Date: Sat, 11 Jul 2009 15:25:13 +0000 (UTC) From: Joel Dahl <joel@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r195619 - head/share/man/man4 Message-ID: <200907111525.n6BFPDrY056196@svn.freebsd.org>
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Author: joel (doc committer) Date: Sat Jul 11 15:25:13 2009 New Revision: 195619 URL: http://svn.freebsd.org/changeset/base/195619 Log: Document the new multichannel support. Reviewed by: ariff Approved by: re (blanket) Modified: head/share/man/man4/pcm.4 Modified: head/share/man/man4/pcm.4 ============================================================================== --- head/share/man/man4/pcm.4 Sat Jul 11 15:02:45 2009 (r195618) +++ head/share/man/man4/pcm.4 Sat Jul 11 15:25:13 2009 (r195619) @@ -25,7 +25,7 @@ .\" .\" $FreeBSD$ .\" -.Dd July 9, 2009 +.Dd July 11, 2009 .Dt SOUND 4 .Os .Sh NAME @@ -141,6 +141,30 @@ To define default values for the differe set the channel to the preferred value using hints, e.g.: .Va hint.pcm.0.line Ns = Ns Qq Li 0 . This will mute the input channel per default. +.Ss Multichannel Audio +Multichannel audio, popularly referred to as +.Dq surround sound +is supported and enabled by default. +The FreeBSD multichannel matrix processor supports up to 18 interleaved +channels, but the limit is currently set to 8 channels (known as 7.1). +The internal matrix mapping can handle reduction, expansion or +re-routing of channels. +This provides a base interface for related multichannel +.Fn ioctl +support. +Works with or without +.Tn VCHANs . +Most bridge device drivers are still missing multichannel matrixing support +, but in most cases this should be trivial to implement. +Use the +.Va dev.pcm.%d.[play|rec].vchanformat +.Xr sysctl(8) +to adjust the number of channels used. +The current multichannel interleaved structure and arrangement was +implemented by inspecting various popular UNIX applications. +There were no single standard, so much care has been taken to try +to satisfy each possible scenario, despite the fact that each +application has its own conflicting standard. .Ss EQ The Parametric Software Equlizer (EQ) enables the use of .Dq tone @@ -407,6 +431,32 @@ Format for mixing. All playback paths will be converted to this format before the mixing process begins. +By default only 2 channels are enabled. +Available options include: +.Bl -tag -width 2n +.It s16le:1.0 +Mono +.It s16le:2.0 +Stereo, 2 channels, (left, right). +.It s16le:2.1 +3 channels (left, right, LFE). +.It s16le:3.0 +3 channels (left, right, rear center). +.It s16le:4.0 +Quadraphonic, 4 channels (front/rear left and right). +.It s16le:4.1 +5 channels (4.0 + LFE). +.It s16le:5.0 +5 channels (4.0 + center). +.It s16le:5.1 +6 channels (4.0 + center + LFE). +.It s16le:6.0 +6 channels (4.0 + front/rear center). +.It s16le:6.1 +7 channels (6.0 + LFE). +.It s16le:7.1 +8 channels (4.0 + center + LFE + left and right side). +.El .It Va dev.pcm.%d.[play|rec].vchanmode .Tn VCHAN format/rate selection.
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