Faders

A plugin for OBS Studio. Faders isn't affiliated with or endorsed by the OBS Project.

Sends your voice, game and music as three separate layers to the Faders hub so viewers can mix them. Your Twitch stream is not touched.

Get it: download the installer from faders.tv/streamers or the latest release, and get your key from the Faders portal. Setup guide: faders.tv/docs/streamer-setup.

• Tools → Faders opens the settings (OBS's own properties window, no custom UI code): key (with a link to the portal to get one), which mixer track is voice / game / music, "only send while streaming". The server is wss://hub.faders.tv/ingest (the key identifies the channel); tests point it elsewhere with the faders_configure procedure.
• OBS 32+ shows Faders and its version in Tools → Plugin Manager (data/manifest.json, written from the project version by CMake).
• Taps OBS mixer tracks with obs_add_raw_audio_callback (default tracks 2/3/4). Assign sources in Edit → Advanced Audio Properties.
• Stereo Opus at 128 kbps per track (at least Twitch's ~160 kbps stereo AAC), 20 ms frames, 500 ms chunks (PROTOCOL.md). Up to ~390 kbps total upload (less for quiet or mono tracks), and 0 while nobody is listening: the hub tells the plugin its listener count, the plugin keeps a 60 s backlog and replays it when the first listener arrives.
• The key goes in an Authorization: Bearer header. Reconnects back off 1 s → 30 s, so a wrong key doesn't hammer the hub. Status shows in the settings window and the OBS log ([faders]).
• Heartbeat: pings the hub every 20 s and reconnects after 60 s without a reply, so a connection silently dropped by a router or proxy recovers on its own.
• When the hub reports a newer release, Tools → Faders shows "Update available" with a link to the download page. The plugin never updates itself.
• Scriptable: procedures faders_configure(server, key, voice, game, music, only_live) and faders_status(out status) on the global proc handler.

One plugin, two platforms

Everything is shared C except the WebSocket transport (src/ws.h):

	macOS	Windows
Transport	ws-apple.m (NSURLSessionWebSocketTask)	ws-win.c (WinHTTP WebSocket API)
Shared	plugin-main.c (settings, Tools menu, events), uplink.c (capture, Opus, chunks, backlog, reconnect)	same
Output	faders.plugin bundle	faders.dll + data/
libobs	links OBS.app frameworks	import libs generated from the release DLLs

Install

Download the installer for your platform from the latest release and run it, then restart OBS and open Tools → Faders:

• macOS 13+ (Apple silicon and Intel): faders-obs-<version>-macos.pkg. Installs for your user into ~/Library/Application Support/obs-studio/plugins. Signed with a Developer ID and notarized by Apple.
• Windows 10/11 x64: faders-obs-<version>-windows.exe. Installs into %ProgramData%\obs-studio\plugins\faders; uninstall from Settings → Apps. The DLL is placed both where OBS 33 looks (faders\faders.dll) and where OBS 32 looks (faders\bin\64bit\), so one installer works with both and OBS 33 doesn't flag it as a legacy plugin. The plugin DLL, installer and uninstaller are code-signed (Azure Trusted Signing).

Build (macOS)

./scripts/fetch-deps.sh     # OBS 32.2.2 (Apple + Intel releases), matching headers, SIMDe, static libopus
./scripts/build-macos.sh    # universal build/faders.plugin (+ arm64 headless test host); FADERS_INTEL=0 for arm64 only
./scripts/install-macos.sh  # → ~/Library/Application Support/obs-studio/plugins
./scripts/package-macos.sh  # → faders-obs-<version>-macos.pkg (signs/notarizes when MACOS_* are set; see the script)

Build (Windows x64, MSVC)

From a "Developer PowerShell for VS 2022":

.\scripts\fetch-deps-windows.ps1              # OBS 32.2.2 DLLs → .lib, headers, static opus
cmake -S . -B build -A x64; cmake --build build --config Release
.\scripts\install-windows.ps1                 # (as admin) → %ProgramData%\obs-studio\plugins\faders

Cross-compiling from macOS or Linux (how releases are built): ./scripts/cross-windows.sh (MinGW-w64) → build-win/faders.dll; scripts/ci/check-windows-dll.py verifies its exports and imports.

Installer: makensis -DVERSION=0.1.0 -DDLL=<path>/faders.dll -DOUTFILE=<path>/faders-obs-0.1.0-windows.exe installer/windows/faders.nsi (NSIS 3, on Windows or Linux). The installer art in installer/ is generated from the Faders brand kit.

CI runs on TeamCity (scripts/ci/): teamcity-macos.sh builds natively, runs the end-to-end test below against test/mock-hub.mjs and packages (zip + .pkg; on main also Developer ID signed and notarized). teamcity-linux-cross.sh (in ubuntu:24.04) cross-builds the Windows release with MinGW, checks the DLL statically and builds the .exe installer; on main it signs the DLL, installer and uninstaller with Azure Trusted Signing (scripts/sign-windows.sh). The signed main builds become a draft GitHub release, which is published by hand.

Test without the OBS GUI

test/mock-hub.mjs is a small stand-in for the Faders hub (same protocol, see PROTOCOL.md):

npm ci && node test/mock-hub.mjs &                       # ws://127.0.0.1:8787, key "dev-token"
build/faders-headless ws://127.0.0.1:8787/ingest/ci_channel dev-token \
  test/media/voice.wav test/media/game.wav test/media/music.wav 40 &
node test/plugin-listener.mjs --channel ci_channel --seconds 20   # PASS/FAIL

Headless host

build/faders-headless runs real libobs, plays three WAVs into tracks 2/3/4, loads the plugin and configures it through its procedures:

build/faders-headless ws://localhost:8787/ingest/<channel> <fdr_live_key> \
  test/media/voice.wav test/media/game.wav test/media/music.wav 60

Verified: wrong key → "server rejected connection (HTTP 401)" with backoff; correct key → pauses at 0 listeners, resumes and replays backlog on the first listener; Chrome decodes every frame and each decoded layer correlates 0.97–0.997 with its own source and ≤0.37 with the others.

Not verified yet

Released as 0.1.0. These parts haven't been tested by hand yet; bug reports are welcome (GitHub issues, or the Faders Discord: discord.gg/TA7Xd8CEAz).

• Windows in the OBS app: the DLL cross-compiles, exports exactly the 8 functions libobs looks up, and every one of its 60 OBS imports exists in the real OBS 32.2.2 DLLs, but it has only run in libobs headlessly (CI), not yet clicked through in the OBS app on Windows.
• Intel Macs: the universal build links each architecture against its own OBS release, but the x86_64 half hasn't been run yet (no Intel Mac / Rosetta in CI).
• GUI check in real OBS: the Tools menu + properties window haven't been clicked through in the OBS app yet (the headless test bypasses the frontend).
• Linux: not supported yet. It needs a libcurl transport (src/ws-curl.c); everything else is shared.

License

GPL-2.0-or-later (see LICENSE), the same as OBS Studio, which this plugin links against. Bundled: Opus (BSD-3-Clause). The Faders hub, website and browser extension are separate programs that talk to this plugin over the network protocol in PROTOCOL.md.