It was created in 2004 under the name Polypaudio but was renamed in 2006 to PulseAudio.[6]
PulseAudio competes with newerPipeWire, which provides a compatible PulseAudio server (known as pipewire-pulse), and PipeWire is now used by default on many Linux distributions, includingFedora Linux,Ubuntu, andDebian.[7][8][9]
TheNT kernel was previously supported viaMinGW (an implementation of theGNU toolchain, which includes various tools such asGCC andbinutils). The NT kernel port has not been updated since 2011, however.[10]
PulseAudio operational flow chartPulseAudio is a daemon that does mixing in software.
In broad termsALSA is a kernel subsystem that provides the sound hardware driver, and PulseAudio is the interface engine between applications and ALSA. However, its use is not mandatory and audio can still be played and mixed together without PulseAudio.
PulseAudio acts as a sound server, where a background process accepting sound input from one or moresources (processes, capture devices, etc.) is created. The background process then redirects these sound sources to one or moresinks (sound cards, remote network PulseAudio servers, or other processes).[11]
One of the goals of PulseAudio is to reroute all sound streams through it, including those from processes that attempt to directly access the hardware (like legacyOSS applications). PulseAudio achieves this by providing adapters to applications using other audio systems, likeaRts andESD.
In a typical installation scenario under Linux, the user configures ALSA to use a virtual device provided by PulseAudio. Thus, applications using ALSA will output sound to PulseAudio, which then uses ALSA itself to access the real sound card. PulseAudio also provides its own native interface to applications that want to support PulseAudio directly, as well as a legacy interface for ESD applications, making it suitable as a drop-in replacement for ESD.
For OSS applications, PulseAudio provides thepadsp utility, which replaces device files such as/dev/dsp, tricking the applications into believing that they have exclusive control over the sound card. In reality, their output is rerouted through PulseAudio.
libSydney is a total replacement for the "PulseAudio streaming API", and plans have been made for libSydney to eventually become the only audio API used in PulseAudio.[15]
An extensible plugin architecture with support for loadable modules
Compatibility with many popular audio applications[17]
Support for multiple audio sources and sinks
Azero-copy memory architecture for processor resource efficiency
Ability to discover other computers using PulseAudio on the local network and play sound through their speakers directly
Ability to change which output device applications use to play sound through while they are playing sound (Applications do not need to support this, PulseAudio is capable of doing this without applications detecting that it has happened)
A command-line interface with scripting capabilities
A sound daemon with command line reconfiguration capabilities
Built-in sample conversion and resampling capabilities
The ability to combine multiplesound cards into one
The ability to synchronize multiple playback streams
Bluetooth audio device support with dynamic detection capabilities
PulseAudio first appeared for regular users inFedora Linux, starting with version 8,[18] then was adopted by major Linux distributions such asUbuntu,Debian,[19]Mandriva Linux, andopenSUSE. There is support for PulseAudio in theGNOME project, and also inKDE, as it is integrated intoPlasma Workspaces, adding support toPhonon (the KDE multimedia framework) andKMix (the integrated mixer application) as well as a "Speaker Setup" GUI to aid the configuration of multi-channel speakers. PulseAudio is also available in theIllumos distributionOpenIndiana, and enabled by default in itsMATE desktop environment.
Tizen, an open-source mobile operating system, which is a project of theLinux Foundation and is governed by a Technical Steering Group (TSG) composed ofIntel andSamsung, uses PulseAudio.
ThePortAudio API was incompatible with PulseAudio's design and needed to be modified.[21] Almost all packages using OSS and many of the packages using ALSA needed to be modified to support PulseAudio.[22] Further development of the glitch-free audio feature required a complete rewrite of the PulseAudio core, and also changes to the ALSA API and internals were needed.[23][24]
When first adopted by distributions, PulseAudio developerLennart Poettering (also the creator ofsystemd) described it as "the software that currently breaks your audio".[25] Poettering later claimed that "Ubuntu didn't exactly do a stellar job. They didn't do their homework" in adopting PulseAudio[26] for Ubuntu "Hardy Heron" (8.04), a problem that was improved with subsequent Ubuntu releases.[27] However, in October 2009, Poettering reported that he was still not happy with Ubuntu's integration of PulseAudio.[28]
Interaction with old sound components by particular software: Certain programs, such asAdobe Flash for Linux, caused instability in PulseAudio.[29][30] Newer implementations of Flash plugins do not require the conflicting elements, and as a result Flash and PulseAudio are now compatible.
Early management of buffer over/underruns: Earlier versions of PulseAudio sometimes started to distort the processed audio due to incorrect handling of buffer over/underruns.[31]
JACK is a sound server that provides real-time,low-latency (i.e. 5 milliseconds or less) audio performance and, since JACK2, supports efficient load balancing by utilizingsymmetric multiprocessing; that is, the load of all audio clients can be distributed among several processors. JACK is the preferred sound server for professional audio applications such asArdour,ReZound, andLinuxSampler; multiple free audio-production distributions use it as the default audio server.
It is possible for JACK and PulseAudio to coexist: while JACK is running, PulseAudio can automatically connect itself as a JACK client, allowing PulseAudio clients to make and record sound at the same time as JACK clients.[36]
PipeWire is an audio and video server that "aims to support the use cases currently handled by both PulseAudio and Jack".[37][38]
BeforeJACK and PulseAudio, sound on these systems was managed by multi-purpose integrated audio solutions. These solutions do not fully cover the mixing and sound streaming process, but they are still used by JACK and PulseAudio to send the final audio stream to the sound card.
ALSA provides a software mixer called dmix, which was developed prior to PulseAudio. This is available on almost all Linux distributions and is a simpler PCM audio mixing solution. It does not provide the advanced features (such as timer-based scheduling and network audio) of PulseAudio. On the other hand, ALSA offers, when combined with corresponding sound cards and software, low latencies.
OSS was the original sound system used in Linux and other Unix operating systems, but was deprecated after the 2.5 Linux kernel.[39] Proprietary development was continued by4Front Technologies, who in July 2007 released sources for OSS underCDDL-1.0 forOpenSolaris and underGPL-2.0-only forLinux.[40] The modern implementation, Open Sound System v4, provides software mixing, resampling, and changing of the volume on a per-application basis; in contrast to PulseAudio, these features are implemented within the kernel. PulseAudio support inOpenIndiana and otherillumos distributions relies on the in-kernel OSS implementation ("Boomer").
^Poettering, Lennart (25 September 2004)."Writing a PortAudio driver".audio.portaudio.devel. git.net.Archived from the original on 1 March 2017. Retrieved28 February 2017.
^An introduction to Linux sound systems and APIs, Linux.com, 9 August 2004, archived fromthe original on 19 October 2014, retrieved23 March 2013,OSS is available not only for Linux but also for BSD OSes and other Unixes. That may be its only advantage, because this system is not very powerful and was officially replaced by ALSA in 2.5 kernels...
