From 1d3039f3e2e9269e69364a9b6da90fd28b36c18f Mon Sep 17 00:00:00 2001
From: skal <pascal.massimino@gmail.com>
Date: Wed, 18 Feb 2026 05:20:39 +0100
Subject: refactor(mq_editor): store only squared amplitude after FFT, drop
 re/im

handoff(Claude): removed full spectrum storage from STFTCache frames;
getFFT() deleted; viewers use squaredAmplitude + 10*log10 directly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 tools/mq_editor/fft.js    | 19 ++++++-------------
 tools/mq_editor/viewer.js | 16 +++++-----------
 2 files changed, 11 insertions(+), 24 deletions(-)

(limited to 'tools/mq_editor')

diff --git a/tools/mq_editor/fft.js b/tools/mq_editor/fft.js
index 36b9936..9b9bc94 100644
--- a/tools/mq_editor/fft.js
+++ b/tools/mq_editor/fft.js
@@ -109,7 +109,7 @@ class STFTCache {
     this.sampleRate = sampleRate;
     this.fftSize = fftSize;
     this.hopSize = hopSize;
-    this.frames = []; // Array of {time, offset, spectrum}
+    this.frames = []; // Array of {time, offset, squaredAmplitude}
     this.compute();
   }
 
@@ -131,18 +131,16 @@ class STFTCache {
         windowed[i] = frame[i] * w;
       }
 
-      // Compute FFT
-      const spectrum = realFFT(windowed);
-
-      // Cache squared amplitudes (re*re + im*im, no sqrt)
+      // Compute FFT, store only squared amplitudes (re*re + im*im, no sqrt)
+      const fftOut = realFFT(windowed);
       const squaredAmplitude = new Float32Array(this.fftSize / 2);
       for (let i = 0; i < this.fftSize / 2; ++i) {
-        const re = spectrum[i * 2];
-        const im = spectrum[i * 2 + 1];
+        const re = fftOut[i * 2];
+        const im = fftOut[i * 2 + 1];
         squaredAmplitude[i] = re * re + im * im;
       }
 
-      this.frames.push({time, offset, spectrum, squaredAmplitude});
+      this.frames.push({time, offset, squaredAmplitude});
     }
   }
 
@@ -175,11 +173,6 @@ class STFTCache {
     return this.getFrameAtIndex(frameIdx);
   }
 
-  getFFT(t) {
-    const frame = this.getFrameAtTime(t);
-    return frame ? frame.spectrum : null;
-  }
-
   getSquaredAmplitude(t) {
     const frame = this.getFrameAtTime(t);
     return frame ? frame.squaredAmplitude : null;
diff --git a/tools/mq_editor/viewer.js b/tools/mq_editor/viewer.js
index 21c0a0c..3ca2f87 100644
--- a/tools/mq_editor/viewer.js
+++ b/tools/mq_editor/viewer.js
@@ -166,7 +166,7 @@ class SpectrogramViewer {
       const frame = stftCache.getFrameAtIndex(frameIdx);
       if (!frame) continue;
 
-      const spectrum = frame.spectrum;
+      const squaredAmp = frame.squaredAmplitude;
 
       // Compute frame time range
       const frameTime = frame.time;
@@ -186,10 +186,7 @@ class SpectrogramViewer {
         const freqNext = (bin + 1) * binFreqWidth;
         if (freqNext < this.freqStart || freq > this.freqEnd) continue;
 
-        const re = spectrum[bin * 2];
-        const im = spectrum[bin * 2 + 1];
-        const mag = Math.sqrt(re * re + im * im);
-        const magDB = 20 * Math.log10(Math.max(mag, 1e-10));
+        const magDB = 10 * Math.log10(Math.max(squaredAmp[bin], 1e-20));
 
         const normalized = (magDB + 80) / 80;
         const clamped = Math.max(0, Math.min(1, normalized));
@@ -488,8 +485,8 @@ class SpectrogramViewer {
     ctx.fillStyle = '#1e1e1e';
     ctx.fillRect(0, 0, width, height);
 
-    const spectrum = cache.getFFT(this.spectrumTime);
-    if (!spectrum) return;
+    const squaredAmp = cache.getSquaredAmplitude(this.spectrumTime);
+    if (!squaredAmp) return;
 
     const fftSize = cache.fftSize;
 
@@ -500,10 +497,7 @@ class SpectrogramViewer {
 
     for (let i = 0; i < numBars; ++i) {
       const binIdx = Math.floor(i * numBins / numBars);
-      const re = spectrum[binIdx * 2];
-      const im = spectrum[binIdx * 2 + 1];
-      const mag = Math.sqrt(re * re + im * im);
-      const magDB = 20 * Math.log10(Math.max(mag, 1e-10));
+      const magDB = 10 * Math.log10(Math.max(squaredAmp[binIdx], 1e-20));
 
       // Normalize to [0, 1]
       const normalized = (magDB + 80) / 80;
-- 
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