Flatpak Multichannel Audio over HDMI

I've recently started using the LE13 nighties on an intel NUC. All the HDMI audio works great in Kodi but apps/add-ons running via Flatpak are limited to stereo and i'm trying to use Moonlight with 5.1 surround.

I've tried tweaking the custom audio device setting in "External programs helper" but i don't think that's where the problem is.

I've added some Pulseaudio daemon config with "default-sample-channels = 6" which did make it start outputting 5.1 but the channel map is all mixed up with audio coming from the wrong speaker. Changing "default-channel-map" in the same config doesn't help.

Anyone have any ideas? it would be really good if this could be streamlined / automatically configured based of the Kodi audio output settings in future.

Interesting thanks, speaker-test works correctly, lists the expected channels and the tones play from the expected speaker.

LibreELEC:~ # speaker-test -Dhdmi:CARD=PCH,DEV=0 -c6

speaker-test 1.2.16

Playback device is hdmi:CARD=PCH,DEV=0
Stream parameters are 48000Hz, S16_LE, 6 channels
Using 16 octaves of pink noise
Rate set to 48000Hz (requested 48000Hz)
Buffer size range from 22 to 349525
Period size range from 11 to 174762
Periods = 4
was set period_size = 12000
was set buffer_size = 48000
 0 - Front Left
 4 - Front Center
 1 - Front Right
 3 - Rear Right
 2 - Rear Left
 5 - LFE

But when I config the pulseaudio to with "default-sample-channels = 6" i get:

LibreELEC:~/.config/pulse-daemon.conf.d # pactl info
Server String: /var/run/pulse/native
Library Protocol Version: 35
Server Protocol Version: 35
Is Local: yes
Client Index: 0
Tile Size: 65472
User Name: root
Host Name: LibreELEC
Server Name: pulseaudio
Server Version: 17.0
Default Sample Specification: s16le 6ch 44100Hz
Default Channel Map: front-left,front-left-of-center,front-center,front-right,front-right-of-center,rear-center
Default Sink: auto_null
Default Source: auto_null.monitor
Cookie: b3b3:64ec

I know pulse is used for Bluetooth audio and that's limited to stereo, maybe some existing config for is getting in the way.

I tried a "default-channel-map" like you suggested in the daemon config, same place I set "default-sample-channels = 6" but it had no effect.

Most other suggestions online talk about editing /etc/pulse/default.pa which is read only for us.

Ok i made some progress hacking stuff around until it worked.

I had to add channels=6 to https://github.com/LibreELEC/Libr…run-wrapper#L42 the created sink then has the correct channel count and mapping.

The next issue was by default it now upmixes stereo output to all the channels, for this the daemon config did work so i created a file as:

enable-remixing = no

So would be really nice if the flatpak-run-wrapper could be properly updated to honour your Kodi channel count, as for the remixing at least that is already fixable via user config.

Might even be best to delegate the channel count config to each flatpak app, because something like VacuumTube only supports stereo and it's nice if that is output at 2 channels to allow the AVR/TV to process it suitably. On the other hand Moonlight works great at 5.1 or 7.1 via 6/8 channels.

Quote from HiassofT

Thanks for the hint that moonlight can support surround sound output, I've now implemented that and added a setting in the moonlight addon https://github.com/LibreELEC/LibreELEC.tv/pull/11985

I also noticed that stereo-upmixing should actually have been disabled by default in LE about 9 years ago, but the change was buggy and had no effect - and no one seems to have noticed that yet

I've also opened a PR for that https://github.com/LibreELEC/LibreELEC.tv/pull/11986

so long,

Hias

That should be perfect, thank you.

On a related note could the display configuration that's currently in the External Programs helper add-on be added to the moonlght add-on settings too? As I would like to be able to run VacuumTube at 4k60 but moonlight at 1440p120.

Quote from HiassofT

I found a good solution and opened a PR: https://github.com/LibreELEC/LibreELEC.tv/pull/11989

so long,

Hias

I can see your PR is merged, and there has been a nightly build, but no add on update in the Libreelec repository, when does the repository get updated?

Thanks

Great, just got the first wave of updates, tested all audio channel settings in moonlight and all are working correctly. Only minor point being default and stereo are the same, but not an issue really.

The new versions are working well for me, audio channel settings still work correctly too.