feat: add heal cut ffmpeg command

core/ffmpeg.py

@@ -314,6 +314,41 @@ def build_audio_delete_command(input_path: str, start: float, end: float,
             "-filter_complex", fc, "-map", "[out]", *codec, out_path]
 
 
+def _auto_heal_crossfade(start: float, end: float,
+                         requested: float | None = None) -> float:
+    if end <= start:
+        raise ValueError("heal delete end must be greater than start")
+    if requested is not None:
+        fade = max(0.0, float(requested))
+    else:
+        fade = min(0.25, max(0.04, (end - start) * 0.25))
+    # Without knowing total duration, clamp only to available pre-roll.
+    fade = min(fade, max(0.0, float(start)))
+    return round(fade, 3)
+
+
+def build_audio_heal_delete_command(input_path: str, start: float, end: float,
+                                    out_path: str,
+                                    crossfade: float | None = None) -> list[str]:
+    """Remove [start, end] and heal the join with a short equal-power crossfade."""
+    if end <= start:
+        raise ValueError("heal delete end must be greater than start")
+    s, e = round(start, 3), round(end, 3)
+    xf = _auto_heal_crossfade(s, e, crossfade)
+    ext = os.path.splitext(out_path)[1].lower()
+    codec = _AUDIO_CODEC_BY_EXT.get(ext, [])
+    if xf <= 0:
+        fc = (f"[0]atrim=end={s},asetpts=PTS-STARTPTS[a];"
+              f"[0]atrim=start={e},asetpts=PTS-STARTPTS[b];"
+              f"[a][b]concat=n=2:v=0:a=1[out]")
+    else:
+        fc = (f"[0]atrim=end={s},asetpts=PTS-STARTPTS[a];"
+              f"[0]atrim=start={e},asetpts=PTS-STARTPTS[b];"
+              f"[a][b]acrossfade=d={xf}:c1=qsin:c2=qsin[out]")
+    return [_bin("ffmpeg"), "-y", "-i", input_path,
+            "-filter_complex", fc, "-map", "[out]", *codec, out_path]
+
+
 def build_audio_silence_command(input_path: str, start: float, end: float,
                                 out_path: str) -> list[str]:
     """Silence the [start, end] region (volume=0 gated by an enable expr)."""