void emit_plain_start (ContentTime from, std::list<dcp::SubtitleString> s);
void emit_plain_start (ContentTime from, sub::Subtitle const & subtitle);
void emit_plain (ContentTimePeriod period, std::list<dcp::SubtitleString> s);
void emit_plain_start (ContentTime from, std::list<dcp::SubtitleString> s);
void emit_plain_start (ContentTime from, sub::Subtitle const & subtitle);
void emit_plain (ContentTimePeriod period, std::list<dcp::SubtitleString> s);