1 files changed, 94 insertions, 0 deletions
diff --git a/tools/mq_editor/mq_extract.js b/tools/mq_editor/mq_extract.js
index 8f6961f..ff38d63 100644
--- a/tools/mq_editor/mq_extract.js
+++ b/tools/mq_editor/mq_extract.js
@@ -432,6 +432,100 @@ function trackFromSeed(frames, seedTime, seedFreq, params) {
   };
 }
 
+// Track an iso-energy contour starting from (seedTime, seedFreq).
+// Instead of following spectral peaks, follows where energy ≈ seedEnergy.
+// Useful for broad/diffuse bass regions with no detectable peaks.
+// Returns a partial with large default spread, or null if seed energy is zero.
+function trackIsoContour(stftCache, seedTime, seedFreq, params) {
+  const { sampleRate, deathAge = 8 } = params;
+  const numFrames = stftCache.getNumFrames();
+  const fftSize   = stftCache.fftSize;
+  const binHz     = sampleRate / fftSize;
+  const halfBins  = fftSize / 2;
+
+  // Find seed frame
+  let seedFrameIdx = 0, bestDt = Infinity;
+  for (let i = 0; i < numFrames; ++i) {
+    const dt = Math.abs(stftCache.getFrameAtIndex(i).time - seedTime);
+    if (dt < bestDt) { bestDt = dt; seedFrameIdx = i; }
+  }
+
+  const seedFrame = stftCache.getFrameAtIndex(seedFrameIdx);
+  const seedBin   = Math.max(1, Math.min(halfBins - 2, Math.round(seedFreq / binHz)));
+  const targetSq  = seedFrame.squaredAmplitude[seedBin];
+  if (targetSq <= 0) return null;
+  const targetDB  = 10 * Math.log10(targetSq);
+
+  const trackingRatio = 0.15; // larger search window than peak tracker
+  const minTrackHz    = 30;
+  const maxDbDev      = 15;   // dB: declare miss if nothing within this range
+
+  // Find bin minimizing |dB(b) - targetDB| near refBin, with mild position bias.
+  function findContourBin(sq, refBin) {
+    const tol     = Math.max(refBin * binHz * trackingRatio, minTrackHz);
+    const tolBins = Math.ceil(tol / binHz);
+    const lo = Math.max(1, refBin - tolBins);
+    const hi = Math.min(halfBins - 2, refBin + tolBins);
+    let bestBin = -1, bestCost = Infinity;
+    for (let b = lo; b <= hi; ++b) {
+      const dE = Math.abs(10 * Math.log10(Math.max(sq[b], 1e-20)) - targetDB);
+      if (dE > maxDbDev) continue;
+      const dPos = Math.abs(b - refBin) / Math.max(1, tolBins);
+      const cost = dE + 3 * dPos; // energy match dominates, position breaks ties
+      if (cost < bestCost) { bestCost = cost; bestBin = b; }
+    }
+    return bestBin;
+  }
+
+  const times = [seedFrame.time];
+  const freqs = [seedBin * binHz];
+  const amps  = [Math.sqrt(Math.max(0, targetSq))];
+
+  // Forward pass
+  let fwdBin = seedBin, fwdAge = 0;
+  for (let i = seedFrameIdx + 1; i < numFrames; ++i) {
+    const frame = stftCache.getFrameAtIndex(i);
+    const b = findContourBin(frame.squaredAmplitude, fwdBin);
+    if (b >= 0) {
+      times.push(frame.time);
+      freqs.push(b * binHz);
+      amps.push(Math.sqrt(Math.max(0, frame.squaredAmplitude[b])));
+      fwdBin = b; fwdAge = 0;
+    } else { if (++fwdAge > deathAge) break; }
+  }
+
+  // Backward pass
+  const bwdTimes = [], bwdFreqs = [], bwdAmps = [];
+  let bwdBin = seedBin, bwdAge = 0;
+  for (let i = seedFrameIdx - 1; i >= 0; --i) {
+    const frame = stftCache.getFrameAtIndex(i);
+    const b = findContourBin(frame.squaredAmplitude, bwdBin);
+    if (b >= 0) {
+      bwdTimes.unshift(frame.time);
+      bwdFreqs.unshift(b * binHz);
+      bwdAmps.unshift(Math.sqrt(Math.max(0, frame.squaredAmplitude[b])));
+      bwdBin = b; bwdAge = 0;
+    } else { if (++bwdAge > deathAge) break; }
+  }
+
+  const allTimes = [...bwdTimes, ...times];
+  const allFreqs = [...bwdFreqs, ...freqs];
+  const allAmps  = [...bwdAmps,  ...amps];
+  if (allTimes.length < 2) return null;
+
+  const freqCurve = fitBezier(allTimes, allFreqs);
+  const ac = fitBezier(allTimes, allAmps);
+  freqCurve.a0 = ac.v0; freqCurve.a1 = ac.v1;
+  freqCurve.a2 = ac.v2; freqCurve.a3 = ac.v3;
+
+  return {
+    times: allTimes, freqs: allFreqs, amps: allAmps,
+    phases: new Array(allTimes.length).fill(0),
+    muted: false, freqCurve,
+    replicas: { decay_alpha: 0.1, jitter: 0.05, spread_above: 0.15, spread_below: 0.15 },
+  };
+}
+
 // Fit cubic bezier to trajectory using least-squares for inner control points
 function fitBezier(times, values) {
   const n = times.length - 1;