TS 102 323 - V1.4.1 - Digital Video Broadcasting (DVB ... - ETSI

6.3 Default authority and abbreviated CRIDs
6.3.1 Abbreviated CRID rules
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ETSI
ETSI TS 102 323 V1.4.1 (2010-01)
In certain situations described in the present document a CRID string may use the following abbreviated forms. These
reduce the overhead of a CRID string by leaving out information that can be inferred from the location of the CRID
entry.
Firstly, the characters "crid://" may be omitted from the start of the string so that the string starts with the first character
of the CRID authority. So the example CRID:
• crid://company.com/foobar
may be encoded as:
• company.com/foobar
Additionally, within the scope of the definition of a default authority (see clause 6.3.2), the CRID authority part of the
string may also be omitted if the CRID's authority matches the current value of default authority. In this case the string
starts with the delimiter between CRID authority and data parts of the CRID (i.e. "/"). Therefore, the example CRID:
• crid://company.com/foobar
may be encoded as:
• /foobar
6.3.2 Scope of a default authority definition
A default authority is defined by the presence of a default authority descriptor. The purpose of the default authority is to
allow a CRID reference within the scope of such a definition to leave out the protocol and authority parts of a CRID
URI, if the CRID authority part of that CRID reference is the same as the defined default authority.
The scope of a particular value of default authority is defined by the location of the default authority descriptor. A value
of default authority defined in a scope overrides any value of default authority already defined for a wider, enclosing
scope. See table 15 for definitions of the permitted locations of the default authority descriptor and which scope
override which others.
Table 15: Permitted locations of default authority descriptor
Default authority descriptor location Scope of
definition
Scopes this definition overrides
First descriptor loop of NIT network none
Transport stream descriptor loop of NIT transport stream bouquet or network
First descriptor loop of BAT bouquet none
Transport stream descriptor loop of BAT transport stream bouquet or network
Service descriptor loop of SDT service transport stream, bouquet or network
The effect of defining a default authority in a BAT that conflicts with a definition of equivalent scope in a NIT is not
defined by the present document.
EXAMPLE: If a default authority is defined at the scope of a network, this can be overridden for a single
service on that transport stream by the inclusion of a default authority descriptor in the service
loop of an SDT on that transport stream.