This has been discussed in detail over on the Infuse forums:
As I understood it, there is no hardware limitation for supporting TrueHD, and Apple could in fact support it through a software update. But unless Apple makes that change, the most any developer could do is decode TrueHD to PCM on the box (which is what Infuse does) but that looses Atmos data in the process.
I went in to more detail on this here:
IMO it’s not so much hardware power (audio passthrough does not require any additional processing) as it is licensing and usability.
Remember these set-top boxes are streaming boxes. TrueHD has a much larger bitrate, and would require more bandwidth from your internet. So it’s a safer solution to support the lossy codecs with smaller bitrates like E-AC3. In the overall consumer space users like us that would benefit from TrueHD and Profile 7 DV are a small percentage of their overall user base.
