I have a MP4 video with a 6 channel AC-3 and a 2 channel AAC audio track. I can get it to passthrough Track 1 or *both* tracks but can't find how to make it ignore Track 1 and only passthrough Track 2.

I got it to include only Track 2 by having it process it, but I don't want to reduce it more, I want it as-is.