TinyVU

A minimalist VU meter plugin built with the same JUCE + WebView (Vite / React / MUI) stack as the sister plugins (ZeroComp / ZeroLimit / ZeroEQ / TestTone). The audio path is fully pass-through — TinyVU only observes the signal and shows it on a classic analog-style VU meter that can be shrunk to almost any size.

Supported formats: VST3 / AU / AAX / Standalone (Windows / macOS) and VST3 / LV2 / CLAP / Standalone (Linux), plus a WebAssembly browser demo.
https://tinyvu-demo.web.app/

Features

• Truly small footprint — the plugin window can be resized down to 240 × 90, and the meter still stays readable.
• Mono / stereo auto-switching — single meter on a mono bus, side-by-side L/R on stereo. When the host window becomes more square-ish than the meter aspect ratio (5:3), the two meters automatically stack vertically so each one stays as large as possible.
• Reference Level (-24..0 dBFS, 1 dB steps) — drag-edit / wheel / click-to-type the value. The needle is calibrated for a sine wave so that a -X dBFS peak sine settles at 0 VU when reference is -X.
• Light / Dark dial themes — only the dial face flips; surrounding chrome stays consistent with the rest of the series.
• Click-to-reset peak indicator — the red peak lamp can be cleared with a single click while it's lit or fading.
• Authentic 2nd-order ballistics — IEC 60268-17 (T₉₉ ≈ 350 ms) critically-damped damping implemented as a closed-form analytical step, so there is no Euler-style overshoot. Asymmetric configurations were tried and rolled back; the current symmetric ballistics matches commercial VU plugins in feel.
• Low-latency rendering — the C++ side runs a 5 ms sliding-window RMS and a 120 Hz timer, the WebView side bypasses React state and writes the needle's transform directly to the DOM in requestAnimationFrame.

Web demo

A browser demo lives alongside the plugin code. It uses the same DSP: wasm/src/vu_meter.h is the plugin's VuMeter.cpp ported to a JUCE-free namespace and compiled to WebAssembly via emscripten, then run inside an AudioWorkletProcessor. The audio source is a built-in sample with optional drag-and-drop file upload, and the visual is the exact same VUMeter React component as the plugin.

• Dev: cd webui && npm run dev:web → http://127.0.0.1:5174
• Build: npm run build:web → emits webui/dist/
• Deploy: npm run deploy:web (Firebase Hosting; project ID tinyvu-demo in .firebaserc)

The browser runs the same RMS, the same +3.01 dB sine calibration, the same ballistics — so the two implementations are visually indistinguishable.

Requirements

• CMake 3.22+
• C++17 toolchain
  • Windows: Visual Studio 2022 (Desktop development with C++)
  • macOS: Xcode 14+
  • Linux: gcc 13+ / clang + the apt packages listed under Building on Linux
• Node.js 18+ and npm (for the WebUI build)
• JUCE (vendored as a git submodule)
• clap-juce-extensions (vendored as a git submodule, used only for Linux CLAP build)
• Optional: AAX SDK (Pro Tools — drop into aax-sdk/)
• Optional: Inno Setup 6 (for the Windows installer)
• Optional (for the web demo): emscripten / emsdk

Getting started

# 1. Clone with submodules
git submodule update --init --recursive

# 2. Install WebUI dependencies
cd webui && npm install && cd ..

# 3. Build a release
# Windows
powershell -ExecutionPolicy Bypass -File build_windows.ps1 -Configuration Release
# macOS
./build_macos.zsh
# Linux (see "Building on Linux" below for required apt packages)
bash build_linux.sh

Building on Linux

Tested on WSL2 Ubuntu 24.04, but should work on any modern glibc-based distro with webkit2gtk-4.1 available.

Install the build dependencies:

sudo apt update
sudo apt install -y \
  build-essential pkg-config cmake ninja-build git \
  libasound2-dev libjack-jackd2-dev libcurl4-openssl-dev \
  libfreetype-dev libfontconfig1-dev \
  libx11-dev libxcomposite-dev libxcursor-dev libxext-dev \
  libxinerama-dev libxrandr-dev libxrender-dev \
  libwebkit2gtk-4.1-dev libglu1-mesa-dev mesa-common-dev libgtk-3-dev

Then:

git submodule update --init --recursive   # JUCE + clap-juce-extensions
bash build_linux.sh                        # Release build of VST3 / LV2 / CLAP / Standalone

Output:

• Build artefacts: build-linux/plugin/TinyVU_artefacts/Release/{VST3,LV2,CLAP,Standalone}/
• Auto-installed: ~/.vst3/TinyVU.vst3, ~/.lv2/TinyVU.lv2, ~/.clap/TinyVU.clap
• Distribution zip: releases/<VERSION>/TinyVU_<VERSION>_Linux_VST3_LV2_CLAP_Standalone.zip

LV2 and CLAP are gated behind if(UNIX AND NOT APPLE) in CMake, so existing Windows / macOS release flows are unaffected. AU and AAX are skipped on Linux as expected.

Manual CMake build (development)

# Windows
cmake -B build -G "Visual Studio 17 2022" -A x64
cmake --build build --config Debug --target TinyVU_VST3

# macOS
cmake -B build -G Xcode
cmake --build build --config Debug --target TinyVU_VST3

Hot-reload dev mode

# Terminal A — Vite dev server for the WebUI
cd webui && npm run dev

# Terminal B — Standalone Debug build (loads the WebUI from 127.0.0.1:5173)
cmake --build build --config Debug --target TinyVU_Standalone

Debug builds load the UI from http://127.0.0.1:5173; Release builds embed the WebUI as zip resources via juce_add_binary_data.

Building the WebAssembly DSP

# Windows
& 'emsdk\emsdk_env.ps1'
cd TinyVU\wasm
Remove-Item -Recurse -Force build -ErrorAction SilentlyContinue
New-Item -ItemType Directory build | Out-Null
cd build
emcmake cmake .. -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build .
Copy-Item -Force dist\tinyvu_dsp.wasm ..\..\webui\public-web\wasm\

If the C++ VuMeter ever changes, rebuild the WASM and copy the artifact into webui/public-web/wasm/. Otherwise the web demo will silently keep running the old DSP.

Window sizing

	Width	Height
Minimum	240	90
Default	600	220
Maximum	32767	32767 (effectively unlimited)

The plugin window has a corner resize grip and the host's native frame; both share the same constrainer. Below ~220 px tall or ~260 px wide the title row and reference / theme controls fold away automatically so the meters keep as much room as possible.

Parameters (APVTS)

ID	Type	Range	Default	Notes
REFERENCE_LEVEL	float	-24..0 dBFS, integer step	-18 dBFS	dBFS that maps to 0 VU. Click the input to type, or drag / wheel to scrub.
THEME	choice	Dark / Light	Dark	Switches only the dial face; the surrounding plugin chrome stays in dark.

DSP

• C++ side (plugin/src/dsp/VuMeter.{h,cpp})
  • processBlock does not modify the buffer; it only feeds samples to per-channel VuMeter instances.
  • 5 ms sliding-window RMS via a ring buffer of squared samples + an incremental runningSum. Recomputed in full at the end of each block to suppress numerical drift.
  • Output is converted to dBFS, clamped at -120 dBFS, and a +3.0103 dB sine calibration offset is added so a -X dBFS sine peak reads -X instead of -X-3 (matching how engineers think about "0 VU = -X dBFS sine").
• Bridge — a 120 Hz juce::Timer reads the per-channel atomics and emits a meterUpdate event to the WebView. Channel layout changes are sent on channelLayoutChanged.
• WebUI ballistics (webui/src/components/VUMeter.tsx)
  • 2nd-order critically-damped step response with T₉₉ = 0.35 s x(t) = target + (A + B·t)·e^(-ω·t), ω = 6.638 / T₉₉
  • Solved analytically per requestAnimationFrame step so the result is bit-exact to the continuous-time solution; no integration overshoot.
  • The needle's CSS transform and the peak lamp's backgroundColor / boxShadow are written directly to the DOM (no setState), to keep visual latency on the order of one display frame.

AAX / PACE signing

• The TinyVU-specific WrapGUID is never committed; it lives in the developer's local .env as PACE_ORGANIZATION. Use a sister repository's .env as a template and overwrite the GUID.
• Setting PACE_USERNAME / PACE_PASSWORD / PACE_KEYPASSWORD / PACE_ORGANIZATION plus a PFX certificate (tinyvu-dev.pfx in the project root, or path via PACE_PFX_PATH) makes both the Windows and macOS build scripts sign the AAX bundle automatically.
• If any of the above is missing, the build still succeeds with an unsigned AAX (suitable for CI / development).

Generating the dev signing certificate (Windows)

For a fresh repo, create a self-signed code-signing PFX matching the password in .env (PACE_KEYPASSWORD=dev-pass-123 for the Zero series). PowerShell:

$cert = New-SelfSignedCertificate `
  -Type CodeSigningCert -KeyUsage DigitalSignature `
  -KeyAlgorithm RSA -KeyLength 2048 -HashAlgorithm SHA256 `
  -NotAfter (Get-Date).AddYears(3) `
  -Subject "CN=TinyVU Dev" -FriendlyName "TinyVU Dev" `
  -CertStoreLocation Cert:\CurrentUser\My
Export-PfxCertificate -Cert $cert `
  -FilePath .\tinyvu-dev.pfx `
  -Password (ConvertTo-SecureString 'dev-pass-123' -Force -AsPlainText) | Out-Null
Remove-Item -Path "Cert:\CurrentUser\My\$($cert.Thumbprint)" -DeleteKey

⚠ Gotcha: PFX must be re-encoded in legacy PKCS#12 format

Windows 11's Export-PfxCertificate writes PKCS#12 with PBES2 / AES-256 key encryption. PACE wraptool's internal Windows code-signing wrapper (ossignaturewin.cpp) cannot extract the private key from this modern format and dies with:

Key file ... doesn't contain a valid signing certificate.

even though the very same PFX works with signtool and Get-PfxCertificate. The fix is to re-encode the PFX with the legacy PBE-SHA1-3DES algorithm and SHA1 MAC using OpenSSL right after exporting:

$env:OPENSSL_MODULES = 'C:\Program Files\Git\mingw64\lib\ossl-modules'
$ossl = 'C:\Program Files\Git\mingw64\bin\openssl.exe'
$tmp = "$env:TEMP\dev.pem"

& $ossl pkcs12 -in tinyvu-dev.pfx -nodes -passin 'pass:dev-pass-123' -out $tmp
& $ossl pkcs12 -export -in $tmp -out tinyvu-dev.pfx -passout 'pass:dev-pass-123' `
    -keypbe PBE-SHA1-3DES -certpbe PBE-SHA1-3DES -macalg SHA1 -legacy
Remove-Item $tmp

The -legacy flag requires legacy.dll to be loadable, hence $env:OPENSSL_MODULES pointing at Git for Windows' ossl-modules. The C:\Program Files\OpenSSL-Win64\ distribution has a broken module search path on some installs, so use the OpenSSL bundled with Git for Windows instead. Output during signing of the form Warning! ... doesn't have a trusted root in the system. is expected for a self-signed dev cert and can be ignored.

Directory layout

TinyVU/
├─ plugin/
│  ├─ src/
│  │  ├─ PluginProcessor.*    # APVTS + per-channel VuMeter; processBlock observes only
│  │  ├─ PluginEditor.*       # WebView init + 120 Hz meterUpdate emitter + ResizableCorner
│  │  ├─ ParameterIDs.h       # REFERENCE_LEVEL / THEME
│  │  ├─ KeyEventForwarder.*  # WebView → host key forwarding
│  │  └─ dsp/
│  │     └─ VuMeter.{h,cpp}   # 5 ms sliding-window RMS detector
│  └─ CMakeLists.txt
├─ webui/
│  ├─ src/
│  │  ├─ App.tsx                                # layout + Reference / Theme controls
│  │  ├─ components/
│  │  │  ├─ VUMeter.tsx                          # SVG dial + 2nd-order ballistics
│  │  │  ├─ NumericDragInput.tsx                 # drag/wheel/click-to-type number control
│  │  │  ├─ MaterialUISwitch.tsx                 # custom sun/moon theme switch
│  │  │  ├─ WebTransportBar.tsx                  # play / loop / seek / bypass / upload (web demo)
│  │  │  ├─ WebDemoMenu.tsx                      # sister-plugin links (web demo)
│  │  │  ├─ LicenseDialog.tsx, GlobalDialog.tsx
│  │  ├─ bridge/
│  │  │  ├─ juce.ts                              # plugin bridge (juce-framework-frontend-mirror)
│  │  │  └─ web/                                 # web demo bridge (alias-resolved at build time)
│  │  │     ├─ WebAudioEngine.ts
│  │  │     ├─ WebBridgeManager.ts
│  │  │     ├─ WebParamState.ts
│  │  │     ├─ juce-shim.ts
│  │  │     └─ web-juce.ts
│  │  └─ hooks/useJuceParam.ts                   # APVTS subscription hooks
│  ├─ public-web/                                # web-demo-only: sample.mp3, wasm, worklet
│  │  ├─ audio/sample.mp3
│  │  ├─ wasm/tinyvu_dsp.wasm
│  │  └─ worklet/dsp-processor.js
│  ├─ vite.config.ts          # plugin build (outputs ../plugin/ui/public)
│  ├─ vite.config.web.ts      # web demo build (outputs dist/)
│  ├─ index.html              # plugin entry
│  ├─ index.web.html          # web demo entry
│  ├─ firebase.json
│  ├─ .firebaserc             # project: tinyvu-demo
│  ├─ scripts/sync-web-demos.cjs
│  └─ package.json
├─ wasm/
│  ├─ src/vu_meter.h          # JUCE-free port of plugin VuMeter
│  ├─ src/wasm_exports.cpp    # C ABI exports
│  └─ CMakeLists.txt          # emscripten build config
├─ cmake/
├─ scripts/
├─ JUCE/                      # git submodule
├─ aax-sdk/                   # optional (AAX SDK)
├─ installer.iss              # Inno Setup script (Windows installer)
├─ build_windows.ps1
├─ build_macos.zsh
├─ VERSION
└─ LICENSE

License

This project is licensed under the GNU Affero General Public License v3.0 or later (AGPL-3.0-or-later) — see the LICENSE file for the full text.

It uses JUCE under the AGPLv3 option of its dual-licensing scheme. Other third-party SDKs (VST3 / AAX / WebView2 / etc.) are governed by their own licenses; the runtime dependency list is shown in the in-app Licenses dialog. The VU dial SVG and ballistics curve are ported from vu-meter-react (same author, MIT licensed).

Credits

Designed and developed by Jun Murakami. Built on the ZeroComp framework and the vu-meter-react component (same author).