I wrote to Meridian Audio this week asking them if they could consider adding transcoding of Dolby Digital Plus (E-AC3) to normal Dolby Digital (AC3). I looked at Dolby's website and it seems like this could be possible.
Originally Posted by Dolby says
Is Dolby Digital Plus content backward-compatible?

Because Dolby Digital Plus is built on core Dolby Digital technologies, content that is encoded with Dolby Digital Plus is fully compatible with the millions of existing home theaters and playback systems worldwide equipped for Dolby Digital playback.

Dolby Digital Plus soundtracks are easily converted to a 640 kbps Dolby Digital signal without decoding and reencoding, for output via S/PDIF. The 640 kbps bit rate, which is higher than the standard 448 kbps used on DVDs, is fully compatible with all existing Dolby Digital decoding products such as A/V receivers, and can provide higher-than-DVD quality from Dolby Digital Plus soundtracks when played back through existing systems.
The new world of Streaming boxes is all over the place with transcoding Dolby Digital +. Some do it like Amazon Fire TV and others do not like Nvidia Sheild. The Netflix App is only outputting Dolby Digital Plus as a more efficient encoding scheme for streaming. If your box does not transcode Dolby Digital Plus your out of luck getting surround sound. Dolby makes it sound like an easy transformation.

I am hoping Meridian could possibly do transcoding in the UHD722 so I sent them a request. Maybe other Meridian fans could do so too.