fix(mux): strip encoding dates from MP4Box and shaka-packager output

MP4Box gets -for-test (non-MP4 inputs keep their tkhd flags) and shaka decrypts get --use_fake_clock_for_muxer, so MP4 and --no-mux files carry no download time.

tests/core/test_mp4_container_routing.py

@@ -96,7 +96,7 @@ def test_dts_uhd_audio_routes_the_mux_to_mp4(tmp_path: Path, monkeypatch: pytest
     assert out.suffix == ".mp4", "a DTS-UHD title must not be delivered as Matroska"
     assert returncode == 0 and not errors
     command = captured[0].args
-    assert command[0] == "MP4Box"
+    assert command[:2] == ["MP4Box", "-for-test"]
     assert command[-2:] == ["-new", str(out)]
     assert f"{tmp_path / 'a.mp4'}:lang=en" in command
     # the child must not inherit the terminal that the live progress tree is drawing on
@@ -170,7 +170,7 @@ def test_mp4_subtitles_get_the_script_their_region_implies(tmp_path: Path, monke
 
     tracks.mux("Title", delete=False, output_path=tmp_path / "out.muxed.mkv")
     command = captured[0].args
-    assert f"{tmp_path / 's.vtt'}:lang=zh-Hant-TW" in command
+    assert f"{tmp_path / 's.vtt'}:lang=zh-Hant-TW:tkhd=enable,movie,preview" in command
     assert any(arg.endswith("=Chinese (Traditional)") for arg in command)
 
 

tests/core/test_stereo_video.py

@@ -123,7 +123,12 @@ def mp4box_commands(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> list[lis
 
     monkeypatch.setattr(binaries, "MP4Box", Path("/bin/MP4Box"), raising=False)
     monkeypatch.setattr(tracks_module.subprocess, "Popen", FakePopen)
-    monkeypatch.setattr(tracks_module, "run_step", lambda command, **kwargs: commands.append([str(c) for c in command]))
+
+    def run_step(command: list[Any], output: Path, **kwargs: Any) -> None:
+        commands.append([str(c) for c in command])
+        output.write_bytes(b"cut")
+
+    monkeypatch.setattr(tracks_module, "run_step", run_step)
     monkeypatch.setattr(config, "sample", None)
     monkeypatch.setattr(config.directories, "temp", tmp_path)
     return commands
@@ -136,6 +141,15 @@ def test_a_3d_mp4_mux_keeps_the_sample_whole(
     Tracks(stereo_video(tmp_path))._mux_mp4(title="Film", output_path=tmp_path / "out.mkv")
     assert len(mp4box_commands) == 1
     assert "-splitx" not in mp4box_commands[0]
+    assert "-for-test" in mp4box_commands[0]
+
+
+def test_a_2d_mp4_sample_cut_keeps_no_date(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, mp4box_commands: list[list[str]]
+) -> None:
+    monkeypatch.setattr(config, "sample", (120.0, 180.0))
+    Tracks(stereo_video(tmp_path, stereo=False))._mux_mp4(title="Film", output_path=tmp_path / "out.mkv")
+    assert mp4box_commands[1][1:3] == ["-for-test", "-splitx"]
 
 
 def test_a_3d_mp4_mux_writes_quicktime_chapters(tmp_path: Path, mp4box_commands: list[list[str]]) -> None:

tests/core/test_zero_kid_fallback.py

@@ -122,6 +122,7 @@ def test_shaka_decrypt_passes_the_built_keys(monkeypatch: pytest.MonkeyPatch, tm
 
     keys = seen[0][seen[0].index("--keys") + 1]
     assert _shaka_zero_entries(keys) == [VIDEO_KEY]
+    assert "--use_fake_clock_for_muxer" in seen[0]
 
 
 def test_a_rebuilt_widevine_does_not_take_the_first_pssh_kid_as_its_own() -> None: