From 0728ece4b8e1c90420a0db4421dd49ff5a3ff8d1 Mon Sep 17 00:00:00 2001
From: Javanaut <javanaut@refulgent.de>
Date: Wed, 15 Apr 2026 00:03:17 +0200
Subject: [PATCH] Fix h265 subtrack unmux

---
 src/ffx/cli.py                        | 13 ++--
 tests/unit/test_cli_unmux_sequence.py | 91 +++++++++++++++++++++++++++
 2 files changed, 99 insertions(+), 5 deletions(-)
 create mode 100644 tests/unit/test_cli_unmux_sequence.py

diff --git a/src/ffx/cli.py b/src/ffx/cli.py
index bd8f8f7..9b380fc 100755
--- a/src/ffx/cli.py
+++ b/src/ffx/cli.py
@@ -631,21 +631,24 @@ def rename(ctx, paths, prefix, season, suffix, dry_run):
 
 
 def getUnmuxSequence(trackDescriptor: TrackDescriptor, sourcePath, targetPrefix, targetDirectory = ''):
+    from ffx.track_codec import TrackCodec
+    from ffx.track_type import TrackType
 
     # executable and input file
     commandTokens = list(FFMPEG_COMMAND_TOKENS) + ['-i', sourcePath]
 
     trackType = trackDescriptor.getType()
+    trackCodec = trackDescriptor.getCodec()
 
     targetPathBase = os.path.join(targetDirectory, targetPrefix) if targetDirectory else targetPrefix
 
     # mapping
-    commandTokens += ['-map',
-            f"0:{trackType.indicator()}:{trackDescriptor.getSubIndex()}",
-            '-c',
-            'copy']
+    commandTokens += ['-map', f"0:{trackType.indicator()}:{trackDescriptor.getSubIndex()}"]
 
-    trackCodec = trackDescriptor.getCodec()
+    if trackType == TrackType.VIDEO and trackCodec == TrackCodec.H265:
+        commandTokens += ['-c:v', 'copy', '-bsf:v', 'hevc_mp4toannexb']
+    else:
+        commandTokens += ['-c', 'copy']
 
     # output format
     codecFormat = trackCodec.format()
diff --git a/tests/unit/test_cli_unmux_sequence.py b/tests/unit/test_cli_unmux_sequence.py
new file mode 100644
index 0000000..b858755
--- /dev/null
+++ b/tests/unit/test_cli_unmux_sequence.py
@@ -0,0 +1,91 @@
+from __future__ import annotations
+
+from pathlib import Path
+import sys
+import unittest
+
+
+SRC_ROOT = Path(__file__).resolve().parents[2] / "src"
+
+if str(SRC_ROOT) not in sys.path:
+    sys.path.insert(0, str(SRC_ROOT))
+
+
+from ffx import cli  # noqa: E402
+from ffx.track_codec import TrackCodec  # noqa: E402
+from ffx.track_descriptor import TrackDescriptor  # noqa: E402
+from ffx.track_type import TrackType  # noqa: E402
+
+
+class UnmuxSequenceTests(unittest.TestCase):
+    def test_h265_video_unmux_uses_annex_b_bitstream_filter(self):
+        track_descriptor = TrackDescriptor(
+            index=0,
+            sub_index=0,
+            track_type=TrackType.VIDEO,
+            codec_name=TrackCodec.H265,
+            tags={},
+            disposition_set=set(),
+        )
+
+        sequence = cli.getUnmuxSequence(
+            track_descriptor,
+            "input.mp4",
+            "episode_0_eng",
+        )
+
+        self.assertEqual(
+            [
+                "ffmpeg",
+                "-y",
+                "-i",
+                "input.mp4",
+                "-map",
+                "0:v:0",
+                "-c:v",
+                "copy",
+                "-bsf:v",
+                "hevc_mp4toannexb",
+                "-f",
+                "h265",
+                "episode_0_eng.h265",
+            ],
+            sequence,
+        )
+
+    def test_non_h265_unmux_keeps_generic_copy_behavior(self):
+        track_descriptor = TrackDescriptor(
+            index=1,
+            sub_index=0,
+            track_type=TrackType.SUBTITLE,
+            codec_name=TrackCodec.SRT,
+            tags={},
+            disposition_set=set(),
+        )
+
+        sequence = cli.getUnmuxSequence(
+            track_descriptor,
+            "input.mkv",
+            "episode_1_eng",
+        )
+
+        self.assertEqual(
+            [
+                "ffmpeg",
+                "-y",
+                "-i",
+                "input.mkv",
+                "-map",
+                "0:s:0",
+                "-c",
+                "copy",
+                "-f",
+                "srt",
+                "episode_1_eng.srt",
+            ],
+            sequence,
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()