path: root/man/
diff options
Diffstat (limited to 'man/')
1 files changed, 68 insertions, 1 deletions
diff --git a/man/ b/man/
index b30f4484..1f53a60b 100644
--- a/man/
+++ b/man/
@@ -28,6 +28,7 @@ USA.
<cmd>pulseaudio [<arg>options</arg>]</cmd>
<cmd>pulseaudio <opt>--help</opt></cmd>
+ <cmd>pulseaudio <opt>--version</opt></cmd>
<cmd>pulseaudio <opt>--dump-conf</opt></cmd>
<cmd>pulseaudio <opt>--dump-modules</opt></cmd>
<cmd>pulseaudio <opt>--dump-resample-methods</opt></cmd>
@@ -363,7 +364,73 @@ USA.
<section name="Real-time and high-priority scheduling">
- Blablub
+ <p>To minimize the risk of drop-outs during playback it is
+ recommended to run PulseAudio with real-time scheduling if the
+ underlying platform supports it. This decouples the scheduling
+ latency of the PulseAudio daemon from the system load and is thus
+ the best way to make sure that PulseAudio always gets CPU time
+ when it needs it to refill the hardware playback
+ buffers. Unfortunately this is a security risk on most systems,
+ since PulseAudio runs as user process, and giving realtime
+ scheduling priviliges to a user process always comes with the risk
+ that the user misuses it to lock up the system -- which is
+ possible since making a process real-time effectively disables
+ preemption.</p>
+ <p>To minimize the risk PulseAudio by default does not enable
+ real-time scheduling. It is however recommended to enable it
+ on trusted systems. To do that start PulseAudio with
+ <opt>--realtime</opt> (see above) or enabled the appropriate option in
+ <file>daemon.conf</file>. Since acquiring realtime scheduling is a
+ priviliged operation on most systems, some special changes to the
+ system configuration need to be made to allow them to the calling
+ user. Two options are available:</p>
+ <p>On newer Linux systems the system resource limit RLIMIT_RTPRIO
+ (see <manref name="setrlimit" section="2"/> for more information)
+ can be used to allow specific users to acquire real-time
+ scheduling. This can be configured in
+ <file>/etc/security/limits.conf</file>, a resource limit of 9 is recommended.</p>
+ <p>Alternatively, the SUID root bit can be set for the PulseAudio
+ binary. Then, the daemon will drop root priviliges immediately on
+ startup, however retain the CAP_NICE capability (on systems that
+ support it), but only if the calling user is a member of the
+ <arg>pulse-rt</arg> group (see above). For all other users all
+ capababilities are dropped immediately. The advantage of this
+ solution is that the real-time priviliges are only granted to the
+ PulseAudio daemon -- not to all the user's processes.</p>
+ <p>Alternatively, if the risk of locking up the machine is
+ considered too big to enable real-time scheduling, high-priority
+ scheduling can be enabled instead (i.e. negative nice level). This
+ can be enabled by passing <opt>--high-priority</opt> (see above)
+ when starting PulseAudio and may also be enabled with the
+ approriate option in <file>daemon.conf</file>. Negative nice
+ levels can only be enabled when the appropriate resource limit
+ RLIMIT_NICE is set (see <manref name="setrlimit" section="2"/> for
+ more information), possibly configured in
+ <file>/etc/security/limits.conf</file>. A resource limit of 31
+ (corresponding with nice level -11) is recommended.</p>
+ </section>
+ <section name="Environment variables">
+ <p>The PulseAudio client libraries check for the existance of the
+ following environment variables and change their local configuration accordingly:</p>
+ <p><arg>$PULSE_SERVER</arg>: the server string specifying the server to connect to when a client asks for a sound server connection and doesn't explicitly ask for a specific server.</p>
+ <p><arg>$PULSE_SINK</arg>: the symbolic name of the sink to connect to when a client creates a playback stream and doesn't explicitly ask for a specific sink.</p>
+ <p><arg>$PULSE_SOURCE</arg>: the symbolic name of the source to connect to when a client creates a record stream and doesn't explicitly ask for a specific source.</p>
+ <p><arg>$PULSE_BINARY</arg>: path of PulseAudio executable to run when server auto-spawning is used.</p>
+ <p><arg>$PULSE_CLIENTCONFIG</arg>: path of file that shall be read instead of <file>client.conf</file> (see above) for client configuration.</p>
+ <p>These environment settings take precedence -- if set -- over the configuration settings from <file>client.conf</file> (see above).</p>
<section name="Authors">