Well, then theres multichannel aac, which roku also claims support for….
Are you sure? Don’t see how it could be possible.
You can’t pass multichannel audio through a pair of analog audio cables, and you can’t pass uncompressed multichannel audio through a traditional digital connection.
Only way would be if, A) your receiver could decode multichannel AAC (not likely!!!) or B) the soundbridge had on-the-fly DTS or AC3 codec (it doesn’t)…