Comrex has long been aware of a particular feature in the Axia Livewire ecosystem that was very useful to customers but incompatible with the AES67 AoIP implementation as delivered in our NX Rack and MultiRack products. This feature is often referred to as “auto-backfeed”. Essentially, devices on a Livewire network can be configured to indicate that they require a “mix-minus” backfeed, and the system will supply that feed automatically, even if the AoIP output of the codec is routed by the Livewire system to a different place. This allows the Livewire system to route codec outputs to different consoles or studios and automatically generate the appropriate return feed. AES67 itself doesn’t define this protocol type, and the AoIP advertisements currently used for AES67 (Bonjour or SAP) aren’t compatible with this feature either.
Thanks to a partnership with Axia, Comrex can now deliver firmware that offers a Livewire-compatible advertisement protocol to solve this issue. The new firmware also adds support for Livewire-compatible GPIO, allowing the contact-closure function to receive and transmit GPIO signals to Livewire systems.
For information on ACCESS MutiRack firmware updates, click here
For information on ACCESS NX Rack firmware updates, click here
You’ll still need a PTPv2 clock source on your network (Configure your Livewire clocking device for Livewire and PTPv2 clock master)
Enable Livewire mode in the AES67 settings of your NX Rack or Multirack web interface.
Enabling Livewire mode on a Comrex codec makes the following changes:
The outgoing AoIP stream from the Comrex codec will change. The multicast address/Livewire channel combo will be assigned (as default) via the “Livewire Strategy”. This takes the last three digits of the IP address of the AoIP interface (usually the codec secondary Ethernet port) and concatenates 01 on the end (01-05 on Multirack, based on instance number). As an example, if your secondary port’s address is 192.168.87.254, the Livewire channel will be set to 25401. The output multicast address will change to match the Livewire channel. This default can be changed manually in the AES67 output settings.
The incoming AoIP channel will default to “Manual Livewire” mode, the incoming channel number will default to the same channel number as the output, and the Livewire “direction” variable will be set to “To Source” (to allow for “auto-backchannel” operation).
The Comrex codec will transmit and receive Livewire advertisements along with the usual SAP and Ravenna (Bonjour) protocols. When viewing the “Source” list (to manually choose an input channel), Livewire sources are prefixed with LW. An additional source is available labeled “Manual Livewire” (described below). Also in the “Source” list, Comrex channel names are truncated to “Access MR@ <MAC address>” to keep to the 16-character Livewire limit
The contact-closure functions are changed to be compatible with Livewire GPIO. Contact closure ins and outs 1-4 are mapped to Livewire GPIO 1-4. Livewire GPIO 5 is not supported.
Set up for Livewire
If your Livewire network conforms to the Livewire “strategy” in channel assignments, and you’ve set the Comrex codec’s secondary Ethernet port to an available static address, then setup is very simple. Enable “Livewire mode” under the main AES67 settings, and your input and output channels will be assigned as detailed above (unless you’ve changed the AES67 input defaults previously. If so, navigate to the input section and choose “default” before enabling Livewire. No other settings should be necessary. If you need to use “non-strategic” manual Livewire channel numbers, start with the output channel if needed.
Manual Output Channel
Open the “Output” section in the AES67 settings, then expand it to view the options. Change the Output Channel number from the default to the desired setting. If no input channel has been set previously (either in AES67 or Livewire mode), it will follow the “auto-backchannel” behavior described above.
Manual Input Channel
If you need to change the input Livewire channel, you can either enter the channel information manually or select the input channel via the scan function.
To choose the input via scan, select the “Source” option under AES67 inputs. Clicking the source list on the right opens a list of all sources detected on the network. Note that if sources advertise in multiple protocols, they will be listed multiple times. Choose your source and press “Apply Changes”.
To set a discrete channel number, open the AES67 Input section and choose the “Source” option. If not chosen already, scroll to the bottom of the scan list and choose “Manual Livewire”. After applying that selection, a new option appears in the input section, allowing you to disable the “Auto Livewire back-channel” setting. You can now set the input Livewire channel number manually to any value (along with the Livewire “to/from” source variable).
© 2026 Comrex Corporation. All Rights Reserved. Livewire compatibility provided in association with and technology licensed from TLS Corporation. Axia and Livewire are registered trademarks of TLS Corporation.