PulseAudio

PulseAudio (or PA for short) is Article description::a multi-platform, open source, sound server that provides a number of features on top of the low-level audio interface, 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.
 * Plugin modules.

Prerequisites
PulseAudio can use but does not need any of:


 * or
 * (remember to add  to global USE flag).

Kernel
For motherboards containing HDA sound cards, use the following kernel option for improved power-saving only on machines that are not or  based:

CONFIG_HIGH_RES_TIMERS is needed to avoid  errors and degraded audio when some applications are using pulseaudio:

See also the for how to configure the kernel to provide the correct permissions for PA. Also see  for setting the right kernel options for sound card detection.

Global
Several packages are aware of the global USE flag to enable support for PulseAudio in other packages. Enabling this USE flag in will pull in  automatically (after following the  section):

Package
These use flags can be the package, independently from the global  USE flag in  (which configures other packages on the system that can use Pulseaudio):

Emerge
After setting USE flags be sure to update the system so the changes take effect:

Additional software

 * - Pulseaudio Volume Control, a based mixer for PulseAudio. Alternatively,  is the  based version.
 * - CLI and curses mixer for PulseAudio
 * - PulseAudio Preferences, a configuration dialogue for PulseAudio.
 * 's Phonon integrated PulseAudio configuration and mixing, but it is not as powerful as pavucontrol or paprefs.
 * - replacement for  USE-flag, may have better sound quality and allows for a codec selection in

Permissions
PulseAudio uses to dynamically give access to the soundcards to the currently "active" user.

To make this possible, ACLs (Access Control Lists) are required:

If a desktop is not being used:
 * for systemd, check that is installed with the   USE flag enabled
 * for OpenRC, check that is installed.

When finished, verify the permissions are working correctly:

Configuring 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

The must be installed with the   USE flag enabled:

Enable the following module in :

Several GConf keys must be set:
 * GStreamer


 * Manual with :

Set the following in :
 * libao

Set the following in :
 * OpenAL

Set the following in :

Without udev or systemd
If using ALSA as a PulseAudio sink (output) and routing ALSA apps to PA but not using udev, 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 (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.

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.

There are warnings in good 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.

Add the following two lines somewhere in the system.pa file:

Replace 1.2.3.0/24 with the network mask for accessing the server.

Tell the init script that we really do want to do this, and then start it up:

Client
For a more permanent solution, add the following to the default.pa file

Now in the pulse audio volume control, there should be the remote server listed under Output Devices. Under playback there should be a button next to the Mute audio button that when clicked will switch that audio stream to whichever output required.

Allow multiple users to use PulseAudio concurrently
In some situations, like software isolation, it may be desirable to run some programs as another users and have access to the Pulseaudio daemon. By default, the PulseAudio daemon does not accept connections by secondary users.

The following configuration runs PulseAudio daemon using a UNIX socket that accepts connections from other users.

The above configuration allows different users to access the same sound server. Users do not need to be in the audio, pulse-access or pulse groups. PulseAudio server may need to be executed at startup (see section {{Link|PulseAudio|section=#Running|Running]]).

Equalizer
Make sure pulseaudio was installed with the  USE flag enabled.

Enabling the required modules
Add the following two lines somewhere in the default.pa file :

Restart the pulseaudio instance. This should be as easy as:

Choosing the equalizer sink
The command should list the index and name of the equalizer sink:

Use or a similar program like  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.

Known issues

 * Short sound events (e.g. the terminal bell) distort ongoing sound streams (e.g. music)

Running
This section contains instructions for starting the PulseAudio daemon.

systemd
To enable PulseAudio for the current user run:

Root can enable PulseAudio for all users:

OpenRC
Running PulseAudio "systemwide" via an init script is strongly discouraged unless there is good reason to do so. It should instead be started by your desktop session;  is a good place to start.

Manually
The PulseAudio daemon may be launched as a daemon using:

For example, if using :

Troubleshooting

 * Freedesktop.org bugtracker: known bugs
 * Freedesktop.org bugtracker: known bugs

Pulseaudio runtime info can be checked with one command:

It prints useful info about all modules loaded and any error can happen while module loading the bootstrap sequence. When there is an issue with PulseAudio, remember to check output to start troubleshooting.

No sound

 * After installation: If there is no sound while using ALSA, consider unmuting the sound card. Launch and make sure each column has a green   under it (use the  key to toggle mute/unmute). Install  and check if there is any output on the pavucontrol panel when playing audio.
 * After installation on Intel Tiger Lake-H HD Audio: If there is no sound on Intel Tiger Lake or newer platforms, they may need to load additional firmware file(s). These platforms likely need the package installed. Then, restart PulseAudio (reboot or relogin to user session).
 * After upgrading the system: pulseaudio's user configuration files can become corrupt. Deleting configuration files and forcing fresh ones to be generated by restarting the daemon may fix no sound condition.

Corrupted audio
Problem: Audio has strange distortion or static when playing an output.

Solution: There is probably an issue with the Pulse server. Kill and restart the server:

On some very rare occasions, pulseaudio may need in case of sound issues:

Enable debug mode
To get more information, set the following in :

Afterward restart the daemon:

Audio/Video out of sync
Problem: Out-of-sync problems experienced when using PulseAudio over a local network.

Solution: Add  to the  file in order to disables time scheduling:

Restart the daemon:

Dummy output
If the only playback device is the Dummy Output, PulseAudio cannot access the system sound devices. Either the user has no permissions (see section or another program is blocking access. Try:

It shows the relevant program. Close the program and reconfigure it to use PulseAudio.

No guarantees on actual latencies
Currently PA provides whatever latency is possible at the moment. This can be be milliseconds to hundreds of a millisecond without regard to what applications require.

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 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).

grsec and PulseAudio
Make sure the CONFIG_GRKERNSEC_SYSFS_RESTRICT kernel symbol is not enabled when using a grsecurity kernel. PulseAudio’s module-udev-detect needs to access 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 the daemon config:

In pavucontrol, unable to change output device for applications that use OpenAL
If changing the output device in pavucontrol has no effect, it could be an application using, which has a configuration option that inhibits sink changes.

To disable this option, create a configuration file for OpenAL :



Or, from the GUI, by running :

Popping noises before playing a sound
Pulseaudio hibernates when no sound is played. If you have a popping noise at boot and each time a sound is played, this is due to pulseaudio (re)starting. A workaround is to disable hibernation by creating with

External resources

 * Getting DTS 5.1+ sound via S/PDIF or HDMI using PulseAudio
 * PulseAudio's Frequently Asked Questions - official FAQ
 * PulseAudio: The Perfect Setup
 * More general troubleshooting tips
 * Why you should care about PulseAudio (and how to start doing it)