It does appear that the M1 has a virtual surround mode. My AVR also has a virtual mode, but I have never found it great. Maybe
@Achim1811 who has experience testing the M1 might know something.
I don't think the Ultra spec sheet mentioned any codecs, but in my tests with FireTV, playback was possible with FireTV audio output set to Dolby Digital Plus or Dolby Digital.
An answer to a question in the spreadsheet here: https://forum.wiimhome.com/threads/meet-wiim-ultra-the-digital-hub-for-your-music.3487/post-52175 “Yes, it supports Dolby Digital 5.1 audio.” Can anyone with the Ultra confirm that this is correct?
forum.wiimhome.com
He also stated that the WiiM team is developing 4.1-channel surround sound playback in multi-room groups using satellite speakers in the future. Whether this will happen or not is not known, but when completed, it will create a non-virtual surround system.
Updated on 5/25/2024 Check out this fuller thread about our official announcement of the WiiM Ultra - https://forum.wiimhome.com/threads/meet-wiim-ultra-the-digital-hub-for-your-music.3487/ Updated on 4/19/2024 Hi Team, We're excited to give you a sneak peek at the WiiM Ultra, your future...
forum.wiimhome.com
However, I have not seen the support team mention it since this post.