auto iop = dynamic_pointer_cast<dcp::InteropSubtitleAsset>(sc);
auto smpte = dynamic_pointer_cast<dcp::SMPTESubtitleAsset>(sc);
if (smpte) {
auto iop = dynamic_pointer_cast<dcp::InteropSubtitleAsset>(sc);
auto smpte = dynamic_pointer_cast<dcp::SMPTESubtitleAsset>(sc);
if (smpte) {