feat: build_crossfade_merge_command — chained acrossfade / concat

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
+from core.ffmpeg import build_audio_clip_command, build_crossfade_merge_command
 from core.annotations import build_annotation_json_path, upsert_clip_annotation
 from main import ProcessedDB
 
@@ -101,6 +101,45 @@ def test_audio_clip_command_appends_filter_chain():
     assert i < len(cmd) - 1 and cmd[-1] == "/o/a.wav"
 
 
+def test_merge_single_clip_reencodes():
+    cmd = build_crossfade_merge_command(["/a.wav"], 0.5, "/o/out.mp3")
+    assert cmd[0] == "ffmpeg"
+    assert cmd.count("-i") == 1
+    assert "libmp3lame" in cmd            # codec by out ext
+    assert "acrossfade" not in " ".join(cmd)
+    assert "-map" not in cmd
+    assert "-filter_complex" not in cmd
+    assert cmd[-1] == "/o/out.mp3"
+
+def test_merge_two_clips_acrossfade():
+    cmd = build_crossfade_merge_command(["/a.wav", "/b.wav"], 0.5, "/o/out.wav")
+    assert cmd.count("-i") == 2
+    fc = cmd[cmd.index("-filter_complex") + 1]
+    assert "[0][1]acrossfade=d=0.5" in fc
+    assert "[out]" in fc
+    assert cmd[cmd.index("-map") + 1] == "[out]"
+    assert "pcm_s16le" in cmd              # codec by out ext (multi-clip path)
+
+def test_merge_three_clips_chains():
+    cmd = build_crossfade_merge_command(["/a.wav", "/b.wav", "/c.wav"], 1.0, "/o/o.wav")
+    fc = cmd[cmd.index("-filter_complex") + 1]
+    assert fc.count("acrossfade=d=1.0") == 2      # two joins
+    assert "[0][1]acrossfade=d=1.0[a1]" in fc
+    assert "[a1][2]acrossfade=d=1.0[out]" in fc
+    assert cmd[cmd.index("-map") + 1] == "[out]"
+
+def test_merge_zero_crossfade_uses_concat():
+    cmd = build_crossfade_merge_command(["/a.wav", "/b.wav"], 0.0, "/o/o.wav")
+    fc = cmd[cmd.index("-filter_complex") + 1]
+    assert "concat=n=2:v=0:a=1" in fc
+    assert "acrossfade" not in fc
+
+def test_merge_empty_raises():
+    import pytest
+    with pytest.raises(ValueError):
+        build_crossfade_merge_command([], 0.5, "/o/o.wav")
+
+
 # --- ProcessedDB ---
 
 def test_db_add_and_get_markers():