SMPTE ST 2052-1:2013

This Standard defines the SMPTE profile of W3C Timed Text Markup Language (TTML), designated SMPTE-TT, which may represent Captions or Subtitles. It identifies the features from TTML required for interoperability between display systems for the format. In order to preserve certain semantic features of the input formats, SMPTE-TT also defines some standard metadata terms to be used, and some extension features not found in TTML.