Hi, I tried to play something in DTS HD MA and i got it decoded to 5.1, but i got 7.1. Dolby Atmos Home Cinema. When i play something in Atmos it is decoded to weird formats like 3.1 Theatre Dimensional.
My settings in audio are 2.0., enable passthrough and enabled formats under it like DTS, AC3 and E-AC3. This works for DTS-HD MA in most of the time. Weird thing is when i set 7.1 in audio setting I got a 5.1.2 sound in output which should be right, but my receiver getting no Atmos (there is a LED which should be lit if Atmos is detected (working in old box S905x).
If you have a 7.1 speaker set-up - you want 7.1 not 2.0 enabled in your sound settings.
Also if you want DTS HD MA and Dolby True HD to be losslessly decoded, you will need to disable DD and DTS passthrough, as otherwise I think it will bitstream passthrough the lossy DD/DTS core/secondary streams rather than decode the lossless DTS HD MA or Dolby True HD losslessly to PCM 5.1/7.1.
You won't get Atmos until HD Audio bitstreaming/passthrough is supported on the Pi 4B - PCM lossless decode is only for Dolby True HD and DTS HD MA - not Dolby True HD with Atmos or DTS:x. (You may - possibly - get DD+ with Atmos - but that's not intentional and usually only used for secondary language audio streams on BD/UHD BD)
If you must have Dolby True HD with Atmos, the Pi 4B isn't currently for you.
However if you want the best quality audio possible with a Pi 4B currently - disable passthrough, configure for 7.1 if you have 7.1 speakers (i.e. Front R,L, Centre, Side R, L and Rear R, L + Sub) or 5.1 if you have 5.1 speakers (note I'm ignoring 7.1.2. or 5.1.2 Atmos in this - if you have 7 speakers but 5.1.2 then configure for 5.1, if you have 9 speakers in 7.1.2 then configure for 7.1)