src/usr.sbin/sndctl/sndctl.8

.\"-
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.Dd April 17, 2026
.Dt SNDCTL 8
.Os
.Sh NAME
.Nm sndctl
.Nd list and modify soundcard properties
.Sh SYNOPSIS
.Nm
.Op Fl -libxo
.Op Fl f Ar device
.Op Fl hov
.Op Ar control Ns Oo = Ns Ar value Oc Ar ...
.Sh DESCRIPTION
The
.Nm
utility is used to set and display sound card properties, using a
control-driven interface, in order to filter and/or set specific properties.
.Pp
The options are as follows:
.Bl -tag -width "-f device"
.It Fl -libxo
Generate output via
.Xr libxo 3
in a selection of different human and machine readable formats.
See
.Xr xo_options 7
for details on command line arguments.
.It Fl f Ar device
Choose a specific audio device
.Pq see Sx FILES .
Userland devices (e.g those registered by
.Xr virtual_oss 8
can also be selected.
.It Fl h
Print a help message.
.It Fl o
Print values in a format suitable for use inside scripts.
.It Fl v
Run in verbose mode.
This option will print all of the device's channel properties.
.El
.Pp
The device controls are as follows:
.Bl -column xxxxxxxxxxxxxxx xxxxx xxxxxxxx xxxxxxxxxxxxxxxxxxx -offset indent
.It Sy Name Ta Sy Type Ta Sy Read/Write Ta Sy Action
.It name Ta String Ta Read Ta Device name
.It desc Ta String Ta Read Ta Device description
.It status Ta String Ta Read Ta Device status
.It devnode Ta String Ta Read Ta Device node
.It from_user Ta Boolean Ta Read Ta Userland device
.It unit Ta Number Ta Read Ta Device unit
.It caps Ta String Ta Read Ta Device OSS capabitilies
.It bitperfect Ta Boolean Ta Read/Write Ta Bit-perfect mode enabled
.It autoconv Ta Boolean Ta Read/Write Ta Auto-conversions enabled
.It realtime Ta Boolean Ta Read/Write Ta Real-time mode enabled
.It eq Ta Boolean Ta Read/Write Ta Equalization enabled
.It eq_preamp Ta String Ta Read/Write Ta Equalization preamp value (in dB)
.It play Ta Group Ta Read Ta Playback properties
.It play.format Ta String Ta Read/Write Ta Playback format
.It play.rate Ta Number Ta Read/Write Ta Playback sample rate
.It play.vchans Ta Boolean Ta Read/Write Ta Playback VCHANs (virtual channels) enabled
.It play.min_rate Ta Number Ta Read Ta Minimum playback sample rate
.It play.max_rate Ta Number Ta Read Ta Maximum playback sample rate
.It play.min_chans Ta Number Ta Read Ta Natively supported minimum playback sample channels
.It play.max_chans Ta Number Ta Read Ta Natively supported maximum playback sample channels
.It play.formats Ta String Ta Read Ta Natively supported playback formats
.It rec Ta Group Ta Read Ta Recording properties
.It rec.format Ta String Ta Read/Write Ta Recording format
.It rec.rate Ta Number Ta Read/Write Ta Recording sample rate
.It rec.vchans Ta Boolean Ta Read/Write Ta Recording VCHANs (virtual channels) enabled
.It rec.min_rate Ta Number Ta Read Ta Minimum recording sample rate
.It rec.max_rate Ta Number Ta Read Ta Maximum recording sample rate
.It rec.min_chans Ta Number Ta Read Ta Natively supported minimum recording sample channels
.It rec.max_chans Ta Number Ta Read Ta Natively supported maximum recording sample channels
.It rec.formats Ta String Ta Read Ta Natively supported recording formats
.El
.Pp
The
.Pa play.format ,
.Pa play.rate ,
.Pa rec.format and
.Pa rec.rate
controls will be read-only if VCHANs are disabled.
.Pp
The device channel controls are as follows:
.Bl -column xxxxxxxxxxxxxxx xxxxx xxxxxxxx xxxxxxxxxxxxxxxxxxx -offset indent
.It Sy Name Ta Sy Type Ta Sy Read/Write Ta Sy Action
.It name Ta String Ta Read Ta Channel name
.It parentchan Ta String Ta Read Ta Parent (primary) channel name
.It unit Ta Number Ta Read Ta Channel unit
.It caps Ta String Ta Read Ta Channel OSS capabilities
.It latency Ta Number Ta Read Ta Channel latency
.It format Ta String Ta Read Ta Channel format
.It rate Ta Number Ta Read Ta Channel sample rate
.It pid Ta Number Ta Read Ta PID of process consuming channel
.It proc Ta String Ta Read Ta Name of process consuming channel
.It interrupts Ta Number Ta Read Ta Number of interrupts since channel was opened
.It xruns Ta Number Ta Read Ta Number of playback underruns/recoring overruns
.It feedcount Ta Number Ta Read Ta Number of bytes fed to channel
.It volume Ta Volume Ta Read Ta Channel left-right volume in normalized form (0.00 to 1.00).
.It hwbuf Ta Group Ta Read Ta Hardware buffer properties
.It hwbuf.format Ta String Ta Read Ta Hardware buffer format
.It hwbuf.rate Ta String Ta Read Ta Hardware buffer sample rate
.It hwbuf.size_bytes Ta Number Ta Read Ta Hardware buffer size in bytes
.It hwbuf.size_frames Ta Number Ta Read Ta Hardware buffer size in frames
.It hwbuf.blksz Ta Number Ta Read Ta Hardware buffer block size
.It hwbuf.blkcnt Ta Number Ta Read Ta Hardware buffer block count
.It hwbuf.free Ta Number Ta Read Ta Hardware buffer free space in bytes
.It hwbuf.ready Ta Number Ta Read Ta Hardware buffer ready space in bytes
.It swbuf Ta Group Ta Read Ta Software buffer properties
.It swbuf.format Ta String Ta Read Ta Software buffer format
.It swbuf.rate Ta String Ta Read Ta Software buffer sample rate
.It swbuf.size_bytes Ta Number Ta Read Ta Software buffer size in bytes
.It swbuf.size_frames Ta Number Ta Read Ta Software buffer size in frames
.It swbuf.blksz Ta Number Ta Read Ta Software buffer block size
.It swbuf.blkcnt Ta Number Ta Read Ta Software buffer block count
.It swbuf.free Ta Number Ta Read Ta Software buffer free space in bytes
.It swbuf.ready Ta Number Ta Read Ta Software buffer ready space in bytes
.It feederchain Ta String Ta Read Ta Channel feeder chain
.El
.Sh FILES
.Bl -tag -width /dev/dspX -compact
.It Pa /dev/dsp
The default audio device.
.It Pa /dev/dspX
The audio device file, where X is the unit of the device, for example
.Ar /dev/dsp0 .
.El
.Sh EXAMPLES
Disable auto-conversions and enable realtime mode to get as low latencies as
possible:
.Bd -literal -offset indent
$ sndctl autoconv=0 realtime=1
.Ed
.Pp
Set the playback sample format to 2-channel signed 24-bit low endian, and sample
rate to 48000 Hz:
.Bd -literal -offset indent
$ sndctl play.format=s24le:2.0 play.rate=48000
.Ed
.Pp
List the PIDs and process names of all channels for
.Pa /dev/dsp1 :
.Bd -literal -offset indent
$ sndctl -f /dev/dsp1 pid proc
.Ed
.Pp
Dump
.Pa /dev/dsp0
information to a file and retrieve back later:
.Bd -literal -offset indent
$ sndctl -f /dev/dsp0 -o > info
\&...
$ sndctl -f /dev/dsp0 `cat info`
.Ed
.Sh SEE ALSO
.Xr sndstat 4 ,
.Xr sound 4 ,
.Xr xo_options 7 ,
.Xr mixer 8 ,
.Xr sysctl 8
.Sh AUTHORS
The
.Nm
utility was implemented by
.An Christos Margiolis Aq Mt christos@FreeBSD.org
under sponsorship from the
.Fx
Foundation.