output: BusFromSCLink1 / Sends: BusToSCLink2

Input: BusToSCLink2 / Output: BusFromSCLink2 / Sends: BusToSCLink1

Remote Record Track 1 (from Source-Connect #1):
Input: BusFromSCLink1 / Output: Main Out

Remote Record Track 2 (from Source-Connect #2):
Input: BusFromSCLink2 / Output: Main Out

This is all that there is to it, we basically juxtapose the remote Source-Connect’s outputs and add our own input to each of their output, adding a couple of record tracks to record the incoming remote signal. Here is what this looks like in a Pro Tools session’s mix window in the same order of tracks, from left to right:

Mix Minus setup

Action: Build your own Mix/Minus session

Play around, what happens when you get the routing wrong? Can you build a session from scratch without reading the instructions? Can you build a session that mutes or lowers the volume of the remote received audio on your monitors when you are talking so you don’t get feedback? What happens if you mute the remote audio and forget to unmute it? Investigate your audio routing setup: can you tell the difference between muted audio and the internet dropping the connection?

Action: Remote Etiquette (If you have time)

In pairs or small groups, choose someone you are going to record. Have them sit in a chair and close their eyes or use a blindfold. Now place a microphone near them and set up a recording session: using only words, ask the blindfolded person to say a few words for a mic check. If you need to make adjustments to the session, let them know what you are doing so they are not waiting without any information. You’ll be able to get an idea of what you need to tell them and how often, so they know what is going on around them. When you are finished, have a discussion about how it felt to be blindfolded and not know exactly what is going on, and how it feels to wait while there is activity going on that you cannot be part of.