DVB-SAD (Synchronised Auxiliary Data)
Carriage of synchronised auxiliary data in DVB transport streams
The Moving Pictures Expert group (MPEG) has specified in ISO/IEC 13818-1  how one or more elementary streams may be carried within a Transport Stream. The present document includes the definition of how two or more elementary streams of a particular service may be encoded so as to observe the rules of a timing model and so ensure that they can be synchronized within the receiver. Whilst the description of this timing model focuses on video and audio, it is applicable to any kind of data stream. Existing Digital Video Broadcasting (DVB) specifications for conveying ITU-R System B Teletext in DVB bitstreams (see ETSI EN 300 472 [i.2]) and Subtitling Systems (see ETSI EN 300 743 [i.3]) already exploit this. However, they are not readily scalable so as to be applicable to the carriage of other kinds of “auxiliary” data that needs to be synchronized. Hence, the present document has been developed to address this issue and so provide a generic method for the carriage of synchronized auxiliary data in DVB transport streams.
The present document describes a method by which auxiliary data, which needs to be synchronized with linear components of a service, such as video and audio streams, may be carried in a DVB transport stream.