+DCPSubtitleDecoder::content_time_period (shared_ptr<const dcp::Subtitle> s) const
+{
+ return {
+ ContentTime::from_seconds(s->in().as_seconds()),
+ ContentTime::from_seconds(s->out().as_seconds())
+ };
+}
+
+
+/** @return time of first subtitle, if there is one */
+optional<ContentTime>
+DCPSubtitleDecoder::first () const
+{
+ if (_subtitles.empty()) {
+ return {};
+ }
+
+ return ContentTime::from_seconds(_subtitles[0]->in().as_seconds());
+}
+
+
+void
+DCPSubtitleDecoder::update_position()