Segmentation of EBU-TT-Live document sequences

Document sequences may contain arbitrary length of documents with irregular issue times. Some output formats or carriage mechanisms may require a regular issuing schedule of documents (i.e. every 2 seconds). Therefore the live sequence supports resegmentation of the subtitle stream into blocks required by the user. The sequence object has the ebu_tt_live.documents.ebutt3.EBUTT3DocumentSequence.extract_segment() function that looks up the internal timeline to find any documents that intersect the requested range and in turn calls ebu_tt_live.documents.ebutt3.EBUTT3Document.extract_segment() on each of them using ebu_tt_live.documents.ebutt3_segmentation.EBUTT3Segmenter and merge the resulting documents into one EBUTT3Document in the end using ebu_tt_live.documents.ebutt3_splicer.EBUTT3Splicer After that these documents can be converted to EBU-TT-D for instance to be embedded into DASH, which requires such a regular document issuing strategy.