feat: add waveform cache to avoid re-reading WAV files

waveform_cache.py

@@ -0,0 +1,29 @@
+"""
+Shared waveform cache — avoids re-reading and re-decoding large WAV files
+when the same file is loaded multiple times (e.g. sync_audio_test → verify).
+"""
+
+from __future__ import annotations
+import os
+import numpy as np
+
+_cache: dict[tuple[str, int], np.ndarray] = {}
+
+
+def cached_load_wav(path: str, target_sr: int = 48000) -> tuple[np.ndarray, int]:
+    """Load a WAV file with caching. Returns (audio_array, sample_rate)."""
+    real_path = os.path.realpath(path)
+    key = (real_path, target_sr)
+    if key in _cache:
+        print(f"  (cached: {os.path.basename(path)})")
+        return _cache[key].copy(), target_sr
+
+    # Import here to avoid circular imports
+    from sync_audio import load_wav
+    data, sr = load_wav(path, target_sr=target_sr)
+    _cache[key] = data
+    return data, sr
+
+
+def clear_cache():
+    _cache.clear()