Overview
IEC 62297-2:2005 specifies transport methods for triggering messages for broadcast applications, describing how trigger data (as defined in IEC 62297-1) are carried over teletext-based delivery channels. The standard defines two teletext transport methods - Page Format‑Clear and Independent Data Line (IDL) format B - using protocols from ETSI EN 300 708 and related teletext specifications. Trigger messages typically include a URL and optional attributes (e.g., countdown or expiry times) that cause a receiver to launch or prioritise an application (alerts, interactive prompts, programme-related content).
Key topics and technical requirements
- Transport methods
- Page Format‑Clear (teletext page-based):
- Serial data stream comprised of Application Data Blocks, Structure Headers, Bundle Information Structures and Block Separators.
- Each application byte is split into two 4‑bit nibbles and Hamming 8/4 encoded (per ETSI EN 300 706).
- Page structure uses packets X/0, X/1–X/25 (data), and X/28/0 (page signature/format 1).
- Default page number: 0x1E7; MIP code for trigger pages: 0xFC.
- Maximum trigger message length limited to 1 022 bytes by Page Format‑Clear encoding.
- Independent Data Line (IDL) format B:
- Designed for efficient serial data broadcast with Forward Error Correction (FEC) protecting user data.
- Protocol stack: Trigger message → Framing protocol → FEC → IDL format B.
- No inherent upper limit on trigger message size when using IDL format B.
- Transmission considerations
- Bundle Information Structures are periodically inserted to identify application types (trigger application type recorded in ETSI TS 101 231).
- Packet X/28/0 format 1 provides an unambiguous page signature to help receivers detect trigger pages.
- Interoperability
- Uses ETSI teletext protocols and references ISO/IEC MPEG extensions where applicable (MPEG-2 / DSM‑CC).
Applications and who uses it
- Practical uses:
- Emergency alerts (severe weather, public safety).
- Programme content warnings (age/extreme content).
- Interactive prompts (voting, registration, commerce links).
- Pushing programme‑related URLs and timed actions to receivers.
- Primary users:
- Broadcasters and service operators implementing data broadcast services.
- Set‑top box and TV manufacturers, receiver firmware developers.
- Middleware and application developers for interactive TV.
- System integrators and regulators specifying broadcast signalling.
Related standards
- IEC 62297-1 - Triggering messages: Format
- ETSI EN 300 708 - Data transmission within Teletext
- ETSI EN 300 706 - Enhanced Teletext specification
- ETSI TS 101 231 - Register of CNI/VPS/Application codes
- ISO/IEC 13818-6 - MPEG-2 DSM‑CC extensions
Keywords: IEC 62297-2, triggering messages, teletext transport, Page Format‑Clear, Independent Data Line, IDL format B, ETSI EN 300 708, Hamming 8/4, broadcast trigger messages, FEC, interactive TV.