rmt-flute

Multicast object-delivery wire formats — ALC / LCT / FLUTE / NORM — the binary headers used to deliver files and streams over IP multicast.

Everything here is IETF RMT (Reliable Multicast Transport): RFC 5651, RFC 5775, RFC 6726 and RFC 5740. No broadcast-specific standard is implemented by this crate. Several delivery systems are built on top of these formats and are consumers of it, not owners of it:

DVB — DVB-IPTV and DVB-MABR (ETSI TS 103 769) file delivery
3GPP — MBMS / eMBMS download delivery
ATSC 3.0 — ROUTE (A/331 Annex A), written as a profile-and-delta on RFC 5651/5775/6726

Renamed from dvb-flute at 0.4.0. The old name implied a DVB standard this crate does not implement, and made it read oddly as a dependency of non-DVB consumers such as ATSC 3.0 ROUTE. All dvb-flute versions are yanked; there is no shim. Same code, accurate name.

Implements:

LctHeader — the Layered Coding Transport header (RFC 5651 §5). The fixed first word carries V/C/PSI/S/O/H/A/B, HDR_LEN and the Codepoint; the C, S, O and H flags then drive the byte-widths of the CCI (4*(C+1)), TSI (4*S+2*H) and TOI (4*O+2*H) fields. The shared H half-word feeds both TSI and TOI. Flag bits and HDR_LEN are recomputed on serialize from the typed field lengths — no raw passthrough.
HeaderExtension — the LCT/NORM header-extension chain (RFC 5651 §5.2): variable-length (HET 0..=127, carries HEL) and fixed-length (HET 128..=255, one word) forms; with ExtTime (EXT_TIME) and the LctExtType registry (EXT_NOP/EXT_AUTH/EXT_TIME).
AlcPacket — an Asynchronous Layered Coding packet (RFC 5775): LCT header
- an opaque FEC Payload ID + the encoding-symbol payload, plus EXT_FTI (HET 64) and the Small-Block-Systematic FecPayloadId128.
ExtFdt / ExtCenc — the FLUTE (RFC 6726) fixed-length LCT extensions EXT_FDT (HET 192) and EXT_CENC (HET 193), plus the TOI = 0 FDT-Instance convention. The FDT Instance body is XML and out of scope of this binary crate — it rides as the packet payload.
NormCommonHeader + NormData / NormCmd / NormFeedback — the NORM (RFC 5740) common header and message types (NORM_DATA / INFO / CMD / NACK / ACK / REPORT).

⚠ FEC Payload ID bit layouts are FEC-scheme dependent (RFC 5052 / the FEC Scheme document) and are not defined by ALC/NORM themselves; this crate exposes them as opaque byte slices (the caller supplies the length), with FecPayloadId128 provided as one concrete illustrative layout.

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

Quick start

use rmt_flute::{LctHeader, LCT_VERSION};

let cci = [0u8; 4]; // C = 0
let tsi = [0u8; 4]; // S = 1, H = 0
let hdr = LctHeader {
    version: LCT_VERSION,
    psi: 0,
    close_session: false,
    close_object: false,
    codepoint: 0,
    cci: &cci,
    tsi: &tsi,
    toi: &[],
    extensions: vec![],
};
let mut buf = vec![0u8; hdr.serialized_len()];
hdr.serialize_into(&mut buf).unwrap();
let (re, used) = LctHeader::parse(&buf).unwrap();
assert_eq!(used, buf.len());
assert_eq!(re, hdr);

Examples

cargo run -p rmt-flute --example build_lct
cargo run -p rmt-flute --example parse_flute

Features

Feature	Default	Description
`std`	yes	Link the standard library. Without it the crate is `#![no_std]` + `alloc`.
`serde`	no	`serde::Serialize` derives on public types.

Minimum Supported Rust Version

1.95.0

License