PulseAudio

PulseAudio is a networked sound server, similar in theory to the Enlightened Sound Daemon (EsounD). PulseAudio is however much more advanced and has numerous features.

A sound server can serve many functions:

Software mixing of multiple audio streams, bypassing any restrictions the hardware has.
Network transparency, allowing an application to play back or record audio on a different machine than the one it is running on.
Sound API abstraction, alleviating the need for multiple backends in applications to handle the wide diversity of sound systems out there.
Generic hardware abstraction, giving the possibility of doing things like individual volumes per application.

PulseAudio comes with many plugin modules. All audio from/to clients and audio interfaces goes through modules.

Manuel Amador created a diagram describing how the different parts of PulseAudio play together. (Not all modules are shown.) Another, simpler architecture diagram is attached to this page (scroll to the bottom).

PulseAudio clients can send audio to "sinks" and receive audio from "sources". A client can be GStreamer, xinelib, MPlayer or any other audio application. Only the device drivers/audio interfaces can be either sources or sinks (they are often hardware in- and out-puts).

OI-Hipster, PulseAudio-10.0 port:

→ /export/home/kmays$ uname -a

SunOS external 5.11 illumos-fd3bae1 i86pc i386 i86pc Solaris

→ /export/home/kmays$ /opt/pulseaudio-10.0/bin/pulseaudio --version

pulseaudio 10.0

→ /export/home/kmays$ /opt/pulseaudio-10.0/bin/pulseaudio --dump-modules

module-allow-passthrough When a passthrough stream is requested, route all the other streams to a dummy device
module-always-sink Always keeps at least one sink loaded even if it's a null one
module-augment-properties Augment the property sets of streams with additional static information
module-card-restore Automatically restore profile of cards
module-cli Command line interface
module-cli-protocol-tcp Command line interface protocol (TCP sockets)
module-cli-protocol-unix Command line interface protocol (UNIX sockets)
module-combine Compatibility module (module-combine rename)
module-combine-sink Combine multiple sinks to one
module-console-kit Create a client for each ConsoleKit session of this user
module-dbus-protocol D-Bus interface
module-default-device-restore Automatically restore the default sink and source
module-detect Detect available audio hardware and load matching drivers
module-device-manager Keep track of devices (and their descriptions) both past and present and prioritise by role
module-device-restore Automatically restore the volume/mute state of devices
module-echo-cancel Echo Cancellation
module-filter-apply Load filter sinks automatically when needed
module-filter-heuristics Detect when various filters are desirable
module-http-protocol-tcp HTTP (TCP sockets)
module-http-protocol-unix HTTP (UNIX sockets)
module-intended-roles Automatically set device of streams based on intended roles of devices
module-ladspa-sink Virtual LADSPA sink
module-loopback Loopback from source to sink
module-match Playback stream expression matching module
module-native-protocol-fd Native protocol autospawn helper
module-native-protocol-tcp Native protocol (TCP sockets)
module-native-protocol-unix Native protocol (UNIX sockets)
module-null-sink Clocked NULL sink
module-null-source Clocked NULL source
module-oss OSS Sink/Source
module-pipe-sink UNIX pipe sink
module-pipe-source UNIX pipe source
module-position-event-sounds Position event sounds between L and R depending on the position on screen of the widget triggering them.
module-raop-discover mDNS/DNS-SD Service Discovery of RAOP devices
module-raop-sink RAOP Sink
module-remap-sink Virtual channel remapping sink
module-remap-source Virtual channel remapping source
module-rescue-streams When a sink/source is removed, try to move its streams to the default sink/source
module-role-cork Mute & cork streams with certain roles while others exist
module-role-ducking Apply a ducking effect based on streams roles
module-rtp-recv Receive data from a network via RTP/SAP/SDP
module-rtp-send Read data from source and send it to the network via RTP/SAP/SDP
module-rygel-media-server UPnP MediaServer Plugin for Rygel
module-simple-protocol-tcp Simple protocol (TCP sockets)
module-simple-protocol-unix Simple protocol (UNIX sockets)
module-sine Sine wave generator
module-sine-source Sine wave generator source
module-solaris Solaris Sink/Source
module-stream-restore Automatically restore the volume/mute/device state of streams
module-suspend-on-idle When a sink/source is idle for too long, suspend it
module-switch-on-connect When a sink/source is added, switch to it or conditionally switch to it
module-switch-on-port-available n/a
module-tunnel-sink Tunnel module for sinks
module-tunnel-sink-new Create a network sink which connects via a stream to a remote PulseAudio server
module-tunnel-source Tunnel module for sources
module-tunnel-source-new Create a network source which connects via a stream to a remote PulseAudio server
module-virtual-sink Virtual sink
module-virtual-source Virtual source
module-virtual-surround-sink Virtual surround sink
module-volume-restore Compatibility module
module-x11-bell X11 bell interceptor
module-x11-cork-request Synthesize X11 media key events when cork/uncork is requested
module-x11-publish X11 credential publisher
module-x11-xsmp X11 session management
module-zeroconf-discover mDNS/DNS-SD Service Discovery
module-zeroconf-publish mDNS/DNS-SD Service Publisher

→ /opt/pulseaudio-10.0/bin/pulseaudio --dump-resample-methods

trivial
speex-float-0
speex-float-1
speex-float-2
speex-float-3
speex-float-4
speex-float-5
speex-float-6
speex-float-7
speex-float-8
speex-float-9
speex-float-10
speex-fixed-0
speex-fixed-1
speex-fixed-2
speex-fixed-3
speex-fixed-4
speex-fixed-5
speex-fixed-6
speex-fixed-7
speex-fixed-8
speex-fixed-9
speex-fixed-10
ffmpeg
auto
copy
peaks

Troubleshooting

After an update, the PulseAudio daemon may fail to start, for example:

$ uname -rosv
SunOS 5.11 illumos-63982b82e6 Solaris

$ pkg info pulseaudio
          Name: library/audio/pulseaudio
       Summary: Sample Rate Converter for audio
      Category: System/Multimedia Libraries
         State: Installed
     Publisher: openindiana.org
       Version: 10.0
        Branch: 2017.0.0.0
Packaging Date: Sun Apr 23 08:35:43 2017
          Size: 12.60 MB
          FMRI: pkg://openindiana.org/library/audio/pulseaudio@10.0-2017.0.0.0:20170423T083543Z
   Project URL: http://www.freedesktop.org/wiki/Software/PulseAudio/
    Source URL: http://freedesktop.org/software/pulseaudio/releases/pulseaudio-10.0.tar.gz

From syslog:

[2017-04-25 14:59:10] xxx pulseaudio[2731]: [ID 295310 user.error] [solaris] sink.c: Assertion '!pa_thread_mq_get()' failed at pulsecore/sink.c:2229, function pa_sink_set_mute(). Aborting.
[2017-04-25 14:59:10] xxx genunix: [ID 603404 kern.notice] NOTICE: core_log: pulseaudio[2731] core dumped: /export/tmp/cores/core.pulseaudio.2731

and you see no elements in mate-volume-control-applet preferences (see ticket: https://www.illumos.org/issues/8110).

This is usually due to regressions in PulseAudio for handling modules and configuration databases: the only known workaround is to make sure the configuration files match the default Hipster files and remove the configuration in the user's home directory. Similar issues have been reported in Linux distributions.

Child pages

PulseAudio

Troubleshooting