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This document is a WORK IN PROGRESS.
This is just a quick personal cheat sheet: treat its contents with caution!

Sound system

WIP

Reference(s)

ALSA (The Advanced Linux Sound Architecture) is a part of the kernel that provides sound card drivers, moreover it's a software framework for high level API development.

ALSA Clients:

ALSA reference(s)

TODO: dedicated ALSA cheat sheet

PA (PulseAudio) is a sound server that provides a lot of features on top of the low-level audio interface ALSA.

PA Clients:

PulseAudio reference(s)

Note

ALSA can be used alone without PulseAudio. For applications only supporting PulseAudio: apulse enable ALSA to be used instead.

TODO: dedicated PulseAudio cheat sheet

JACK TODO

Jack reference(s)

  • TODO

TODO: dedicated JACK cheat sheet

GStreamer TODO

GStreamer reference(s)

  • TODO

TODO: dedicated GStreamer cheat sheet

PipeWire PipeWire is a low-level multimedia framework. It aims to offer capture and playback for both audio and video with minimal latency and support for PulseAudio, JACK, ALSA and GStreamer-based applications. TODO

PipeWire reference(s)

TODO: dedicated PipeWire cheat sheet

On Arch Linux, installing PipeWire is as easy as: 

$ sudo pacman -S pipewire pipewire-pulse pipewire-jack wireplumber
$ systemctl --user start pipewire-pulse
$ pactl info && echo OK || echo KO

Why wireplumber and not pipewire-media-session?

According to Debian wiki: wireplumber and pipewire-media-session are two possible session managers for PipeWire. The one often used by default, pipewire-media-session, is primitive, and is best when using PipeWire just for its basic functionality like screen sharing. When using PipeWire as your system’s sound server, the maintainer recommends installing the more advanced wireplumber instead.

You can use PulseAudio front-ends (e.g. like pulsemixer) for managing PulseAudio thanks to pipewire-pulse.

Reference(s)

Table of contents

Install

In order to find your audio driver, run this command and search for the "Audio device" section: 

$ hwinfo | less
(E.g. my audio driver is snd_hda_intel.)

Now, a correct kernel config is needed: 

$ cd /usr/src/linux
# make nconfig # or `# make menuconfig`

    # ALSA
    ######
    # Double check here: <https://wiki.gentoo.org/wiki/ALSA#Kernel>
    #
    > Device Drivers --->
    >     <*> Sound card support # Symbol: SOUND [=y]
    >         <*> Advanced Linux Sound Architecture ---> # Symbol: SND [=y]
    >             [*] PCI sound devices  ---> # Symbol: SND_PCI [=y]
    #
    # Here enable the driver for your audio controller ###

    > Device Drivers --->
    >     <*> Sound card support # Symbol: SOUND [=y]
    >         <*> Advanced Linux Sound Architecture ---> # Symbol: SND [=y]
    >             HD-Audio  --->
    >                 <*> HD Audio PCI # Symbol: SND_HDA_INTEL [=y]
    #
    #                 Select a codec or enable all (every option starting with "build")
    #                 and let the generic parse choose the right one:
    #
    >                 [*] Build ...
    >                 [*] ...
    >                 ...
    >                 -*- Enable generic HD-audio codec parser # Symbol: SND_HDA_GENERIC [=y]
    >
    > General setup --->
    >     [*] System V IPC # Symbol: SYSVIPC [=y]

    # If the system has more than 8 sound outputs (Each HDMI output on a GPU will count as one),
    # the max number of sound cards will need to be increased:
    #
    > Device Drivers --->
    >     <*> Sound card support # Symbol: SOUND [=y]
    >         <*> Advanced Linux Sound Architecture ---> # Symbol: SND [=y]
    >             [*] Dynamic device file minor numbers # Symbol: SND_DYNAMIC_MINORS [=y]
    >             (32) Max number of sound cards # Symbol: SND_MAX_CARDS [=32]
    ######

    # PA
    ####
    # Double check here: <https://wiki.gentoo.org/wiki/PulseAudio#Kernel>
    # And here: <https://wiki.gentoo.org/wiki/PulseAudio#Permissions>

    # For motherboards containing Intel HDA sound cards, use the following kernel option for
    # improved power-saving:
    #
    > Device Drivers  --->
    >     <*> Sound card support # Symbol: SOUND [=y]
    >         <*> Advanced Linux Sound Architecture ---> # Symbol: SND [=y]
    >             (2048) Pre-allocated buffer size for HD-audio driver # Symbol: SND_HDA_PREALLOC_SIZE [=2048]

    # CONFIG_HIGH_RES_TIMERS is needed to avoid (snd_pcm_recover) underrun errors and degraded audio
    # when some applications are using PA:
    #
    > General setup  --->
    >     Timers subsystem  --->
    >         [*] High Resolution Timer Support # Symbol: HIGH_RES_TIMERS [=y]

    # PA uses udev and ConsoleKit to dynamically give access to the soundcards to the
    # currently "active" nr. When running Systemd this will be handled without needing ConsoleKit.
    # To make this possible, ACLs (Access Control Lists) are required:
    #
    > File systems  --->
    >    Pseudo filesystems  --->
    >       [*] Tmpfs virtual memory file system support (former shm fs) # Symbol: TMPFS [=y]
    >       [*]    Tmpfs POSIX Access Control Lists # Symbol: TMPFS_POSIX_ACL [=y]
    ####

After configuring the kernel don't forget to do a kernel make and rebuild!

Append pulseaudio to the USE variable in your make.conf: 

# euse -E lm_sensors
# vi /etc/portage/make.conf # check that the use flag "pulseaudio" has been append:
    > ...
    > USE="... pulseaudio"
    > ...

After modifying the USE variable in your make.conf, don't forget to update the system using the following command so the changes take effect: # emerge --ask --changed-use --deep @world

Install alsa-utils (e.g. for alsamixer, amixer and other ALSA utility tools):

# emerge -a alsa-utils

# pacman -S alsa-utils

# apt install alsa-utils

# yum install alsa-utils

# dnf install alsa-utils

Optionally install PulseAudio:

# emerge -a media-sound/pulseaudio

# pacman -S pulseaudio

# apt install pulseaudio

# yum install pulseaudio

# dnf install pulseaudio

Config

Check that consolekit is installed with the acl use flag: 

$ emerge -pv consolekit
    > [ebuild   R    ] sys-auth/consolekit-1.2.1::gentoo  USE="acl ...

Check that pambase is installed with the "consolekit" use flag: 

$ emerge -pv pambase
    > [ebuild   R    ] sys-auth/pambase-20150213-r2::gentoo  USE="consolekit ...

ConsoleKit should be running: 

# rc-service consolekit status
    > * status: started

If ConsoleKit isn't running, enable it at boot time: 

# rc-update add consolekit default

Add this command to your .xinitrc (really necessary?): 

> ...
> start-pulseaudio-x11 &
> ...

Use

Troubleshooting

Headphone Jack not working

See https://askubuntu.com/questions/132440/headphone-jack-not-working.

$ alsactl restore

No HDMI sound

If you have an HDMI port but no HDMI driver appears when running $ aplay -L (or in alsamixer) then this fix might help: https://devtalk.nvidia.com/default/topic/1024022/linux/gtx-1060-no-audio-over-hdmi-only-hda-intel-detected-azalia/post/5211273/.

Create the following script in locale.d (see https://wiki.gentoo.org/wiki//etc/local.d): 

# sudo vi /etc/locale.d/fix-hdmi-audio-with-pci-bit.start
    > #!/bin/sh
    >
    > setpci -s 01:00.0 0x488.l=0x2000000:0x2000000
    > echo 1 > /sys/bus/pci/devices/0000:01:00.0/remove
    > echo 1 > /sys/bus/pci/devices/0000:00:01.0/rescan

Then make it executable and add it to OpenRC: 

# chmod +x /etc/locale.d/fix-hdmi-audio-with-pci-bit.start
# rc-update add local default
Now after reboot you should see your HDMI sound driver in $ aplay -l.

Crackeling/popping/stuttering/chopping/skipping/hiccups sound issues

Here are a few interesting links:

Most of this kind of issues can be solved by playing with some options in /etc/pulse/daemon.conf, e.g. like so: 

$ sudo vi /etc/pulse/daemon.conf
    > ...
    > ; resample-method = speex-float-1
    > resample-method = src-sinc-best-quality
    >
    > ; realtime-scheduling = yes
    > realtime-scheduling = no # if disabling `tsched` like described below
    > ...

And/or by disabling tsched in /etc/pulse/default.pa: 

$ sudo vi /etc/pulse/default.pa
    > ...
    > #load-module module-udev-detect
    > load-module module-udev-detect tsched=0
    > ...

After saving changes in those files, don't forget to stop pulseaudio (it will restart automatically whenever an application requires it): 

$ sudo pulseaudio --kill

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