The field ‘FT’ signals the type of data carried by the payload which can be either MPU metadata, Movie Fragment metadata, or MFUs, Payload with MPU metadata type can include ‘ftyp’, ‘mmpu’, ‘moov’, and ‘meta’ boxes as well as any other boxes that appear in between and payload withMovie Fragment metadatatype can include ‘moof’ box and ‘mdat’ box excluding all media data inside.