OpenBSD sndio via ALSA on ARCH Linux works

[purple-mountains]

How to get OpenBSD sndio working through ALSA on Linux

I used ARCH Linux

$ sudo pacman -S sndio

$ cat /etc/conf.d/sndiod
OPTS="-f rsnd/1"

Assumes your bdwrt5677 card is the second device. If it's the first device, use

OPTS="-f rsnd/0"

but you won't get full audio from 0-max volume, on say mplayer or mpv.

Try it as an exercise - change your index in the .conf file in /etc.modprobe-d/, and notice the lower volume range to be much louder when it's our second device, versus setting it as the first device, "...index=0".

Start sndiod as user or root

$ sndiod -dddd -f rsnd/1

$ sudo sndiod -dddd -a on -f rsnd/1

For some reason, I need the "-a on" flag when starting it as root.

If I try

$ sudo sndiod -dddd -f rsnd/1

sndiod won't open it's first device when called upon to play audio, sndiod first device, snd/0, is mapped to rsnd/1 - our bdwrt5677 card.

If I try

OPTS="-a on -f rsnd/1"

in /etc/conf.d/sndiod, and start it through systemctl, sndiod won't open snd/0 for some reason. It won't open snd/0 either, if I try "-a off", or no -a option. Starting it through systemctl seems to be broken, or I'm missing something.

In the ARCH install, I manually added /var/lib/sndiod - doesn't seem to create it, on installation.

I only get success starting it as the same user, or sudo sndiod with -a on.

A copy of .asoundrc, see below, was made to /etc/asound.conf whilst getting sndiod to start via systemctl.

Thanks to http://billauer.co.il/blog/2014/04/alsa-pipe-playback-capture/ for hints on creating my asound.conf file. I couldn't work out why I was getting scrambled noise, till I read it.

$ cat $HOME/.asoundrc

pcm.sndio {
type asym
playback.pcm "sndio-play"

hint {
	show on description "OpenBSD sndio"
}

}

pcm.sndio-play {
type plug
slave {
pcm "sndio-raw"
rate 48000
format s16_le
channels 2
}
}

pcm.sndio-raw {
type file
slave.pcm null

format raw
file "| aucat -f snd/0 -i -"

}
pcm.default sndio

Note: We need "channels 2" in the config, else we get scrambled output, like it's played at twice the speed. Try commenting it out, and hear the difference.

$ aplay -L

should show our new OpenBSD sndio PCM device

If you don't want sndio as the default just comment out "pcm.default sndio"

Test it works

$ aplay -D sndio -i /usr/share/sounds/alsa/Side_Right.wav
$ aplay -D default -i /usr/share/sounds/alsa/Side_Right.wav
$ aplay -i /usr/share/sounds/alsa/Side_Right.wav

and watch the messages scroll in the window we started sndiod.

mplayer doesn't sink audio / video in time, but it illustrates sndio via ALSA works.

$ mplayer -ao alsa:device=sndio _VIDEO_AUDIO_FILE

if sndio is our default device

$ mplayer -ao alsa _VIDEO_AUDIO_FILE

Enjoy!

[purple-mountains]

To run sndiod from systemd, we cannot have

User=sndiod /* this is wrong */

in sndiod.service

sndiod can be run either as any local user, or root, and not user "sndiod".

Either set

User=root

or remove User, defaults to root, on ARCH Linux.

[unsafe-andrew-old]

Thank you so much! Finally got it working

[jobbautista9]

I've found a way to improve the latency. It's still not perfect, but may be acceptable for some playing say Touhou in wine. Set both sndiod and aucat to use a buffer size of 512 (-b 512). This should give you a latency close to 20ms.