Audio Routing For Broadcast Radio Live (generating a clean feed / mix minus)

Note - In this article we discuss 'clean feeds' by which we mean an audio feed from a mixing console that excludes one or more channel inputs. This is not to be confused with the cleanfeed.net service which is a 3rd party AoIP service that is unrelated to this article.

In order to use Broadcast Radio Live (BR Live) to connect audio from a live studio or automation PC to a remote presenter and use the remote presenters voice as part of your broadcast, you need to consider the audio routing that will feed the combined output from your mixer or playout system TO the remote user, but not their own voice.

This is known as a "clean feed" (or sometimes a "mix-minus") and is essential to avoid the remote voice sounding like an echo on the final broadcast.

In addition, the final broadcast also needs to be a mix of the Myriad Playout output and the remote voice.

In general there are two scenarios you will face when considering this setup:

1. Using a mixing console with a 'clean feed' output
2. Automation PCs with no mixing console

Using a mixing console with a 'clean feed' output

Most broadcast radio mixing consoles include the ability to generate one or more clean feed (or mix-minus) outputs which exclude specific channel inputs from the clean feed output. Commonly these are referred to as 'Telco' channels but different mixers sometimes use alternative terminology.

The diagram below shows you how you should configure the audio routing for BR Live when working in a studio equipped with a mixing console with a clean feed output.

In this example, the SRM mixer is used to mix all the audio channels as well as generate the clean feed output. The Myriad Playout system is configured to use standard audio sound devices to output analogue audio which is fed to the corresponding Myriad faders on the mixer. 

The BR Live Studio software is configured such that the input device is being fed from the clean feed output from the SRM (so you will need a 5th sound device in the PC).

The output device for the BR Live software needs to be a soundcard output that is physically fed to the 'Telelphone' channel input on the SRM.

Finally, leave all the Myriad faders and the Telephone fader up for unattended broadcast and route the SRM PGM output to your transmission chain (encoder, transmitter etc).

Obviously the setup will differ for different mixing consoles but the base concept is the same.

Automation PCs with no mixing console

Things get a little more complex if you are setting up BR Live to work on an automation PC that is not attached to a mixing console. The objective remains the same, to send the remote presenter a version of the Myriad Playout output that does not include their voice, and mix their voice into the final output that is fed to your encoder or transmitter.

Whilst it is more tricky to set this up without the benefit of a mixer, it is possible to do so using a combination of two sound devices (which can be physical or virtual).

This solution works in the following way:

1. Myriad Playout is configured to output all Media Players through Sound Device A.
2. BR Live Studio is configured so the Input Device is Sound Device A (meaning BR Live will only send Myriad Media Players to the remote presenter).
3. BR Live Output Device is set to Sound Device B (this will just be the presenter voice / audio from the remote location).
4. So now the Myriad Media Players are on Sound Device A and the remote voice is on Sound Device B but we need to have a mixture of both for encoding or sending to our transmission chain.
   
   Luckily we can use the 'listen to' feature in Windows 10 to mix Sound Device A and Sound Device B so that we have a combined output to feed our transmission chain.
   
   
5. Click on Start then type Sound Settings. When the Sound Settings window opens, click on the Sound Control Panel option on the top right.
   
   
   
   
6. Click on the Recording tab and right click on Sound Device A (in the example below we are using Virtual Audio Cables but a physical device would also work).
   
   
   
   
7. Click on the Listen tab and then tick the Listen to this device option. Finally select Sound Device B from the list of devices to playback through. Then click on OK.
   
   
   
   
   What this does is effectively routes the audio on Sound Device A to the Sound Device B output proving the final mix we need for the broadcast.
   
   
8. If you are using a web encoder (BR Encoder or similar) then make sure the audio device output that is being encoded is Sound Device B. If you are using a physical output (for transmitter etc) then Sound Device B must be a physical device and this is the output you need to use.

What if you have mixer that does not have a clean feed output?

Unfortunately, in this scenario your options are limited. If you have an AUX bus on your mixer then you may be able to manually create a clean feed using the AUX bus and allowing all fader channels except for the one that BR Live is feeding remote voice to. This will have the same end result but we are not able to provide specific assistance in setting this type of configuration up. 

It may also be possible to use a dedicated hardware solution such as the Sonifex RB Mix Minus generator (Sonifex RB-MM1 Mix-Minus Generator). We recommend talking to Sonifex about your configuration to see if this is a possible solution.

You could also try using a software mixer such as the VoiceMeter Banana mixer offered by VB- Audio (VB-Audio VoiceMeeter Banana (vb-audio.com) ,this allows routing and mixing of virtual or physical sound devices and could be configured to generate a clean feed. Our testing indicates that there are some longterm stability issues with such a solution but you should conduct your own evaluation of the software.

Useful Links

In this article, the screen shots were taken from a system using virtual audio cables instead of physical sound devices. If you are encoding your output using software (eg BR Encoder etc) then there is no requirement for physical sound devices in the system and virtual audio devices provide a flexible and low cost alternative. The virtual audio cables used in this example are from VB-Audio.

• VB-Audio Virtual Apps (vb-audio.com)