How to Convert Between Surround Audio Channel Layouts in Pro Tools

This guide will show you how to convert between surround audio channel layouts properly when using Pro Tools, Source-Connect Pro X, and Source-Nexus to do a remote surround sound mix review session.

It is necessary to convert between channel layouts because Pro Tools and Source-Connect Pro X use different surround channel orders. Pro Tools uses the Film channel order (5.1: L C R Ls Rs LFE) whereas Source-Connect Pro X uses the SMPTE channel order (5.1: L R C LFE Ls Rs). The main issue that can happen if you route audio from Pro Tools in Film order to Source-Connect Pro X, which is in SMPTE order, is that the LFE channel will not line up, and, since the LFE channel is a reduced bandwidth channel, this will cause the audio being transmitted on channel 4 in Source-Connect Pro X to be not be transmitted at full bandwidth. 

In 5.1 surround, this can be abated by running Source-Connect Pro X in 6 channel mode instead of 5.1 surround mode, which gives you 6 full bandwidth channels and so there should be no issues because of the LFE channel. However if you need to run Source-Connect Pro X in 7.1 surround mode, either to have additional channels with a 5.1 mix, or for a 7.1 mix, then the LFE channel will still be an issue.

In Pro Tools, it is possible to create a bus in the I/O setup to convert between these surround audio channel orders. Here are the steps to create a 7.1 channel order conversion bus in Pro Tools.

1. Go to the I/O settings under Setup -> I/O in Pro Tools.
2. Create a new path by clicking "New Path...", select the desired channel configuration and name it. Auto-create sub paths should be UNCHECKED.
3. Select the surround bus that was just created. Then, click "New Sub-Path" and add a sub path with the same channel configuration and name it to something different. Create default sub paths should be UNCHECKED.
4. Move the channels in the sub path in the desired order.

Now, the conversion bus that was created can be used to feed a Source-Nexus plugin, which can then feed into Source-Connect Pro X in the correct surround channel order.