V45.16: freeze playhead khi seek master FX active (het playhead chay truoc am ~128ms) v=202608311143

app/static/js/app.jsx

@@ -309,6 +309,8 @@ let _dbgFirstAudiblePending = false;
 let _fxRtPlayheadSnapPending = false;
 let _fxRtFreezeTimer = null;
 let _fxRtFreezeTries = 0;
+let _fxRtSeekFreeze = false;
+let _fxRtSeekFreezeTimer = null;
 const _nativeTrackUrls = {};
 const _nativeTrackPending = {};
 // ── MIDI overlap cleanup + polyphony gain (spec midi_polyphony_loudness) ─
@@ -21004,6 +21006,17 @@ const App = () => {
     if (fxRt && fxRt.active) {
       _fxRtPlayheadSnapPending = false;
       fxRtAnchorProcessed();
+      // V45.16: seek/restart FX active — giữ playhead tại startOffset cho tới khi
+      // worklet phát block đầu (fx_play_first). Trước đây playhead chạy theo
+      // processedSamples trong lúc re-buffer FILL 24 (~128ms) → playhead trước
+      // âm (Bug 1b). Fail-safe 1500ms: engine không phát (session fail) → thả.
+      _fxRtSeekFreeze = true;
+      if (_fxRtSeekFreezeTimer) { clearTimeout(_fxRtSeekFreezeTimer); }
+      _fxRtSeekFreezeTimer = setTimeout(function () {
+        _fxRtSeekFreeze = false;
+        _fxRtSeekFreezeTimer = null;
+        fxRtAnchorProcessed();
+      }, 1500);
       return;
     }
     // V41: gate theo CHAIN (không chỉ active) — session FX warm (stop giữ warm,
@@ -21034,6 +21047,13 @@ const App = () => {
     }, _estMs);
   };
   window.__fxRtSnapPlayhead = function () {
+    // V45.16: hết seek-freeze — playhead bắt đầu từ startOffset tại mẫu nghe được.
+    if (_fxRtSeekFreeze) {
+      _fxRtSeekFreeze = false;
+      if (_fxRtSeekFreezeTimer) { clearTimeout(_fxRtSeekFreezeTimer); _fxRtSeekFreezeTimer = null; }
+      fxRtAnchorProcessed();
+      return;
+    }
     if (fxRt && fxRt.active && _fxRtPlayheadSnapPending) {
       _fxRtPlayheadSnapPending = false;
       startAudioTimeRef.current = getAudioContext().currentTime;
@@ -24573,9 +24593,11 @@ const App = () => {
     const updatedTime = startOffsetTimeRef.current + elapsed;
     // G3: playhead display engine-derived khi FX active (wrap/loop trigger giu
     // wall-clock — transport truth).
-    const _playheadSec = (fxRt && fxRt.active && typeof fxRt.processedSamples === 'number' && fxRt.processedAnchor != null)
-      ? Math.max(startOffsetTimeRef.current, startOffsetTimeRef.current + (fxRt.processedSamples - fxRt.processedAnchor - (fxRt.latencyTotal || 0)) / (context.sampleRate || 44100))
-      : updatedTime;
+    const _playheadSec = (_fxRtSeekFreeze && fxRt && fxRt.active)
+      ? startOffsetTimeRef.current
+      : ((fxRt && fxRt.active && typeof fxRt.processedSamples === 'number' && fxRt.processedAnchor != null)
+          ? Math.max(startOffsetTimeRef.current, startOffsetTimeRef.current + (fxRt.processedSamples - fxRt.processedAnchor - (fxRt.latencyTotal || 0)) / (context.sampleRate || 44100))
+          : updatedTime);
 
     // Selection Loop - LOOP_MAKER.md + LOOP_EDITOR_2.md §4.2
     // If selection cleared by user, play linearly (don't loop)