Kinda at my wits end here. Thinking the problem is ultimately with my TV, but maybe someone here can suggest something I haven’t thought of.
Setup: Shield pro > HDMI input on TCL R635 Roku TV > eArc to Bose Smart Soundbar 600 with rear speakers+subwoofer.
Anything with surround sound on Plex (various formats, AAC 5.1+7.1, AC3 and EAC3) through the Shield comes through as LCPM 2.0 (plex is not transcoding). I have HDMI passthrough enabled in the plex app, I’ve tried disabling dolby processing, manually selecting audio formats on the Shield, and setting the TV to passthrough. Other apps on the Shield do surround sound no problem. Plex on the Roku TV will also do surround sound no problem.
One thing I’ve seen suggested is connecting the Shield to the soundbar, and then the soundbar to TV through eARC. Unfortunately this particular soundbar only has one HDMI port, which is the eARC going to the TV, so I can’t do that. The fact that every other app on the Shield can do surround sound makes me think that this setup should be able to work, I just can’t figure out what else I might need to do.
Edit: After some more digging, I found that going into the specific HDMI port settings on the TV and changing the HDMI standard from “Auto” to “Standard” allows for AC3 and EAC3 to play properly through Plex, which is great! Unfortunately, anything using AAC surround is still getting turned into stereo, even though Plex is direct playing. I would be totally fine if Plex would just transcode AAC to AC3, but I can’t figure out how to make it do that, it only direct plays.
