Pro Tools Fundamentals - Mapped Output Busses

10-25-2014 10:00 AM

The last point in my article on busses touched on the fact that outputs in Pro Tools are no longer simply connections to physical outputs in your system. Since Pro Tools 9 they have been busses which are “mapped” to these physical outputs and it is this intermediary buss which builds in the flexibility into the system to allow easier transfer of projects between systems with different outputs.
Why Do Outputs Become Unavailable?

As your sessions become more complex they become less “portable”. By that I mean when you try to transfer to a new system there might be more outputs which are unavailable, either because they don’t exist on the new system or because they do exist but are called something else and quite possibly use different hardware. For example if you are working on a system in “Shed Studio” - a fictitious ITB studio with main outputs named “Stereo” and you transfer to a new system at “Fancy SSL Studio” with individual outputs connected to a mixer. When opening the session saved with the IO settings for “Shed Studio” the output “Stereo” isn’t available. Under the old system the session would open with all faders greyed out, still mapped to this unavailable “Stereo” output. Under the new system the output isn’t mapped directly to this unavailable output but to a buss called “Stereo”instead. This buss can be remapped to an output which is available and Pro Tools will make a “best guess” as to which available output it should substitute in place of the unavailable one.

Naming Conventions To Aid Transfer

Pro Tools saves a system ID based on the computer’s MAC address in the Pro Tools session for each computer it is opened on. When opening a session, if Pro Tools finds a matching system ID then the relevant output paths are restored. If there is no matching system ID then Pro Tools attempts to re-map outputs according to the output’s name and its channel format or if it can’t find a matching name then by channel format only.

This system is far from infallible and you will probably find yourself giving it a little help from time to time. There are things you can do to help the system figure out which of the available outputs is the most appropriate one to re-map to. If you are regularly exchanging projects with another system then following a common naming scheme will help a lot. In the example above naming the outputs connected to a particular pair of channels “stereo” might help encourage the system to map the main outputs onto that pair of channels. If in one studio you have a headphone mix output labelled “Cans” and in another studio the equivalent output is labelled “Cue” then Pro Tools might not map appropriately. If both systems called their outputs “Headphones” (or anything else, just as long as it was the same on both systems) then the issues should be alleviated and the outputs would re-map without incident.

Manually Fixing Unavailable Outputs

Inevitably you will have to manually reassign outputs at some point and a way to approach doing this might be by manually selecting tracks assigned to a particular unavailable output and option-shift clicking to the desired output. This is very effective in simple sessions but as the session becomes more complex it becomes laborious and the potential for mistakes increases. A far more effective solution is to open IO setup and in the busses tab click on the N/A output to access a drop down list of all the available alternatives. Selecting a suitable alternative from here will re-patch all relevant tracks to the new output.

Sessions Overwrite Current IO

The default behaviour in Pro Tools is that a session’s IO will be adapted to fit the available outputs on the system on which it is being opened. This “best fit” is possible because of the flexibility introduced by mapped output busses. If you wish you can force the system to inherit the IO saved with the session by ticking the “Sessions Overwrite Current IO” box in the buss tab.