fix: skip loudnorm when measured loudness is -inf (silent segment)

extract.py

@@ -359,6 +359,18 @@ def extract_audio_loudnorm(input_file: str, duration: int, start_sec: float,
     offset = measured.get("target_offset", "0")
     print(f"[loudness] {stem}: measured I={mi} LUFS, TP={mtp} dBTP, LRA={mlra}, offset={offset} dB")
 
+    # ─── Guard: silent segment produces -inf — skip loudnorm ───
+    if mi == "-inf" or mtp == "-inf" or "inf" in str(mi).lower() or "inf" in str(mtp).lower():
+        print(f"[loudness] {stem}: segment is silent or near-silent, skipping loudnorm", file=sys.stderr)
+        if loud_gate:
+            cmd_fallback = base + ["-af", "lowpass=f=2000,highpass=f=100,agate=threshold=0.02:ratio=20:attack=5:release=50", *AUDIO_CODEC, out_path]
+        else:
+            cmd_fallback = base + [*AUDIO_CODEC, out_path]
+        r2 = subprocess.run(cmd_fallback, capture_output=True, text=True)
+        if r2.returncode != 0:
+            sys.exit(f"ffmpeg (audio) failed:\n{r2.stderr}")
+        return
+
     # ─── Pass 2: apply with measured values ───
     print(f"[loudness] {stem}: pass 2/2 applying loudnorm → {TARGET_LUFS} LUFS…")
     apply_af = (f"loudnorm=I={TARGET_LUFS}:TP={TARGET_TP}:LRA={TARGET_LRA}"