2004-09-07 22:40:43 +00:00
<?xml version="1.0" encoding="iso-8859-1"?> <!-- - * - html - helper - * - -->
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
< html xmlns = "http://www.w3.org/1999/xhtml" >
< head >
< title > polypaudio: FAQ< / title >
< link rel = "stylesheet" type = "text/css" href = "style.css" / >
< / head >
< body >
< h1 > Frequently Asked Questions< / h1 >
< ol >
< li > < p > < b > How does Polypaudio compare with ESOUND/aRts/NAS?< / b > < / p >
< p > Polypaudio is sound daemon similar to ESOUND and NAS, but much more
powerful. aRts is a realtime-synthesizer-cum-sound-server, i.e. it
does much more than Polypaudio. However, I believe that Polypaudio
does what it does much better than any other free sound server.< / p >
< / li >
< li > < p > < b > What about ESOUND compatibility?< / b > < / p >
< p > Polypaudio is a drop in replacement for ESOUND. That means: you can
load a esound compatibility module which implements an ESOUND
compatible protocol which allows you to use most of the classic ESOUND
compatible programs (including the command line programs like
< tt > esdcat< / tt > ).< / p >
< / li >
< li > < p > < b > Is Polypaudio a GNOME program?< / b > < / p >
< p > No, Polypaudio has no dependency on GNOME/GTK/GLIB. All it requires
is a UNIX-like operating system and very few dependency
libraries. However, the accompanying GUI tools are writen with
gtkmm, i.e. require both GLIB and GTK.< / p > < / li >
< li > < p > < b > Can I integrate Polypaudio in my GLIB/GTK/GNOME application?< / b > < / p >
< p > Yes! Polypaudio comes with a GLIB main loop adapter. You can embed
both the client library and the daemon (!) into your GLIB based
application.< / p > < / li >
< li > < p > < b > Can I integrate Polypaudio in my Qt/KDE application?< / b > < / p >
< p > Yes! Polypaudio uses a main loop abstraction layer that allows you
to integrate Polypaudio in any program that supports main
loops. Unfortunately there is no adapter for Qt publicly available yet.< / p > < / li >
< li > < p > < b > I want to write a new driver for Polypaudio, are there any docs?< / b > < / p >
< p > Currently, only the client API is documented with doxygen. Read
the source and base your work on a simple module like
< tt > module-pipe-sink< / tt > .< / p > < / li >
< li > < p > < b > What about compatibility with NAS?< / b > < / p >
< p > Is not available (yet?). It is doable, but noone has implemented it yet.< / p > < / li >
< li > < p > < b > What about compatibility with aRts?< / b > < / p >
< p > Is not available. Since aRts is as synthesizer application you'd have to
reimplement very much code for Polypaudio. It should be easy to
implement limited support for < tt > libartsc< / tt > based
applications. Noone has done this yet. It is probably a better idea to
run < tt > arts< / tt > on top of Polypaudio (through a polypaudio driver
for aRts, which nobody has written yet). Another solution would be to
embed Polypaudio in the aRts process.< / p > < / li >
< li > < p > < b > I often hear noises when playing back with Polypaudio, what can I do?< / b > < / p >
2004-09-23 23:26:15 +00:00
< p > There are to possible solutions: run polypaudio with argument
< tt > --high-priority=1< / tt > and make yourself member of the group
< tt > realtime< / tt > , or increase the fragment sizes of the audio
2004-09-07 22:40:43 +00:00
drivers. The former will allow Polypaudio to activate
< tt > SCHED_FIFO< / tt > high priority scheduling (root rights are dropped
2004-09-23 23:26:15 +00:00
immediately after this) Keep in mind that this is a potential security hole!< / p > < / li >
< li > < p > < b > The < tt > polypaudio< / tt > executable is installed SUID root by default. Why this? Isn't this a potential security hole?< / b > < / p >
< p > Polypaudio activates < tt > SCHED_FIFO< / tt > scheduling if the user
passes < tt > --high-priority=1< / tt > . This will only succeed when
executed as root, therefore the binary is marked SUID root by
default. Yes, this is a potential security hole. However, polypaudio
tries its best to minimize the security threat: immediately after
startup polypaudio drops all capabilities except
< tt > CAP_SYS_NICE< / tt > (At least on systems that support it, like Linux; see < tt > man 7
capabilities< / tt > for more information). If the calling user is not a
member of the group < tt > realtime< / tt > (which is required to have a GID
< 1000 ) , root rights are dropped immediately . This means , you can
install polypaudio SUID root, but only a subset of your users (the
members of the group < tt > realtime< / tt > ) may make use of realtime
scheduling. Keep in mind that these users might load their own binary
modules into the polypaudio daemon which may freeze the machine. The
daemon has a minimal protection against CPU hogging (the daemon is
killed after hogging more than 70% CPU for 5 seconds), but this may
be circumvented easily by evildoers.< / p > < / li >
< li > < p > < b > I want to run polypaudio only when it is needed, how do I do this?< / b > < / p >
2004-09-20 20:52:35 +00:00
< p > Set < tt > autospawn = yes< / tt > in < tt > client.conf< / tt > . That
configuration file may be found either in < tt > /etc/polypaudio/< / tt > or
in < tt > ~/.polypaudio/< / tt > .< / p > < / li >
< li > < p > < b > How do I list all polypaudio modules installed?< / b > < / p >
< p > < tt > polypaudio --dump-modules< / tt > < / p >
< p > Add < tt > -v< / tt > for terse usage instructions.< / p >
2004-09-23 23:26:15 +00:00
< li > < p > < b > How do I use polypaudio over the network?< / b > < / p >
< p > Just set < tt > $POLYP_SERVER< / tt > to the host name of the polypaudio server.< / p >
< li > < p > < b > Is polypaudio capable of providing synchronized audio playback over the network for movie players like < tt > mplayer< / tt > ?< / b > < / p >
< p > Yes! Unless your network is congested in some way (i.e. transfer latencies vary strongly) it works perfectly. Drop me an email for experimental patches for MPlayer.< / p >
< li > < p > < b > What environment variables does polypaudio care about?< / b > < / p >
2004-09-20 20:52:35 +00:00
< p > The client honors: < tt > POLYP_SINK< / tt > (default sink to connect to), < tt > POLYP_SOURCE< / tt > (default source to connect to), < tt > POLYP_SERVER< / tt > (default server to connect to, like < tt > ESPEAKER< / tt > ), < tt > POLYP_BINARY< / tt > (the binary to start when autospawning a daemon), < tt > POLYP_CLIENTCONFIG< / tt > (path to the client configuration file).< / p >
< p > The daemon honors: < tt > POLYP_SCRIPT< / tt > (default CLI script file run after startup), < tt > POLYP_CONFIG< / tt > (default daemon configuration file), < tt > POLYP_DLPATH< / tt > (colon separated list of paths where to look for modules)< / p > < / li >
2004-09-23 23:26:15 +00:00
< li > < p > < b > I saw that SIGUSR2 provokes loading of the module < tt > module-cli-protocol-unix< / tt > . But how do I make use of that?< / b > < / p >
< p > A brilliant guy named Lennart Poettering once wrote a nifty tool
for that purpose: < a
href="http://0pointer.de/lennart/projects/bidilink/">bidilink< / a > . To
connect to a running polypaudio daemon try using the following commands:< / p >
< pre > killall -USR2 polypaudio
bidilink unix-client:/tmp/polypaudio/cli< / pre >
< p > < i > BTW: Someone should package that great tool for Debian!< / i > < / p >
< / li >
2004-09-07 22:40:43 +00:00
< / ol >
< hr / >
< address class = "grey" > Lennart Poettering < @PACKAGE_BUGREPORT@> , September 2004< / address >
< div class = "grey" > < i > $Id$< / i > < / div >
< / body > < / html >
