st12-1

SMPTE ST 12-1:2014 "Time and Control Code" — the §9 Linear Time Code (LTC) 80-bit logical codeword, no_std.

• [LtcFrame] — the 80-bit LTC codeword (§9.2): BCD hours/minutes/ seconds/frames, the drop-frame and color-frame flags, the four rate-dependent flag bits (polarity correction / BGF0 / BGF1 / BGF2 — resolved via [FrameRate], since the codeword itself carries no self-describing frame-rate field), the eight 4-bit binary groups ("user bits"), and the fixed synchronization word.
• [FrameRate] — which of ST 12-1 Table 3's three flag-bit-position columns (30-frame / 25-frame / 24-frame) applies.
• [BinaryGroupUsage] / [BinaryGroupFlags] — Table 1's classification of what the binary groups contain.

See docs/st12-1.md for the curated ST 12-1 §8/§9 transcription this crate implements field-for-field, including a verified-against-the-rendered-PDF note on Table 3's frame-rate-dependent bit-position swap.

Scope

This crate models only the already-demodulated logical 80-bit codeword — never the §9.3 biphase-mark-encoded physical/analog audio waveform LTC is carried as on a wire. That line-encoding/clock-recovery layer is out of scope for this project (the same way it never decodes PCM or AC-3 audio samples).

#![no_std]; depends only on broadcast-common.

Quick start

use broadcast_common::{Parse, Serialize};
use st12_1::LtcFrame;

let frame = LtcFrame {
    hours: 1,
    minutes: 23,
    seconds: 45,
    frames: 13,
    drop_frame_flag: false,
    color_frame_flag: true,
    flag_bit_27: true,
    flag_bit_43: true,
    flag_bit_58: false,
    flag_bit_59: true,
    user_bits: [1, 2, 3, 4, 5, 6, 7, 8],
};
let mut bytes = [0u8; st12_1::FRAME_LEN];
frame.serialize_into(&mut bytes).unwrap();
assert_eq!(LtcFrame::parse(&bytes).unwrap(), frame);

Examples

cargo run -p st12-1 --example build_frame
cargo run -p st12-1 --example parse_frame

Features

Minimum Supported Rust Version

1.95.0

License

MIT OR Apache-2.0