HDMI Multichannel issue (channels randomly swapping)

[challenge]

version too old, updates in posts below for new moode versions.
Hello Tim
I have an issue that seems to happen only on moode (I run 6.7.1, don't know other versions).
Kernel modded to support 8ch. (bcm2835-pcm.c)
Using the HDMI output, from CLI, every time I do a "speaker-test -Dhw:0,0 -c 8", channels mappings kinda randomly swap.
I mean on first iteration of speaker-test, "0-front left" is really the front left. Then I stop the script, I rerun it and the same channel plays on a different speaker.

I tried raspbios stable and it's not happening there. Same kernel version*, same kernel mods.
*I hope to have built the same version, tried quite a few and could have made mistakes. Will double check.  Double checked, same version from same build both on raspbian and moode and it does it only on Moode.

- Is there something that could cause this on the moode-customization side? or it must be kernel?


Moode 6.7.1 - Raspberry Pi 4B
Raspbian 10.3 | 5.4.51-v7l #1 | armv7l (32-bit)

also tried all of these and no changes

Code:

dtparam=audio=on
hdmi_force_edid_audio=1
hdmi_drive=2
hdmi_force_hotplug=1
hdmi_group=1
hdmi_mode=16
hdmi_blanking=1
dtoverlay=vc4-fkms-v3d
max_framebuffers=2

[challenge]

@Tim Curtis
updating after quite a few years and several moode releases
Just found a bunch of people talking about it and forgot to update this, now that I'm seeing discussions on multichannel hdmi here too.
FYI this issue is not moode's fault... 
there is a long going issue with HDMI channels randomly swapping on raspberry.
It happens right after a buffer underrun, the channel order is not being respected or something like that.
Still no bug filed:
https://forums.raspberrypi.com/viewtopic.php?t=364156

The "quick" solution for now is to restart camilladsp.
It was discussed here a few months ago here page 3 and 4:
https://www.audiosciencereview.com/forum...233/page-3

It has been proposed to patch camilladsp and its systemd service to automatically restart itself when it happens, discussed here:
https://www.diyaudio.com/community/threa...st-7430848

Pretty sure some of those people are here too.
Will try that soon as it seem the only working solution. Not sure how to do it with moode but will look at it later.
Till now I still haven't found a stable config that can 100% trust (thinking active crossover and channels randomly swapping   ).
also in bookworm there's the new iec thing too 

[Tim Curtis]

I didn't experience any channel swapping when I last tested moOde 9 Bookworm HDMI but this was without CamillaDSP since it needed some build and other patches to run on Bookworm/pi5/pi4.

I'm planning to make pre-release 5 this week and also do some cursory testing with CamillaDSP but may not get to HDMI tests before the code drop. Hopefully some users can do this and let me know the results :-)

[challenge]

Can confirm that it happens even in moode 9 pre6 (not moode's fault obliviously) running speaker-test in cli.

How to repro:
run the script linked below and you'll see/hear channels swapping position, till you stop the process and then it starts again in the correct order.
e.g. i saw channel that was rear left becoming front right etc everytime an underrun was generated it swapped position.
https://forums.raspberrypi.com/viewtopic...0#p2194020

This is trying it in cli with speaker-test, would like to try if it happens with camillladsp in moode but must think how... maybe running stress while camilladsp is playing as this guy does in his script
https://forums.raspberrypi.com/viewtopic...3#p2186453

[challenge]

just adding this here for posterity, 
it seems this bug has been fixed, but it's hard to trace the specific commit?
I had no time to test this to find out if it's already there in the latest 9.2.x moode releases.
But if any of you know when it was fixed please report here.

https://forums.raspberrypi.com/viewtopic.php?t=381812

Memory says there was a fix a good number of months ago around FIFO configuration that resolved this issue. I don't recall any complaints from the Kodi / Libreelec folk for a while on multi-channel audio.