Honest PictureInfo population for VC-1 — completes the set (MPEG-2, H.264, HEVC,
VC-1 all populate now).
- Read the advanced-profile sequence header INTERLACE flag (SMPTE 421M §6.1.1,
bit 41), de-escaping emulation-prevention bytes as parse_vc1_resolution does.
- For a PROGRESSIVE sequence, decode the picture-layer PTYPE VLC (0=P, 10=B,
110=I, 1110=BI→I, 1111=Skipped→P) from the first bits after the frame start
code. For INTERLACED (FCM/FPTYPE precede PTYPE) or simple/main/unknown, decline
→ coding stays None: honestly absent, never read at a wrong bit offset.
- Set coding = coding_type_only(...) and source = pes.source; field order is not
decoded, so field_order() is honestly None.
- Reuses the shared startcode::BitReader (no new primitive).
- Tests: progressive I/P/B from real PTYPE VLCs + source carry + field-order
absence; interlaced honest-decline.
Matthew Jackson
e064bc7055