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diff --git a/datafeatures.tex b/datafeatures.tex index 3a67fa8..7622b46 100644 --- a/datafeatures.tex +++ b/datafeatures.tex @@ -1,5 +1,30 @@ % 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 |