st291

SMPTE ST 291-1 — ancillary (ANC) data content. ST 291-1 defines the ANC data packet: the generic carrier for VANC/HANC payloads (captions, AFD, timecode, audio metadata, …) multiplexed into a professional video signal. This crate is about that content, not any one carriage mechanism — ST 291-1 packets can be conveyed over more than one transport, and this crate grows to cover each as it is added.

Transports

• ts (default) — SMPTE ST 2038:2021 carriage of ANC data packets in an MPEG-2 Transport Stream. Implements the two wire structures from §4:
  • AncDataDescriptor — the anc_data_descriptor (tag 0xC4) in the PMT ES loop, plus the "VANC" registration_descriptor format_identifier 0x56414E43 and stream_type 0x06 (§4.1, Table 1).
  • AncDataPacket — the ANC data PES packet (stream_id == 0xBD, PTS, PES_header_data_length == 0x05) carrying a list of bit-packed AncPacket records followed by 0xFF stuffing (§4.2, Table 2).
• rtp — RFC 8331 / ST 2110-40 carriage of ANC data packets over RTP (issue #648). AncRtpPayload is the §2.1 payload (Extended Sequence Number/Length/ANC_Count/F/reserved + a list of RtpAncPackets), riding on an rtp_packet::RtpPacket's payload (the RTP fixed header, RFC 3550, is the rtp-packet crate's responsibility). Length/ANC_Count are always recomputed on serialize and cross-validated on parse; the F field is a #[non_exhaustive] FieldSense enum whose Invalid (0b01) variant parses successfully rather than being rejected.

The per-ANC-packet DID/SDID/data_count/user_data_word/checksum_word content fields are a contiguous MSB-first 10-bit bit stream, identical across both transports (the always-compiled AncContent type). Per §4.2.1/ §2.1 the user_data_word loop counter uses only the low 8 bits of data_count; the full 10-bit values are stored verbatim. ST 291-1 parity/checksum is not validated here (deferred to ST 291-1, which is not vendored).

#![no_std] + alloc; depends only on broadcast-common (plus rtp-packet, optionally, for the rtp feature).

Quick start

use st291::{AncDataPacket, AncPacket};

let pkt = AncDataPacket {
    pes_priority: false,
    copyright: false,
    original_or_copy: false,
    pts: 90_000,
    anc_packets: vec![AncPacket {
        c_not_y_channel_flag: false,
        line_number: 9,
        horizontal_offset: 0,
        did: 0x161,
        sdid: 0x101,
        data_count: 0x002,
        user_data_words: vec![0x2CF, 0x101],
        checksum: 0x233,
    }],
    stuffing_bytes: 0,
};
let mut bytes = vec![0u8; pkt.serialized_len()];
pkt.serialize_into(&mut bytes).unwrap();
assert_eq!(AncDataPacket::parse(&bytes).unwrap(), pkt);

Examples

cargo run -p st291 --example build_anc
cargo run -p st291 --example parse_anc
cargo run -p st291 --example build_anc_rtp --features rtp
cargo run -p st291 --example parse_anc_rtp --features rtp

Features

Minimum Supported Rust Version

1.95.0

License

MIT OR Apache-2.0