Date: Mon, 15 Jul 2002 14:28:15 -0400 (EDT) From: Munish Chopra <mchopra@engmail.uwaterloo.ca> To: FreeBSD-gnats-submit@FreeBSD.org Subject: docs/40609: Add information about vchans to sound chapter in handbook Message-ID: <20020715182815.422CEC30@CPE0030ab0ef2bb.cpe.net.cable.rogers.com>
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>Number: 40609
>Category: docs
>Synopsis: Add information about vchans to sound chapter in handbook
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-doc
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: change-request
>Submitter-Id: current-users
>Arrival-Date: Mon Jul 15 11:30:03 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator: Munish Chopra
>Release: FreeBSD 5.0-CURRENT i386
>Organization:
>Environment:
System: FreeBSD CPE0030ab0ef2bb.cpe.net.cable.rogers.com 5.0-CURRENT FreeBSD 5.0-CURRENT #2: Sun Jul 14 20:26:50 EDT 2002 munish@CPE0030ab0ef2bb.cpe.net.cable.rogers.com:/usr/obj/usr/src/sys/ARCADIA i386
>Description:
The Handbook has been lacking documentation of the vchans feature for
quite a while now. Thanks to Orion Hodson <orion@freebsd.org> for
filling me in on the details. My apologies for the diff, I didn't
check out the docs sources. It is to be applied to:
doc/en_US.ISO8859-1/books/handbook/sound/chapter.sgml
>How-To-Repeat:
>Fix:
--- chapter.sgml Mon Jul 15 13:43:02 2002
+++ vchans.sgml Mon Jul 15 14:22:44 2002
@@ -366,6 +366,36 @@
</sect2>
</sect1>
+ <sect2>
+ <title>Utilizing Multiple Sound Sources</title>
+
+ <para>It is often desirable to have multiple sources of sound that are able to
+ play simultaneously, such as when <application>esound</application> or
+ <application>artsd</application> don't support sharing of the sound device
+ with a certain application.</para>
+
+ <para>FreeBSD lets you do this through `Virtual Sound Channels', which can be
+ set with the &man.sysctl.8; facility. Virtual channels allow you to multiplex
+ your sound card's playback channels by mixing sound in the kernel.</para>
+
+ <para>To set the number of virtual channels, there are two sysctl knobs which,
+ if you are the <username>root</username> user, can be set like this:</para>
+
+ <screen>&prompt.root; sysctl hw.snd.pcm0.vchans=4 &prompt.root;
+ sysctl hw.snd.maxautovchans=4</screen>
+
+ <para><literal>hw.snd.pcm0.vchans</literal> is the number of vchans pcm0 has,
+ and is configurable once a device has been attached.<literal>hw.snd.maxautovchans
+ </literal> is the number of vchans a new audio device is given when it is
+ attached using &man.kldload.8;. Since the pcm module can be loaded independently
+ of the hardware drivers, <literal>hw.snd.maxautovchans</literal> can store how
+ many vchans any devices which are attached later will be given.</para>
+
+ <para>If you are not using &man.devfs.5;, you will have to point your applications
+ at <devicename>/dev/dsp0</devicename>.x, where 'x' is 0 to 3 if <literal>
+ hw.snd.pcm.0.vchans</literal> is set to 4. On a system using devfs, the above
+ will automatically be allocated transparently to the user.</para>
+
<sect1 id="sound-mp3">
<sect1info>
<authorgroup>
>Release-Note:
>Audit-Trail:
>Unformatted:
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