i.set_in (i.in() - dcp::Time (_period.from.seconds(), i.in().tcr));
i.set_out (i.out() - dcp::Time (_period.from.seconds(), i.out().tcr));
_subtitle_asset->add (i);
i.set_in (i.in() - dcp::Time (_period.from.seconds(), i.in().tcr));
i.set_out (i.out() - dcp::Time (_period.from.seconds(), i.out().tcr));
_subtitle_asset->add (i);