fix(mq_editor): offset playhead to partial t_start when playing single partial (key 3)HEADmain

handoff(Claude): playhead offset fix for single partial playback

1 files changed, 5 insertions, 3 deletions

diff --git a/tools/mq_editor/app.js b/tools/mq_editor/app.js
index 1c6d548..55b8d25 100644
--- a/tools/mq_editor/app.js
+++ b/tools/mq_editor/app.js
@@ -388,7 +388,7 @@ for (const el of [birthPersistenceEl, deathAgeEl, phaseErrorWeightEl, minLengthE
   el.addEventListener('change', () => { if (stftCache) runExtraction(); });
 }
 
-function playAudioBuffer(buffer, statusMsg) {
+function playAudioBuffer(buffer, statusMsg, timeOffset = 0) {
   const startTime = audioContext.currentTime;
   currentSource = audioContext.createBufferSource();
   currentSource.buffer = buffer;
@@ -406,7 +406,7 @@ function playAudioBuffer(buffer, statusMsg) {
   setStatus(statusMsg, 'info');
   function tick() {
     if (!currentSource) return;
-    viewer.setPlayheadTime(audioContext.currentTime - startTime);
+    viewer.setPlayheadTime(timeOffset + audioContext.currentTime - startTime);
     requestAnimationFrame(tick);
   }
   tick();
@@ -530,7 +530,9 @@ document.addEventListener('keydown', (e) => {
     const partial = extractedPartials[sel];
     if (!partial) return;
     stopAudio();
-    playAudioBuffer(getAudioBuffer([partial], 0.05), `Playing partial #${sel}...`);
+    const tStart = Math.min(...partial.times);
+    const offset = Math.max(0, tStart - 0.05);
+    playAudioBuffer(getAudioBuffer([partial], 0.05), `Playing partial #${sel}...`, offset);
   } else if (e.code === 'KeyP') {
     e.preventDefault();
     if (viewer) viewer.togglePeaks();