feat: destructive audio op command builders (delete/silence/reverse region)

core/ffmpeg.py

@@ -301,6 +301,45 @@ def build_crossfade_merge_command(clips: list[str], crossfade,
     return cmd + ["-filter_complex", fc, "-map", "[out]", *codec, out_path]
 
 
+def build_audio_delete_command(input_path: str, start: float, end: float,
+                               out_path: str) -> list[str]:
+    """Remove [start, end] from the audio: keep [0,start] + [end,inf], concat."""
+    s, e = round(start, 3), round(end, 3)
+    ext = os.path.splitext(out_path)[1].lower()
+    codec = _AUDIO_CODEC_BY_EXT.get(ext, [])
+    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]")
+    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)."""
+    s, e = round(start, 3), round(end, 3)
+    ext = os.path.splitext(out_path)[1].lower()
+    codec = _AUDIO_CODEC_BY_EXT.get(ext, [])
+    # commas inside between() must be escaped so the filtergraph parser doesn't
+    # treat them as filter separators.
+    af = f"volume=0:enable='between(t\\,{s}\\,{e})'"
+    return [_bin("ffmpeg"), "-y", "-i", input_path, "-af", af, *codec, out_path]
+
+
+def build_audio_reverse_command(input_path: str, start: float, end: float,
+                                out_path: str) -> list[str]:
+    """Reverse only the [start, end] segment; head and tail unchanged."""
+    s, e = round(start, 3), round(end, 3)
+    ext = os.path.splitext(out_path)[1].lower()
+    codec = _AUDIO_CODEC_BY_EXT.get(ext, [])
+    fc = (f"[0]atrim=end={s},asetpts=PTS-STARTPTS[a];"
+          f"[0]atrim=start={s}:end={e},asetpts=PTS-STARTPTS,areverse[b];"
+          f"[0]atrim=start={e},asetpts=PTS-STARTPTS[c];"
+          f"[a][b][c]concat=n=3:v=0:a=1[out]")
+    return [_bin("ffmpeg"), "-y", "-i", input_path,
+            "-filter_complex", fc, "-map", "[out]", *codec, out_path]
+
+
 def detect_hw_encoders() -> list[str]:
     """Probe ffmpeg for available H.264 hardware encoders.