Overview
ISO/IEC 21000-18:2007 - part of the MPEG‑21 multimedia framework - specifies tools for Digital Item Streaming. Its primary tool is the Bitstream Binding Language (BBL), a declarative mechanism that defines how a Digital Item (Digital Item Declaration, metadata and resources) is mapped and fragmented into delivery channels such as MPEG‑2 Transport Streams and the Real‑time Transport Protocol (RTP). The standard supports incremental, time‑aware delivery so receivers can progressively consume a Digital Item as Packets arrive.
Key topics and requirements
- Bitstream Binding Language (BBL): core language for mapping source documents to packets and streams.
- Bindings and Instances: reusable binding descriptions and BBL instances that process concrete source documents.
- Packets & Packet Streams: fragments of a Digital Item that carry content and temporal metadata (Delivery Time, Repetition Period, Duration).
- Fragmentation model: rules and constraints for splitting Digital Items into consumable fragments (Fragmentation Rule, Fragmentation Constraint).
- Handlers: plug‑ins that output Packets to delivery channels (examples include MPEG‑2 TS and RTP handlers described in the standard).
- Binary Documents & BS Schema: support for binary resources through bitstream syntax schemas to enable XPath‑style processing.
- Processing model & attributes: defined BBL attributes, encoders, and a processing lifecycle for creating streams.
- Normative dependencies: leverages MPEG‑2 systems, RTP, XML/W3C specs and other MPEG‑21 parts.
- Supporting material: XML Schema for BBL, RTP handler details, examples and a registration procedure (in annexes).
Practical applications and users
ISO/IEC 21000-18 is relevant for anyone building end‑to‑end multimedia delivery systems that require interoperable, fine‑grained control over how content is packaged and streamed:
- Broadcast and multicast systems using MPEG‑2 Transport Streams.
- Live and real‑time streaming platforms using RTP-based delivery.
- IPTV, set‑top box and middleware developers who must fragment and schedule content for progressive consumption.
- Content packaging and distribution engineers who need to map DID/DIDL structures into transport streams.
- Standards integrators and implementers working with other MPEG‑21 parts (DID, REL, Binary Format) or with DRM/IPMP workflows.
Benefits include predictable, standards‑based mapping of structured Digital Items to delivery channels, temporal control for progressive consumption, and reuse across broadcast and IP delivery systems.
Related standards
- ISO/IEC 21000 (MPEG‑21) parts - notably Part 2 (Digital Item Declaration), Part 9 (File Format), Part 16 (Binary Format), Part 17 (Fragment Identification).
- ISO/IEC 13818‑1 (MPEG‑2 Systems) and RTP (IETF RFC 3550).
- W3C XML, XML Namespaces, XPath and DOM specifications.
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