BS.1770 true-peak

.github/workflows/main.yml

@@ -193,6 +193,9 @@ jobs:
       - name: Test native vectorscope calibration
         run: npm run test:vectorscope-native
 
+      - name: Test native BS.1770 true-peak calibration
+        run: npm run test:lufsmeter-native
+
       - name: Build and test Prism TUI
         run: npm run test:tui
 

.github/workflows/release.yml

@@ -127,6 +127,9 @@ jobs:
       - name: Test native vectorscope calibration
         run: npm run test:vectorscope-native
 
+      - name: Test native BS.1770 true-peak calibration
+        run: npm run test:lufsmeter-native
+
       - name: Build and test Prism TUI
         run: npm run test:tui
 

README.md

@@ -27,7 +27,7 @@ Prism includes seven real-time scopes and meters:
 * **Vectorscope** — Full-band stereo phase analysis with XY, Polar, and M/S Linear views, calibrated references, adjustable zoom, and optional multiband RGB
 * **Spectrogram** — Scrolling frequency-over-time display with Log/Mel/Linear scales, stereo-energy analysis, and frequency reassignment in Sharp and Sharper modes
 * **VU Meter** — 300 ms metering with adjustable 0 VU reference, stereo correlation, and needle or bar displays
-* **Loudness Meter** — ITU-R BS.1770 momentary, short-term, and integrated LUFS metering with stereo peak activity
+* **Loudness Meter** — ITU-R BS.1770 momentary, short-term, and integrated LUFS metering with BS.1770 true-peak activity
 * **Waveform** — Scrolling mono or stereo waveform with transient-preserving min/max sampling and optional multiband energy visualization
 
 Every scope can be configured independently. Resize and rearrange them into a rack, rotate supported scopes, pop them into separate windows, or pin them on top of other applications.
@@ -98,7 +98,8 @@ Most of Prism's analysis runs in native C++, with the same DSP implementations r
 * −70 LUFS absolute gate
 * Relative gate at −10 LU below ungated programme loudness
 * Momentary, short-term, and integrated LUFS are calculated independently
-* Peak readouts are sample peak, not true peak
+* Stereo true-peak reconstruction uses a rate-aware 48-tap-per-phase FIR at 2× to 8× oversampling for common 44.1–192 kHz host rates
+* Held L/R true-peak markers and a reset-scoped combined maximum are reported in dBTP
 
 ### VU and correlation
 
@@ -277,12 +278,19 @@ npm run build            # Build application assets
 npm run configure:tui    # Configure the standalone CMake project
 npm run build:tui        # Build prism-tui
 npm run test:tui         # Build and run native TUI tests
+npm run test:lufsmeter-native # Run generated BS.1770/EBU true-peak vectors
 npm run dist             # Package for current platform
 npm run dist:mac         # macOS
 npm run dist:win         # Windows
 npm run dist:linux       # Linux
 ```
 
+If you have downloaded and extracted the official [EBU Loudness Test Set](https://tech.ebu.ch/publications/ebu_loudness_test_set) for internal testing, run cases 15–23 without copying the WAVs into the repository. The files are not downloaded or redistributed by Prism, in accordance with the [EBU test-sequence usage terms](https://tech.ebu.ch/files/live/sites/tech/files/shared/testmaterial/use%20of%20EBU%20AUDIO%20test%20sequences.pdf).
+
+```bash
+npm run test:lufsmeter-ebu -- /path/to/extracted-ebu-loudness-test-set
+```
+
 The TUI build downloads the pinned FTXUI source through CMake. Linux also requires the PulseAudio development package.
 
 The DAW plugins build with CMake from the [`plugin/`](plugin/) directory. See [`plugin/README.md`](plugin/README.md) for per-platform build and installation details.

native/src/lufsmeter.cpp

@@ -31,10 +31,37 @@ constexpr double RLB_FILTER_F0_HZ = 38.13547087613982;
 constexpr double RLB_FILTER_Q = 0.5003270373223665;
 
 constexpr double VU_INTEGRATION_WINDOW_MS = 300.0;
-constexpr double VU_PEAK_HOLD_MS = 750.0;
+constexpr double TRUE_PEAK_HOLD_MS = 750.0;
-constexpr double VU_PEAK_DECAY_DB_PER_SECOND = 18.0;
+constexpr double TRUE_PEAK_DECAY_DB_PER_SECOND = 18.0;
 constexpr double BAR_ATTACK_MS = 5.0;
 constexpr double BAR_RELEASE_MS = 180.0;
+constexpr double TRUE_PEAK_MIN_OUTPUT_RATE_HZ = 320000.0;
+constexpr size_t TRUE_PEAK_TAPS_PER_PHASE = 48;
+constexpr size_t TRUE_PEAK_MAX_OVERSAMPLE_FACTOR = 64;
+constexpr double TRUE_PEAK_KAISER_BETA = 8.6;
+
+double besselI0(double value) {
+    const double absoluteValue = std::abs(value);
+    if (absoluteValue < 3.75) {
+        const double ratio = value / 3.75;
+        const double squared = ratio * ratio;
+        return 1.0 + squared * (3.5156229 + squared * (3.0899424 + squared * (1.2067492
+            + squared * (0.2659732 + squared * (0.0360768 + squared * 0.0045813)))));
+    }
+
+    const double ratio = 3.75 / absoluteValue;
+    return (std::exp(absoluteValue) / std::sqrt(absoluteValue))
+        * (0.39894228 + ratio * (0.01328592 + ratio * (0.00225319 + ratio * (-0.00157565
+            + ratio * (0.00916281 + ratio * (-0.02057706 + ratio * (0.02635537
+            + ratio * (-0.01647633 + ratio * 0.00392377))))))));
+}
+
+double normalizedSinc(double value) {
+    if (std::abs(value) < 1e-12) {
+        return 1.0;
+    }
+    return std::sin(PI * value) / (PI * value);
+}
 
 LUFSMeterSnapshot makeInitialSnapshot() {
     return {
@@ -47,6 +74,7 @@ LUFSMeterSnapshot makeInitialSnapshot() {
         static_cast<float>(VU_METER_MIN_DB),
         static_cast<float>(VU_METER_MIN_DB),
         static_cast<float>(VU_METER_MIN_DB),
+        static_cast<float>(VU_METER_MIN_DB),
         0.0f,
     };
 }
@@ -82,6 +110,7 @@ void LUFSMeterAnalyzer::configureForSampleRate(float sampleRate) {
     integratedHistogramPowerSums_.assign(INTEGRATED_HISTOGRAM_BIN_COUNT, 0.0);
 
     configureFastMeter();
+    configureTruePeakDetector();
     reset();
 }
 
@@ -102,6 +131,44 @@ void LUFSMeterAnalyzer::configureFastMeter() {
     barReleaseCoeff_ = std::exp(-1.0 / (static_cast<double>(sampleRate_) * (BAR_RELEASE_MS / 1000.0)));
 }
 
+void LUFSMeterAnalyzer::configureTruePeakDetector() {
+    truePeakOversampleFactor_ = 1;
+    while (static_cast<double>(sampleRate_) * truePeakOversampleFactor_ < TRUE_PEAK_MIN_OUTPUT_RATE_HZ
+        && truePeakOversampleFactor_ < TRUE_PEAK_MAX_OVERSAMPLE_FACTOR) {
+        truePeakOversampleFactor_ *= 2;
+    }
+
+    truePeakCoefficients_.assign(truePeakOversampleFactor_ * TRUE_PEAK_TAPS_PER_PHASE, 0.0);
+    truePeakHistoryL_.assign(TRUE_PEAK_TAPS_PER_PHASE * 2, 0.0);
+    truePeakHistoryR_.assign(TRUE_PEAK_TAPS_PER_PHASE * 2, 0.0);
+
+    const double windowRadius = static_cast<double>(TRUE_PEAK_TAPS_PER_PHASE) / 2.0;
+    const double inverseI0Beta = 1.0 / besselI0(TRUE_PEAK_KAISER_BETA);
+    // Each phase is a causal fractional-delay reconstruction. The 24-sample
+    // delay keeps the 48 source taps centered without requiring future input.
+    for (size_t phase = 0; phase < truePeakOversampleFactor_; phase += 1) {
+        const double fraction = static_cast<double>(phase) / truePeakOversampleFactor_;
+        double coefficientSum = 0.0;
+        for (size_t tap = 0; tap < TRUE_PEAK_TAPS_PER_PHASE; tap += 1) {
+            const double distance = static_cast<double>(tap) - windowRadius + fraction;
+            const double normalizedDistance = distance / windowRadius;
+            const double windowArgument = std::sqrt(std::max(0.0, 1.0 - normalizedDistance * normalizedDistance));
+            const double window = std::abs(normalizedDistance) <= 1.0
+                ? besselI0(TRUE_PEAK_KAISER_BETA * windowArgument) * inverseI0Beta
+                : 0.0;
+            const double coefficient = normalizedSinc(distance) * window;
+            truePeakCoefficients_[phase * TRUE_PEAK_TAPS_PER_PHASE + tap] = coefficient;
+            coefficientSum += coefficient;
+        }
+
+        if (std::abs(coefficientSum) > 1e-12) {
+            for (size_t tap = 0; tap < TRUE_PEAK_TAPS_PER_PHASE; tap += 1) {
+                truePeakCoefficients_[phase * TRUE_PEAK_TAPS_PER_PHASE + tap] /= coefficientSum;
+            }
+        }
+    }
+}
+
 void LUFSMeterAnalyzer::reset() {
     std::fill(ringBufferL_.begin(), ringBufferL_.end(), 0.0);
     std::fill(ringBufferR_.begin(), ringBufferR_.end(), 0.0);
@@ -131,6 +198,10 @@ void LUFSMeterAnalyzer::reset() {
     lastPeakUpdateMs_ = 0.0;
     hasLastPeakUpdate_ = false;
 
+    std::fill(truePeakHistoryL_.begin(), truePeakHistoryL_.end(), 0.0);
+    std::fill(truePeakHistoryR_.begin(), truePeakHistoryR_.end(), 0.0);
+    truePeakHistoryWriteIndex_ = 0;
+
     snapshot_ = makeInitialSnapshot();
 }
 
@@ -140,27 +211,35 @@ void LUFSMeterAnalyzer::pushSamples(const float* leftChannel, const float* right
     }
 
     const double nowMs = currentTimeMs();
-    advancePeaks(nowMs);
+    advanceTruePeaks(nowMs);
 
-    double maxPeakL = 0.0;
+    double maxTruePeakL = 0.0;
-    double maxPeakR = 0.0;
+    double maxTruePeakR = 0.0;
 
     for (size_t index = 0; index < length; index += 1) {
         const float left = leftChannel[index];
         const float right = rightChannel[index];
         processLoudnessSample(left, right);
-        processFastMeterSample(left, right, maxPeakL, maxPeakR);
+        processFastMeterSample(left, right);
+        processTruePeakSample(left, right, maxTruePeakL, maxTruePeakR);
     }
 
-    maybeUpdatePeak(amplitudeToDb(maxPeakL), nowMs, true);
+    const double truePeakLDb = truePeakAmplitudeToDb(maxTruePeakL);
-    maybeUpdatePeak(amplitudeToDb(maxPeakR), nowMs, false);
+    const double truePeakRDb = truePeakAmplitudeToDb(maxTruePeakR);
+    maybeUpdateTruePeak(truePeakLDb, nowMs, true);
+    maybeUpdateTruePeak(truePeakRDb, nowMs, false);
+    snapshot_.maxTruePeakDb = static_cast<float>(std::max({
+        static_cast<double>(snapshot_.maxTruePeakDb),
+        truePeakLDb,
+        truePeakRDb,
+    }));
     recomputeFastSnapshot();
     updateMomentaryShortTermLoudness();
     snapshot_.integratedLUFS = static_cast<float>(computeGatedIntegratedLoudness());
 }
 
 LUFSMeterSnapshot LUFSMeterAnalyzer::getSnapshot() {
-    advancePeaks(currentTimeMs());
+    advanceTruePeaks(currentTimeMs());
     recomputeFastSnapshot();
     return snapshot_;
 }
@@ -303,7 +382,7 @@ double LUFSMeterAnalyzer::applyBiquad(const BiquadCoeffs& coeffs, BiquadState& s
     return output;
 }
 
-void LUFSMeterAnalyzer::processFastMeterSample(float left, float right, double& maxPeakL, double& maxPeakR) {
+void LUFSMeterAnalyzer::processFastMeterSample(float left, float right) {
     if (fastSqL_.empty()) {
         return;
     }
@@ -334,16 +413,44 @@ void LUFSMeterAnalyzer::processFastMeterSample(float left, float right, double&
     const double coeffR = absR > barEnvelopeR_ ? barAttackCoeff_ : barReleaseCoeff_;
     barEnvelopeL_ = coeffL * barEnvelopeL_ + (1.0 - coeffL) * absL;
     barEnvelopeR_ = coeffR * barEnvelopeR_ + (1.0 - coeffR) * absR;
-
-    if (absL > maxPeakL) {
-        maxPeakL = absL;
-    }
-    if (absR > maxPeakR) {
-        maxPeakR = absR;
-    }
 }
 
-void LUFSMeterAnalyzer::advancePeaks(double nowMs) {
+void LUFSMeterAnalyzer::processTruePeakSample(
+    float left,
+    float right,
+    double& maxTruePeakL,
+    double& maxTruePeakR
+) {
+    if (truePeakHistoryL_.empty() || truePeakCoefficients_.empty()) {
+        return;
+    }
+
+    const double leftSample = static_cast<double>(left);
+    const double rightSample = static_cast<double>(right);
+    truePeakHistoryL_[truePeakHistoryWriteIndex_] = leftSample;
+    truePeakHistoryL_[truePeakHistoryWriteIndex_ + TRUE_PEAK_TAPS_PER_PHASE] = leftSample;
+    truePeakHistoryR_[truePeakHistoryWriteIndex_] = rightSample;
+    truePeakHistoryR_[truePeakHistoryWriteIndex_ + TRUE_PEAK_TAPS_PER_PHASE] = rightSample;
+
+    for (size_t phase = 0; phase < truePeakOversampleFactor_; phase += 1) {
+        const size_t coefficientOffset = phase * TRUE_PEAK_TAPS_PER_PHASE;
+        double reconstructedL = 0.0;
+        double reconstructedR = 0.0;
+        const size_t newestHistoryIndex = truePeakHistoryWriteIndex_ + TRUE_PEAK_TAPS_PER_PHASE;
+        for (size_t tap = 0; tap < TRUE_PEAK_TAPS_PER_PHASE; tap += 1) {
+            const size_t historyIndex = newestHistoryIndex - tap;
+            const double coefficient = truePeakCoefficients_[coefficientOffset + tap];
+            reconstructedL += coefficient * truePeakHistoryL_[historyIndex];
+            reconstructedR += coefficient * truePeakHistoryR_[historyIndex];
+        }
+        maxTruePeakL = std::max(maxTruePeakL, std::abs(reconstructedL));
+        maxTruePeakR = std::max(maxTruePeakR, std::abs(reconstructedR));
+    }
+
+    truePeakHistoryWriteIndex_ = (truePeakHistoryWriteIndex_ + 1) % TRUE_PEAK_TAPS_PER_PHASE;
+}
+
+void LUFSMeterAnalyzer::advanceTruePeaks(double nowMs) {
     if (!std::isfinite(nowMs)) {
         return;
     }
@@ -358,23 +465,23 @@ void LUFSMeterAnalyzer::advancePeaks(double nowMs) {
         return;
     }
 
-    snapshot_.peakLDb = static_cast<float>(applyPeakDecay(snapshot_.peakLDb, peakHoldUntilL_, nowMs));
+    snapshot_.truePeakLDb = static_cast<float>(applyPeakDecay(snapshot_.truePeakLDb, peakHoldUntilL_, nowMs));
-    snapshot_.peakRDb = static_cast<float>(applyPeakDecay(snapshot_.peakRDb, peakHoldUntilR_, nowMs));
+    snapshot_.truePeakRDb = static_cast<float>(applyPeakDecay(snapshot_.truePeakRDb, peakHoldUntilR_, nowMs));
     lastPeakUpdateMs_ = nowMs;
 }
 
-void LUFSMeterAnalyzer::maybeUpdatePeak(double peakDb, double nowMs, bool leftChannel) {
+void LUFSMeterAnalyzer::maybeUpdateTruePeak(double peakDb, double nowMs, bool leftChannel) {
     if (leftChannel) {
-        if (peakDb > snapshot_.peakLDb) {
+        if (peakDb > snapshot_.truePeakLDb) {
-            snapshot_.peakLDb = static_cast<float>(peakDb);
+            snapshot_.truePeakLDb = static_cast<float>(peakDb);
-            peakHoldUntilL_ = nowMs + VU_PEAK_HOLD_MS;
+            peakHoldUntilL_ = nowMs + TRUE_PEAK_HOLD_MS;
         }
         return;
     }
 
-    if (peakDb > snapshot_.peakRDb) {
+    if (peakDb > snapshot_.truePeakRDb) {
-        snapshot_.peakRDb = static_cast<float>(peakDb);
+        snapshot_.truePeakRDb = static_cast<float>(peakDb);
-        peakHoldUntilR_ = nowMs + VU_PEAK_HOLD_MS;
+        peakHoldUntilR_ = nowMs + TRUE_PEAK_HOLD_MS;
     }
 }
 
@@ -384,7 +491,7 @@ double LUFSMeterAnalyzer::applyPeakDecay(double currentDb, double holdUntilMs, d
         return currentDb;
     }
 
-    const double decayAmount = ((nowMs - decayStartMs) / 1000.0) * VU_PEAK_DECAY_DB_PER_SECOND;
+    const double decayAmount = ((nowMs - decayStartMs) / 1000.0) * TRUE_PEAK_DECAY_DB_PER_SECOND;
     return std::max(VU_METER_MIN_DB, currentDb - decayAmount);
 }
 
@@ -424,6 +531,13 @@ double LUFSMeterAnalyzer::amplitudeToDb(double amplitude) {
     return clampDb(20.0 * std::log10(std::max(amplitude, 1e-10)), VU_METER_MIN_DB, VU_METER_MAX_DB);
 }
 
+double LUFSMeterAnalyzer::truePeakAmplitudeToDb(double amplitude) {
+    if (!std::isfinite(amplitude) || amplitude <= 0.0) {
+        return VU_METER_MIN_DB;
+    }
+    return std::max(VU_METER_MIN_DB, 20.0 * std::log10(std::max(amplitude, 1e-10)));
+}
+
 double LUFSMeterAnalyzer::clampDb(double db, double minDb, double maxDb) {
     return std::max(minDb, std::min(maxDb, db));
 }

native/src/lufsmeter.h

@@ -14,8 +14,9 @@ struct LUFSMeterSnapshot {
     float vuRDb;
     float barLDb;
     float barRDb;
-    float peakLDb;
+    float truePeakLDb;
-    float peakRDb;
+    float truePeakRDb;
+    float maxTruePeakDb;
     float correlation;
 };
 
@@ -47,6 +48,7 @@ private:
     void configureForSampleRate(float sampleRate);
     void configureKWeighting();
     void configureFastMeter();
+    void configureTruePeakDetector();
     void processLoudnessSample(float left, float right);
     void updateMomentaryShortTermLoudness();
     double computeGatedIntegratedLoudness() const;
@@ -54,13 +56,15 @@ private:
     double histogramLufsAtIndex(size_t index) const;
     double applyBiquad(const BiquadCoeffs& coeffs, BiquadState& state, double input);
 
-    void processFastMeterSample(float left, float right, double& maxPeakL, double& maxPeakR);
+    void processFastMeterSample(float left, float right);
-    void advancePeaks(double nowMs);
+    void processTruePeakSample(float left, float right, double& maxTruePeakL, double& maxTruePeakR);
-    void maybeUpdatePeak(double peakDb, double nowMs, bool leftChannel);
+    void advanceTruePeaks(double nowMs);
+    void maybeUpdateTruePeak(double peakDb, double nowMs, bool leftChannel);
     double applyPeakDecay(double currentDb, double holdUntilMs, double nowMs) const;
     void recomputeFastSnapshot();
     static double currentTimeMs();
     static double amplitudeToDb(double amplitude);
+    static double truePeakAmplitudeToDb(double amplitude);
     static double clampDb(double db, double minDb, double maxDb);
     static BiquadCoeffs preFilterCoeffs(double sampleRate);
     static BiquadCoeffs rlbFilterCoeffs(double sampleRate);
@@ -99,6 +103,12 @@ private:
     double lastPeakUpdateMs_ = 0.0;
     bool hasLastPeakUpdate_ = false;
 
+    size_t truePeakOversampleFactor_ = 1;
+    std::vector<double> truePeakCoefficients_;
+    std::vector<double> truePeakHistoryL_;
+    std::vector<double> truePeakHistoryR_;
+    size_t truePeakHistoryWriteIndex_ = 0;
+
     LUFSMeterSnapshot snapshot_{};
 };
 

native/src/main.cpp

@@ -690,8 +690,9 @@ Napi::Value LUFSMeterGetSnapshot(const Napi::CallbackInfo& info) {
     obj.Set("vuRDb", Napi::Number::New(env, snapshot.vuRDb));
     obj.Set("barLDb", Napi::Number::New(env, snapshot.barLDb));
     obj.Set("barRDb", Napi::Number::New(env, snapshot.barRDb));
-    obj.Set("peakLDb", Napi::Number::New(env, snapshot.peakLDb));
+    obj.Set("truePeakLDb", Napi::Number::New(env, snapshot.truePeakLDb));
-    obj.Set("peakRDb", Napi::Number::New(env, snapshot.peakRDb));
+    obj.Set("truePeakRDb", Napi::Number::New(env, snapshot.truePeakRDb));
+    obj.Set("maxTruePeakDb", Napi::Number::New(env, snapshot.maxTruePeakDb));
     obj.Set("correlation", Napi::Number::New(env, snapshot.correlation));
     return obj;
 }

package.json

@@ -27,6 +27,8 @@
     "test:spectrum-native": "node --test test/spectrum-native.test.mjs",
     "test:spectrogram-native": "node --test test/spectrogram-native.test.mjs",
     "test:vectorscope-native": "node --test test/vectorscope-native.test.mjs",
+    "test:lufsmeter-native": "node --test test/lufsmeter-native.test.mjs",
+    "test:lufsmeter-ebu": "node scripts/run-ebu-true-peak-tests.mjs",
     "test:tui": "node scripts/build/build-tui.cjs --test",
     "test:build-metadata": "node scripts/run-build-metadata-tests.mjs",
     "test:updates": "node scripts/run-update-tests.mjs",

plugin/Source/LUFSMeterEngine.h

@@ -5,9 +5,9 @@
 
 /**
  * Loudness (LUFS) meter engine. Pushes stereo audio into the reused
- * `Visualizer::LUFSMeterAnalyzer` (K-weighting + gated integration + the same fast
+ * `Visualizer::LUFSMeterAnalyzer` (K-weighting, gated integration, true peak, and
- * VU/peak/correlation block) and emits its scalar snapshot each frame. Like the VU
+ * the same fast VU/correlation block) and emits its scalar snapshot each frame.
- * engine the frame is plain numbers (no base64); getSnapshot() advances peak decay
+ * The frame is plain numbers (no base64); getSnapshot() advances true-peak decay
  * on the steady clock, so it's safe to call every frame. configure() is a no-op —
  * LUFS settings (mode/readout) are render-side.
  */
@@ -44,8 +44,9 @@ public:
         obj->setProperty("vuRDb", snap.vuRDb);
         obj->setProperty("barLDb", snap.barLDb);
         obj->setProperty("barRDb", snap.barRDb);
-        obj->setProperty("peakLDb", snap.peakLDb);
+        obj->setProperty("truePeakLDb", snap.truePeakLDb);
-        obj->setProperty("peakRDb", snap.peakRDb);
+        obj->setProperty("truePeakRDb", snap.truePeakRDb);
+        obj->setProperty("maxTruePeakDb", snap.maxTruePeakDb);
         obj->setProperty("correlation", snap.correlation);
         return juce::var(obj);
     }

scripts/run-ebu-true-peak-tests.mjs

@@ -0,0 +1,126 @@
+import { readFile, readdir, stat } from 'node:fs/promises'
+import { basename, join, resolve } from 'node:path'
+import { createRequire } from 'node:module'
+
+const require = createRequire(import.meta.url)
+const { lufsmeter } = require('../native/build/Release/visualizer_dsp.node')
+
+const sourcePath = process.argv[2]
+if (!sourcePath) {
+  console.error('Usage: npm run test:lufsmeter-ebu -- /path/to/extracted-ebu-loudness-test-set')
+  process.exit(2)
+}
+
+async function collectFiles(path) {
+  const details = await stat(path)
+  if (details.isFile()) return [path]
+  if (!details.isDirectory()) return []
+
+  const files = []
+  for (const entry of await readdir(path, { withFileTypes: true })) {
+    files.push(...await collectFiles(join(path, entry.name)))
+  }
+  return files
+}
+
+function decodeWave(buffer) {
+  if (buffer.length < 12 || buffer.toString('ascii', 0, 4) !== 'RIFF'
+    || buffer.toString('ascii', 8, 12) !== 'WAVE') {
+    throw new Error('not a RIFF/WAVE file')
+  }
+
+  let format = null
+  let data = null
+  for (let offset = 12; offset + 8 <= buffer.length;) {
+    const chunkId = buffer.toString('ascii', offset, offset + 4)
+    const chunkSize = buffer.readUInt32LE(offset + 4)
+    const chunkOffset = offset + 8
+    if (chunkOffset + chunkSize > buffer.length) throw new Error(`truncated ${chunkId} chunk`)
+
+    if (chunkId === 'fmt ') {
+      if (chunkSize < 16) throw new Error('invalid fmt chunk')
+      let formatTag = buffer.readUInt16LE(chunkOffset)
+      if (formatTag === 0xfffe && chunkSize >= 40) {
+        formatTag = buffer.readUInt16LE(chunkOffset + 24)
+      }
+      format = {
+        formatTag,
+        channels: buffer.readUInt16LE(chunkOffset + 2),
+        sampleRate: buffer.readUInt32LE(chunkOffset + 4),
+        blockAlign: buffer.readUInt16LE(chunkOffset + 12),
+        bitsPerSample: buffer.readUInt16LE(chunkOffset + 14),
+      }
+    } else if (chunkId === 'data') {
+      data = buffer.subarray(chunkOffset, chunkOffset + chunkSize)
+    }
+    offset = chunkOffset + chunkSize + (chunkSize % 2)
+  }
+
+  if (!format || !data) throw new Error('missing fmt or data chunk')
+  if (format.channels < 1 || format.blockAlign < 1 || format.sampleRate < 1) {
+    throw new Error('invalid WAVE format')
+  }
+
+  const bytesPerSample = Math.ceil(format.bitsPerSample / 8)
+  const frameCount = Math.floor(data.length / format.blockAlign)
+  const left = new Float32Array(frameCount)
+  const right = new Float32Array(frameCount)
+  const readSample = (offset) => {
+    if (format.formatTag === 3 && format.bitsPerSample === 32) return data.readFloatLE(offset)
+    if (format.formatTag !== 1) throw new Error(`unsupported WAVE format tag ${format.formatTag}`)
+    if (format.bitsPerSample === 16) return data.readInt16LE(offset) / 0x8000
+    if (format.bitsPerSample === 24) return data.readIntLE(offset, 3) / 0x800000
+    if (format.bitsPerSample === 32) return data.readInt32LE(offset) / 0x80000000
+    throw new Error(`unsupported PCM depth ${format.bitsPerSample}`)
+  }
+
+  for (let frame = 0; frame < frameCount; frame += 1) {
+    const frameOffset = frame * format.blockAlign
+    left[frame] = readSample(frameOffset)
+    right[frame] = format.channels > 1 ? readSample(frameOffset + bytesPerSample) : left[frame]
+  }
+  return { sampleRate: format.sampleRate, left, right }
+}
+
+function expectedDbtp(caseNumber) {
+  if (caseNumber >= 15 && caseNumber <= 18) return -6
+  if (caseNumber === 19) return 3
+  return 0
+}
+
+const files = await collectFiles(resolve(sourcePath))
+const cases = new Map()
+for (const file of files) {
+  const match = basename(file).match(/3341[-_ ](1[5-9]|2[0-3])(?:\D|$)/i)
+  if (match && /\.wav(?:\.wav)?$/i.test(file)) cases.set(Number(match[1]), file)
+}
+
+const missing = []
+for (let caseNumber = 15; caseNumber <= 23; caseNumber += 1) {
+  if (!cases.has(caseNumber)) missing.push(caseNumber)
+}
+if (missing.length > 0) {
+  console.error(`Could not find EBU Tech 3341 WAV cases: ${missing.join(', ')}`)
+  process.exit(2)
+}
+
+let failed = false
+for (let caseNumber = 15; caseNumber <= 23; caseNumber += 1) {
+  const file = cases.get(caseNumber)
+  try {
+    const wave = decodeWave(await readFile(file))
+    lufsmeter.setSampleRate(wave.sampleRate)
+    lufsmeter.reset()
+    lufsmeter.pushSamples(wave.left, wave.right)
+    const actual = lufsmeter.getSnapshot().maxTruePeakDb
+    const expected = expectedDbtp(caseNumber)
+    const passed = actual >= expected - 0.4 && actual <= expected + 0.2
+    console.log(`${passed ? 'PASS' : 'FAIL'}  EBU 3341-${caseNumber}: ${actual.toFixed(3)} dBTP (expected ${expected}, +0.2/-0.4)`)
+    failed ||= !passed
+  } catch (error) {
+    failed = true
+    console.error(`FAIL  EBU 3341-${caseNumber}: ${error instanceof Error ? error.message : String(error)}`)
+  }
+}
+
+process.exit(failed ? 1 : 0)

scripts/run-tests.mjs

@@ -19,6 +19,7 @@ const testScripts = [
   'test:spectrum-native',
   'test:spectrogram-native',
   'test:vectorscope-native',
+  'test:lufsmeter-native',
 ]
 
 const npmCommand = process.platform === 'win32' ? 'npm.cmd' : 'npm'

src/plugin-ui/BridgeLUFSMeterAnalyzer.ts

@@ -3,7 +3,7 @@ import type { LUFSMeterNativeAnalyzer, LUFSMeterNativeSnapshot } from '../render
 /**
  * Drop-in `LUFSMeterNativeAnalyzer` for the plugin webview.
  *
- * The loudness DSP (K-weighting, gated integration, fast VU/peak/correlation) runs
+ * The loudness DSP (K-weighting, gated integration, true peak, fast VU/correlation) runs
  * in the C++ plugin, which pushes a finished scalar snapshot each frame. This shim
  * caches that snapshot and serves it through the interface `LUFSMeter` consumes.
  * `pushSamples` is a no-op (audio never flows through the webview); `reset` clears

src/plugin-ui/juceBridge.ts

@@ -275,16 +275,25 @@ export interface LUFSMeterFrame {
   vuRDb: number
   barLDb: number
   barRDb: number
-  peakLDb: number
+  truePeakLDb: number
-  peakRDb: number
+  truePeakRDb: number
+  maxTruePeakDb: number
   correlation: number
 }
 
-function decodeLUFSMeterFrame(payload: unknown): LUFSMeterFrame | null {
+export function decodeLUFSMeterFrame(
+  payload: unknown,
+  previousMaxTruePeakDb = -60,
+): LUFSMeterFrame | null {
   if (typeof payload !== 'object' || payload === null) return null
   const p = payload as Record<string, unknown>
   const num = (key: string, fallback: number): number =>
     typeof p[key] === 'number' && Number.isFinite(p[key]) ? (p[key] as number) : fallback
+  const truePeakLDb = num('truePeakLDb', num('peakLDb', -60))
+  const truePeakRDb = num('truePeakRDb', num('peakRDb', -60))
+  const explicitMaximum = typeof p.maxTruePeakDb === 'number' && Number.isFinite(p.maxTruePeakDb)
+    ? p.maxTruePeakDb
+    : null
   return {
     sampleRate: num('sampleRate', 48000) > 0 ? num('sampleRate', 48000) : 48000,
     momentaryLUFS: num('momentaryLUFS', -70),
@@ -294,8 +303,13 @@ function decodeLUFSMeterFrame(payload: unknown): LUFSMeterFrame | null {
     vuRDb: num('vuRDb', -60),
     barLDb: num('barLDb', -60),
     barRDb: num('barRDb', -60),
-    peakLDb: num('peakLDb', -60),
+    truePeakLDb,
-    peakRDb: num('peakRDb', -60),
+    truePeakRDb,
+    maxTruePeakDb: explicitMaximum ?? Math.max(
+      Number.isFinite(previousMaxTruePeakDb) ? previousMaxTruePeakDb : -60,
+      truePeakLDb,
+      truePeakRDb,
+    ),
     correlation: num('correlation', 0),
   }
 }
@@ -309,6 +323,8 @@ export function connectLUFSMeterBridge(handlers: LUFSMeterBridgeHandlers): () =>
   let disposed = false
   let listenerId: number | null = null
   let mockRaf: number | null = null
+  let maxTruePeakDb = -60
+  let previousSampleRate = 0
 
   const startMock = (): void => {
     handlers.onConnected?.(true)
@@ -320,6 +336,9 @@ export function connectLUFSMeterBridge(handlers: LUFSMeterBridgeHandlers): () =>
       const lufs = (offset: number): number => -24 + Math.sin(phase + offset) * 6
       const vuL = -36 + (Math.sin(phase) * 0.5 + 0.5) * 30
       const vuR = -36 + (Math.sin(phase + 0.7) * 0.5 + 0.5) * 30
+      const truePeakLDb = vuL + 3
+      const truePeakRDb = vuR + 3
+      maxTruePeakDb = Math.max(maxTruePeakDb, truePeakLDb, truePeakRDb)
       handlers.onFrame({
         sampleRate: 48000,
         momentaryLUFS: lufs(0),
@@ -329,8 +348,9 @@ export function connectLUFSMeterBridge(handlers: LUFSMeterBridgeHandlers): () =>
         vuRDb: vuR,
         barLDb: vuL,
         barRDb: vuR,
-        peakLDb: vuL + 3,
+        truePeakLDb,
-        peakRDb: vuR + 3,
+        truePeakRDb,
+        maxTruePeakDb,
         correlation: Math.sin(phase * 0.3),
       })
       mockRaf = requestAnimationFrame(tick)
@@ -342,8 +362,15 @@ export function connectLUFSMeterBridge(handlers: LUFSMeterBridgeHandlers): () =>
     if (disposed) return
     if (backend) {
       listenerId = backend.addEventListener('lufsmeterFrame', (payload) => {
-        const frame = decodeLUFSMeterFrame(payload)
+        let frame = decodeLUFSMeterFrame(payload, maxTruePeakDb)
-        if (frame) handlers.onFrame(frame)
+        if (frame && previousSampleRate > 0 && Math.abs(frame.sampleRate - previousSampleRate) > 1) {
+          frame = decodeLUFSMeterFrame(payload, -60)
+        }
+        if (frame) {
+          previousSampleRate = frame.sampleRate
+          maxTruePeakDb = frame.maxTruePeakDb
+          handlers.onFrame(frame)
+        }
       })
       handlers.onConnected?.(false)
       console.log('[prism-plugin] connected to JUCE host (lufsmeter)')

src/renderer/audio/native/visualizer-dsp.d.ts

@@ -54,8 +54,9 @@ export interface LUFSMeterNativeSnapshot {
   vuRDb: number;
   barLDb: number;
   barRDb: number;
-  peakLDb: number;
+  truePeakLDb: number;
-  peakRDb: number;
+  truePeakRDb: number;
+  maxTruePeakDb: number;
   correlation: number;
 }
 

src/renderer/visualizers/LUFSMeter.ts

@@ -73,6 +73,7 @@ const TARGET_LUFS = -14
 const METER_MIN_DB = -60
 const MAX_METER_VIEWPORT_CSS_WIDTH = 240
 const FULL_READOUT_WIDTH_SAMPLE = '-00.0LUFS'
+const TRUE_PEAK_EMPTY_DB = METER_MIN_DB
 
 const INITIAL_NATIVE_SNAPSHOT: LUFSMeterNativeSnapshot = {
   momentaryLUFS: METER_MIN_LUFS,
@@ -82,8 +83,9 @@ const INITIAL_NATIVE_SNAPSHOT: LUFSMeterNativeSnapshot = {
   vuRDb: METER_MIN_DB,
   barLDb: METER_MIN_DB,
   barRDb: METER_MIN_DB,
-  peakLDb: METER_MIN_DB,
+  truePeakLDb: METER_MIN_DB,
-  peakRDb: METER_MIN_DB,
+  truePeakRDb: METER_MIN_DB,
+  maxTruePeakDb: TRUE_PEAK_EMPTY_DB,
   correlation: 0,
 }
 
@@ -104,12 +106,20 @@ function normalizeNativeSnapshot(snapshot: LUFSMeterNativeSnapshot | null): LUFS
     vuRDb: finiteNumber(snapshot.vuRDb, METER_MIN_DB),
     barLDb: finiteNumber(snapshot.barLDb, METER_MIN_DB),
     barRDb: finiteNumber(snapshot.barRDb, METER_MIN_DB),
-    peakLDb: finiteNumber(snapshot.peakLDb, METER_MIN_DB),
+    truePeakLDb: finiteNumber(snapshot.truePeakLDb, METER_MIN_DB),
-    peakRDb: finiteNumber(snapshot.peakRDb, METER_MIN_DB),
+    truePeakRDb: finiteNumber(snapshot.truePeakRDb, METER_MIN_DB),
+    maxTruePeakDb: finiteNumber(snapshot.maxTruePeakDb, TRUE_PEAK_EMPTY_DB),
     correlation: finiteNumber(snapshot.correlation, 0),
   }
 }
 
+export function formatMaxTruePeakDb(maxTruePeakDb: number, compact = false): string {
+  const value = Number.isFinite(maxTruePeakDb) && maxTruePeakDb > TRUE_PEAK_EMPTY_DB
+    ? `${maxTruePeakDb >= 0 ? '+' : '−'}${Math.abs(maxTruePeakDb).toFixed(1)}`
+    : '−∞'
+  return compact ? `${value}dBTP` : `MAX TP ${value} dBTP`
+}
+
 // ---- Loudness meter class ----
 
 export class LUFSMeter {
@@ -383,8 +393,12 @@ export class LUFSMeter {
 
     const paddingX = Math.round(Math.max(4, Math.floor(cssWidth * 0.012)) * dpr)
     const paddingY = Math.round(Math.max(4, Math.floor(cssHeight * 0.025)) * dpr)
+    const footerFontSizeCss = Math.max(7, Math.min(11, Math.floor(cssHeight * 0.052)))
+    const footerFontSize = Math.max(1, Math.round(footerFontSizeCss * dpr))
+    const footerHeight = Math.max(1, Math.round((footerFontSizeCss + 4) * dpr))
+    const footerGap = Math.max(1, Math.round(4 * dpr))
     const meterTop = paddingY
-    const meterBottom = height - paddingY
+    const meterBottom = Math.max(meterTop + 1, height - paddingY - footerHeight - footerGap)
     const meterHeight = Math.max(1, meterBottom - meterTop)
     const availableViewportWidth = Math.max(1, width - paddingX * 2)
     const viewportWidth = Math.max(1, Math.min(
@@ -448,7 +462,7 @@ export class LUFSMeter {
       barWidth,
       meterHeight,
       this.snapshot.barLDb,
-      this.snapshot.peakLDb,
+      this.snapshot.truePeakLDb,
       tint,
       dpr,
     )
@@ -458,7 +472,7 @@ export class LUFSMeter {
       barWidth,
       meterHeight,
       this.snapshot.barRDb,
-      this.snapshot.peakRDb,
+      this.snapshot.truePeakRDb,
       tint,
       dpr,
     )
@@ -509,6 +523,29 @@ export class LUFSMeter {
     ctx.textBaseline = 'middle'
     ctx.fillStyle = this.contrastForLevelColor()
     ctx.fillText(readoutLayout.text, tagX + tagPadding, tagY + tagHeight / 2)
+
+    const fullTruePeakText = formatMaxTruePeakDb(this.snapshot.maxTruePeakDb)
+    const compactTruePeakText = formatMaxTruePeakDb(this.snapshot.maxTruePeakDb, true)
+    ctx.font = `700 ${footerFontSize}px "JetBrains Mono", "SF Mono", monospace`
+    const truePeakText = viewportCssWidth >= 160
+      && ctx.measureText(fullTruePeakText).width <= viewportWidth
+      ? fullTruePeakText
+      : compactTruePeakText
+    const truePeakLayout = this.resolveReadoutTextLayout(
+      [truePeakText],
+      viewportWidth,
+      footerFontSize,
+      Math.max(1, Math.round(7 * dpr)),
+    )
+    ctx.font = `700 ${truePeakLayout.fontSize}px "JetBrains Mono", "SF Mono", monospace`
+    ctx.textAlign = 'center'
+    ctx.textBaseline = 'middle'
+    ctx.fillStyle = this.options.labelColor
+    ctx.fillText(
+      truePeakLayout.text,
+      Math.round(width / 2),
+      Math.round(meterBottom + footerGap + footerHeight / 2),
+    )
   }
 
   dispose(): void {

test/lufsmeter-native.test.mjs

@@ -0,0 +1,234 @@
+import assert from 'node:assert/strict'
+import { createRequire } from 'node:module'
+import test from 'node:test'
+
+const require = createRequire(import.meta.url)
+const { lufsmeter } = require('../native/build/Release/visualizer_dsp.node')
+
+const EBU_SAMPLE_RATE = 48000
+const EBU_TOLERANCE_BELOW_DB = 0.4
+const EBU_TOLERANCE_ABOVE_DB = 0.2
+const SILENCE_DB = -60
+
+function assertEbuTolerance(actual, expected, label) {
+  assert.ok(
+    actual >= expected - EBU_TOLERANCE_BELOW_DB
+      && actual <= expected + EBU_TOLERANCE_ABOVE_DB,
+    `${label}: expected ${expected} dBTP (+${EBU_TOLERANCE_ABOVE_DB}/-${EBU_TOLERANCE_BELOW_DB}), got ${actual}`,
+  )
+}
+
+function createPhaseTone(
+  sampleRate,
+  frequency,
+  amplitude,
+  phaseDegrees,
+  durationSeconds = 0.1,
+) {
+  const length = Math.max(1, Math.round(sampleRate * durationSeconds))
+  const taperSamples = Math.max(1, Math.round(sampleRate * 0.01))
+  const phaseRadians = phaseDegrees * Math.PI / 180
+  const samples = new Float32Array(length)
+  for (let index = 0; index < length; index += 1) {
+    const fadeIn = Math.min(1, index / taperSamples)
+    const fadeOut = Math.min(1, (length - 1 - index) / taperSamples)
+    const taper = Math.max(0, Math.min(fadeIn, fadeOut))
+    samples[index] = amplitude
+      * Math.sin((2 * Math.PI * frequency * index) / sampleRate + phaseRadians)
+      * taper
+  }
+  return samples
+}
+
+function pushStereo(left, right = left, chunkSizes = null) {
+  if (!chunkSizes) {
+    lufsmeter.pushSamples(left, right)
+    return
+  }
+
+  let offset = 0
+  let chunkIndex = 0
+  while (offset < Math.min(left.length, right.length)) {
+    const requestedSize = chunkSizes[chunkIndex % chunkSizes.length]
+    const length = Math.min(requestedSize, left.length - offset, right.length - offset)
+    lufsmeter.pushSamples(
+      left.subarray(offset, offset + length),
+      right.subarray(offset, offset + length),
+    )
+    offset += length
+    chunkIndex += 1
+  }
+}
+
+function measure(sampleRate, left, right = left, chunkSizes = null) {
+  lufsmeter.setSampleRate(sampleRate)
+  lufsmeter.reset()
+  pushStereo(left, right, chunkSizes)
+  return lufsmeter.getSnapshot()
+}
+
+function besselI0(value) {
+  let sum = 1
+  let term = 1
+  const squaredQuarter = value * value / 4
+  for (let index = 1; index < 40; index += 1) {
+    term *= squaredQuarter / (index * index)
+    sum += term
+    if (term < sum * 1e-15) break
+  }
+  return sum
+}
+
+function createTransientReferenceAt4x(sampleRate = EBU_SAMPLE_RATE) {
+  const oversample = 4
+  const highRate = sampleRate * oversample
+  const durationSeconds = 0.12
+  const length = Math.round(highRate * durationSeconds)
+  const source = new Float64Array(length)
+  const taperSamples = Math.round(highRate * 0.01)
+
+  for (let index = 0; index < length; index += 1) {
+    const taper = Math.max(0, Math.min(
+      1,
+      index / taperSamples,
+      (length - 1 - index) / taperSamples,
+    ))
+    source[index] = 0.5 * Math.sin((2 * Math.PI * (sampleRate / 6) * index) / highRate) * taper
+  }
+
+  const transientStart = Math.floor(length / 2) - 8
+  for (let index = 0; index < 16; index += 1) {
+    source[transientStart + index] += Math.sin(Math.PI * index / 8)
+  }
+
+  const tapCount = 129
+  const half = (tapCount - 1) / 2
+  const cutoff = 0.5 / oversample
+  const beta = 8.6
+  const inverseI0Beta = 1 / besselI0(beta)
+  const coefficients = new Float64Array(tapCount)
+  let coefficientSum = 0
+  for (let tap = 0; tap < tapCount; tap += 1) {
+    const distance = tap - half
+    const sincArgument = 2 * cutoff * distance
+    const sinc = Math.abs(sincArgument) < 1e-12
+      ? 1
+      : Math.sin(Math.PI * sincArgument) / (Math.PI * sincArgument)
+    const ratio = distance / half
+    const window = besselI0(beta * Math.sqrt(Math.max(0, 1 - ratio * ratio))) * inverseI0Beta
+    coefficients[tap] = 2 * cutoff * sinc * window
+    coefficientSum += coefficients[tap]
+  }
+  for (let tap = 0; tap < tapCount; tap += 1) coefficients[tap] /= coefficientSum
+
+  const filtered = new Float64Array(length)
+  for (let index = half; index < length - half; index += 1) {
+    let value = 0
+    for (let tap = 0; tap < tapCount; tap += 1) {
+      value += coefficients[tap] * source[index + tap - half]
+    }
+    filtered[index] = value
+  }
+
+  let maximum = 0
+  for (const value of filtered) maximum = Math.max(maximum, Math.abs(value))
+  for (let index = 0; index < filtered.length; index += 1) filtered[index] /= maximum
+  return filtered
+}
+
+function downsample4x(reference, offset) {
+  const length = Math.floor((reference.length - offset) / 4)
+  const samples = new Float32Array(length)
+  for (let index = 0; index < length; index += 1) {
+    samples[index] = reference[index * 4 + offset]
+  }
+  return samples
+}
+
+test('BS.1770 true peak passes EBU Tech 3341 phase-tone cases 15-19', () => {
+  const cases = [
+    { number: 15, divisor: 4, amplitude: 0.5, phase: 0, expected: -6 },
+    { number: 16, divisor: 4, amplitude: 0.5, phase: 45, expected: -6 },
+    { number: 17, divisor: 6, amplitude: 0.5, phase: 60, expected: -6 },
+    { number: 18, divisor: 8, amplitude: 0.5, phase: 67.5, expected: -6 },
+    { number: 19, divisor: 4, amplitude: 1.41, phase: 45, expected: 3 },
+  ]
+
+  for (const vector of cases) {
+    const tone = createPhaseTone(
+      EBU_SAMPLE_RATE,
+      EBU_SAMPLE_RATE / vector.divisor,
+      vector.amplitude,
+      vector.phase,
+    )
+    const snapshot = measure(EBU_SAMPLE_RATE, tone)
+    assertEbuTolerance(snapshot.maxTruePeakDb, vector.expected, `EBU case ${vector.number}`)
+    assertEbuTolerance(snapshot.truePeakLDb, vector.expected, `EBU case ${vector.number} left marker`)
+    assertEbuTolerance(snapshot.truePeakRDb, vector.expected, `EBU case ${vector.number} right marker`)
+  }
+})
+
+test('BS.1770 true peak passes four phase offsets of a filtered transient (EBU cases 20-23)', () => {
+  const reference = createTransientReferenceAt4x()
+  for (let offset = 0; offset < 4; offset += 1) {
+    const samples = downsample4x(reference, offset)
+    const snapshot = measure(EBU_SAMPLE_RATE, samples)
+    assertEbuTolerance(snapshot.maxTruePeakDb, 0, `EBU transient case ${20 + offset}`)
+  }
+})
+
+test('true-peak state is independent of arbitrary audio chunk boundaries', () => {
+  const tone = createPhaseTone(EBU_SAMPLE_RATE, EBU_SAMPLE_RATE / 4, 1.41, 45)
+  const contiguous = measure(EBU_SAMPLE_RATE, tone).maxTruePeakDb
+  const irregular = measure(EBU_SAMPLE_RATE, tone, tone, [1, 7, 113, 2, 509, 31]).maxTruePeakDb
+  assert.ok(Math.abs(contiguous - irregular) < 1e-6, `${contiguous} vs ${irregular}`)
+})
+
+test('true peak supports common host rates with rate-aware oversampling', () => {
+  for (const sampleRate of [44100, 48000, 96000, 192000]) {
+    const tone = createPhaseTone(sampleRate, sampleRate / 4, 1.41, 45)
+    const snapshot = measure(sampleRate, tone)
+    assertEbuTolerance(snapshot.maxTruePeakDb, 3, `${sampleRate} Hz`)
+  }
+})
+
+test('true-peak channels preserve polarity and remain independent', () => {
+  const positive = createPhaseTone(EBU_SAMPLE_RATE, EBU_SAMPLE_RATE / 4, 1.41, 45)
+  const negative = Float32Array.from(positive, (sample) => -sample)
+  const silence = new Float32Array(positive.length)
+
+  const positiveSnapshot = measure(EBU_SAMPLE_RATE, positive, silence)
+  assertEbuTolerance(positiveSnapshot.truePeakLDb, 3, 'left channel')
+  assert.equal(positiveSnapshot.truePeakRDb, SILENCE_DB)
+
+  const negativeSnapshot = measure(EBU_SAMPLE_RATE, negative, silence)
+  assert.ok(Math.abs(negativeSnapshot.truePeakLDb - positiveSnapshot.truePeakLDb) < 1e-6)
+  assert.equal(negativeSnapshot.truePeakRDb, SILENCE_DB)
+})
+
+test('maximum true peak persists across quieter input and clears on reset', () => {
+  const loud = createPhaseTone(EBU_SAMPLE_RATE, EBU_SAMPLE_RATE / 4, 1.41, 45)
+  const quiet = createPhaseTone(EBU_SAMPLE_RATE, EBU_SAMPLE_RATE / 4, 0.1, 45)
+  const silence = new Float32Array(1024)
+
+  lufsmeter.setSampleRate(EBU_SAMPLE_RATE)
+  lufsmeter.reset()
+  pushStereo(loud)
+  const loudSnapshot = lufsmeter.getSnapshot()
+  assert.ok(loudSnapshot.maxTruePeakDb > 0)
+
+  pushStereo(quiet)
+  assert.equal(lufsmeter.getSnapshot().maxTruePeakDb, loudSnapshot.maxTruePeakDb)
+
+  lufsmeter.reset()
+  assert.deepEqual(
+    {
+      truePeakLDb: lufsmeter.getSnapshot().truePeakLDb,
+      truePeakRDb: lufsmeter.getSnapshot().truePeakRDb,
+      maxTruePeakDb: lufsmeter.getSnapshot().maxTruePeakDb,
+    },
+    { truePeakLDb: SILENCE_DB, truePeakRDb: SILENCE_DB, maxTruePeakDb: SILENCE_DB },
+  )
+  pushStereo(silence)
+  assert.equal(lufsmeter.getSnapshot().maxTruePeakDb, SILENCE_DB)
+})

test/renderer-helpers.test.ts

@@ -115,11 +115,11 @@ import {
   HEAT_MIN_DB,
   normalizeHeatDb,
 } from '../src/renderer/visualizers/heatScale'
-import { LUFSMeter } from '../src/renderer/visualizers/LUFSMeter'
+import { LUFSMeter, formatMaxTruePeakDb } from '../src/renderer/visualizers/LUFSMeter'
 import { Oscilloscope } from '../src/renderer/visualizers/Oscilloscope'
 import { SpectrumAnalyzer, type SpectrumAnalyzerOptions } from '../src/renderer/visualizers/SpectrumAnalyzer'
 import { BridgeSpectrumAnalyzer } from '../src/plugin-ui/BridgeSpectrumAnalyzer'
-import { decodeSpectrumFrame } from '../src/plugin-ui/juceBridge'
+import { decodeLUFSMeterFrame, decodeSpectrumFrame } from '../src/plugin-ui/juceBridge'
 import { formatSpectrumPeakDbfs } from '../src/plugin-ui/peakOverlay'
 import { spectrogramSettingsToOptions } from '../src/plugin-ui/spectrogramOptions'
 import { spectrumSettingsToOptions } from '../src/plugin-ui/spectrumOptions'
@@ -6296,8 +6296,9 @@ function createFakeLUFSMeterNativeAnalyzer(
       vuRDb: -13,
       barLDb: -10,
       barRDb: -12,
-      peakLDb: -4,
+      truePeakLDb: -4,
-      peakRDb: -5,
+      truePeakRDb: -5,
+      maxTruePeakDb: -4,
       correlation: 0.5,
       ...snapshotOverrides,
     } satisfies LUFSMeterNativeSnapshot,
@@ -6319,7 +6320,45 @@ function createFakeLUFSMeterNativeAnalyzer(
   return analyzer
 }
 
-test('LUFSMeter draws compact fast bars, a thicker LUFS bar, scale labels, and attached readout', () => {
+test('LUFSMeter formats positive, negative, compact, and reset true-peak maxima', () => {
+  assert.equal(formatMaxTruePeakDb(3), 'MAX TP +3.0 dBTP')
+  assert.equal(formatMaxTruePeakDb(-4.25), 'MAX TP −4.3 dBTP')
+  assert.equal(formatMaxTruePeakDb(3, true), '+3.0dBTP')
+  assert.equal(formatMaxTruePeakDb(-60), 'MAX TP −∞ dBTP')
+  assert.equal(formatMaxTruePeakDb(Number.NaN, true), '−∞dBTP')
+})
+
+test('loudness bridge decodes true-peak fields and accumulates legacy peak maxima', () => {
+  const current = decodeLUFSMeterFrame({
+    sampleRate: 96000,
+    truePeakLDb: 1.25,
+    truePeakRDb: -2,
+    maxTruePeakDb: 2.5,
+  })
+  assert.ok(current)
+  assert.equal(current.sampleRate, 96000)
+  assert.equal(current.truePeakLDb, 1.25)
+  assert.equal(current.truePeakRDb, -2)
+  assert.equal(current.maxTruePeakDb, 2.5)
+
+  const firstLegacy = decodeLUFSMeterFrame({ peakLDb: -3, peakRDb: -5 }, -60)
+  assert.ok(firstLegacy)
+  assert.equal(firstLegacy.truePeakLDb, -3)
+  assert.equal(firstLegacy.truePeakRDb, -5)
+  assert.equal(firstLegacy.maxTruePeakDb, -3)
+
+  const quieterLegacy = decodeLUFSMeterFrame({ peakLDb: -9, peakRDb: -7 }, firstLegacy.maxTruePeakDb)
+  assert.equal(quieterLegacy?.maxTruePeakDb, -3)
+
+  const explicitReset = decodeLUFSMeterFrame({
+    truePeakLDb: -60,
+    truePeakRDb: -60,
+    maxTruePeakDb: -60,
+  }, 2.5)
+  assert.equal(explicitReset?.maxTruePeakDb, -60)
+})
+
+test('LUFSMeter draws fast bars, true-peak markers, LUFS readout, and maximum dBTP footer', () => {
   const dom = installFakeCanvasDom()
   const recorder = createFakeCanvasRecorder()
   const leftChunk = new Float32Array(4800)
@@ -6343,7 +6382,12 @@ test('LUFSMeter draws compact fast bars, a thicker LUFS bar, scale labels, and a
     isPlaying: () => true,
     subscribeToSessionChanges: () => () => {},
   }
-  const nativeAnalyzer = createFakeLUFSMeterNativeAnalyzer({ momentaryLUFS: -18.4 })
+  const nativeAnalyzer = createFakeLUFSMeterNativeAnalyzer({
+    momentaryLUFS: -18.4,
+    truePeakLDb: 3,
+    truePeakRDb: -5,
+    maxTruePeakDb: 3,
+  })
   const meter = new LUFSMeter(createFakeCanvas(recorder), {
     dataSource,
     nativeAnalyzer,
@@ -6392,6 +6436,10 @@ test('LUFSMeter draws compact fast bars, a thicker LUFS bar, scale labels, and a
       recorder.fillTexts.some((text) => text.text.endsWith('LUFS') && text.fillStyle === 'rgba(0, 0, 0, 0.9)'),
       true,
     )
+    assert.equal(
+      recorder.fillTexts.some((text) => text.text === 'MAX TP +3.0 dBTP' && text.fillStyle === 'rgb(7, 8, 9)'),
+      true,
+    )
   } finally {
     meter.dispose()
     dom.restore()
@@ -6419,7 +6467,7 @@ test('LUFSMeter fits readout text inside narrow tags', () => {
     isPlaying: () => true,
     subscribeToSessionChanges: () => () => {},
   }
-  const nativeAnalyzer = createFakeLUFSMeterNativeAnalyzer({ momentaryLUFS: -8.1 })
+  const nativeAnalyzer = createFakeLUFSMeterNativeAnalyzer({ momentaryLUFS: -8.1, maxTruePeakDb: 3 })
   const meter = new LUFSMeter(createFakeCanvas(recorder, 180, 360), {
     dataSource,
     nativeAnalyzer,
@@ -6444,6 +6492,7 @@ test('LUFSMeter fits readout text inside narrow tags', () => {
     const fontSize = Number(readout.font.match(/(\d+(?:\.\d+)?)px/)?.[1] ?? 0)
     const estimatedTextWidth = readout.text.length * fontSize * 0.62
     assert.equal(estimatedTextWidth <= tagRect.width - 8, true)
+    assert.equal(recorder.fillTexts.some((text) => text.text === 'MAX TP +3.0 dBTP'), true)
   } finally {
     meter.dispose()
     dom.restore()
@@ -6475,7 +6524,7 @@ test('LUFSMeter centers wide layouts in a bounded viewport', () => {
     const tracks = recorder.fillRects.filter((rect) => rect.fillStyle === '#111111')
     const target = recorder.fillRects.find((rect) => rect.fillStyle === '#222222')
     const tag = recorder.fillRects.find((rect) => rect.fillStyle === '#123456' && rect.height <= 22)
-    const readout = recorder.fillTexts[recorder.fillTexts.length - 1]
+    const readout = recorder.fillTexts.find((text) => text.text.endsWith('LUFS'))
     const viewportLeft = (canvas.width - 240) / 2
     const viewportRight = viewportLeft + 240
 
@@ -6503,7 +6552,7 @@ test('LUFSMeter keeps minimum-width layout and compact readout inside canvas bou
   const dom = installFakeCanvasDom()
   const recorder = createFakeCanvasRecorder()
   const canvas = createFakeCssSizedCanvas(recorder, 112, 196)
-  const nativeAnalyzer = createFakeLUFSMeterNativeAnalyzer({ shortTermLUFS: -8.7 })
+  const nativeAnalyzer = createFakeLUFSMeterNativeAnalyzer({ shortTermLUFS: -8.7, maxTruePeakDb: 3 })
   const meter = new LUFSMeter(canvas, {
     dataSource: {
       getPendingLUFSMeterSamples: () => [],
@@ -6527,11 +6576,17 @@ test('LUFSMeter keeps minimum-width layout and compact readout inside canvas bou
       && rect.height > 2
       && rect.height <= 22
     ))
-    const readout = recorder.fillTexts[recorder.fillTexts.length - 1]
+    const readout = recorder.fillTexts.find((text) => text.text === '-8.7')
 
     assert.deepEqual(tracks.map((rect) => rect.width), [6, 6, 12])
     assert.ok(tag)
     assert.equal(readout?.text, '-8.7')
+    const truePeakReadout = recorder.fillTexts.find((text) => text.text.endsWith('dBTP'))
+    assert.equal(truePeakReadout?.text, '+3.0dBTP')
+    const truePeakFontSize = Number(truePeakReadout?.font.match(/(\d+(?:\.\d+)?)px/)?.[1] ?? 0)
+    const truePeakWidth = (truePeakReadout?.text.length ?? 0) * truePeakFontSize * 0.62
+    assert.ok((truePeakReadout?.x ?? 0) - truePeakWidth / 2 >= 0)
+    assert.ok((truePeakReadout?.x ?? 0) + truePeakWidth / 2 <= canvas.width)
 
     for (const rect of recorder.fillRects) {
       assert.ok(rect.x >= 0, `rectangle starts before canvas: ${JSON.stringify(rect)}`)