headroom

AGC + compressor + true-peak limiter daemon for PipeWire, in Rust.

Headroom puts a per-application audio safety net between noisy sources (browsers, voice chat, random video) and your speakers, while leaving the things you don't want compressed (music players, games, DAWs) untouched.

• Hard −0.1 dBTP ceiling on the processed route, with proper inter-sample-peak handling, enforced inline so the contract holds regardless of control-plane state. Streams routed bypass ride the real sink directly and are not in scope of the contract — that's the trade-off that makes the per-app exclusion useful.
• Per-app exclusion with profile-driven rules.
• Layer A per-app level control (peak + RMS detector → smoothed channelVolumes writes) for taming individual streams without touching the bus path. Zero added signal-path latency; safe to use on bypass-routed streams.
• Single binary daemon + CLI, controlled over a Unix-domain socket with a documented JSON wire protocol (see IPC.md).
• First-party Rust crate (headroom-client) for programmatic use; third-party clients (Qt panels, status bars, …) target the wire protocol directly.
• Live profile reload — edit a TOML file in $XDG_CONFIG_HOME/headroom/profiles/ and the daemon picks up changes within ~500 ms; the audio thread doesn't glitch.

See PLAN.md for the full design and roadmap.

Status

Alpha. The signal chain (AGC, compressor, two-tier limiter, Layer A per-app), the routing engine (explicit-link enforcement, sink hotplug, sticky default sink), the IPC server with topic subscriptions, the headroom monitor TUI, and live profile reload all work end-to-end. Packaging exposes a systemd user unit and Nix modules. What's missing is real-world soak time on multi-rate / Bluetooth setups and other distros' init systems.

Installing

Nix (flake)

This repo is a flake; the daemon plus its systemd user unit and the canonical profiles are exposed as a package.

nix run github:amaanq/headroom -- daemon          # one-shot run
nix profile install github:amaanq/headroom        # add to $PATH

For Home Manager, add the flake as an input and enable the module:

{
  inputs.headroom.url = "github:amaanq/headroom";

  # In your Home Manager configuration:
  imports = [ inputs.headroom.homeModules.default ];
  services.headroom.enable = true;
}

The module symlinks the shipped profiles into $XDG_CONFIG_HOME/headroom/profiles/, drops the systemd user unit into the user's services dir, and the unit starts after PipeWire and WirePlumber come up. services.headroom.extraProfiles lets you add your own.

For NixOS (system-wide binary install + systemd-user discovery):

{
  inputs.headroom.url = "github:amaanq/headroom";

  # In your NixOS configuration:
  imports = [ inputs.headroom.nixosModules.default ];
  programs.headroom.enable = true;
}

Then any user can systemctl --user enable --now headroom.

Other distros (manual)

cargo install --path crates/headroom-cli   # or: cargo build --release
# Profiles
mkdir -p ~/.config/headroom/profiles
cp profiles/*.toml ~/.config/headroom/profiles/
# systemd user unit (edit the ExecStart path to point at your binary)
install -Dm644 contrib/systemd/headroom.service \
  ~/.config/systemd/user/headroom.service
sed -i "s|@bindir@|$(dirname "$(command -v headroom)")|" \
  ~/.config/systemd/user/headroom.service
systemctl --user daemon-reload
systemctl --user enable --now headroom

Usage

Once the daemon is running:

headroom status                 # JSON snapshot — sinks, streams, active profile
headroom profile list           # available profiles
headroom profile use night      # activate one
headroom monitor                # full-screen TUI (bus gauges + per-stream)
headroom monitor --json meters  # line-delimited JSON, for scripting
headroom route set firefox processed
headroom set compressor.threshold_db -28
headroom bypass on              # kill switch — straight to the real sink

See headroom --help for the full surface.

Building

nix develop          # toolchain + pipewire dev libs + helpers
cargo build          # iterate
cargo test --workspace
nix build            # final packaged headroom binary

License

GPL-3.0-or-later for the daemon and CLI. headroom-dsp and headroom-ipc are MPL-2.0 so they can be reused by non-GPL plugin hosts and clients.