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.
Matthew Jackson
534eca502c