Type 0 Extension 18 - mattpascoe135/dab GitHub Wiki

#Extension 18 - Announcement support The announcement support feature is encoded in Extension 18 of FIG type 0 (FIG 0/18). Figure 50 shows the structure of announcement support field which is part of the Type 0 field (see also figure 4).

This feature shall use the SIV signalling (see clause 5.2.2.1). The database shall be divided by use of a database key. Changes to the database shall be signalled using the CEI.

The following definitions apply:

###SId (Service Identifier): this 16-bit field shall identify the service (see clause 6.3.1).

###ASu (Announcement support) flags: this 16-bit flag field shall specify the type(s) of announcements by which it is possible to interrupt the reception of the service. The interpretation of this field shall be as defined in TS 101 756 [16], table 14.

The flags shall be coded as follows:

bi (i = 0 to 15);

0: Announcement type not supported;

1: Announcement type supported.

###Rfa: this 3-bit field shall be reserved for future additions. The bits shall be set to zero until they are defined.

###Number of clusters: this 5-bit field, coded as an unsigned binary number, shall specify the number of the following Cluster Ids (maximum 23).

###Cluster Id: this 8-bit field shall identify the announcement cluster, for which the announcement is intended. From the service point of view the cluster identifies a group of services which share the same announcement interruption privileges. Several cluster Ids may be included in the announcement support field. Cluster Id = "0000 0000" and Cluster Id = "1111 1111" are pre-defined and shall not be signalled in the announcement support field.

Cluster Id = "0000 0000" and Cluster Id = "1111 1111" may be used with the announcement switching information (see clause 8.1.6.2).

The database key comprises the OE and P/D flags (see clause 5.2.2.1) and the SId field.

The Change Event Indication (CEI) is signalled by the Number of Clusters field = 0 and the ASu flags field = 0.