From d14fc669d2da4d2c6664b5cbadf29759d3ea1073 Mon Sep 17 00:00:00 2001
From: skal <pascal.massimino@gmail.com>
Date: Wed, 18 Feb 2026 12:04:53 +0100
Subject: feat(mq_editor): LP/HP filter sliders with frequency display in
 Synthesis panel

Add k1/k2 range sliders for post-synthesis LP/HP filters. Display maps
coefficients to -3dB cutoff frequency using exact IIR formulas; shows
'bypass' at k=1.0. Uses audioBuffer.sampleRate when loaded, falls back
to 44100 Hz.

handoff(Claude): LP k1 and HP k2 sliders added to Synthesis panel with Hz display.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 tools/mq_editor/index.html | 46 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 45 insertions(+), 1 deletion(-)

(limited to 'tools/mq_editor/index.html')

diff --git a/tools/mq_editor/index.html b/tools/mq_editor/index.html
index 61ff1ac..b37eaaf 100644
--- a/tools/mq_editor/index.html
+++ b/tools/mq_editor/index.html
@@ -349,6 +349,18 @@
         <label><input type="checkbox" id="disableJitter"> Disable jitter</label>
         <label><input type="checkbox" id="disableSpread"> Disable spread</label>
         <label title="Test mode: force resonator synthesis for all partials (ignores per-partial mode setting)"><input type="checkbox" id="forceResonator"> Resonator (all)</label>
+        <div style="margin-top:6px;">
+          <label style="display:flex;align-items:center;gap:6px;" title="LP filter coefficient k1 in (0,1]. 1.0 = bypass.">
+            LP k1
+            <input type="range" id="lpK1" min="0.001" max="1.0" step="0.001" value="1.0" style="flex:1;min-width:0;">
+            <span id="lpK1Val" style="width:44px;text-align:right;">bypass</span>
+          </label>
+          <label style="display:flex;align-items:center;gap:6px;" title="HP filter coefficient k2 in (0,1]. 1.0 = bypass.">
+            HP k2
+            <input type="range" id="hpK2" min="0.001" max="1.0" step="0.001" value="1.0" style="flex:1;min-width:0;">
+            <span id="hpK2Val" style="width:44px;text-align:right;">bypass</span>
+          </label>
+        </div>
       </div>
     </div>
   </div>
@@ -363,6 +375,34 @@
   <script src="viewer.js"></script>
   <script src="editor.js"></script>
   <script>
+    // LP: y[n] = k*x[n] + (1-k)*y[n-1]  => -3dB at cos(w) = (2-2k-k²)/(2(1-k))
+    function k1ToHz(k, sr) {
+      if (k >= 1.0) return sr / 2;
+      const cosW = (2 - 2*k - k*k) / (2*(1 - k));
+      return Math.acos(Math.max(-1, Math.min(1, cosW))) * sr / (2 * Math.PI);
+    }
+    // HP: y[n] = k*(y[n-1]+x[n]-x[n-1])  => -3dB from peak at cos(w) = 2k/(1+k²)
+    function k2ToHz(k, sr) {
+      if (k >= 1.0) return 0;
+      const cosW = 2*k / (1 + k*k);
+      return Math.acos(Math.max(-1, Math.min(1, cosW))) * sr / (2 * Math.PI);
+    }
+    function fmtHz(f) {
+      return f >= 1000 ? (f/1000).toFixed(1) + 'k' : Math.round(f) + 'Hz';
+    }
+    function getSR() { return (typeof audioBuffer !== 'undefined' && audioBuffer) ? audioBuffer.sampleRate : 44100; }
+
+    // LP/HP slider live display
+    document.getElementById('lpK1').addEventListener('input', function() {
+      const k = parseFloat(this.value);
+      const f = k1ToHz(k, getSR());
+      document.getElementById('lpK1Val').textContent = k >= 1.0 ? 'bypass' : fmtHz(f);
+    });
+    document.getElementById('hpK2').addEventListener('input', function() {
+      const k = parseFloat(this.value);
+      const f = k2ToHz(k, getSR());
+      document.getElementById('hpK2Val').textContent = k >= 1.0 ? 'bypass' : fmtHz(f);
+    });
     let audioBuffer = null;
     let viewer = null;
     let audioContext = null;
@@ -632,8 +672,12 @@
       const disableJitter   = document.getElementById('disableJitter').checked;
       const disableSpread   = document.getElementById('disableSpread').checked;
       const forceResonator  = document.getElementById('forceResonator').checked;
+      const lpK1Raw = parseFloat(document.getElementById('lpK1').value);
+      const hpK2Raw = parseFloat(document.getElementById('hpK2').value);
+      const k1 = lpK1Raw < 1.0 ? lpK1Raw : null;
+      const k2 = hpK2Raw < 1.0 ? hpK2Raw : null;
       const pcm = synthesizeMQ(partialsToUse, audioBuffer.sampleRate, audioBuffer.duration,
-                               integratePhase, {disableJitter, disableSpread, forceResonator});
+                               integratePhase, {disableJitter, disableSpread, forceResonator, k1, k2});
 
       if (viewer) {
         viewer.setSynthStftCache(new STFTCache(pcm, audioBuffer.sampleRate, fftSize, parseInt(hopSize.value)));
-- 
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