Module Name: src
Committed By: nat
Date: Fri Oct 27 19:00:07 UTC 2017
Modified Files:
src/share/man/man4: audio.4
Log Message:
Document the hw.driverN.latency sysctl variable.
To generate a diff of this commit:
cvs rdiff -u -r1.80 -r1.81 src/share/man/man4/audio.4
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/share/man/man4/audio.4
diff -u src/share/man/man4/audio.4:1.80 src/share/man/man4/audio.4:1.81
--- src/share/man/man4/audio.4:1.80 Mon Jul 3 21:30:58 2017
+++ src/share/man/man4/audio.4 Fri Oct 27 19:00:07 2017
@@ -1,4 +1,4 @@
-.\" $NetBSD: audio.4,v 1.80 2017/07/03 21:30:58 wiz Exp $
+.\" $NetBSD: audio.4,v 1.81 2017/10/27 19:00:07 nat Exp $
.\"
.\" Copyright (c) 1996 The NetBSD Foundation, Inc.
.\" All rights reserved.
@@ -112,6 +112,7 @@ variables.
.It hw.driverN.precision
.It hw.driverN.frequency
.It hw.driverN.channels
+.It hw.driverN.latency
.It hw.driverN.multiuser
.El
.Pp
@@ -124,10 +125,28 @@ hw.hdafg0.channels, hw.hdafg0.precision,
For best results, values close to the underlying hardware should be chosen.
These variables may only be changed when the sampling device is not in use.
.Pp
-An additional
+The hw.driverN.latency
+.Xr sysctl 8
+variable controls the latency of the in-kernel mixer by varying the hardware
+blocksize.
+It accepts a value in milliseconds(ms), fractional values are not allowed.
+A value of zero will default to 150ms.
+.Pp
+If a static blocksize is enforced by the underlying hardware driver this value
+cannot be changed.
+.Pp
+For audio applications that do not specify a preferred blocksize when configuring
+the audio device, this will be the latency these applications have.
+.Pp
+For audio applications that
+.Xr mmap 2
+the audio device for play back the resultant latency is a third (1/3) of the value
+of the hw.driverN.latency variable.
+.Pp
+The hw.driverN.multiuser
.Xr sysctl 8
variable determines if multiple users are allowed to access the sampling
-device, hw.driverN.multiuser.
+device.
.Pp
By default it is set to false.
This means that the sampling device may be only used by
