1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
|
% LICENSE: see LICENCE
\section{Data Features}
\subsection{FIG 1 Labels and FIG 2 Extended Labels}
The specification offers two ways to carry ensemble, service and component
labels: through FIG 1 and through FIG 2, specified in clauses 5.2.2.2 and 5.2.2.3
of ETSI EN 300 401~\cite{etsidab}.
Most receivers are only able to show FIG 1 Labels encoded in the Complete EBU
Latin character set (defined in ETSI TS 101 756 clause
5.2~\cite{etsidabtables}). Some are able to display Unicode FIG 1 Labels,
encoded either in UTF-8 or UCS-2, and, as of early 2019, receiver support for
FIG 2 Extended Labels is practically absent.
The main downside of carrying Unicode FIG 1 Labels is the length limitation: 16
bytes will only encode eight characters in alphabets that require two bytes per
character. FIG 2 supports up to 32 bytes labels to alleviate this.
The intention is that new ensembles in countries requiring labels in non-latin
alphabets transmit only FIG 2 Extended Labels, whereas currently operating
ensembles keep transmitting FIG 1 Labels. This entices receiver manufacturers to
support FIG 2 without impacting functionality of receivers currently in use.
Transmitting both FIG 1 and FIG 2 is discouraged by the specification.
The way FIG 2 is encoded has been redefined, which is why ODR-DabMux supports
two variants: FIG 2 with character flag being the old variant, and FIG 2 with
text control that will become the default variant.
\subsection{Announcements}
The ODR-DabMux multiplexer supports the insertion of FIG 0/18 and FIG 0/19 that
are used to define and trigger announcements according to ETSI TR 101 496-2
Clause 3.6.8~\cite{etsitr1014962}.
An example configuration is available in the ODR-DabMux repository, in
\texttt{doc/advanced.mux}.
The best known application for announcements is traffic information, but other
kinds of announcements can also be signalled. ODR-DabMux allows triggering the
announcements through the telnet and ZMQ remote control interfaces.
\subsection{Service Linking}
ODR-DabMux also supports the ability to inform receivers about other ways to
receive a given service, through the FIGs 0/6, 0/21 and 0/24. FIG 0/6
communicates the identifiers of services linked together, 0/21 informs the
receiver about other frequencies, and 0/24 includes information about other DAB
ensembles carrying the linked service.
Their interaction is outlined in ETSI TS 103 176~\cite{etsits103176}.
You will find an example configuration in the ODR-DabMux repository, in
\texttt{doc/servicelinking.mux}.
% vim: spl=en spell tw=80 et
|
