FerroMix

Voicemeeter for Linux. A PipeWire mixer that routes any app to any output or virtual mic, keeps routes alive by name (a VoIP call ending doesn't destroy your patch), and refuses to build the feedback loops that ruin a mix-minus.

One binary, one launch: open it and it owns PipeWire for as long as it's running; close it and every FerroMix device/link is torn down, PipeWire goes straight back to stock behavior. Nothing to enable, nothing left running in the background.

Built because the alternatives don't cut it: qpwgraph makes you redraw a line every time a call ends; Pulsemeeter lumps everything into two virtual inputs and looks like 2009.

The model (identical to Voicemeeter)

INPUT STRIPS                        BUSES
  pick any source per strip:          A1  A2   hardware outputs (pick a device)
    • Virtual Input  (see below)      B1  B2   virtual mics (apps pick as input)
    • any hardware mic
    • any running app

Each strip has an assign stack — light A1 and it plays out your headset; light B1 and Discord hears it. Exactly the Voicemeeter workflow:

Strip	A1	B1	B2	result
Mic	●	●	●	you're heard in Discord and the SIP call
Browser	●	●	●	browser audio to you + Discord + SIP
Discord	●	—	●	Discord audio into the SIP call (B1 = echo, blocked)
SIP phone	●	●	—	call audio into Discord (B2 = echo back to caller, blocked)

Mix-minus is safe by construction. If a strip's app also listens to a B-bus, sending that app back into the same bus is an echo loop. FerroMix detects it, refuses the link, and paints the button red.

Virtual Input (the VAIO trick)

FerroMix creates a FerroMix Input sink. Set it as your system default output (Settings → Sound → Output) and everything you haven't routed per-app lands on the "Virtual Input" strip — one fader for all your loose system audio.

Routes stick

Assignments are keyed by app name, never by PipeWire ids. End a call, close an app, restart FerroMix itself — when it (or the app) comes back, the reconciler re-links it. The strip stays visible (marked offline) so your intent is never lost.

Upgrading from an earlier build — read this

v3.0.0 merged the daemon into the GUI. There is no more ferromix2-daemon binary and no more ferromix2.service. If you had the old service enabled:

systemctl --user disable --now ferromix2.service
rm -f ~/.config/systemd/user/ferromix2.service
systemctl --user daemon-reload

Your ~/.config/ferromix2/config.toml (routing, faders, DSP) is untouched and still applies — just launch ferromix2 itself from now on.

Separately: versions before 0.5 created their virtual devices with object.linger, so the devices outlived the daemon and every run left another copy behind (FerroMix A1, FerroMix A1-1, …). That's long gone — devices now die with the process (and always did the reconnect-safe way, sweeping any leftover ferromix.* node at startup) — noted here only because it's the reason process exit was always a safe, complete teardown even before v3.0.0 made that the whole app's behavior, not just the daemon's.

Fedora

sudo dnf install rust cargo clang-devel pkgconf-pkg-config pipewire-devel ladspa-swh-plugins
cargo build --release

# install
sudo install -Dm755 target/release/ferromix2 /usr/bin/

ferromix2            # badge reads LIVE the moment it's connected to PipeWire

That's it — no service to enable. Check it's alive:

pw-cli ls Node | grep -i ferromix      # your buses + virtual input

(or just watch the header: green dot + LIVE means it's routing; the LOG tab in the app itself shows the same live log a journalctl -f used to.)

Then in each app: point Discord's input at FerroMix B1, your softphone's input at FerroMix B2, and pick a real device for A1 in the GUI.

Ubuntu/Debian: swap the deps for libpipewire-0.3-dev clang pkg-config build-essential. Arch: swap the deps for pipewire clang pkgconf, or use packaging/PKGBUILD.

The gate/compressor DSP on each strip needs ladspa-swh-plugins (or your distro's equivalent) installed at runtime for the compressor stage; the gate is a PipeWire builtin and needs nothing extra.

Recommended: disable role-based loopback routing

Fedora's default WirePlumber config routes PipeWire-pulse clients (Spotify, Firefox, most desktop apps) through role-based loopback sinks before FerroMix can claim them — FerroMix detects and redirects this after the fact (you'll see REDIRECT in the log), but it's strictly better to remove the race entirely:

mkdir -p ~/.config/wireplumber/wireplumber.conf.d
cp packaging/wireplumber/91-ferromix-disable-role-loopbacks.conf \
   ~/.config/wireplumber/wireplumber.conf.d/
systemctl --user restart wireplumber wireplumber-pipewire pipewire pipewire-pulse

This is optional and system-wide — it also turns off Fedora's role-based ducking (e.g. notification sounds ducking music) for every app, not just FerroMix. See the comment in that file for the full trade-off. FerroMix routes correctly either way; this just makes it proactive instead of reactive.

Troubleshooting

Window crashes on launch with wgpu/EGL/dmabuf errors (seen on hybrid- GPU laptops — an NVIDIA discrete + Intel integrated GPU under native Wayland): fixed as of v3.0.2 — FerroMix now detects this at startup and automatically relaunches itself once under XWayland, no action needed. If you're still on an older build, launch it with the two Wayland-selecting variables cleared so it falls back to XWayland on its own:

WAYLAND_DISPLAY= WAYLAND_SOCKET= ferromix2

(WINIT_UNIX_BACKEND=x11, the traditional fix for this class of issue, does not work on the windowing library version this app currently uses — it has no env-var override anymore, only this Wayland-variable fallback.)

Config

~/.config/ferromix2/config.toml — the header's SAVE indicator writes it back (autosaves ~1.5s after the last change, or click SAVE directly).

feedback_guard = true

[[buses]]
label = "A1"
kind = "hw"
device = "corsair"       # substring of the output device; omit = default

[[buses]]
label = "B1"
kind = "virtual"         # apps select "FerroMix B1" as their microphone

[[strip]]
input = "discord"        # app name substring, a mic, or "ferromix.vin.0"
assign = ["A1", "B2"]    # buses this strip feeds

Architecture

mixer-core (model/engine/config/mock) · mixer-pw (PipeWire: devices, declarative link reconciler, VU taps, recorder, per-strip DSP) · mixer-gui-iced (ferromix2, the single binary — Iced console + matrix + settings + log, owning the PipeWire worker thread directly).

One process. Launch it and it owns PipeWire; close it and every FerroMix device/link is torn down, no lingering state. See docs/ARCHITECTURE.md.

License

MIT.