---
name: "sndctl"
section: "8"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/sndctl"
---

# sndctl(8)

list and modify soundcard properties

## NAME

**sndctl** – list and modify soundcard properties

## SYNOPSIS

**sndctl** \[**--libxo**\] \[**-f** *device*\] \[**-hov**\] \[*control*\[=*value*\] *...*\]

## DESCRIPTION

The **sndctl** utility is used to set and display sound card properties, using a control-driven interface, in order to filter and/or set specific properties.

The options are as follows:

- **--libxo**

  Generate output via [libxo(3)](/libxo/3.md) in a selection of different human and machine readable formats. See [xo\_options(7)](/xo_options/7.md) for details on command line arguments.

- **-f** *device*

  Choose a specific audio device (see FILES). Userland devices (e.g those registered by [virtual\_oss(8)](/virtual_oss/8.md) can also be selected.

- **-h**

  Print a help message.

- **-o**

  Print values in a format suitable for use inside scripts.

- **-v**

  Run in verbose mode. This option will print all of the device's channel properties.

The device controls are as follows:

| | | | |
| --- | --- | --- | --- |
| **Name** | **Type** | **Read/Write** | **Action** |
| name | String | Read | Device name |
| desc | String | Read | Device description |
| status | String | Read | Device status |
| devnode | String | Read | Device node |
| from\_user | Boolean | Read | Userland device |
| unit | Number | Read | Device unit |
| caps | String | Read | Device OSS capabitilies |
| bitperfect | Boolean | Read/Write | Bit-perfect mode enabled |
| autoconv | Boolean | Read/Write | Auto-conversions enabled |
| realtime | Boolean | Read/Write | Real-time mode enabled |
| eq | Boolean | Read/Write | Equalization enabled |
| eq\_preamp | String | Read/Write | Equalization preamp value (in dB) |
| play | Group | Read | Playback properties |
| play.format | String | Read/Write | Playback format |
| play.rate | Number | Read/Write | Playback sample rate |
| play.vchans | Boolean | Read/Write | Playback VCHANs (virtual channels) enabled |
| play.min\_rate | Number | Read | Minimum playback sample rate |
| play.max\_rate | Number | Read | Maximum playback sample rate |
| play.min\_chans | Number | Read | Natively supported minimum playback sample channels |
| play.max\_chans | Number | Read | Natively supported maximum playback sample channels |
| play.formats | String | Read | Natively supported playback formats |
| rec | Group | Read | Recording properties |
| rec.format | String | Read/Write | Recording format |
| rec.rate | Number | Read/Write | Recording sample rate |
| rec.vchans | Boolean | Read/Write | Recording VCHANs (virtual channels) enabled |
| rec.min\_rate | Number | Read | Minimum recording sample rate |
| rec.max\_rate | Number | Read | Maximum recording sample rate |
| rec.min\_chans | Number | Read | Natively supported minimum recording sample channels |
| rec.max\_chans | Number | Read | Natively supported maximum recording sample channels |
| rec.formats | String | Read | Natively supported recording formats |

The *play.format*, *play.rate*, *rec.format* *and* *rec.rate* controls will be read-only if VCHANs are disabled.

The device channel controls are as follows:

| | | | |
| --- | --- | --- | --- |
| **Name** | **Type** | **Read/Write** | **Action** |
| name | String | Read | Channel name |
| parentchan | String | Read | Parent (primary) channel name |
| unit | Number | Read | Channel unit |
| caps | String | Read | Channel OSS capabilities |
| latency | Number | Read | Channel latency |
| format | String | Read | Channel format |
| rate | Number | Read | Channel sample rate |
| pid | Number | Read | PID of process consuming channel |
| proc | String | Read | Name of process consuming channel |
| interrupts | Number | Read | Number of interrupts since channel was opened |
| xruns | Number | Read | Number of playback underruns/recoring overruns |
| feedcount | Number | Read | Number of bytes fed to channel |
| volume | Volume | Read | Channel left-right volume in normalized form (0.00 to 1.00). |
| hwbuf | Group | Read | Hardware buffer properties |
| hwbuf.format | String | Read | Hardware buffer format |
| hwbuf.rate | String | Read | Hardware buffer sample rate |
| hwbuf.size\_bytes | Number | Read | Hardware buffer size in bytes |
| hwbuf.size\_frames | Number | Read | Hardware buffer size in frames |
| hwbuf.blksz | Number | Read | Hardware buffer block size |
| hwbuf.blkcnt | Number | Read | Hardware buffer block count |
| hwbuf.free | Number | Read | Hardware buffer free space in bytes |
| hwbuf.ready | Number | Read | Hardware buffer ready space in bytes |
| swbuf | Group | Read | Software buffer properties |
| swbuf.format | String | Read | Software buffer format |
| swbuf.rate | String | Read | Software buffer sample rate |
| swbuf.size\_bytes | Number | Read | Software buffer size in bytes |
| swbuf.size\_frames | Number | Read | Software buffer size in frames |
| swbuf.blksz | Number | Read | Software buffer block size |
| swbuf.blkcnt | Number | Read | Software buffer block count |
| swbuf.free | Number | Read | Software buffer free space in bytes |
| swbuf.ready | Number | Read | Software buffer ready space in bytes |
| feederchain | String | Read | Channel feeder chain |

## FILES

- */dev/dsp*

  The default audio device.

- */dev/dspX*

  The audio device file, where X is the unit of the device, for example */dev/dsp0*.

## EXAMPLES

Disable auto-conversions and enable realtime mode to get as low latencies as possible:

```
$ sndctl autoconv=0 realtime=1
```

Set the playback sample format to 2-channel signed 24-bit low endian, and sample rate to 48000 Hz:

```
$ sndctl play.format=s24le:2.0 play.rate=48000
```

List the PIDs and process names of all channels for */dev/dsp1*:

```
$ sndctl -f /dev/dsp1 pid proc
```

Dump */dev/dsp0* information to a file and retrieve back later:

```
$ sndctl -f /dev/dsp0 -o > info
...
$ sndctl -f /dev/dsp0 `cat info`
```

## SEE ALSO

[sndstat(4)](/sndstat/4.md), [sound(4)](/sound/4.md), [xo\_options(7)](/xo_options/7.md), [mixer(8)](/mixer/8.md), [sysctl(8)](/sysctl/8.md)

## AUTHORS

The **sndctl** utility was implemented by Christos Margiolis ⟨*christos@FreeBSD.org*⟩ under sponsorship from the FreeBSD Foundation.