+ boost::shared_ptr<dcp::SubtitleAsset> _subtitle_asset;
+ std::map<DCPTextTrack, boost::shared_ptr<dcp::SubtitleAsset> > _closed_caption_assets;
+ boost::shared_ptr<dcp::AtmosAsset> _atmos_asset;
+ boost::shared_ptr<dcp::AtmosAssetWriter> _atmos_asset_writer;