fix(latency): threadpool renders + RENDER_LOCK + client pre-render cache

app/core/render_engine.py

@@ -11,6 +11,7 @@ from app.core.vst_engine import (
     HAS_PEDALBOARD,
     HAS_PYFLUIDSYNTH,
     apply_preset_to_plugin,
+    RENDER_LOCK,
 )
 
 logger = logging.getLogger(__name__)
@@ -451,30 +452,31 @@ class PythonRenderEngine:
         return session_buffer
 
     def render_project(self, project_json: dict, output_filepath: str):
-        bpm = project_json["metadata"]["bpm"]
-        time_sig_num = project_json["metadata"].get("time_signature_numerator", 4)
-        main_session = project_json["main_session"]
-        section_store = project_json.get("section_store", {})
+        with RENDER_LOCK:
+            bpm = project_json["metadata"]["bpm"]
+            time_sig_num = project_json["metadata"].get("time_signature_numerator", 4)
+            main_session = project_json["main_session"]
+            section_store = project_json.get("section_store", {})
 
-        # Compute total project samples
-        total_bars = main_session.get("length_bars", 16.0)
-        total_samples = self.bars_to_samples(total_bars, bpm, time_sig_num)
-        
-        # Render main session
-        master_buffer = self.render_session_container(
-            session=main_session,
-            section_store=section_store,
-            bpm=bpm,
-            time_sig_num=time_sig_num,
-            total_samples=total_samples,
-            _cache={},
-        )
+            # Compute total project samples
+            total_bars = main_session.get("length_bars", 16.0)
+            total_samples = self.bars_to_samples(total_bars, bpm, time_sig_num)
 
-        # Normalization to prevent clipping
-        max_peak = np.max(np.abs(master_buffer))
-        if max_peak > 1.0:
-            master_buffer /= max_peak
+            # Render main session
+            master_buffer = self.render_session_container(
+                session=main_session,
+                section_store=section_store,
+                bpm=bpm,
+                time_sig_num=time_sig_num,
+                total_samples=total_samples,
+                _cache={},
+            )
 
-        # Write final output file
-        sf.write(output_filepath, master_buffer.T, self.sample_rate)
-        return output_filepath
+            # Normalization to prevent clipping
+            max_peak = np.max(np.abs(master_buffer))
+            if max_peak > 1.0:
+                master_buffer /= max_peak
+
+            # Write final output file
+            sf.write(output_filepath, master_buffer.T, self.sample_rate)
+            return output_filepath

app/core/vst_engine.py

@@ -3,8 +3,21 @@ import os
 import json
 import numpy as np
 import functools
+import threading
 from ctypes import c_char_p
 
+# pedalboard VST3 + pyfluidsynth KHÔNG thread-safe: tuần tự hóa mọi native render
+RENDER_LOCK = threading.RLock()
+
+
+def _render_locked(fn):
+    """Chạy hàm native (VST3/pyfluidsynth) dưới RENDER_LOCK — không thread-safe."""
+    @functools.wraps(fn)
+    def wrapper(*args, **kwargs):
+        with RENDER_LOCK:
+            return fn(*args, **kwargs)
+    return wrapper
+
 
 def _ensure_fluidsynth_dll_on_path():
     """Frozen (PyInstaller): pyfluidsynth tim dll qua ctypes.util.find_library
@@ -25,6 +38,7 @@ def midi_note_to_freq(note_number: int) -> float:
     return 440.0 * (2.0 ** ((note_number - 69) / 12.0))
 
 
+@_render_locked
 def render_soundfont_midi_to_audio(midi_events: list, sf_path: str, bank: int = 0,
                                    program: int = 0, sr: int = 44100, bpm: float = 120.0) -> np.ndarray:
     """Native FluidSynth (pyfluidsynth) — render MIDI events bằng soundfont THẬT.
@@ -92,6 +106,7 @@ def render_soundfont_midi_to_audio(midi_events: list, sf_path: str, bank: int =
         except Exception:
             pass
 
+@_render_locked
 def render_midi_events_to_audio(midi_events: list, sr: int = 44100, bpm: float = 120.0, instrument: str = 'synth') -> np.ndarray:
     beat_duration_sec = 60.0 / max(30.0, bpm)
     max_duration_sec = 2.0
@@ -336,6 +351,7 @@ class PluginManager:
                     }
         return list(sf_map.values())
 
+    @_render_locked
     def load_vst(self, plugin_name: str, preset_data: dict = None):
         if not HAS_PEDALBOARD:
             return None