path: root/doc/artsbuilder/faq.docbook

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<chapter id="faq">
<title>Questions and answers</title>

<para>
This section answers some frequently asked questions about &arts;.
</para>

<qandaset id="faq-general">
<title>General Questions</title>

<qandaentry>
<question>
<para>
Does &kde; support my sound card for audio output?
</para>
</question>

<answer>
<para>
&kde; uses &arts; to play sound, and &arts; uses the &Linux; kernel
sound drivers, either <acronym>OSS</acronym> or <acronym>ALSA</acronym>
(using <acronym>OSS</acronym> emulation). If your sound card is
supported by either <acronym>ALSA</acronym> or <acronym>OSS</acronym>
and properly configured (&ie; any other &Linux; application can output
sound), it will work. There are however some problems with some specific
hardware, please read the <link linkend="faq-hardware-specific">section
for hardware specific problems</link> if you're having problems with artsd
on your machine.
</para>
<para>
Meanwhile also support for various other platforms has been added. Here is
a complete list of how the most recent version of &arts; can play sound. If
you have an unsupported platform, please consider porting &arts; to your
platform.
</para>

<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>&arts; audio I/O method</entry>
<entry>Comment</entry>
</row>
</thead>

<tbody>
<row>
<entry>paud</entry>
<entry>Support for AIX Personal Audio Device</entry>
</row>

<row>
<entry>alsa</entry>
<entry>Linux ALSA-0.5 and ALSA-0.9 drivers</entry>
</row>

<row>
<entry>libaudioio</entry>
<entry>Support for generic LibAudioIO library which works on Solaris</entry>
</row>

<row>
<entry>nas</entry>
<entry>NAS sound server, useful for X Terminals with NAS support</entry>
</row>

<row>
<entry>null</entry>
<entry>Null audio device, discards sound silently</entry>
</row>

<row>
<entry>oss</entry>
<entry>OSS (Open Sound System) support (works on Linux, various BSDs and
       other platforms with OSS drivers installed)</entry>
</row>

<row>
<entry>toss</entry>
<entry>Threaded OSS support, which works better in some cases where the
       standard OSS support doesn't work well</entry>
</row>

<row>
<entry>sgi</entry>
<entry>SGI Direct Media support for IRIX</entry>
</row>

<row>
<entry>sun</entry>
<entry>Solaris support</entry>
</row>

</tbody>
</tgroup>
</informaltable>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>
I can't play <literal role="extension">wav</literal> files with &artsd;!
</para>
</question>

<answer>
<para>
Check that &artsd; is linked to <filename>libaudiofile</filename>
(<userinput><command>ldd</command>
<parameter>artsd</parameter></userinput>). If it isn't, download
kdesupport, recompile everything, and it will work.
</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>
I hear sound when logged in as <systemitem
class="username">root</systemitem> but no other users have sound!
</para>
</question>

<answer>
<para>
The permissions of the file <filename
class="devicefile">/dev/dsp</filename> affect which users will have
sound. To allow everyone to use it, do this:
</para>

<procedure>
<step>
<para>
Log in as <systemitem class="username">root</systemitem>.
</para>
</step>

<step>
<para>
Open a &konqueror; window.
</para>
</step>

<step>
<para>
Go into the <filename class="directory">/dev</filename> folder.
</para>
</step>

<step>
<para>
Click on the file <filename>dsp</filename> with the
<mousebutton>right</mousebutton> mouse button, and choose properties.
</para>
</step>

<step>
<para>
Click on the <guilabel>Permissions</guilabel> tab.
</para>
</step>

<step>
<para>
Check the <guilabel>Read</guilabel> and <guilabel>Write</guilabel> check
boxes in all sections.
</para>
</step>

<step>
<para>
Click on <guibutton>OK</guibutton>.
</para>
</step>
</procedure>

<para>
You can achieve the same effect in a terminal window using the command
<userinput><command>chmod</command> <option>666</option>
<parameter>/dev/dsp</parameter></userinput>.
</para>

<para>
For restricting access to sound to specific users, you can use group
permissions. On some &Linux; distributions, for instance Debian/Potato,
<filename class="devicefile">/dev/dsp</filename> is already owned by a
group called <systemitem class="groupname">audio</systemitem>, so all
you need to do is add the users to this group.
</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>
This helps for &artsd;, but what about &kmix;, &kmid;, &kscd;,&etc;?
</para>
</question>
<answer>

<para>
There are various other devices which provide functionality accessed by
multimedia applications. You can treat them in the same way, either by
making them accessible for everyone, or using groups to control
access. Here is a list, which may still be incomplete (also if there are
various devices in a form like <filename
class="devicefile">midi0</filename>, <filename
class="devicefile">midi1</filename>, ..., then only the 0-version is
listed here):
</para>

<itemizedlist>
<listitem>
<para>
<filename class="devicefile">/dev/admmidi0</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/adsp0</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/amidi0</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/amixer0</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/audio</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/audio0</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/cdrom</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/dmfm0</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/dmmidi0</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/dsp</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/dsp0</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/midi0</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/midi0</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/midi00</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/midi00</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/mixer</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/mixer0</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/mpu401data</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/mpu401stat</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/music</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/rmidi0</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/rtc</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/sequencer</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/smpte0</filename>
</para>
</listitem>
<listitem>
<para>
<filename class="devicefile">/dev/sndstat</filename>
</para>
</listitem>
</itemizedlist>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>What can I do if artsd doesn't start or crashes while running?</para>
</question>

<answer>
<para>
First of all: try using the default settings in &kcontrol; (or if you
are starting manually, don't give additional options besides maybe
<userinput><option>-F</option><parameter>10</parameter>
<option>-S</option><parameter>4096</parameter></userinput> for
latency). Especially <emphasis>full duplex is likely to break</emphasis>
with various drivers, so try disabling it.
</para>

<para>
A good way to figure out why &artsd; doesn't start (or crashes while
running) is to start it manually. Open a &konsole; window, and do:
</para>

<screen width="40"><prompt>%</prompt> <userinput><command>artsd</command> <option>-F</option><parameter>10</parameter> <option>-S</option><parameter>4096</parameter></userinput></screen>

<para>
You can also add the <option>-l0</option> option, which will print more
information about what is happening, like this:
</para>
<screen width="40"><prompt>%</prompt> <userinput><command>artsd</command> <option>-l0</option> <option>-F</option><parameter>10</parameter> <option>-S</option><parameter>4096</parameter></userinput></screen>

<para>
Doing so, you will probably get some useful information why it didn't
start. Or, if it crashes when doing this-and-that, you can do
this-and-that, and see <quote>how</quote> it crashes. If you want to
report a bug, producing a backtrace with <command>gdb</command> and/or
an <command>strace</command> may help finding the problem.
</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>Can I relocate &artsd; (move compiled files to another
folder)?</para>
</question>

<answer>
<para>
You can't relocate &arts; perfectly. The problem is that &artswrapper;
has the location of &artsd; compiled in due to security reasons. You can
however use the <filename>.mcoprc</filename> file
(TraderPath/ExtensionPath entries) to at least make a relocated &artsd;
find it's components. See the <link linkend="the-mcoprc-file">chapter
about the <filename>.mcoprc</filename> file</link> for details on how to
do this.
</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>Can I compile &arts; with gcc-3.0?</para>
</question>

<answer>
<para>
Short answer: no, &arts; will not work if you compile it with gcc-3.0.
</para>

<para>
Long answer: In the official release, there are two gcc-3.0 bugs which affect
&arts;. The first, gcc-3.0 bug c++/2733 is relatively harmless (and has to do
with problems with the asm statement). It breaks compilation of convert.cc. It
has been fixed in the gcc-3.0 CVS, and will no longer be a problem with
gcc-3.0.1 and higher. A workaround has also been added to the CVS version
of KDE/aRts.
</para>
<para>
The second gcc-3.0 bug, c++/3145 (which is generation of wrong code for some
cases of multiple virtual inheritance) is critical. Applications like &artsd;
will simply crash on startup when compiled with gcc-3.0. Even if some progress
has been made in the gcc-3.0 branch at time of this writing, still &artsd;
crashes quite often, unpredictably.
</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>What applications run under &arts;?</para>
</question>
<answer>

<para>
Obviously, all of the applications included with &kde; are
&arts;-aware. This includes:
</para>

<itemizedlist>
<listitem><para>&noatun;</para></listitem>
<listitem><para>&arts-builder;</para></listitem>
<listitem><para>&aktion;</para></listitem>
<listitem><para>&kmid;</para></listitem>
<listitem><para>&kmidi;</para></listitem>
<listitem><para>&kmix;</para></listitem>
<listitem><para>&kscd;</para></listitem>
<listitem><para>&kde; games such as &kpoker; and
&ktuberling;</para></listitem>
</itemizedlist>

<para>
Some &kde; applications that are not yet included in the &kde; release
(&eg; in kdenonbeta) also support &arts;, including:
</para>

<itemizedlist>
<listitem><para>&brahms;</para></listitem>
<listitem><para><application>Kaboodle</application></para></listitem>
<listitem><para><application>Kdao</application></para></listitem>
</itemizedlist>

<para>
The following non-&kde; applications are known to work with &arts;:
</para>

<itemizedlist>
<listitem><para><application>xmms</application> (with &arts;
plug-in)</para></listitem>
<listitem><para>Real Networks <application>RealPlayer</application> 8.0
(works with &artsdsp;; native &arts; support is being
considered)</para></listitem>
</itemizedlist>

<para>
The following applications are known <emphasis>not</emphasis> to work
with &arts;:
</para>

<itemizedlist>
<listitem><para>none</para></listitem>
</itemizedlist>

<para>
See also the answers to the questions in the section on
<link linkend="faq-non-arts">non-&arts; applications</link>.
</para>

<para>
This section is incomplete -- if you have more information on supported
and unsupported applications, please send them to the author so they can
be included here.
</para>
</answer>
</qandaentry>

</qandaset>

<qandaset id="faq-non-arts">
<title>Non-&arts; Applications</title>

<qandaentry>
<question>
<para>
As soon as &kde; is running, no other application can access my sound device!
</para>
</question>
<answer>
<para>
Since the &arts; sound server used by &kde; is running, it is using the
sound device. If the server is idle for 60 seconds, it will
auto-suspend and release it automatically.
</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>
You said it suspends after 60 seconds, it doesn't for me!
</para>
</question>
<answer>
<para>
If you start artsd from the KDE control panel, the default is to suspend
after 60 seconds. If you start artsd from the command line you need to
use the -s option to specify the autosuspend time, otherwise it will
default to disabling the autosuspend feature.
</para>
<para>
Currently it doesn't suspend when using full duplex. Turn full duplex
off from the &kcontrol; and it will suspend. Disabling full duplex is
generally a good idea anyway if you only use &arts; for playing audio
and not recording.
</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>
How can I run old, non-&arts; applications?
</para>
</question>

<answer>
<para>
Run them using the &artsdsp;. For instance, if you normally would run:
</para>

<screen><prompt>&percnt;</prompt> <userinput><command>mpg123</command> <option>foo.mp3</option></userinput></screen>

<para>instead use:</para>

<screen><prompt>&percnt;</prompt> <userinput><command>artsdsp</command> <option>mpg123 foo.mp3</option></userinput></screen>

<para>
This will redirect the sound output to &arts;. This method doesn't
require changes to the applications. It is something of an ugly hack
however, and does not yet fully support all features of the sound card
device, so some applications may not work.
</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>
I can't run &artsdsp; with any application, it always crashes!
</para>
</question>
<answer>
<para>
You need a recent version of the glibc library; &artsdsp; will not work
reliably on some older &Linux; distributions. For instance, on Debian
2.1 (which is glibc 2.0 based) it doesn't work, while on Debian 2.2
(which is glibc 2.1.3 based), it does.
</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>
Are there theoretical limitations with some applications that will
prevent them from ever working with &artsdsp;?
</para>
</question>
<answer>
<para>
No. Using &artsdsp; can result in slightly more latency and
<acronym>CPU</acronym> usage that using the &arts;
<acronym>API</acronym>s directly. Other than that, any application that
doesn't work should be considered a bug in &artsdsp;. The technique used
by &artsdsp; should, if implemented properly, allow
<emphasis>every</emphasis> application to work with it (including large
applications like <application>Quake</application> 3).
</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>
What can I do if an application doesn't work with &artsdsp;?
</para>
</question>
<answer>
<para>
You can wait for &artsd; to suspend or use the command
<userinput><command>artsshell</command>
<option>suspend</option></userinput> to ask the server to suspend
itself. You will only be able to suspend the server if no &arts;
applications are currently using it, and no &arts; applications will be
able to run when the server is suspended.
</para>

<para>
If the server is busy, a crude but effective way to get rid of it is:
</para>


<screen><prompt>&percnt;</prompt> <userinput><command>killall</command> <option>artsd</option> ; <command>killall</command> <option>artswrapper</option></userinput>
<lineannotation>Now start your own application.</lineannotation>
<prompt>&percnt;</prompt> <userinput><command>kcminit</command> <option>arts</option></userinput>
</screen>

<para>
Any currently running &arts; applications may crash, however, once you
kill the server.
</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>
What about applications written for &kde; 1.x?
</para>
</question>
<answer>
<para>
If you are running &kde; 1.x applications, which output sound via the
&kde; 1 audio server, you will need to run
<application>kaudioserver</application> to make it work. You can start
<application>kaudioserver</application> in the same way than other
non-&arts;-applications:
</para>

<screen>
<prompt>&percnt;</prompt> <userinput><command>artsdsp</command> <option>kaudioserver</option></userinput>
</screen>

<para>
You will need to have installed kaudioserver (from the same source where
you got your &kde; 1.x applications from) - it belongs to &kde; 1.x, not
&kde; 2.
</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>
What about applications using the enlightened sound daemon,
<acronym>ESD</acronym>?
</para>
</question>
<answer>
<para>
The issue is similar than with
<application>kaudioserver</application>. Such applications will need a
running esd server. You can start <command>esd</command> via &artsdsp;,
and every <acronym>ESD</acronym> aware application should work fine,
like this:
</para>
<screen>
<prompt>&percnt;</prompt> <userinput><command>artsdsp</command> <option>esd</option></userinput>
</screen>
<para>
Newer versions of aRts (>= 1.2.0) also can also use the enlightened sound
daemon instead of directly accessing the soundcard. On the command line, you
can use the -a option, such as
</para>
<screen>
<prompt>&percnt;</prompt> <userinput><command>artsd</command> <option>-a esd</option></userinput>
</screen>
<para>
to get EsounD support, whereas in KDE, you can use kcontrol to configure artsd
to use esd via Sound -&gt; Sound Server -&gt; Sound I/O.
</para>
</answer>
</qandaentry>

</qandaset>

<qandaset id="faq-latency">
<title>Latency</title>

<qandaentry>
<question>
<para>
I sometimes hear short pauses when listening to music, is this a bug?
</para>
</question>
<answer>
<para>
This is most likely not a bug, but caused by the fact that the &Linux;
kernel is not very good at real-time scheduling. There are situations
where &arts; will not be able to keep up with playback. You can,
however, enable real-time rights (via &kcontrol;), and use a large
latency setting (like <guilabel>250ms</guilabel> or <guilabel>don't
care</guilabel>), which should improve the situation.
</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>
What's the effect of the response time setting?
</para>
</question>
<answer>
<para>
The help text for this setting in the &kcontrol; can be misleading.  A
lower value means that &arts; will take less time to respond to external
events (&ie;. the time that it takes between closing a window and
hearing a sound played by &artsd;). It will also use more
<acronym>CPU</acronym> resources, and be more likely to cause
dropouts.</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>
Is there anything else I can do to prevent pauses?
</para>
</question>
<answer>
<para>
For users of <acronym>IDE</acronym> drives, you can use the
<command>hdparm</command> command to put your <acronym>IDE</acronym>
drive in <acronym>DMA</acronym> mode. A word of warning: this does not
work on all hardware, and can result in having to do a hard reset or in
rare cases, data loss. Read the documentation for the
<command>hdparm</command> command for more details. I have successfully
used the following command:
</para>

<screen>
<prompt>&percnt;</prompt> <userinput><command>hdparm</command> <option>-c1</option> <option>-d1</option> <option>-k1</option> <option>-K1</option> <parameter>/dev/hda</parameter></userinput>
</screen>

<para>
You need to run this after every boot, so you might want to place it in
a system startup script (how to do this distribution specific, on Debian
&Linux; it is usually put in <filename>/etc/rc.boot</filename>).
</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>
Realtime priority doesn't seem to have any effect for me?
</para>
</question>
<answer>
<para>
Verify that artswrapper is really installed suid <systemitem class="username">root</systemitem>, like it is supposed to
be. A lot of distributions (SuSE7.x for instance) don't do this. You can verify
this using: ls -l $(which artswrapper). Good:
<screen>
<prompt>&percnt;</prompt> <userinput><command>ls</command> <option>-l</option> <parameter>$(which artswrapper)</parameter></userinput>
-rwsr-xr-x    1 root     root         4556 Sep 24 18:05 /opt/kde2/bin/artswrapper
</screen>
Bad:
<screen>
<prompt>&percnt;</prompt> <userinput><command>ls</command> <option>-l</option> <parameter>$(which artswrapper)</parameter></userinput>
-rwxr-xr-x    1 root     root         4556 Sep 24 18:05 /opt/kde2/bin/artswrapper
</screen>
If you are not having the s, you can get it using:
<screen>
<prompt>&percnt;</prompt> <userinput><command>chown</command> <option>root</option> <parameter>$(which artswrapper)</parameter></userinput>
<prompt>&percnt;</prompt> <userinput><command>chmod</command> <option>4755</option> <parameter>$(which artswrapper)</parameter></userinput>
</screen>
</para>

<para>If you make &artswrapper; SUID <systemitem
class="username">root</systemitem>, it will likely improve the quality
of your audio playback by reducing gaps in the music.  However, it
also increases the risk that a bug in the code or a malicious user can
crash or otherwise harm your machine.  In addition, on multi-user
machines, prioritizing high-quality audio may result in deteriorated
performance for the users who are trying to make
<quote>productive</quote> use of the machine.</para>

</answer>
</qandaentry>


<qandaentry>
<question>
<para>
Why is &artsd; taking so much <acronym>CPU</acronym> time?
</para>
</question>
<answer>
<para>
Check your response time settings. However, the current version is not
yet really optimized. This will improve, and until then no real
prediction can be made how fast &artsd; can or can't be.
</para>
</answer>
</qandaentry>
</qandaset>

<qandaset id="faq-network">
<title>Network Transparency</title>

<qandaentry>
<question>
<para>
What do I need for network transparency?
</para>
</question>
<answer>
<para>
Enable it in the &kcontrol; <guilabel>Sound Server</guilabel> settings
(<guilabel>enable X11 server for security information</guilabel> and
<guilabel>network transparency</guilabel>). Then copy your
<filename>.mcoprc</filename> to all machines you plan to use network
transparency from. Log in again. Make sure that the hosts that interact
know each other by name (&ie; they have resolvable names or are in
<filename>/etc/hosts</filename>).
</para>

<para>
This should be all you need to do. However, if it still doesn't work
here are some additional details. The &arts; sound server process,
&artsd;, should only run on one host, the one with the sound card where
the sound should be played. It can be started automatically on login by
&kde; (if you configure that in &kcontrol;), or manually using something
like:
</para>

<screen>
<prompt>&percnt;</prompt> <userinput><command>artsd</command> <option>-n</option> <option>-F</option> <parameter>5</parameter> <option>-S</option> <parameter>8192</parameter></userinput>
</screen>

<para>
The <option>-n</option> parameter is for network transparency, while the
others configure latency.
</para>

<para>
Your <filename>.mcoprc</filename> file should have this entry:
</para>

<screen>
<userinput>GlobalComm=Arts::X11GlobalComm</userinput>
</screen>

<para>
on all machines involved, in order for network transparency to work,
This is what is enabled by the <guilabel>X11 server for security
information</guilabel> control panel setting.
</para>

<para>
Finally, in any &kde; version in the 2.0.x series, there is a bug which
applies if you don't have a domain name set. Clients of &artsd; try to
find where to connect to via the <systemitem
class="systemname"><replaceable>hostname</replaceable>.<replaceable>domainname</replaceable></systemitem>
combination. If your domain name is empty, it will try to connect to
<systemitem
class="systemname"><replaceable>hostname</replaceable></systemitem>. (note
the extra dot). Adding an entry like this to
<filename>/etc/hosts</filename> (&ie; <userinput>orion.</userinput> if
your hostname is <systemitem class="systemname">orion</systemitem>)
works around the problem.
</para>
</answer>
</qandaentry>


<qandaentry>
<question>
<para>
How do I debug network transparency if it doesn't work?
</para>
</question>
<answer>
<para>
Assuming you have the &kde; source code, go to <filename
class="directory">kdelibs/arts/examples</filename>, and run
<userinput><command>make</command> <option>check</option></userinput> to
compile some programs, including
<application>referenceinfo</application>. Then run
</para>

<screen>
<prompt>&percnt;</prompt> <userinput><command>./referenceinfo</command> <option>global:Arts&lowbar;SimpleSoundServer</option></userinput>
</screen>

<para>
The output will indicate the host name and port being used by
&arts;. For example, <computeroutput>tcp:orion:1698</computeroutput>
would mean that any client trying to use network transparency should
know how to reach host <systemitem
class="systemname">orion</systemitem>.
</para>
</answer>
</qandaentry>

</qandaset>

<qandaset id="faq-hardware-specific">
<title>Hardware specific questions</title>

<qandaentry>
<question>
<para>
What hardware artsd doesn't work well with?
</para>
</question>
<answer>
<para>
It seems that there are a few linux drivers which don't work well with aRts in
some kernel versions. Please read this list before reporting a bug. If you
find that some information in this list is incomplete, please don't hesitate
to let us know.

<informaltable>
<tgroup cols="4">
<thead>
<row>
<entry>Linux Driver / Soundcard</entry>
<entry>Fails under</entry>
<entry>Works under</entry>
<entry>Remarks</entry>
</row>
</thead>

<tbody>
<row>
<entry>i810 driver (Intel 810 + AC97 Audio)</entry>
<entry>2.4.9</entry>
<entry>2.4.18, 2.2.20, commercial oss driver, alsa-0.5.12a with OSS emulation</entry>
<entry>driver causes cpu overload (see below)</entry>
</row>

<row>
<entry>maestro 3/4 chipset</entry>
<entry>2.4.9</entry>
<entry>?</entry>
<entry>driver sometimes causes cpu overload (see below)</entry>
</row>

<row>
<entry>aureal8820, aureal8830 drivers from sourceforge</entry>
<entry>2.4.17</entry>
<entry>?</entry>
<entry>driver triggers assertion / causes cpu overload (see below)</entry>
</row>

<row>
<entry>OSS Commercial 3.9.4g with Aureal Vortex</entry>
<entry>?</entry>
<entry>?</entry>
<entry>system lockup</entry>
</row>

<row>
<entry>ymfpci</entry>
<entry>2.4.0, 2.4.12</entry>
<entry>2.4.17</entry>
<entry>driver triggers assertion (see below)</entry>
</row>



</tbody>
</tgroup>
</informaltable>
</para>
</answer>
</qandaentry>



<qandaentry>
<question>
<para>
Why are there hardware specific problems and how do I see them?
</para>
</question>
<answer>
<para>
The usual problem is that the driver doesn't supply aRts with enough or accurate
enough information on when to write sound data. Most OSS drivers do supply
correct information, but not all.
</para>
<para>
You might notice that some other applications (like xmms) may not need this
data, and thus work correctly even with your hardware. However, &arts; needs
this data, so artsd might fail. This is still a bug in the driver, and not
in &arts;.
</para>
<para>
There are two kinds of behavior that artsd exposes on being run on an incorrect
driver. Either, it continously tries to feed new data, but never really
succeeds, which eventually leads to consuming all CPU power and reporting
<emphasis>cpu overload</emphasis> and exiting. The other problem is that artsd
might get supplied with wrong information how much to write. Artsd will then
<emphasis>stop with an assertion</emphasis> like:
<screen>
artsd: audiosubsys.cc:458: void Arts::AudioSubSystem::handleIO(int):
Assertion `len == can_write' failed.
Aborted
</screen>
</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>
What is wrong in the driver if I get the cpu overload problem?
</para>
</question>
<answer>
<para>
Usually, artsd uses select() to find out when to write new data. Then, it
uses an ioctl(...GETOSPACE...) to find out how much data to write. Finally,
it writes this data.
</para>
<para>
A problem occurs if artsd is woken up either always or if there are minimal
amounts of data to write. The OSS documentation specifies that select() only
wakes up a process if there is at least one fragment to write. However, if
artsd is woken up if there isn't data to write, or very little, for instance
one sample, then it will keep writing little pieces of audio data, which can
be very costly, and eventually overload the cpu.
</para>
<para>
To fix this, the driver should wake up artsd only if there is a full fragment
to write.
</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>
What is wrong in the driver if I get the assertion?
</para>
</question>
<answer>
<para>
Usually, artsd uses select() to find out when to write new data. Then, it
uses an ioctl(...GETOSPACE...) to find out how much data to write. Finally,
it writes this data.
</para>
<para>
If artsd can't write as much data as indicated by the ioctl, it will fail in
the assertion. To fix this, the driver should supply the correct amount of
free space.
</para>
</answer>
</qandaentry>
</qandaset>

<qandaset id="faq-other">
<title>Other Issues</title>

<qandaentry>
<question>
<para>
I can't use &arts-builder;. It crashes when executing a module!
</para>
</question>
<answer>
<para>
The most likely cause is that you are using old structures or modules
which aren't supported with the &kde; 2 version. Unfortunately the
documentation which is on the web refers to &arts;-0.3.4.1 which is
quite outdated. The most often reported crash is: that performing an
execute structure in &arts-builder; results in the error message
<errorname>[artsd] Synth_PLAY: audio subsystem is already
used.</errorname>
</para>

<para>
You should use a Synth_AMAN_PLAY instead of a Synth_PLAY module and the
problem will go away. Also see the &arts-builder; help file (hit
<keycap>F1</keycap> in &arts-builder;).
</para>

<para>
Recent versions of &arts-builder; (&kde; 2.1 beta 1 and later) come with
a set of examples which you can use.
</para>
</answer>
</qandaentry>

</qandaset>

</chapter>