---
name: "fwisound"
section: "4"
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/fwisound"
---

# fwisound(4)

Apple FireWire audio driver

## NAME

**fwisound** – Apple FireWire audio driver

## SYNOPSIS

**device firewire** **device fwisound** **device sound**

## DESCRIPTION

The **fwisound** driver provides audio capture from Apple FireWire devices that use a proprietary isochronous audio protocol (not IEC 61883/AMDTP).

The driver attaches to unit directories in the device CSR configuration ROM with Apple OUI (0x000a27) and decodes the "sght" packet signature to deliver stereo PCM audio to the [sound(4)](/sound/4.md) framework.

The device attaches as a standard [sound(4)](/sound/4.md) capture device accessible at */dev/dspX*. The fixed audio format is 48000 Hz, 2-channel, signed 16-bit big-endian (S16BE).

## HARDWARE

The **fwisound** driver supports Apple FireWire devices with the following unit directory:

- *unit\_spec\_ID*

  0x000a27 (Apple OUI)

- *unit\_sw\_version*

  0x000010

Known compatible hardware:

- Apple iSight (FireWire cylinder)

## SYSCTLS

- *hw.firewire.fwisound.iso\_channel*

  Isochronous receive channel (default 1). Can be set as a tunable in [loader.conf(5)](/loader.conf/5.md). Must not conflict with *hw.firewire.fwcam.iso\_channel* (default 0).

## FILES

- */dev/dspX*

  PCM capture device created by [sound(4)](/sound/4.md).

## EXAMPLES

Record five seconds of audio:

```
rec -r 48000 -c 2 -e signed-integer -b 16 -B /tmp/out.wav trim 5
```

If multiple sound devices are present, address the device explicitly:

```
sox -t ossdsp /dev/dsp4 -r 48000 -c 2 -e signed-integer -b 16 \
    /tmp/out.wav trim 5
```

## SEE ALSO

[firewire(4)](/firewire/4.md), [fwohci(4)](/fwohci/4.md), [sound(4)](/sound/4.md), [sysctl(8)](/sysctl/8.md)

## HISTORY

The **fwisound** driver first appeared in FreeBSD 16.0.

## AUTHORS

Abdelkader Boudih ⟨*freebsd@seuros.com*⟩

Protocol reverse-engineered by Clemens Ladisch.