Equalizer, mixing control for audio device (external USB)

    I have a 6 channel external USB audio device (5.1?), which is a generic no-name brand, with SPDiF in/out, front, rear, center/bass out with a line & mic-in. It works without trouble or any extra needed driver on both Raspberry PI 3b and Intel i5 systems I tested. I do not use the SPDif, it simply works when I patch in the 3.5mm front, rear, center jacks into my amplified speakers.

    The device will identify "ICUSBAUDIO7D" with aplay -l:

    Code
    card 2: ICUSBAUDIO7D [ICUSBAUDIO7D], device 0: USB Audio [USB Audio]
Subdevices: 1/1
Subdevice #0: subdevice #0

    I am looking to tune the output of the channels, equalize settings on front, rear, and center/bass, with volume fader controls. This would optimize my sound in the room with the placement of the speakers.

    I have not found anything obvious exploring the whole application, and probably exhausted my efforts reading the online documents so far. I thought about buying a hardware equalizer, but figured this is a computer media system, and the tuning controls should just be in the menu somewhere, even if I had to ssh into a terminal at first to get it working, if it doesn't already exist.

    Is there an add-on or other Linux function utility I can update/patch in, to control frequency output on all of those 5.1 (or 6) channels? Or if it is a function of Kodi / Librelelec, does anyone know where that is, please?

    Edited once, last by DrStein99 (December 7, 2022 at 4:26 PM).

    There is a new equalizer add-on under development. Install it from its own repository:

    • login by SSH
    • download the repository ZIP file into your /storage folder by wget https://github.com/wastis/LinuxAddonRepo/raw/master/repository.linuxaddons-1.0.0.zip
    • go to LE's add-on menu, and install the repository ZIP by clicking on it (after that you can delete the ZIP file, if you want)
    • install the equalizer add-on from the new repository

    I was unable to make it work with my default audio on RPi3B+, but maybe you're lucky with your external DAC.

    Here is the GitHub page for documentation and useful links: Kodi PulseEqualizer GUI Addon

    The intiial issue with that add-on will be that LE only uses Pulse audio for streaming output to BlueTooth speakers, we use alsa for all other output. It's possible to reconfigure LE to use Pulse though. The wiki describes some other configurations, see https://wiki.libreelec.tv/configuration/pulseaudio - not specifically your requirements, but at least explains what the config files and required touch points are to make an alternative configuration. There are probably threads in this forum about using Pulse too.

    The challenge with alsa plugins is they need to be built and baked-into the image to use, and then users need to create custom alsa configs to use them. Creating alsa configs is, err, one of the Linux 'dark arts' and where most people will come unstuck.

    Quote from Da Flex

    I was unable to make it work with my default audio on RPi3B+, but maybe you're lucky with your external DAC.

    Here is the GitHub page for documentation and useful links: Kodi PulseEqualizer GUI Addon

    There are problems with the repository, I had to change the .XML in order for that to install. I believe the code structure was possibly out of date.

    After I got to install, it does not work on my system. I began to debug, and got caught up in this libreleec bash prompt does not have any linux commands I am used to, simply apt-get and sudo commands are not there, so I am lost without a standard command set.

    Quote from DrStein99

    After I got to install, it does not work on my system. I began to debug, and got caught up in this libreleec bash prompt does not have any linux commands I am used to, simply apt-get and sudo commands are not there, so I am lost without a standard command set.

    LE has no sudo, because you're already root user after SSH login. Also no apt-get, because LE only uses add-ons for packages.

    Workaround

    Take a spare microSD, and install RPiOS (which has sudo / apt-get) with Kodi: Click!

    Install an ALSA EQ (Raspbian is outdated, but instructions hopefully also work on RPiOS): Click!

    If everything works, you can autostart Kodi on RPiOS, and try a similar approach on your Intel system (Ubuntu & Kodi).

    Quote from chewitt

    The challenge with alsa plugins is they need to be built and baked-into the image to use, and then users need to create custom alsa configs to use them. Creating alsa configs is, err, one of the Linux 'dark arts' and where most people will come unstuck.

    Can you move to pulseaudio so audio processing plugins such eq are available?

    I understand. I'm an audiophile linux enthusiast planning to build an A/V Kodi Libreelec RPI4 player with an Spdif digital transport hat. Direct ALSA hardware out is the most direct, least latency output. Pulseaudio has its problems (latency,samplerate conversion..), and it's being phased out in Linux in favour of the newer PipeWire. Kodi being multiplatform shouldn't be bound to any sound server for plugins.

    Libreelec being a sandbox machine does not need an additional audio API.(even if it has Pulseaudio for Bluetooth and Network). If I did, I would move to RPIOS on debian or a specialized PC.

    I agree keeping ALSA by default is the best choice. Having eq in Kodi would be nice, but we always have ALSA to tinker with.