Looking at the specification from
the channels are decoded correctly for 7.1 aac files but it looks like they're mapped/mixed in the wrong way resulting in the following output behaviour:
left -> left + center
center -> center
right -> right + center
right surround -> right
left surround -> left
right rear surround -> right rear surround
left rear surround -> left rear surround
lfe -> lfe
As a side note VLC seems to map these channels correctly but that's the only decoder / player which was able to play 7.1 aac files correctly so far. The issue itself probably lies within the audio systems (drivers) not being able to handle recognize/handle left center and right center channels correctly. I'd say I could ignore the issue if it was fixable with a custom matrix but since even the matrix mixer does not support / handle this setup correctly this is no possible.
If you need a test sample refer to the dropbox link here:
If you need anything I'll be willing to help as far as I can.