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PulseAudio
PulseAudio (or PA for short) is a sound server that provides a number of features on top of the low-level audio interface ALSA on Linux, such as:
- Networking support (P2P and server mode).
- Per-application volume controls.
- Better cross-platform support.
- Dynamic latency adjustment, which can be used to save power.
Installation
Prerequisites
PulseAudio uses:
Kernel
For motherboards containing Intel HDA sound cards, use the following kernel option for improved power-saving:
Device Drivers ---> <*> Sound card support ---> <*> Advanced Linux Sound Architecture ---> (2048) Pre-allocated buffer size for HD-audio driver
CONFIG_HIGH_RES_TIMERS is needed to avoid (snd_pcm_recover) underrun errors and degraded audio when some applications are using pulseaudio:
General setup ---> Timers subsystem ---> [*] High Resolution Timer Support
Not all applications require CONFIG_HIGH_RES_TIMERS to operate properly however it is recommended for applications like audacity and it is good practice to enable it anyway to ensure compatibility with more advanced audio applications.
USE flags
Global
Portage knows the pulseaudio as a global USE flag for enabling support for PulseAudio in other packages. Enabling this USE flag will pull in media-sound/pulseaudio automatically:
/etc/portage/make.confUSE="pulseaudio"
Package
USE flags for media-sound/pulseaudio A meta package for PulseAudio (networked sound server)
bluetooth
|
Enable Bluetooth Support |
daemon
|
Build the pulseaudio binary (not-needed for pipewire-pulse) |
glib
|
Add support to dev-libs/glib-based mainloop for the libpulse client library, to allow using libpulse on glib-based programs. Build the GSettings PA module. |
jack
|
Add support for the JACK Audio Connection Kit |
ofono-headset
|
Build with oFono HFP backend for bluez 5, requires net-misc/ofono. |
Emerge
After setting USE flags be sure to update the system so the changes take effect:
root #emerge --ask --changed-use --deep @worldAdditional software
- media-sound/pavucontrol - Pulseaudio Volume Control, a GTK+ based mixer for PulseAudio.
- media-sound/paprefs - PulseAudio Preferences, a configuration dialogue for PulseAudio.
- KDE's Phonon integrated PulseAudio configuration and mixing, but it is not as powerful as pavucontrol or paprefs.
Configuration
Permissions
This is the only supported configuration by upstream and Gentoo developers.
PulseAudio 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) [*] Tmpfs POSIX Access Control Lists
If a desktop profile is not being used, check that sys-auth/consolekit or sys-apps/systemd are installed with the acl USE flag enabled, and (if using OpenRC) that sys-auth/pambase is installed with the consolekit USE flag enabled. ConsoleKit should be running on systems using OpenRC as the init system:
root #rc-service consolekit status* status: started
If not, enable it at boot time:
root #rc-update add consolekit defaultYou may find it necessary to start your X session with ck-launch-session.
When finished, verify the permissions are working correctly:
user $getfacl /dev/snd/controlC0 | grep -Eo "user:.+:" | cut -d: -f2For consoleKit/systemd logind managed permissions to be respected, no one may be part of the audio group (not even even the user pulse). Remove any and all users from the audio group:
root #gpasswd -d <user> audioConfiguring other applications
Some applications need to be configured to output to PulseAudio by default. A detailed list of these can be found on the PulseAudio wiki's PerfectSetup page.
- ALSA
If you previous had followed this article, upon upgrade to a fixed version (there should also be an einfo reminder), please remove the asound.conf file.
The media-plugins/alsa-plugins must be installed with the pulseaudio USE flag enabled:
root #emerge --ask media-plugins/alsa-pluginsYou need to enable the following module in /etc/pulse/default.pa:
/etc/pulse/default.paload-module module-oss
- GStreamer
Several GConf keys must be set:
- Manual with gconftool:
user $gconftool-2 -t string --set /system/gstreamer/0.10/default/audiosink pulsesink
user $gconftool-2 -t string --set /system/gstreamer/0.10/default/audiosrc pulsesrc
Some programs might still require GStreamer output plugin to be manually set to PulseAudio Audio Sink.
- ESD
Enable the following module in /etc/pulse/default.pa:
/etc/pulse/default.paload-module module-protocol-esound-unix
Also eselect the PulseAudio implementation:
root #eselect esd set esdcompat- libao
Set the following in /etc/libao.conf:
/etc/libao.confdefault_driver=pulse
- OpenAL
Set the following in /etc/openal/alsoft.conf:
/etc/openal/alsoft.confdrivers = pulse
Set the following in /etc/mplayer/mplayer.conf:
/etc/mplayer/mplayer.confao=pulse
Without udev or systemd
Using PulseAudio without udev or systemd is not recommended. It should be noted that this breaks both auto-detection and hot-plugging -- needlessly making your life harder -- as well as disabling ConsoleKit, essentially voiding the article. Please, if you have the possibility to use udev (and you most certainly have), just use it.
If you are using ALSA as a PulseAudio sink (output) and routing ALSA apps to PA but not using udev, you must set a specific device to be used. Otherwise, PulseAudio will use the ALSA device "default" as the sink, which may be routed back to PulseAudio, forming a loop. To avoid this, add the parameter device=hw:0,0 (you can find the correct IDs by running aplay -l). In the following example, we use two soundcards, of which card 0, device 0 is used as a sink (audio output, e.g. speakers) and card 1, device 0 as a source (audio input, e.g. microphone). PulseAudio will still be able to access other cards than these but it needs these settings to avoid looping the default device in this setup.
/etc/pulse/default.paUsing a specific ALSA device as PulseAudio sink/sourceload-module module-alsa-sink device=hw:0,0 load-module module-alsa-source device=hw:1,0
If you forget to specify this when using the ALSA sink/source modules, you may not notice any problems until you restart PulseAudio (e.g. by logging out and back in or rebooting). You will be left with (obviously) no audio, a slow desktop environment and hanging applications until you resolve the loop, restart alsasound and kill all running pulseaudio processes.
Headless server
These instructions are for setting up a headless pulse audio server. Meaning a server which has no display on it but does have speakers. This provides the ability to use the remote server's speakers for audio output.
You will get warned in a dozen places for doing this, but it is the proper method.
Server
First configure USE flags and emerge the package. The system-wide USE flag is masked, so we have to unmask it.
root #mkdir -p /etc/portage/profileroot #echo "-system-wide" >> /etc/portage/profile/use.maskroot #echo "media-sound/pulseaudio system-wide" >> /etc/portage/package.useroot #emerge --ask --oneshot pulseaudioAdd the following two lines somewhere in the system.pa file:
/etc/pulse/system.paload-module module-native-protocol-tcp auth-ip-acl=1.2.3.0/24 load-module module-alsa-sink
Replace 1.2.3.0/24 with the network mask that you want to be able to access the server.
If you have multiple ALSA devices, you will need to specify the device to use by adding device or device_id to the module-alsa-sink module
Tell the init script that we really do want to do this, and then start it up:
root #echo "PULSEAUDIO_SHOULD_NOT_GO_SYSTEMWIDE=1" >> /etc/conf.d/pulseaudio
root #rc-update add pulseaudio defaultroot #rc-service pulseaudio start
Client
user $pacmd load-module module-tunnel-sink server=1.2.3.4For a more permanent solution you can add the following to your default.pa file
/etc/pulse/default.paload-module module-tunnel-sink server=1.2.3.4
Now in the pulse audio volume control you should see the remote server listed under Output Devices. Under playback you should have a button next to the Mute audio button that when clicked will let you switch that audio stream to whichever output you want.
Equalizer
The equalizer module is considered unstable and might be removed from pulseaudio. For more, see the mailing list.
Make sure you installed pulseaudio with the equalizer USE flag enabled.
Enabling the required modules
Add the following two lines somewhere in the default.pa file :
/etc/pulse/default.paload-module module-dbus-protocol load-module module-equalizer-sink
Restart the pulseaudio instance. This should be as easy as:
user $pulseaudio -k user $pulseaudio --startChoosing the equalizer sink
The command should list the index and name of the equalizer sink:
user $pacmd list-sinks | grep -B1 -e "name:.*equalizer"Use pavucontrol or a similar program to select the equalizer sink for sound output. It may be listed as a device starting with FFT based equalizer.
Control the equalizer levels
The equalizer levels can now be controlled with the Qt GUI called qpaeq.
Known issues
- Short sound events (e.g. the terminal bell) distort ongoing sound streams (e.g. music)
Troubleshooting
No sound after installation
If you have no sound while using ALSA, consider unmuting the sound card. Launch alsamixer and make sure each column has a green 00 under it (use the m key to toggle mute/unmute). Install media-sound/pavucontrol and check if there is any output on the pavucontrol panel when playing an audio.
Enable debug mode
To get more informations you need to set the following in /etc/pulse/daemon.conf:
/etc/pulse/daemon.conflog-level=debug
Afterward restart the daemon:
user $pulseaudio -kAudio/Video out of sync
When using PulseAudio over your local network, you can experience out-of-sync problems. Solve this by adding tsched=0:
/etc/pulse/default.paload-module module-udev-detect tsched=0
This disables time scheduling. Afterwards restart the daemon:
user $pulseaudio -kDummy output
If the only playback device is the Dummy Output, PulseAudio cannot access your sound devices. Either the user has no permissions (see section Permissions or another program blocks the access. Try:
user $fuser -v /dev/snd/*It shows the relevant program. Close the program and reconfigure it to use PulseAudio.
No guarantees on actual latencies
Currently PA provides whatever latency at that moment is possible be it some milliseconds to hundreds of milliseconds without regard to what applications ask for.
In case of buffer under-run latencies are never decreased
Currently, if a buffer under-run occurs, PA buffers for longer increasing latency, but it then never tries to buffer for less until restart.
Re-sampling using up a lot of CPU time
Re-sampling can require quite a lot of computational power, PA defaults are rather conservative but in certain cases can still take a significant toll, in such cases edit /etc/pulse/daemon.conf and consider changing resample-method to something less CPU intensive, default-sample-format and default-sample-rate can also affect CPU utilization with higher bit-depth and larger difference in sample-rate generally needing more resources (e.g. re-sampling 44.1 kHz to 48 kHz is faster than re-sampling either to 192 kHz). Since re-sampling is done per each channel per input, channel configuration and number of applications can affect performance as well.
Starting with version 7.0 there is also soxr resamplers made available by enabling the sox USE flag. In particular resample-method = soxr-mq should provide acceptable quality while even the higher quality and hence slower soxr-hq is still cheaper than the default speex-float-1. But be warned that the soxr resamplers have roughly 5-20 times higher latency than speex-float, in terms of time the worst case for soxr-mq/hq can be as high as 20 ms while soxr-vhq latency can in few specific setups reach over 27 ms. In terms of feeling 20 ms can range from unnoticeable to irritating depending on person and use case (the usual PA latency's lower bound is around 20-25 ms and more commonly often around 70-90 ms, for comparison).
Using a version of PA with Orc support can noticeably decrease CPU usage, too. Also PA has the ability, if certain conditions are met, to automatically switch sinks between common sampling rates, this effectively can avoid some re-sampling.
grsec and PulseAudio
Make sure CONFIG_GRKERNSEC_SYSFS_RESTRICT is not enabled if you are using a grsecurity kernel. PulseAudio’s module-udev-detect needs to access /sys to discover what cards are available on the system, and that kernel option disallows this for anyone but root.
Volume gets randomly louder or reset to 100%
This may be caused by misbehaving PulseAudio-enabled programs when PulseAudio has flat volumes feature enabled. Disable it in daemon config:
/etc/pulse/daemon.confflat-volumes = no
FAQ
See PulseAudio's Frequently Asked Questions.
See also
- ALSA — describes the setup of a sound card with ALSA (Advanced Linux Sound Architecture).