From 43bdd1868f37395d8235393a8d78e1b136b67a54 Mon Sep 17 00:00:00 2001
From: "Matthias P. Braendli" <matthias.braendli@mpb.li>
Date: Sat, 16 Feb 2019 17:00:15 +0100
Subject: Explain FIG1 and FIG2 usage

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 datafeatures.tex | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

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diff --git a/datafeatures.tex b/datafeatures.tex
index 3a67fa8..7622b46 100644
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 % 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
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