sound-setup.html

FreeBSD操作系统的详细使用手册

class="CITEREFENTRY"><span class="REFENTRYTITLE">cdcontrol</span>(1)</span></a>:</p>

<pre class="SCREEN">
<samp class="PROMPT">%</samp> <kbd class="USERINPUT">cdcontrol -f /dev/acd0 play 1</kbd>
</pre>

<p>Various applications, such as <a
href="http://www.FreeBSD.org/cgi/url.cgi?ports/audio/workman/pkg-descr"><tt
class="FILENAME">audio/workman</tt></a> can provide a friendlier interface. You may want
to install an application such as <a
href="http://www.FreeBSD.org/cgi/url.cgi?ports/audio/mpg123/pkg-descr"><tt
class="FILENAME">audio/mpg123</tt></a> to listen to MP3 audio files. A quick way to test
the card is sending data to the <tt class="FILENAME">/dev/dsp</tt>, like this:</p>

<pre class="SCREEN">
<samp class="PROMPT">%</samp> <kbd class="USERINPUT">cat <var
class="REPLACEABLE">filename</var> &gt; /dev/dsp</kbd>
</pre>

<p>where <var class="REPLACEABLE">filename</var> can be any file. This command line
should produce some noise, confirming the sound card is actually working.</p>

<div class="NOTE">
<blockquote class="NOTE">
<p><b>Note:</b> FreeBSD&nbsp;4.X users need to create the sound card device nodes before
being able to use it. If the card showed up in message buffer as <tt
class="DEVICENAME">pcm0</tt>, you will have to run the following as <tt
class="USERNAME">root</tt>:</p>

<pre class="SCREEN">
<samp class="PROMPT">#</samp> <kbd class="USERINPUT">cd /dev</kbd>
<samp class="PROMPT">#</samp> <kbd class="USERINPUT">sh MAKEDEV snd0</kbd>
</pre>

<p>If the card detection returned <tt class="DEVICENAME">pcm1</tt>, follow the same steps
as shown above, replacing <tt class="DEVICENAME">snd0</tt> with <tt
class="DEVICENAME">snd1</tt>.</p>

<p><tt class="COMMAND">MAKEDEV</tt> will create a group of device nodes that will be used
by the different sound related applications.</p>
</blockquote>
</div>

<p>Sound card mixer levels can be changed via the <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=mixer&sektion=8"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">mixer</span>(8)</span></a> command. More
details can be found in the <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=mixer&sektion=8"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">mixer</span>(8)</span></a> manual
page.</p>

<div class="SECT3">
<h3 class="SECT3"><a id="TROUBLESHOOTING" name="TROUBLESHOOTING">7.2.2.1 Common
Problems</a></h3>

<div class="INFORMALTABLE"><a id="AEN8349" name="AEN8349"></a>
<table border="0" frame="void" class="CALSTABLE">
<col />
<col />
<thead>
<tr>
<th>Error</th>
<th>Solution</th>
</tr>
</thead>

<tbody>
<tr>
<td>``<tt class="ERRORNAME">unsupported subdevice XX</tt>''</td>
<td>
<p>One or more of the device nodes was not created correctly. Repeat the steps above.</p>
</td>
</tr>

<tr>
<td>``<tt class="ERRORNAME">sb_dspwr(XX) timed out</tt>''</td>
<td>
<p>The I/O port is not set correctly.</p>
</td>
</tr>

<tr>
<td>``<tt class="ERRORNAME">bad irq XX</tt>''</td>
<td>
<p>The IRQ is set incorrectly. Make sure that the set IRQ and the sound IRQ are the
same.</p>
</td>
</tr>

<tr>
<td>``<tt class="ERRORNAME">xxx: gus pcm not attached, out of memory</tt>''</td>
<td>
<p>There is not enough available memory to use the device.</p>
</td>
</tr>

<tr>
<td>``<tt class="ERRORNAME">xxx: can't open /dev/dsp!</tt>''</td>
<td>
<p>Check with <tt class="COMMAND">fstat | grep dsp</tt> if another application is holding
the device open. Noteworthy troublemakers are <b class="APPLICATION">esound</b> and <b
class="APPLICATION">KDE</b>'s sound support.</p>
</td>
</tr>
</tbody>
</table>
</div>
</div>
</div>

<div class="SECT2">
<h2 class="SECT2"><a id="AEN8384" name="AEN8384">7.2.3 Utilizing Multiple Sound
Sources</a></h2>

<i class="AUTHORGROUP"><span class="CONTRIB">Contributed by</span> Munish Chopra.</i> 

<p>It is often desirable to have multiple sources of sound that are able to play
simultaneously, such as when <b class="APPLICATION">esound</b> or <b
class="APPLICATION">artsd</b> do not support sharing of the sound device with a certain
application.</p>

<p>FreeBSD lets you do this through <span class="emphasis"><i class="EMPHASIS">Virtual
Sound Channels</i></span>, which can be set with the <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=sysctl&sektion=8"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">sysctl</span>(8)</span></a> facility.
Virtual channels allow you to multiplex your sound card's playback channels by mixing
sound in the kernel.</p>

<p>To set the number of virtual channels, there are two sysctl knobs which, if you are
the <tt class="USERNAME">root</tt> user, can be set like this:</p>

<pre class="SCREEN">
<samp class="PROMPT">#</samp> <kbd class="USERINPUT">sysctl hw.snd.pcm0.vchans=4</kbd>
<samp class="PROMPT">#</samp> <kbd class="USERINPUT">sysctl hw.snd.maxautovchans=4</kbd>
</pre>

<p>The above example allocates four virtual channels, which is a practical number for
everyday use. <var class="VARNAME">hw.snd.pcm0.vchans</var> is the number of virtual
channels <tt class="DEVICENAME">pcm0</tt> has, and is configurable once a device has been
attached. <var class="LITERAL">hw.snd.maxautovchans</var> is the number of virtual
channels a new audio device is given when it is attached using <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=kldload&sektion=8"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">kldload</span>(8)</span></a>. Since the
<tt class="DEVICENAME">pcm</tt> module can be loaded independently of the hardware
drivers, <var class="VARNAME">hw.snd.maxautovchans</var> can store how many virtual
channels any devices which are attached later will be given.</p>

<p>If you are not using <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=devfs&sektion=5&manpath=FreeBSD+6-current">
<span class="CITEREFENTRY"><span class="REFENTRYTITLE">devfs</span>(5)</span></a>, you
will have to point your applications at <tt class="FILENAME">/dev/dsp0</tt>.<var
class="REPLACEABLE">x</var>, where <var class="REPLACEABLE">x</var> is 0 to 3 if <var
class="VARNAME">hw.snd.pcm.0.vchans</var> is set to 4 as in the above example. On a
system using <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=devfs&sektion=5&manpath=FreeBSD+6-current">
<span class="CITEREFENTRY"><span class="REFENTRYTITLE">devfs</span>(5)</span></a>, the
above will automatically be allocated transparently to the user.</p>
</div>

<div class="SECT2">
<h2 class="SECT2"><a id="AEN8427" name="AEN8427">7.2.4 Setting Default Values for Mixer
Channels</a></h2>

<i class="AUTHORGROUP"><span class="CONTRIB">Contributed by</span> Josef El-Rayes.</i> 

<p>The default values for the different mixer channels are hardcoded in the sourcecode of
the <a href="http://www.FreeBSD.org/cgi/man.cgi?query=pcm&sektion=4"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">pcm</span>(4)</span></a> driver. There
are a lot of different applications and daemons that allow you to set values for the
mixer they remember and set each time they are started, but this is not a clean solution,
we want to have default values at the driver level. This is accomplished by defining the
appropriate values in <tt class="FILENAME">/boot/device.hints</tt>. E.g.:</p>

<pre class="PROGRAMLISTING">
hint.pcm.0.vol="100"
</pre>

<p>This will set the volume channel to a default value of 100, as soon as the <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=pcm&sektion=4"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">pcm</span>(4)</span></a> module gets
loaded.</p>

<div class="NOTE">
<blockquote class="NOTE">
<p><b>Note:</b> Only FreeBSD 5.3 and above support this.</p>
</blockquote>
</div>
</div>
</div>

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