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LAC — Lo Audio Codec

LAC is a lossless audio codec: integer-only, bit-exact, streaming-oriented. Designed for real-time voice (QUIC / MCU conferencing) and offline file compression. Compression is FLAC-class on speech (0.96-0.99× FLAC size) and within 5-7% of FLAC on music, while meeting realtime deadlines with hundreds of times' headroom on every platform tested (x86-64, aarch64, riscv64).

Install

# Cargo.toml
[dependencies]
lac = "0.1"

Rust 1.87+. no_std with alloc.

Minimal example

use lac::{encode_frame, decode_frame};

let samples: Vec<i32> = /* signed integer PCM, |s| ≤ 2²³ − 1 */ Vec::new();
let bytes = encode_frame(&samples);
let recovered = decode_frame(&bytes)?;
assert_eq!(recovered, samples);
# Ok::<(), lac::DecodeError>(())

Full API reference at docs.rs/lac. Buffer-reusing (encode_frame_into / decode_frame_into), MCU fanout patterns, and packet-loss concealment strategies are all in the repository's README.

Wiki contents

• Specification — the normative wire format. This is the authority on byte layout, field semantics, and encoder/decoder constraints. Second-team implementations should work from here.
• Security Policy — vulnerability reporting, supported versions, disclosure timeline.

Project links

• Repository: git.lo.sh/lo/lac
• Crate: crates.io/crates/lac
• API docs: docs.rs/lac
• License: AGPL-3.0-only

Status

Pre-1.0 (0.1.x). Wire format is stable — frames encoded by 0.1.0 will decode correctly on any future version with sync word 0x1ACC. Public API may still change; all changes follow semver within the 0.x range.