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.
 

tests/test_utils.py

@@ -1,6 +1,6 @@
 import tempfile, os, json
 from main import build_export_path, format_time, build_ffmpeg_command, build_sequence_dir, build_audio_extract_command, resolve_keyframe, apply_keyframes_to_jobs
-from core.ffmpeg import build_audio_clip_command, build_crossfade_merge_command
+from core.ffmpeg import build_audio_clip_command, build_crossfade_merge_command, build_audio_delete_command, build_audio_silence_command, build_audio_reverse_command
 from core.annotations import build_annotation_json_path, upsert_clip_annotation
 from main import ProcessedDB
 
@@ -192,6 +192,45 @@ def test_merge_three_clips_zero_concat_chain():
     assert "acrossfade" not in fc
 
 
+# --- destructive audio region ops (delete/silence/reverse) ---
+
+def test_audio_delete_command():
+    cmd = build_audio_delete_command("/in.wav", 1.0, 3.0, "/o/o.wav")
+    assert cmd[0] == "ffmpeg"
+    assert cmd.count("-i") == 1
+    fc = cmd[cmd.index("-filter_complex") + 1]
+    assert "atrim=end=1.0" in fc            # keep [0,1]
+    assert "atrim=start=3.0" in fc          # keep [3,end]
+    assert "concat=n=2:v=0:a=1[out]" in fc
+    assert cmd[cmd.index("-map") + 1] == "[out]"
+    assert "pcm_s16le" in cmd               # codec by ext
+    assert cmd[-1] == "/o/o.wav"
+
+def test_audio_silence_command():
+    cmd = build_audio_silence_command("/in.wav", 1.0, 3.0, "/o/o.mp3")
+    af = cmd[cmd.index("-af") + 1]
+    # volume=0 gated to the region; commas inside between() are escaped for the filtergraph
+    assert af == "volume=0:enable='between(t\\,1.0\\,3.0)'"
+    assert "libmp3lame" in cmd
+    assert cmd[-1] == "/o/o.mp3"
+
+def test_audio_reverse_command():
+    cmd = build_audio_reverse_command("/in.wav", 1.0, 3.0, "/o/o.wav")
+    fc = cmd[cmd.index("-filter_complex") + 1]
+    assert "atrim=end=1.0" in fc            # head [0,1]
+    assert "atrim=start=1.0:end=3.0" in fc  # middle [1,3]
+    assert "areverse" in fc                 # reversed middle
+    assert "atrim=start=3.0" in fc          # tail [3,end]
+    assert "concat=n=3:v=0:a=1[out]" in fc
+    assert cmd[cmd.index("-map") + 1] == "[out]"
+
+def test_audio_delete_empty_head():
+    # deleting from 0 still produces a valid 2-branch concat (head is empty but harmless)
+    cmd = build_audio_delete_command("/in.wav", 0.0, 2.0, "/o/o.wav")
+    fc = cmd[cmd.index("-filter_complex") + 1]
+    assert "atrim=end=0.0" in fc and "atrim=start=2.0" in fc
+
+
 # --- ProcessedDB ---
 
 def test_db_add_and_get_markers():