1 files changed, 38 insertions, 0 deletions
diff --git a/tools/mq_editor/mq_extract.js b/tools/mq_editor/mq_extract.js
index 2293d52..8a0ea0e 100644
--- a/tools/mq_editor/mq_extract.js
+++ b/tools/mq_editor/mq_extract.js
@@ -16,6 +16,9 @@ function extractPartials(params, stftCache) {
 
   const partials = trackPartials(frames);
 
+  // Second pass: extend partials leftward to recover onset frames
+  expandPartialsLeft(partials, frames);
+
   for (const partial of partials) {
     partial.freqCurve = fitBezier(partial.times, partial.freqs);
     partial.ampCurve = fitBezier(partial.times, partial.amps);
@@ -144,6 +147,41 @@ function trackPartials(frames) {
   return partials;
 }
 
+// Second pass: extend each partial leftward to recover onset frames missed
+// by the birthPersistence requirement in the forward pass.
+function expandPartialsLeft(partials, frames) {
+  const trackingRatio = 0.05;
+  const minTrackingHz = 20;
+
+  // Build time → frame index map
+  const timeToIdx = new Map();
+  for (let i = 0; i < frames.length; ++i) timeToIdx.set(frames[i].time, i);
+
+  for (const partial of partials) {
+    let startIdx = timeToIdx.get(partial.times[0]);
+    if (startIdx == null || startIdx === 0) continue;
+
+    for (let i = startIdx - 1; i >= 0; --i) {
+      const frame = frames[i];
+      const refFreq = partial.freqs[0];
+      const tol = Math.max(refFreq * trackingRatio, minTrackingHz);
+
+      let bestIdx = -1, bestDist = Infinity;
+      for (let j = 0; j < frame.peaks.length; ++j) {
+        const dist = Math.abs(frame.peaks[j].freq - refFreq);
+        if (dist < tol && dist < bestDist) { bestDist = dist; bestIdx = j; }
+      }
+
+      if (bestIdx < 0) break;
+
+      const pk = frame.peaks[bestIdx];
+      partial.times.unshift(frame.time);
+      partial.freqs.unshift(pk.freq);
+      partial.amps.unshift(pk.amp);
+    }
+  }
+}
+
 // Fit cubic bezier to trajectory using samples at ~1/3 and ~2/3 as control points
 function fitBezier(times, values) {
   const n = times.length - 1;