Honest PictureInfo population for HEVC, on the same principle as H.264.
- Consolidate the bit reader: hevc.rs had its own BitReader (used by the SPS
parser); h264 just gained one in startcode. Promote startcode's to the single
shared pub(crate) reader (adds read_bits) and delete hevc's copy — one proven
primitive, reused (SPS parse + both slice-type decoders).
- hevc: decode slice_type from the first coded slice's slice_segment_header
(H.265 §7.3.6.1) → I/P/B (§7.4.7.1). The offset to slice_type depends on
num_extra_slice_header_bits, which lives in the PPS — so we parse it from the
ACTIVE PPS (§7.3.2.3) and only measure slice_type when that PPS is known.
With no active PPS we decline rather than guess: coding stays None, honestly
absent. Set coding = coding_type_only(...) and source = pes.source; field
order (pic_struct SEI) is not decoded, so field_order() is honestly None.
- Tests: I/P/B from real slice headers, source carry, field-order absence, and
the no-PPS honest-omission case.
Honest PictureInfo population for H.264 — the foundation that lets the video
index claim a frame's type and be believed (a faked "P" on a B-frame would make
the index confidently wrong).
- startcode: shared minimal MSB-first BitReader with Exp-Golomb ue(v), reused by
H.264 (and next HEVC). Documents the emulation-prevention caveat: only the
leading slice-header fields are read, where 00 00 03 cannot intervene.
- h264: decode first_mb_in_slice + slice_type (H.264 §7.3.3) from the first
coded slice and map to I/P/B (§7.4.3 Table 7-6; SP→P, SI→I). Set
coding = PictureInfo::coding_type_only(...) and source = pes.source. Field
order is NOT decoded here, so field_order() stays None — honestly absent,
never guessed.
- Tests: I/P/B from real ue-encoded slice headers, source carry, field-order
absence; BitReader Exp-Golomb table + truncation.
Test-hardening release, no runtime changes. Adds spec-grounded unit tests
across the silent-corruption surfaces — UDF/MPLS/CLPI/IFO parsing, BD/DVD
title + extent assembly, AACS/CSS key handling, TS/PS demux + codec parsers,
MKV/EBML container output, the mux pipeline, sector prefetch + decrypt
decorator, drive/SCSI sense decoding, label extraction, and core I/O. Each
test is grounded in the format spec or real on-disc behavior and verified to
fail under a targeted source mutation. No behavior changed.
Library-wide review-and-fix pass: tightened AACS keydb/handshake/variant
handling and trailing-partial-unit policy, corrected MPLS mark offset and
added UDF allocation bounds, hardened the mux/codec framing and M2TS paths,
guarded SCSI READ CAPACITY short transfers and unified error mapping, added
overflow guards on untrusted disc input, and made prefetch shutdown
deterministic. Release profile now builds with thin LTO + single codegen unit.
Matthew Jackson