Audio

AU-01 // AUDIO

FreeBSD uses the Open Sound System (OSS), a kernel-level audio mixer. Applications write to /dev/dsp directly. No PipeWire. No PulseAudio. No WirePlumber. No daemons.

How It Works

The kernel mixes up to 256 virtual channels. Each application gets its own channel. Volume is controlled per-channel or globally via sysctl or /dev/mixer.

# Check loaded sound modules
cat /dev/sndstat

# Output (example)
Installed devices:
pcm0: <Realtek ALC1220 (Rear Analog)> (play/rec) default
pcm1: <Realtek ALC1220 (Front Analog)> (play/rec)
pcm2: <HDMI/DP (NVIDIA)> (play)

Stack Comparison

Layer	FreeBSD	Linux (PipeWire)
Application	writes to /dev/dsp	PipeWire client API
Session manager	—	WirePlumber
Sound server	—	PipeWire daemon
Compat layer	—	PulseAudio emulation (libpipewire-pulse)
Kernel driver	snd_hda (kernel module)	ALSA (kernel module)

FreeBSD audio requires one kernel module and zero daemons. Simpler means fewer failure modes.

Commands

volume

The volume script wraps sysctl and mixer for quick keyboard-driven control:

volume up        # +5%
volume down      # -5%
volume mute      # toggle mute
volume set 60    # set to 60%
volume status    # print current level

These are bound to the media keys in Hyprland by default. See Keybindings.

audio-setup

audio-setup

Interactive audio configuration. Lets you:

• Select the default output device
• Set per-application volumes
• Configure sample rate and bit depth
• Test audio output

# List available devices
audio-setup list

# Set default output device by index
audio-setup default 1

Configuration

Audio settings persist via sysctl.conf and loader.conf:

# /etc/sysctl.conf
hw.snd.default_unit=0          # default audio device index
hw.snd.default_auto=1          # auto-switch to new devices
dev.pcm.0.play.vchanmixer=100  # master volume (0-100)

# /boot/loader.conf
snd_hda_load="YES"    # Intel HDA (most systems)
snd_uaudio_load="YES" # USB audio devices

Bluetooth Audio

Bluetooth requires virtual_oss to bridge the Bluetooth device to an OSS virtual device:

pkg install virtual_oss

# Pair device first
bluetoothctl
  > scan on
  > pair AA:BB:CC:DD:EE:FF
  > connect AA:BB:CC:DD:EE:FF

# Bridge Bluetooth to OSS
virtual_oss -T /dev/sndstat -C 2 -c 2 -r 48000 -b 16 \
  -s 1024 -f /dev/dsp -d dsp

rc.conf entry for virtual_oss at boot

sudo sysrc virtual_oss_enable=YES
sudo sysrc virtual_oss_dsp="/dev/dsp"

Then configure /usr/local/etc/virtual_oss.conf with your device parameters.

Troubleshooting

No audio output

# Verify device loaded
cat /dev/sndstat

# Check default device
sysctl hw.snd.default_unit

# Test playback
cat /dev/urandom | dd bs=4096 count=4 > /dev/dsp

If /dev/dsp does not exist, the kernel module is not loaded. Add snd_hda_load="YES" to /boot/loader.conf and reboot.

Wrong output device

# List devices with index
cat /dev/sndstat | grep pcm

# Set default (replace 1 with your device index)
sudo sysctl hw.snd.default_unit=1

# Persist
echo 'hw.snd.default_unit=1' | sudo tee -a /etc/sysctl.conf

Volume control has no effect

Verify you are targeting the correct mixer device. The volume script uses sysctl targeting hw.snd.default_unit. If you have multiple sound cards, ensure hw.snd.default_unit points to the active output.