I've tried out devel-20210426184100-eeb359a on Orange Pi One Plus, with a Marantz NR1605. AVR is configured for 5.1 speakers but will downmix from 7.1. I've locked the gui to 1080p @60 and disabled refresh rate switching.
*Passthrough of at least Dolby Digital (5.1 and 4.1, using the movie app), DTS 5.1 (including from a DTS audio cd rip using the music app and also movie audio using the movie app), and DTS-MA (bluray rip using the movie app, 5.1 and 7.1) works fine.
* With the primary audio output set to allwinner-hdmi-MJI marantz-AVR any multichannel FLAC gets downmixed to stereo, and plays fine (including 96kHz, which does play at 96kHz).
* With the audio output set to allwinner-hdmi-5091000.i2s-i2s-hifi, multichannel FLAC 96kHz is full of distortion, and stereo flac just gives silence. At least the multichannel flac is showing up as multichannel on the amp though.
* CEC doesn't seem to work very often, but does occasionally. I get lots of 'dw_hdmi_cec_hardirq: stat=11 LOW_DRIVE' in dmesg. And occasionally 'cec-dw_hdmi: message 20 04 timed out'
* Also, I sometimes when I turn the TV off, it turns straight back on again, which suggests the device is frequently sending "TV on" CEC messages?
I do have a raspberry pi B+ connected to the AVR as well, which I may be able to use to watch events on the CEC bus, so I'll try and find time to give that a go over the weekend.
Happy to test out anything else. (The AVR is too old for Atmos etc).
Cheers
David