mirror of
https://github.com/freemkv/libfreemkv.git
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Matthew Jackson
6e14fc0c0c
Security - Remove the unsafe Vec::set_len over recycled sector buffers — UB reachable from safe code (GHSA-j8ww-f5fg-9pmh, low). Uses Vec::resize; pooling unchanged. CI / tooling - clippy on stable with the MSRV single-sourced from Cargo.toml; cargo-deny dependency-audit gate with first-party git sources allowed (#15); audience-based comment-guard (#17). Docs - README (keydb ownership, BD-J parser count), drive-access transport/reset notes, mux timeline module-doc links.
96 lines
4.9 KiB
Markdown
96 lines
4.9 KiB
Markdown
# `src/labels/mpls_universal.rs`
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Universal MPLS-based stream labels — the confidence-tier "floor" for the
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`labels` registry.
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## Why this module exists
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Unlike the framework-specific parsers in `src/labels/` (dbp, pixelogic, ctrm,
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criterion, ...), this module is the floor: every Blu-ray ships with MPLS
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playlists under `/BDMV/PLAYLIST/`, and every MPLS file has an STN table with
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per-stream ISO 639-2 language codes plus coding-type / channel-layout /
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sample-rate bytes from the BD spec.
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The framework parsers extract richer editorial labels ("English Dolby Atmos",
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"Director's Commentary") when the disc was authored with a recognized tool.
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When none of them match (e.g. a "no BD-J" disc, or an authoring framework we
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haven't catalogued), MPLS still gives us language + codec on every stream —
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enough to render something more useful than the bare PID.
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Output confidence is Low: MPLS carries language + codec but never
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purpose/qualifier info (no way to tell "Commentary" from "Normal" from the STN
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table alone). Higher-confidence framework parsers, when present, always win on
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the registry's max-by-confidence tiebreaker — MPLS is only chosen when nothing
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else matched.
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## `build_labels`
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Converts every stream entry across `playlists` into one `StreamLabel` per
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physical stream. Factored out of `parse` so unit tests can drive the actual
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conversion logic (stream-type mapping, identity, slot numbering) directly from
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already-parsed `crate::mpls::Playlist` values, without needing a synthetic
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on-disc UDF image.
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Identity is `(clip, PID)` — what the STN entry states — and it is both the
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dedup key and the label's `StreamId`. A stream twenty playlists list is one
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label; two clips that both open their first audio at 0x1100 are two. This
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replaced a disc-global dense counter that numbered surviving entries 1, 2, 3,
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… in playlist-directory order: that number was not an STN slot in anything,
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but it was handed to a binder that reads `stream_number` as one.
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## `label_type_for`
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Which per-type numbering list an STN entry belongs to, or `None` when it is
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not a labellable stream at all.
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This MUST agree with the stream list `disc::bluray` builds from the same
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entries, because that list is what `labels::apply_labels` counts against when
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it binds `stream_number`. The two counters run over the same STN entries in
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the same order, so any entry one side keeps and the other drops — or files
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under a different type — shifts every later label of that type onto the wrong
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stream. Three rules, all mirroring `disc::bluray`:
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* `coding_type == 0` is the STN table's empty/padding slot. Not a stream on
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either side.
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* a PG coding_type in an audio STN slot is a subtitle, not audio.
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`mpls::parse_stream_entry` has a dedicated arm for this layout, so it is an
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authored shape rather than a corruption.
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* video (1 / 6 / 7 = primary, secondary, Dolby Vision EL) and IG (4) have no
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`StreamLabelType`; they are numbered in their own STN lists and never
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interleave with the audio or PG lists.
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## Test helpers and fixtures
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`playlist_with`: a playlist over clip "00001". `Playlist::streams` is read out
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of the first play item's STN table, so a playlist that has streams always has
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a play item to have read them from — the fixture carries one so tests exercise
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the shape production sees, and so each label gets the `(clip, PID)` identity
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it is bound by.
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`labels_from_playlists`: drives the actual production conversion logic
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(`build_labels`, the function `parse()` calls) starting from already-parsed
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Playlists, so tests don't have to synthesize valid on-disc MPLS/UDF bytes.
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This calls the *real* code under test rather than a hand-written
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re-implementation, so mutations inside `build_labels` (stream-type mapping,
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dedup key, counters) are actually caught here.
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`padding_stn_entry_does_not_consume_a_label_slot`: `stream_number` is bound by
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`labels::apply_labels` against the title's own stream list, which
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`disc::bluray` builds from these same STN entries. That builder DROPS an entry
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whose `coding_type` is 0 — the STN table's empty/padding slot — so it must not
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be counted here either. Counting it advances the audio counter past a stream
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that never materializes, and every label behind it binds one stream late.
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`pg_coding_type_in_an_audio_slot_counts_as_a_subtitle`: a PG coding_type
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sitting in an audio STN slot is a real, documented shape —
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`mpls::parse_stream_entry` has an explicit arm for it, and `disc::bluray`
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builds it as a Subtitle stream, not an Audio one. This module must classify it
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the same way, or the audio counter runs one ahead and the subtitle counter one
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behind for every later stream.
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`same_pid_in_two_clips_is_two_streams`: the same PID in two DIFFERENT clips is
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two different streams — a PID is only unique within one clip. Deduping on the
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PID alone (as the old key's `(type, language, codec_hint, pid)` did across
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clips) collapses them into one label, and the second clip's stream is then
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described by the first clip's.
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