dvb-emsg

MPEG-DASH Event Message Box (emsg) — inband DASH/CMAF timed events (SCTE 35 splice signalling, ID3 metadata, ad/tracking triggers): version 0/1 FullBox parse + serialize.

Implements:

• EmsgBox — the 'emsg' ISOBMFF FullBox (size / 'emsg' / version / flags) plus both version bodies: the two null-terminated UTF-8 strings (scheme_id_uri, value), the integer fields (timescale, event_duration, id), the version-discriminated presentation-time field, and the opaque message_data[]. size and version are recomputed/derived on serialize from the typed fields (no raw passthrough).
• PresentationTime — the version-discriminated timing field: presentation_time_delta (u32, version 0, segment-relative) vs presentation_time (u64, version 1, representation-relative). Selecting a variant is selecting the box version.
• EmsgVersion — the version byte (0 / 1) with its spec label.
• EmsgBox::is_scte35 — recognises the SCTE 35 scheme (SCTE35_SCHEME_PREFIX, urn:scte:scte35…), in which case message_data carries a SCTE 35 splice_info_section.

Note the v0/v1 field ordering differs: version 0 places the two strings first (before the integers); version 1 places the integers first and the strings last. Both orderings are parsed and serialized.

⚠ Source footing — softer than the fully-free crates

The emsg field semantics and types are render-verified from a free source: DASH-IF IOP Part 10 V5.0.0, §6.1 + Table 6-2 (transcribed in docs/emsg.md). But the normative ISOBMFF box syntax — the aligned(8) class EventMessageBox extends FullBox('emsg', version, flags = 0) declaration, the exact byte-level field ordering, the version-gated branch, and the null-terminated-string layout — lives in ISO/IEC 23009-1 §5.10.3.3, which is paid and NOT vendored in this repo. The box layout here is implemented from the well-known public emsg structure (widely reproduced in MPEG-DASH / CMAF) combined with the free DASH-IF Part 10 semantics, with ISO/IEC 23009-1 §5.10.3.3 cited as the formal (paid) normative source. This is softer footing than the fully-free crates in this workspace — flagged per project policy.

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

Quick start

use dvb_emsg::{EmsgBox, PresentationTime};

let scte35 = [0xFCu8, 0x30, 0x11]; // start of a splice_info_section
let b = EmsgBox {
    scheme_id_uri: "urn:scte:scte35:2013:bin",
    value: "",
    timescale: 90_000,
    presentation_time: PresentationTime::Delta(0),
    event_duration: 0xFFFF_FFFF,
    id: 1,
    message_data: &scte35,
};
assert!(b.is_scte35());
let bytes = b.to_vec().unwrap();
assert_eq!(EmsgBox::parse(&bytes).unwrap(), b);

Examples

cargo run -p dvb-emsg --example build_emsg
cargo run -p dvb-emsg --example parse_emsg

Features

Minimum Supported Rust Version

1.81

License

MIT OR Apache-2.0