You can modify the autorun.brs script used by BrightAuthor and change the audio output setting. In the example below, which works with BrightAuthor version 2.3 to 3.0, we are modifying the function that launches videos before the video is actually played. This change will redirect audio output to the SPDIF output of the expander.
Find the following function in the autorun.brs script published with a BrightAuthor project:
Then, add these two lines: