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I am having difficulty figuring out how to enable audio through the built-in speakers on my armv7 Chromebook (which is running Parabola GNU/Linux, based on Arch). The speakers seem to work fine with pulseaudio, so I know the sounds card works and the speakers are functional. However, I don't want to use pulseaudio - I want to use ALSA direct. However, when I uninstall pulse, I can't seem to get the speakers to output through ALSA. The headphones work if I unmute the headphone channel in alsamixer and there is a series of channels labelled 'Speaker'; however, unmuting them and turning up the gain doesn't seem to give anything through the speakers.

According to alsamixer, the built-in sounds card is 'VEYRON-I2S' and it shows a frankly ludicrous number of different channels. There must be literally over 100 channels listed (compared to about 8 for the built-in card on my x86 desktop), ranging from fairly obvious things like 'Headphones' and 'Speaker' to more obscure things like 'Biquad', 'Digital EQ 5 Band', 'LINEB Ext Resistor Gain Mode', 'ALC Compression Ratio' and many more (despite the fact that the device only has built-in speakers, a single 3.5mm audio jack and HDMI).

So:

  1. How can I find more information about what all these different channels are for?
  2. Is there some way I can figure out what settings pulseaudio is using to get the speakers to work?

Given the large number of channels, I think it would take a long time to try to figure it out by trial and error.

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  • Asking at the pulse audio list would be the best way. They are friendly people but they may frown at your attempt. You could have just disabled pulseaudio instead of ripping it out of the DE. It's possible that they will give you an answer like: this happens due to this and that, ALSA cannot do that so we create feature x in PA. You will find that PA developers also have an ALSA developer hat.
    – LiveWireBT
    Commented May 8, 2020 at 8:48
  • @LiveWireBT Thanks for your suggestion. However, why shouldn't I remove pulseaudio from my DE? Is it a mandatory requirement for audio on Linux?
    – Time4Tea
    Commented May 8, 2020 at 11:44
  • It is not mandatory AFAIK. I have not checked dependencies on Arch Linux but on Ubuntu for example you break a meta package that provides the DE. You can certainly run without and you are probably the only one who is going to use your computer but having a standard out of the box experience with less invasive changes has its benefits when you have a bad day. By all means, tinker with everything you can when you can, but if I were you I'd commit the PulseAudio configuration that disables PA to my dotfiles git and work my way to ALSA configuration depending on the host I am on.
    – LiveWireBT
    Commented May 8, 2020 at 17:42

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I figured out how to enable the speakers on this device:

Near the far right-hand-side of the alsamixer channel listing are some channels labelled 'Left Speaker Mixer Left DAC' and 'Left Speaker Mixer Right DAC' (and similar channels for the Right Speaker). These have to be enabled and then the speaker gain can be controlled by the more obvious Speaker gain channels, as usual. These channels apparently enable/disable DACs for the speakers.

It seems there are quite a few channels that appear in the 'playback' filter of alsamixer that shouldn't be there (such as many channels relating to ADCs, which I assume are related to recording).

I also haven't been able to find any option for auto-muting, so it seems it is necessary to manually mute/unmute the speaker/headphone channels, as necessary.

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