Specification for conveying ITU-R System B Teletext in DVB bitstreams
The present document specifies the method by which ITU-R System B Teletext (Recommendation ITU-R BT.653), also known as EBU Teletext (see ETSI EN 300 706), may be carried in DVB bitstreams. This transport mechanism is intended to satisfy the following requirements:
- to support the transcoding of the Teletext data into the Vertical Blanking Interval (VBI) of analogue video. The transcoded signal should be compatible with existing TV receivers with Teletext decoders;
- the maximum data rate for each Teletext service is equivalent to 16 lines per field so that the service is always suitable for transcoding into the VBI;
- the transmission mechanism should be capable of transmitting subtitles with accurate timing with respect to the video (i.e. to within or near frame accuracy).
A more general data transport mechanism for conveying new types of data services is outside the scope of the present
document, but the transport syntax specified here can also be adapted for other data.