Fix NaN drift in VU

src/renderer/visualizers/VUMeter.ts

@@ -606,7 +606,7 @@ export class VUMeter {
     x: number, y: number, _w: number, h: number,
     db: number
   ): void {
-    const displayDb = Math.max(VU_METER_MIN_DB, Math.min(0, db))
+    const displayDb = Number.isFinite(db) ? Math.max(VU_METER_MIN_DB, Math.min(0, db)) : VU_METER_MIN_DB
     const text = displayDb <= VU_METER_MIN_DB + 1 ? '-∞' : `${displayDb.toFixed(1)}`
     ctx.fillStyle = alphaColor(this.options.labelColor, 0.8)
     ctx.font = `${Math.min(20, Math.max(9, h * 0.55))}px "JetBrains Mono", monospace`
@@ -620,7 +620,7 @@ export class VUMeter {
     x: number, y: number, w: number, h: number,
     db: number
   ): void {
-    const displayDb = Math.max(VU_METER_MIN_DB, Math.min(0, db))
+    const displayDb = Number.isFinite(db) ? Math.max(VU_METER_MIN_DB, Math.min(0, db)) : VU_METER_MIN_DB
     const text = displayDb <= VU_METER_MIN_DB + 1 ? '-∞' : `${displayDb.toFixed(1)}`
     ctx.fillStyle = alphaColor(this.options.labelColor, 0.8)
     ctx.font = `${Math.min(16, Math.max(8, h * 0.5))}px "JetBrains Mono", monospace`
@@ -1088,6 +1088,7 @@ export class VUMeter {
   }
 
   private formatNeedleDb(db: number): string {
+    if (!Number.isFinite(db)) return '-∞'
     const displayDb = clamp(db, VU_METER_MIN_DB, VU_METER_MAX_DB)
     return displayDb <= VU_METER_MIN_DB + 1 ? '-∞' : displayDb.toFixed(1)
   }

src/renderer/visualizers/vuMeterBallistics.ts

@@ -36,6 +36,9 @@ function clampSampleRate(sampleRate: number): number {
 }
 
 function amplitudeToDb(amplitude: number): number {
+  if (!Number.isFinite(amplitude) || amplitude <= 0) {
+    return VU_METER_MIN_DB
+  }
   const db = 20 * Math.log10(Math.max(amplitude, 1e-10))
   return Math.max(VU_METER_MIN_DB, Math.min(VU_METER_MAX_DB, db))
 }
@@ -119,8 +122,11 @@ export class VUMeterBallistics {
         const cross = left * right
 
         if (this.sampleCount === this.integrationWindowSamples) {
-          this.sumSqL -= this.sqL[this.writeIndex]
-          this.sumSqR -= this.sqR[this.writeIndex]
+          // Clamp running sums to non-negative: floating-point cancellation in
+          // the slide-out subtraction can drift them by ~1e-15 below zero on
+          // near-silent content, which would propagate as NaN through sqrt.
+          this.sumSqL = Math.max(0, this.sumSqL - this.sqL[this.writeIndex])
+          this.sumSqR = Math.max(0, this.sumSqR - this.sqR[this.writeIndex])
           this.sumCross -= this.cross[this.writeIndex]
         } else {
           this.sampleCount += 1
@@ -163,9 +169,9 @@ export class VUMeterBallistics {
       return
     }
 
-    const meanSqL = this.sumSqL / this.sampleCount
-    const meanSqR = this.sumSqR / this.sampleCount
-    const denominator = Math.sqrt(this.sumSqL * this.sumSqR)
+    const meanSqL = Math.max(0, this.sumSqL) / this.sampleCount
+    const meanSqR = Math.max(0, this.sumSqR) / this.sampleCount
+    const denominator = Math.sqrt(Math.max(0, this.sumSqL) * Math.max(0, this.sumSqR))
 
     this.snapshot.vuLDb = amplitudeToDb(Math.sqrt(meanSqL))
     this.snapshot.vuRDb = amplitudeToDb(Math.sqrt(meanSqR))

test/renderer-helpers.test.ts

@@ -3512,6 +3512,31 @@ test('VUMeterBallistics produces the same VU, bar, and correlation for contiguou
   assertAlmostEqual(irregularSnapshot.correlation, contiguousSnapshot.correlation, 1e-6, 'correlation should be chunking-invariant')
 })
 
+test('VUMeterBallistics keeps RMS finite across loud-then-silent sequences (NaN-drift regression)', () => {
+  const sampleRate = 48000
+  const meter = new VUMeterBallistics(sampleRate)
+  const windowSamples = Math.round((sampleRate * VU_INTEGRATION_WINDOW_MS) / 1000)
+
+  // Run loud audio long enough to fully populate the sliding-window buffer.
+  meter.process([createFilledStereoChunk(0.7, 0.7, windowSamples * 2)], 100)
+
+  // Then feed many windows of digital silence. Floating-point cancellation in
+  // the running-sum slide-out used to drift sumSqL/sumSqR slightly below zero,
+  // producing NaN through Math.sqrt. After the fix, the RMS must remain finite
+  // and decay all the way to VU_METER_MIN_DB.
+  let nowMs = 100
+  for (let i = 0; i < 20; i += 1) {
+    nowMs += 50
+    meter.process([createFilledStereoChunk(0, 0, windowSamples)], nowMs)
+  }
+
+  const snapshot = meter.getSnapshot()
+  assert.ok(Number.isFinite(snapshot.vuLDb), 'left VU must stay finite (no NaN)')
+  assert.ok(Number.isFinite(snapshot.vuRDb), 'right VU must stay finite (no NaN)')
+  assert.equal(snapshot.vuLDb, VU_METER_MIN_DB)
+  assert.equal(snapshot.vuRDb, VU_METER_MIN_DB)
+})
+
 test('VUMeterBallistics lets the bar outrun the VU needle while peak hold remains highest', () => {
   const sampleRate = 48000
   const meter = new VUMeterBallistics(sampleRate)
@@ -3696,8 +3721,16 @@ test('LUFSMeter draws compact fast bars, a thicker LUFS bar, scale labels, and a
       recorder.fillRects.some((rect) => rect.fillStyle === 'rgb(255, 0, 96)' && rect.width > 12 && rect.width < 80),
       true,
     )
+    // Readout tag pill: drawn with line color, fits to text width with padding,
+    // and uses the compact tag height. Sized smaller than the LUFS level bar.
     assert.equal(
-      recorder.fillRects.some((rect) => rect.fillStyle === 'rgb(255, 0, 96)' && rect.width > 120 && rect.height <= 34),
+      recorder.fillRects.some((rect) =>
+        rect.fillStyle === 'rgb(255, 0, 96)'
+        && rect.width >= 40
+        && rect.width <= 100
+        && rect.height >= 14
+        && rect.height <= 24,
+      ),
       true,
     )
     assert.equal(recorder.fillRects.some((rect) => rect.fillStyle === 'rgb(1, 2, 3)'), true)