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.

docs/guide/output-and-naming.md

@@ -482,11 +482,11 @@ Set `default_subtitle_type` to give the subtitle default to a different type. `d
 
 A few muxing behaviors are automatic and not configurable:
 
-- `--no-date` is always passed for privacy (no timestamps embedded).
+- The output has no encoding date: mkvmerge gets `--no-date` and MP4Box gets `-for-test`.
 - Descriptive audio gets the visually-impaired flag. SDH subtitles get the hearing-impaired flag. Forced subtitles get the forced flag.
 - unshackle writes the chapters from the title's chapter list (see [Chapters](#chapters-naming) below).
 
-The `--no-mux` flag skips muxing entirely and writes the individual track files, each with a track-type suffix, into the same output/folder structure.
+The `--no-mux` flag skips muxing entirely and writes the individual track files, each with a track-type suffix, into the same output/folder structure. A track that shaka-packager decrypts has its date set to 1970-01-01; other tracks keep the date of the source file.
 
 ## Sample files
 

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:

unshackle/core/drm/clearkey_cenc.py

@@ -289,6 +289,7 @@ class ClearKeyCENC:
                     "label={}:key_id={}:key={}".format(i, kid.hex, key.lower())
                     for i, (kid, key) in enumerate(self.content_keys.items())
                 ),
+                "--use_fake_clock_for_muxer",
                 "--temp_dir",
                 config.directories.temp,
             ]

unshackle/core/drm/playready.py

@@ -654,6 +654,7 @@ class PlayReady:
                 "--enable_raw_key_decryption",
                 "--keys",
                 drm_key_args.shaka_keys(self.content_keys, self.own_kids()),
+                "--use_fake_clock_for_muxer",
                 "--temp_dir",
                 config.directories.temp,
             ]

unshackle/core/drm/widevine.py

@@ -404,6 +404,7 @@ class Widevine:
                 "--enable_raw_key_decryption",
                 "--keys",
                 drm_key_args.shaka_keys(self.content_keys, self.own_kids()),
+                "--use_fake_clock_for_muxer",
                 "--temp_dir",
                 config.directories.temp,
             ]

unshackle/core/tracks/tracks.py

@@ -69,10 +69,9 @@ def file_track_ids(path: Path) -> dict[str, int]:
     return ids or {"video": 0, "audio": 1}
 
 
-def mp4_track_count(path: Path) -> int:
+def mp4_track_count(moov: Optional[bytes]) -> int:
-    """How many tracks ``MP4Box -add`` takes from a file: each ``trak`` of an MP4, or 1 for any other file."""
+    """How many tracks ``MP4Box -add`` takes from a file: each ``trak`` of its moov, or 1 for a file with none."""
-    moov = read_top_level_box(path, b"moov") or b""
+    return sum(1 for kind, _, _ in children(moov or b"", 8) if kind == b"trak") or 1
-    return sum(1 for kind, _, _ in children(moov, 8) if kind == b"trak") or 1
 
 
 class Tracks:
@@ -677,7 +676,8 @@ class Tracks:
         (MV-HEVC) video, whose second view mkvmerge drops. MP4 carries far less: it drops the
         forced, hearing-impaired and original flags, holds no attachments at all, and leaves
         out a subtitle it has no format for rather than mangling it. Losing those beats
-        shipping audio no player can name or a 3D film as 2D.
+        shipping audio no player can name or a 3D film as 2D. ``-for-test`` drops the dates and
+        the GPAC version tag; ``tkhd`` restores the flags it clears on a non-MP4 input.
 
         Returns the same (path, returncode, errors) shape as the Matroska mux.
         """
@@ -688,7 +688,7 @@ class Tracks:
         progress = progress or partial(lambda **kwargs: None)
 
         stereo = any(v.stereo for v in self.videos)
-        cl = [str(mp4box)]
+        cl = [str(mp4box), "-for-test"]
         sample_base = self.sample_base
         names: list[str] = []
         cleaned: list[Path] = []
@@ -723,11 +723,13 @@ class Tracks:
                 candidate.unlink()
 
             delay = round((track.sample_start - sample_base) * 1000) if config.sample else 0
-            cl.extend(["-add", f"{source}:lang={track.mux_language}" + (f":delay={delay}" if delay else "")])
+            moov = read_top_level_box(source, b"moov")
+            flags = "" if moov else ":tkhd=enable,movie,preview"
+            cl.extend(["-add", f"{source}:lang={track.mux_language}{flags}" + (f":delay={delay}" if delay else "")])
             name = "" if isinstance(track, Video) else (track.get_track_name() or "")
             if name:
                 names.extend(["-name", f"{track_id + 1}={name}"])
-            track_id += mp4_track_count(source)
+            track_id += mp4_track_count(moov)
 
         if not track_id:
             raise ValueError("No tracks provided, at least one track must be provided.")
@@ -806,7 +808,7 @@ class Tracks:
                 cut_path = output_path.with_suffix(".cut.mp4")
                 try:
                     run_step(
-                        [mp4box, "-splitx", f"{start:.3f}:{end:.3f}", output_path, "-out", cut_path],
+                        [mp4box, "-for-test", "-splitx", f"{start:.3f}:{end:.3f}", output_path, "-out", cut_path],
                         output=cut_path,
                         label="MP4Box sample cut",
                     )