restore q value to shelves

src/app/(tabs)/eq.tsx

@@ -58,8 +58,7 @@ import {
   EQ_MIN_FREQUENCY,
   EQ_MIN_PREAMP_DB,
   EQ_MIN_Q,
-  isPassEQBandType,
+  isPassEQBandType
-  isShelfEQBandType
 } from '@/audio/eq';
 import { parseAutoEQ } from '@/audio/autoEQParser';
 import { buildGraphicBands } from '@/audio/graphicEq';
@@ -728,7 +727,6 @@ function getValueEditConfig(kind: EQEditableValue, band: EQBand) {
         parseValue: parseDb,
       };
     case 'Q':
-      if (isShelfEQBandType(band.type)) return null;
       return {
         title: 'Edit Q',
         initialValue: band.Q.toFixed(2),

src/audio/eq.test.mts

@@ -44,27 +44,46 @@ test('peaking filter reaches requested gain at center frequency', () => {
   assertClose(computeEQFilterMagnitude(boost, 1200, 48000), 5.5, 1e-6);
 });
 
-test('shelf filters ignore Q like Web Audio BiquadFilterNode', () => {
+test('shelf filters use Q in their coefficients and response', () => {
-  const lowLoose = band({ type: 'lowshelf', frequency: 100, gain: 6, Q: 0.1 });
+  const lowWide = band({ type: 'lowshelf', frequency: 100, gain: 6, Q: 0.5 });
-  const lowTight = band({ type: 'lowshelf', frequency: 100, gain: 6, Q: 18 });
+  const lowNarrow = band({ type: 'lowshelf', frequency: 100, gain: 6, Q: 2 });
-  const highLoose = band({ type: 'highshelf', frequency: 8000, gain: -4, Q: 0.1 });
+  const highWide = band({ type: 'highshelf', frequency: 8000, gain: -4, Q: 0.5 });
-  const highTight = band({ type: 'highshelf', frequency: 8000, gain: -4, Q: 18 });
+  const highNarrow = band({ type: 'highshelf', frequency: 8000, gain: -4, Q: 2 });
 
-  assertCoefficientsClose(
+  assertCoefficientsClose(computeEQFilterCoefficients(lowWide, 48000), {
-    computeEQFilterCoefficients(lowLoose, 48000),
+    b0: 1.004523905875,
-    computeEQFilterCoefficients(lowTight, 48000)
+    b1: -1.978032948597,
+    b2: 0.973748440145,
+    a1: -1.978092655842,
+    a2: 0.978212638774,
+  });
+  assertCoefficientsClose(computeEQFilterCoefficients(highWide, 48000), {
+    b0: 0.746848511923,
+    b1: -0.319264680328,
+    b2: 0.034120017138,
+    a1: -0.641024137473,
+    a2: 0.102727986206,
+  });
+
+  assert.notDeepEqual(
+    computeEQFilterCoefficients(lowWide, 48000),
+    computeEQFilterCoefficients(lowNarrow, 48000)
   );
-  assertCoefficientsClose(
+  assert.notDeepEqual(
-    computeEQFilterCoefficients(highLoose, 48000),
+    computeEQFilterCoefficients(highWide, 48000),
-    computeEQFilterCoefficients(highTight, 48000)
+    computeEQFilterCoefficients(highNarrow, 48000)
   );
-  assertClose(
+  assert.ok(
-    computeEQFilterMagnitude(lowLoose, 40, 48000),
+    Math.abs(
-    computeEQFilterMagnitude(lowTight, 40, 48000)
+      computeEQFilterMagnitude(lowWide, 200, 48000) -
+        computeEQFilterMagnitude(lowNarrow, 200, 48000)
+    ) > 0.1
   );
-  assertClose(
+  assert.ok(
-    computeEQFilterMagnitude(highLoose, 12000, 48000),
+    Math.abs(
-    computeEQFilterMagnitude(highTight, 12000, 48000)
+      computeEQFilterMagnitude(highWide, 4000, 48000) -
+        computeEQFilterMagnitude(highNarrow, 4000, 48000)
+    ) > 0.1
   );
 });
 

src/audio/eq.ts

@@ -1,7 +1,6 @@
-// Parametric EQ math + helpers — ported from desktop `src/renderer/utils/eq.ts`.
+// Parametric EQ math + helpers. Audio EQ Cookbook biquad math drives the response
-// Web Audio BiquadFilterNode-compatible math drives the response curve in the EQ
+// curve in the EQ screen. Native playback computes matching coefficients in Kotlin
-// screen. Native playback computes matching coefficients in Kotlin at the real
+// at the real stream sample rate — here we also flatten band params for the bridge.
-// stream sample rate — here we also flatten band params for the native bridge.
 
 import type { EQBand, EQBandType, EQMode, EQPreset } from '../types/audio';
 
@@ -88,10 +87,6 @@ export function isPassEQBandType(type: EQBandType): boolean {
   return type === 'highpass' || type === 'lowpass';
 }
 
-export function isShelfEQBandType(type: EQBandType): boolean {
-  return type === 'lowshelf' || type === 'highshelf';
-}
-
 /** Pass filters carry no gain — force it to 0. */
 export function normalizeEQBand<T extends EQBand>(band: T): T {
   if (!isPassEQBandType(band.type) || band.gain === 0) {
@@ -185,7 +180,7 @@ export function serializeEQPresetData(
 }
 
 // ---------------------------------------------------------------------------
-// Response curve magnitude (Web Audio BiquadFilterNode) — for the Skia response curve.
+// Response curve magnitude (Audio EQ Cookbook) — for the Skia response curve.
 // ---------------------------------------------------------------------------
 
 export interface EQFilterCoefficients {
@@ -227,7 +222,6 @@ export function computeEQFilterCoefficients(band: EQBand, sampleRate: number): E
   const cosW0 = Math.cos(w0);
   const alphaQ = sinW0 / (2 * Math.max(band.Q, MIN_FILTER_Q));
   const alphaQDb = sinW0 / (2 * Math.pow(10, band.Q / 20));
-  const alphaShelf = (sinW0 / 2) * Math.SQRT2;
 
   let b0 = 1;
   let b1 = 0;
@@ -247,22 +241,22 @@ export function computeEQFilterCoefficients(band: EQBand, sampleRate: number): E
       break;
     case 'lowshelf': {
       const sqrtA = Math.sqrt(A);
-      b0 = A * (A + 1 - (A - 1) * cosW0 + 2 * sqrtA * alphaShelf);
+      b0 = A * (A + 1 - (A - 1) * cosW0 + 2 * sqrtA * alphaQ);
       b1 = 2 * A * (A - 1 - (A + 1) * cosW0);
-      b2 = A * (A + 1 - (A - 1) * cosW0 - 2 * sqrtA * alphaShelf);
+      b2 = A * (A + 1 - (A - 1) * cosW0 - 2 * sqrtA * alphaQ);
-      a0 = A + 1 + (A - 1) * cosW0 + 2 * sqrtA * alphaShelf;
+      a0 = A + 1 + (A - 1) * cosW0 + 2 * sqrtA * alphaQ;
       a1 = -2 * (A - 1 + (A + 1) * cosW0);
-      a2 = A + 1 + (A - 1) * cosW0 - 2 * sqrtA * alphaShelf;
+      a2 = A + 1 + (A - 1) * cosW0 - 2 * sqrtA * alphaQ;
       break;
     }
     case 'highshelf': {
       const sqrtA = Math.sqrt(A);
-      b0 = A * (A + 1 + (A - 1) * cosW0 + 2 * sqrtA * alphaShelf);
+      b0 = A * (A + 1 + (A - 1) * cosW0 + 2 * sqrtA * alphaQ);
       b1 = -2 * A * (A - 1 + (A + 1) * cosW0);
-      b2 = A * (A + 1 + (A - 1) * cosW0 - 2 * sqrtA * alphaShelf);
+      b2 = A * (A + 1 + (A - 1) * cosW0 - 2 * sqrtA * alphaQ);
-      a0 = A + 1 - (A - 1) * cosW0 + 2 * sqrtA * alphaShelf;
+      a0 = A + 1 - (A - 1) * cosW0 + 2 * sqrtA * alphaQ;
       a1 = 2 * (A - 1 - (A + 1) * cosW0);
-      a2 = A + 1 - (A - 1) * cosW0 - 2 * sqrtA * alphaShelf;
+      a2 = A + 1 - (A - 1) * cosW0 - 2 * sqrtA * alphaQ;
       break;
     }
     case 'lowpass':

src/components/eq/BandConsole.tsx

@@ -8,7 +8,6 @@ import { AppPressable, SCROLL_PRESS_DELAY } from '@/components/AppPressable';
 import {
   EQ_MAX_GAIN_DB,
   isPassEQBandType,
-  isShelfEQBandType,
 } from '@/audio/eq';
 import type { EQBand } from '@/types/audio';
 import { VerticalEQSlider } from './VerticalEQSlider';
@@ -78,7 +77,6 @@ export function BandConsole({
       {bands.map((band, index) => {
         const isActive = band.id === activeBandId;
         const isPass = isPassEQBandType(band.type);
-        const isShelf = isShelfEQBandType(band.type);
         return (
           <AppPressable
             key={band.id}
@@ -152,8 +150,8 @@ export function BandConsole({
             />
             <Readout
               label="Q"
-              value={isShelf ? '—' : band.Q.toFixed(2)}
+              value={band.Q.toFixed(2)}
-              onPress={isShelf ? undefined : () => onEditValue(band.id, 'Q')}
+              onPress={() => onEditValue(band.id, 'Q')}
             />
           </AppPressable>
         );

src/components/eq/BandDetailPanel.tsx

@@ -18,8 +18,7 @@ import {
   EQ_MAX_Q,
   EQ_MIN_FREQUENCY,
   EQ_MIN_Q,
-  isPassEQBandType,
+  isPassEQBandType
-  isShelfEQBandType
 } from '@/audio/eq';
 import { EQSlider } from './EQSlider';
 import {
@@ -55,7 +54,6 @@ export function BandDetailPanel({ band, bandNumber, onUpdate, onEditType, onEdit
   }
 
   const isPass = isPassEQBandType(band.type);
-  const isShelf = isShelfEQBandType(band.type);
 
   return (
     <View style={styles.card}>
@@ -98,18 +96,16 @@ export function BandDetailPanel({ band, bandNumber, onUpdate, onEditType, onEdit
         onValuePress={() => onEditValue('gain')}
         disabled={isPass}
       />
-      {!isShelf ? (
+      <EQSlider
-        <EQSlider
+        label="Q"
-          label="Q"
+        value={band.Q}
-          value={band.Q}
+        min={EQ_MIN_Q}
-          min={EQ_MIN_Q}
+        max={EQ_MAX_Q}
-          max={EQ_MAX_Q}
+        log
-          log
+        format={(v) => v.toFixed(2)}
-          format={(v) => v.toFixed(2)}
+        onChange={(v) => onUpdate({ Q: v })}
-          onChange={(v) => onUpdate({ Q: v })}
+        onValuePress={() => onEditValue('Q')}
-          onValuePress={() => onEditValue('Q')}
+      />
-        />
-      ) : null}
     </View>
   );
 }

vendor/kotlinaudio/kotlin-audio/src/main/java/com/doublesymmetry/kotlinaudio/scope/EqCoefficients.kt

@@ -7,7 +7,7 @@ import kotlin.math.sin
 import kotlin.math.sqrt
 
 /**
- * Web Audio BiquadFilterNode coefficients, a0-normalized as b0,b1,b2,a1,a2.
+ * Audio EQ Cookbook coefficients, a0-normalized as b0,b1,b2,a1,a2.
  * Type ordinals match EQ_BAND_TYPE_ORDINAL in src/audio/eq.ts:
  * 0 lowshelf, 1 peaking, 2 highshelf, 3 highpass, 4 lowpass.
  */
@@ -34,7 +34,6 @@ internal object EqCoefficients {
     val a = 10.0.pow(gainDb / 40.0)
     val alphaQ = sinW0 / (2.0 * q.coerceAtLeast(MIN_FILTER_Q.toFloat()))
     val alphaQDb = sinW0 / (2.0 * 10.0.pow(q / 20.0))
-    val alphaShelf = (sinW0 / 2.0) * sqrt(2.0)
 
     var b0 = 1.0; var b1 = 0.0; var b2 = 0.0
     var a0 = 1.0; var a1 = 0.0; var a2 = 0.0
@@ -46,21 +45,21 @@ internal object EqCoefficients {
       }
       0 -> { // lowshelf
         val sqrtA = sqrt(a)
-        b0 = a * (a + 1 - (a - 1) * cosW0 + 2 * sqrtA * alphaShelf)
+        b0 = a * (a + 1 - (a - 1) * cosW0 + 2 * sqrtA * alphaQ)
         b1 = 2 * a * (a - 1 - (a + 1) * cosW0)
-        b2 = a * (a + 1 - (a - 1) * cosW0 - 2 * sqrtA * alphaShelf)
+        b2 = a * (a + 1 - (a - 1) * cosW0 - 2 * sqrtA * alphaQ)
-        a0 = a + 1 + (a - 1) * cosW0 + 2 * sqrtA * alphaShelf
+        a0 = a + 1 + (a - 1) * cosW0 + 2 * sqrtA * alphaQ
         a1 = -2 * (a - 1 + (a + 1) * cosW0)
-        a2 = a + 1 + (a - 1) * cosW0 - 2 * sqrtA * alphaShelf
+        a2 = a + 1 + (a - 1) * cosW0 - 2 * sqrtA * alphaQ
       }
       2 -> { // highshelf
         val sqrtA = sqrt(a)
-        b0 = a * (a + 1 + (a - 1) * cosW0 + 2 * sqrtA * alphaShelf)
+        b0 = a * (a + 1 + (a - 1) * cosW0 + 2 * sqrtA * alphaQ)
         b1 = -2 * a * (a - 1 + (a + 1) * cosW0)
-        b2 = a * (a + 1 + (a - 1) * cosW0 - 2 * sqrtA * alphaShelf)
+        b2 = a * (a + 1 + (a - 1) * cosW0 - 2 * sqrtA * alphaQ)
-        a0 = a + 1 - (a - 1) * cosW0 + 2 * sqrtA * alphaShelf
+        a0 = a + 1 - (a - 1) * cosW0 + 2 * sqrtA * alphaQ
         a1 = 2 * (a - 1 - (a + 1) * cosW0)
-        a2 = a + 1 - (a - 1) * cosW0 - 2 * sqrtA * alphaShelf
+        a2 = a + 1 - (a - 1) * cosW0 - 2 * sqrtA * alphaQ
       }
       4 -> { // lowpass
         b0 = (1 - cosW0) / 2; b1 = 1 - cosW0; b2 = (1 - cosW0) / 2

vendor/kotlinaudio/kotlin-audio/src/test/java/com/doublesymmetry/kotlinaudio/scope/EqCoefficientsTest.kt

@@ -1,6 +1,7 @@
 package com.doublesymmetry.kotlinaudio.scope
 
 import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
 import org.junit.Test
 
 class EqCoefficientsTest {
@@ -29,15 +30,34 @@ class EqCoefficientsTest {
   }
 
   @Test
-  fun shelfFiltersIgnoreQ() {
+  fun shelfFiltersUseQ() {
+    val lowWide = coeffs(type = 0, freq = 100f, gainDb = 6f, q = 0.5f)
+    val lowNarrow = coeffs(type = 0, freq = 100f, gainDb = 6f, q = 2f)
+    val highWide = coeffs(type = 2, freq = 8000f, gainDb = -4f, q = 0.5f)
+    val highNarrow = coeffs(type = 2, freq = 8000f, gainDb = -4f, q = 2f)
+
     assertCoefficients(
-      coeffs(type = 0, freq = 100f, gainDb = 6f, q = 0.1f),
+      lowWide,
-      coeffs(type = 0, freq = 100f, gainDb = 6f, q = 18f)
+      doubleArrayOf(
+        1.004523905875,
+        -1.978032948597,
+        0.973748440145,
+        -1.978092655842,
+        0.978212638774
+      )
     )
     assertCoefficients(
-      coeffs(type = 2, freq = 8000f, gainDb = -4f, q = 0.1f),
+      highWide,
-      coeffs(type = 2, freq = 8000f, gainDb = -4f, q = 18f)
+      doubleArrayOf(
+        0.746848511923,
+        -0.319264680328,
+        0.034120017138,
+        -0.641024137473,
+        0.102727986206
+      )
     )
+    assertCoefficientsDiffer(lowWide, lowNarrow)
+    assertCoefficientsDiffer(highWide, highNarrow)
   }
 
   private fun coeffs(type: Int, freq: Float, gainDb: Float, q: Float): FloatArray {
@@ -59,4 +79,12 @@ class EqCoefficientsTest {
       assertEquals("coefficient $i", expected[i].toDouble(), actual[i].toDouble(), 0.0)
     }
   }
+
+  private fun assertCoefficientsDiffer(first: FloatArray, second: FloatArray) {
+    assertEquals("coefficient count", first.size, second.size)
+    assertTrue(
+      "expected at least one coefficient to change",
+      first.indices.any { i -> kotlin.math.abs(first[i] - second[i]) > 1e-6f }
+    )
+  }
 }