Commit 4cd9b7b ("key the DVD crack on the disc, not on the container") fixed a
real bug — a decrypted HD-DVD hit E7023 (CssKeyMissing) because the per-title
CSS crack keyed on the MPEG-PS container, which DVD and HD-DVD share — but did
it by adding a required `disc_format: DiscFormat` parameter to the PUBLIC
`DiscStream::new` and `build_iso_pipeline`, a `disc_format` field to
`MuxInput::Iso`/`Live`, and `DiscFormat::may_have_css`, threading the axis down
through mux/driver and mux/resolve. That changed the public API and broke every
downstream caller's compilation (freemkv-engine's integration test now needed 8
args, autorip's MuxInput arms a new field). 1.6.4 shipped and worked with these
exact signatures; a bug fix must not reshape them, and needing a whole
disc-format plumb for HD-DVD was a code smell.
Revert all of that plumbing (public signatures restored to their pre-4cd9b7b
form; no `disc_format` parameter or field, no `may_have_css`, anywhere), and fix
the ACTUAL bug where it lives: the scramble-detection heuristic.
Root cause: `is_scrambled_pack` counted a sector as CSS scramble evidence on
pack-start (00 00 01 BA) + bits 4-5 of byte 0x14. Offset 0x14 is only the PES
scrambling-control field when the sector is a genuine elementary-stream pack. An
HD-DVD `.evo` RDI navigation pack is private_stream_2 (stream_id 0xBF), an
MPEG-PS pack exactly like a DVD VOB, whose byte 0x14 is raw nav payload that
routinely has bits 4-5 set. On a decrypted HD-DVD (None keys, MPEG-PS, so it
reaches the crack) those nav packs flipped the scan's `saw_scrambled` flag; the
crack then found no key — there is no CSS on an HD-DVD — and the scan returned
ScrambledUncracked, hard-failing a good disc with E7023.
Fix: exclude the MPEG-PS structural stream_ids CSS never scrambles — system
header (0xBB), padding (0xBE), private_stream_2 (0xBF) — by the stream_id at
offset 0x11. This is the refinement the DVD design notes already called for
("matches CrackTitleKey"). It needs no format plumbing because byte 0x11 lives
in the CSS-clear header (0x00-0x7F, untouched by scrambling), so it is the true
stream_id even on ciphertext. A decrypted HD-DVD now scans to Unencrypted and
muxes cleanly.
The DVD CSS crack is preserved and proven: a genuinely CSS-scrambled DVD sector
is always video (0xE0-0xEF) or private_stream_1 (0xBD), never an excluded id, so
its scrambled packs still set saw_scrambled and still hard-fail an uncrackable
disc — the "ciphertext muxed as plaintext at rc=0" catastrophe cannot slip
through. Red-before-green both directions: dropping the 0x11 exclusion turns the
decrypted-HD-DVD case back into E7023; inverting it (only nav ids count) turns a
real uncrackable DVD into Unencrypted and strands a crackable one. Both mutations
are caught by tests.
Gate (cargo +1.97): fmt, clippy --all-targets -D warnings, 3539 tests green;
freemkv-engine and autorip both compile against this tree again; precommit.sh
libfreemkv clean.
Matthew Jackson
25893f1be4