Overview
IEC 62297-1:2005 defines the format of triggering messages for broadcast applications - the information sent by a TV service provider as part of a data broadcast to start, stop or control an application in a receiver. It standardizes the syntax, semantics and life‑cycle behaviour of trigger messages (and the derived event messages) for teletext-based transport and can also be applied to MPEG-2 DSM‑CC sections. Transport specifics are covered in IEC 62297-2.
Key topics and technical requirements
- Trigger message structure: mandatory URL field, descriptive trigger_text, and optional attribute elements that convey action, filtering and timing.
- Character coding: default character set is ISO 8859‑1; allowed trigger characters are in the 0x20–0x7E range. Characters outside that range must be percent-encoded (e.g. ‘%25’ for ‘%’, ‘%5B’ for ‘[’).
- Time formats: supports absolute UTC DateTime (yyyymmddThhmmss) and RelativeTime values measured in seconds and video frames.
- Objects and life cycles: defines a TriggerObject (information from triggers referencing the same URL) and ApplicationObject (data about an application started/modified by triggers). Life‑cycle attributes include CountdownValue and ActiveTimeValue, updated at video frame rate.
- Priority and filtering: triggers carry a priority attribute. The ‘emergency’ priority should always be processed (even if trigger handling is disabled), and is reserved for genuine emergencies.
- Receiver behaviour rules: viewer interaction (how users enable/disable triggers) and icon/display behaviour are left to receiver manufacturers. Receivers should ignore unknown attributes for future compatibility.
- Syntax constraints: attribute strings exclude square brackets; URL strings exclude angle brackets. Normative references include ISO 8859‑1, ETSI TS 101 231 and ETSI EN 300 706.
Applications
IEC 62297-1 is intended for practical broadcast uses such as:
- Emergency alerting and severe weather warnings (high-priority triggers)
- On-screen notifications or rating advisories
- Launching interactive services: voting, programme-related content, EPG links, teletext/Superteletext/Internet page display
- Application control in hybrid broadcast/broadband TV systems
Who uses this standard
- Broadcasters and service providers defining in‑band data services
- Receiver and set‑top box manufacturers implementing trigger handling
- Middleware and application developers for interactive TV
- System integrators working with teletext or DSM‑CC service delivery
- Standards and compliance engineers validating trigger implementations
Related standards
- IEC 62297-2 (Transport methods for trigger messages)
- ISO 8859‑1 (character encoding)
- ETSI TS 101 231, ETSI EN 300 706 (teletext and CNI/VPS application codes)
Keywords: IEC 62297-1, trigger messages, broadcast applications, TV broadcasting, data broadcasting, teletext, DSM‑CC, trigger format, emergency priority.