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Diffstat (limited to 'man/pulseaudio.1.xml.in')
| -rw-r--r-- | man/pulseaudio.1.xml.in | 69 |
1 files changed, 68 insertions, 1 deletions
diff --git a/man/pulseaudio.1.xml.in b/man/pulseaudio.1.xml.in index b30f4484..1f53a60b 100644 --- a/man/pulseaudio.1.xml.in +++ b/man/pulseaudio.1.xml.in @@ -28,6 +28,7 @@ USA. <synopsis> <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> <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> <section name="Authors"> |