snd_mixer_selem_get_enum_items: Assertion `(elem)->type == SND_MIXER_ELEM_SIMPLE' failed

[naftulikay]

I'm on Ubuntu 18.04, kernel 5.4.0-96-generic.

I have installed build dependencies like so:

sudo apt-get build-dep x42-plugins
sudo apt install -y libasound2-dev

I am able to run make and compile the program.

However, when it starts, it immediately exits:

scarlett-mixer: simple.c:914: snd_mixer_selem_get_enum_items: Assertion `(elem)->type == SND_MIXER_ELEM_SIMPLE' failed.

The device is a Scarlett 18i8 and has a USB ID of 1235:8214.

Are there any other prerequisites that I am not aware of?

I had this same issue, and the problem is just kernel support for your device. The instructions for this other GUI explain how the kernel module is disabled by default for these devices. Create a file /etc/modprobe.d/scarlett.conf and add this line for your device:

options snd_usb_audio vid=0x1235 pid=0x8214 device_setup=1

Reboot and it should work.

https://github.com/geoffreybennett/alsa-scarlett-gui/blob/master/USAGE.md