1 files changed, 273 insertions, 0 deletions
diff --git a/packages/meshbay-node/tests/test_stream_video_transcode.py b/packages/meshbay-node/tests/test_stream_video_transcode.py
new file mode 100644
index 0000000..69f4c2d
--- /dev/null
+++ b/packages/meshbay-node/tests/test_stream_video_transcode.py
@@ -0,0 +1,273 @@
+"""
+A video the browser cannot decode is re-encoded to H264, never refused and
+never copied. There are two kinds of those, and both are here.
+
+**A codec string that is real but useless.** A real HEVC/EAC3 WEB-DL streamed
+fine over MNP (ffprobe/VLC play it) but the browser reported "Codec not
+supported for streaming: hev1.1.6.L93.B0,mp4a.40.2" from
+MediaSource.isTypeSupported — Chrome has no HEVC decoder on most non-Apple
+platforms. "-c:v copy" on such a codec is not a mux failure the way EAC3 audio
+is (test_stream_audio_transcode.py); ffmpeg happily remuxes it, and the browser
+is the one that then refuses it, silently, at playback rather than at
+stream_init. That is what BROWSER_INCOMPATIBLE_VIDEO_CODECS names.
+
+**No codec string at all.** MPEG-4 Part 2 (Xvid, DivX), MPEG-2, VC-1, WMV and
+Theora have no MediaSource decoder anywhere, so `probe_video` maps them to
+None — there is nothing to put in `stream_init` for the client to check. Until
+2026-09-09 the streaming path read that None as "unsupported" and refused, with
+"Unsupported video codec", on files ffmpeg re-encodes in real time. Reported
+live against an episode rip in a `.avi` — mpeg4 video, mp3 audio, 720x404 —
+which the reporting machine re-encodes at about six times playback speed. The setting
+that governs it, `transcode_incompatible_video`, was documented from the start
+as covering "HEVC *and other browser-incompatible video codecs*" (draft-v6
+§2.11); only HEVC was ever wired up.
+
+These tests spawn real ffmpeg/ffprobe against small synthetic files (lavfi
+test sources, ~1s), the same style as test_stream_audio_transcode.py.
+"""
+
+import shutil
+import subprocess
+from pathlib import Path
+
+import pytest
+from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
+
+from meshbay_common.crypto import generate_gek
+from meshbay_common.webcrypto import chunk_key_aes, decrypt_chunk_aes
+from meshbay_node.indexer.group_index import GroupIndex
+from meshbay_node.transport.webrtc_server import WebRTCPeerSession, _probe_video
+
+from conftest import needs_subprocess, one_root
+
+_HAVE_FFMPEG = shutil.which("ffmpeg") and shutil.which("ffprobe")
+_ENCODERS = subprocess.run(["ffmpeg", "-hide_banner", "-encoders"],
+                           capture_output=True).stdout if _HAVE_FFMPEG else b""
+# libx265 gates the HEVC cases and only those: an ffmpeg without it still
+# encodes MPEG-4 Part 2 (a built-in) and can therefore still prove the half of
+# this policy that has no codec string. Marking the whole module on it skipped
+# the reported defect on any box without x265.
+_HAVE_HEVC_ENCODER = b"libx265" in _ENCODERS
+_HAVE_MP3_ENCODER = b"libmp3lame" in _ENCODERS
+pytestmark = [
+    pytest.mark.asyncio,
+    pytest.mark.skipif(not _HAVE_FFMPEG, reason="ffmpeg/ffprobe not installed"),
+    needs_subprocess,
+]
+needs_hevc = pytest.mark.skipif(not _HAVE_HEVC_ENCODER,
+                                reason="ffmpeg built without libx265")
+needs_mp3 = pytest.mark.skipif(not _HAVE_MP3_ENCODER,
+                               reason="ffmpeg built without libmp3lame")
+
+
+def _make_mpeg4_clip(path: Path) -> None:
+    """~1s of Xvid-style MPEG-4 Part 2 video + MP3 audio in an AVI.
+
+    The same shape as the reported file, down to the container: ffprobe reports
+    `codec_name: mpeg4`, which is what an Xvid encoder produces and what
+    `probe_video` has no MSE string for.
+    """
+    subprocess.run(
+        ["ffmpeg", "-hide_banner", "-loglevel", "error", "-y",
+         "-f", "lavfi", "-i", "testsrc=size=320x240:rate=25:duration=1",
+         "-f", "lavfi", "-i", "sine=frequency=440:duration=1:sample_rate=48000",
+         "-c:v", "mpeg4", "-c:a", "libmp3lame",
+         str(path)],
+        check=True, capture_output=True,
+    )
+
+
+def _make_hevc_clip(path: Path) -> None:
+    """~1s of HEVC video + AAC audio — a minimal stand-in for a real HEVC WEB-DL."""
+    subprocess.run(
+        ["ffmpeg", "-hide_banner", "-loglevel", "error", "-y",
+         "-f", "lavfi", "-i", "testsrc=size=320x240:rate=25:duration=1",
+         "-f", "lavfi", "-i", "sine=frequency=440:duration=1:sample_rate=48000",
+         "-c:v", "libx265", "-preset", "ultrafast", "-c:a", "aac",
+         str(path)],
+        check=True, capture_output=True,
+    )
+
+
+def _session(video_path: Path, gek: bytes, *, transcode_incompatible_video: bool = True):
+    import blake3
+    file_bytes = video_path.read_bytes()
+    file_id = blake3.blake3(file_bytes).hexdigest()
+
+    sk_node = Ed25519PrivateKey.generate()
+    index = GroupIndex(group_id="g" * 32, sk_node=sk_node, gek=gek)
+    from meshbay_common.protocol import IndexEntry
+    index.add_entry(IndexEntry(
+        id=file_id, name=video_path.name, path=video_path.parent.name,
+        size=len(file_bytes), type="video", added_at=0))
+
+    session = WebRTCPeerSession.__new__(WebRTCPeerSession)
+    session._ctx = {
+        "roots": one_root(video_path.parent),
+        "index": index,
+        "gek": gek,
+        "sk_node": sk_node,
+        "max_concurrent_streams": 4,
+        "transcode_incompatible_video": transcode_incompatible_video,
+    }
+    session._group_id = None
+    session._user_id = "tester"
+    session._stream_stopped = False
+    session._stream_keepalives = 0
+    session.sent = []
+    session._send = session.sent.append
+    session._audit = lambda *a, **k: None
+    return session, file_id
+
+
+def _reassemble(sent: list[dict], gek: bytes, file_id: str) -> bytes:
+    file_hash = bytes.fromhex(file_id)
+    segments = sorted(
+        (m for m in sent if m.get("type") == "stream_data"),
+        key=lambda m: m["segment_index"])
+    out = b""
+    for m in segments:
+        key = chunk_key_aes(gek, file_hash, m["segment_index"])
+        out += decrypt_chunk_aes(key, m["nonce"], m["ct"])
+    return out
+
+
+def _output_video_codec(path: Path) -> str:
+    probe = subprocess.run(
+        ["ffprobe", "-v", "error", "-select_streams", "v:0",
+         "-show_entries", "stream=codec_name", "-of", "csv=p=0", str(path)],
+        check=True, capture_output=True, text=True)
+    return probe.stdout.strip()
+
+
+@needs_hevc
+async def test_hevc_video_is_transcoded_to_h264_by_default(tmp_path):
+    clip = tmp_path / "clip.mkv"
+    _make_hevc_clip(clip)
+    gek = generate_gek()
+    session, file_id = _session(clip, gek)
+
+    await session._stream_video_inner({"file_id": file_id, "start": 0, "credits": 0})
+
+    errors = [m for m in session.sent if m.get("type") == "error"]
+    assert not errors, f"streaming must not fail: {errors}"
+
+    init = next(m for m in session.sent if m.get("type") == "stream_init")
+    assert init["codec"].startswith("avc1."), (
+        "the reported codec must be the transcoded H264 string, never the "
+        f"source's hev1 string a browser cannot decode: {init['codec']}")
+
+    remuxed = _reassemble(session.sent, gek, file_id)
+    out_path = tmp_path / "out.mp4"
+    out_path.write_bytes(remuxed)
+    assert _output_video_codec(out_path) == "h264", \
+        "the bytes on the wire must actually be H264, not just the reported label"
+
+
+@needs_hevc
+async def test_hevc_transcode_can_be_disabled_by_the_operator(tmp_path):
+    clip = tmp_path / "clip.mkv"
+    _make_hevc_clip(clip)
+    gek = generate_gek()
+    session, file_id = _session(clip, gek, transcode_incompatible_video=False)
+
+    await session._stream_video_inner({"file_id": file_id, "start": 0, "credits": 0})
+
+    assert not [m for m in session.sent if m.get("type") == "error"]
+    init = next(m for m in session.sent if m.get("type") == "stream_init")
+    assert init["codec"].startswith("hev1."), (
+        "with the fallback disabled, the source is copied as-is and the "
+        f"original HEVC codec string must be reported unchanged: {init['codec']}")
+
+    remuxed = _reassemble(session.sent, gek, file_id)
+    out_path = tmp_path / "out.mp4"
+    out_path.write_bytes(remuxed)
+    assert _output_video_codec(out_path) == "hevc", \
+        "with the fallback disabled, the wire bytes must still be copied HEVC"
+
+
+@needs_hevc
+async def test_probe_video_reports_raw_codec_name_for_hevc(tmp_path):
+    clip = tmp_path / "clip.mkv"
+    _make_hevc_clip(clip)
+
+    codec, duration, has_audio, width, height, raw_codec = await _probe_video(str(clip))
+
+    assert raw_codec == "hevc"
+    assert codec is not None and codec.startswith("hev1.")
+
+
+@needs_mp3
+async def test_probe_video_reports_no_codec_string_for_mpeg4(tmp_path):
+    """The other shape, and the reason the streaming path has to read it as
+    "re-encode this" rather than as a verdict on the file: there is no MSE
+    string for MPEG-4 Part 2 because no browser has a decoder to give one to.
+    The raw name is still reported, which is what the caller decides on."""
+    clip = tmp_path / "clip.avi"
+    _make_mpeg4_clip(clip)
+
+    codec, duration, has_audio, width, height, raw_codec = await _probe_video(str(clip))
+
+    assert raw_codec == "mpeg4"
+    assert codec is None, (
+        "a codec string for MPEG-4 Part 2 would be one no browser can act on")
+    assert has_audio is True
+    assert (width, height) == (320, 240)
+
+
+@needs_mp3
+async def test_a_codec_with_no_mse_string_is_transcoded_not_refused(tmp_path):
+    """The reported defect.
+
+    An Xvid/MP3 .avi answered "Unsupported video codec" — a refusal, on a file
+    ffmpeg re-encodes faster than it plays. Nothing about the source changed;
+    the node simply never reached its own re-encode path.
+    """
+    clip = tmp_path / "clip.avi"
+    _make_mpeg4_clip(clip)
+    gek = generate_gek()
+    session, file_id = _session(clip, gek)
+
+    await session._stream_video_inner({"file_id": file_id, "start": 0, "credits": 0})
+
+    errors = [m for m in session.sent if m.get("type") == "error"]
+    assert not errors, (
+        f"a source with no MSE codec string was refused instead of re-encoded: "
+        f"{errors}")
+
+    init = next(m for m in session.sent if m.get("type") == "stream_init")
+    assert init["codec"].startswith("avc1."), (
+        "stream_init must advertise the H264 the client is about to receive; "
+        f"there is no string for the source and none may be invented: {init['codec']}")
+
+    remuxed = _reassemble(session.sent, gek, file_id)
+    out_path = tmp_path / "out.mp4"
+    out_path.write_bytes(remuxed)
+    assert _output_video_codec(out_path) == "h264", (
+        "the bytes on the wire must actually be H264, not just the label")
+
+
+@needs_mp3
+async def test_the_operator_can_refuse_the_re_encode_and_says_so(tmp_path):
+    """`transcode_incompatible_video = false` still means what it says.
+
+    HEVC falls back to a copy there (the case above), because there is a codec
+    string to report. Here there is none, so a copy is not a lesser answer —
+    it is a stream_init the client refuses before the first byte. The refusal
+    has to name the setting: "Unsupported video codec" is what sent the last
+    reader to look at a file that was fine.
+    """
+    clip = tmp_path / "clip.avi"
+    _make_mpeg4_clip(clip)
+    gek = generate_gek()
+    session, file_id = _session(clip, gek, transcode_incompatible_video=False)
+
+    await session._stream_video_inner({"file_id": file_id, "start": 0, "credits": 0})
+
+    errors = [m for m in session.sent if m.get("type") == "error"]
+    assert errors, "a stream that cannot be produced must be refused, not started"
+    detail = errors[0]["detail"]
+    assert "transcoding" in detail, (
+        f"the refusal must point at the setting that caused it: {detail!r}")
+    assert not [m for m in session.sent if m.get("type") == "stream_init"], (
+        "a stream_init went out with no codec string the client could check")