It will enable the delivery of next generation subtitles in transport streams for broadcast television services, based on W3C Timed Text Markup Language (TTML). The new spec will complement the bitmap-based subtitling solution that has been in use for over 20 years.
DVB Technical Module Chair, Kevin Murray, said: “The approval of the transport stream carriage of the TTML specification adds a very important component to the DVB specifications, most notably providing support for UHD subtitles. This also provides a common subtitling mechanism between transport stream and DASH delivered content and, being a textual based format, opens up a range of new possibilities for enhancing accessibility of services.”
TTML subtitles are increasingly being adopted, including by standards bodies ARIB, ATSC, EBU, SMPTE, ISO/MPEG in the Common Media Application Format specification and many others including platform specifications such as HbbTV.
TTML subtitles were initially chosen by DVB for internet delivery of services using the DVB profile of MPEG DASH (TS103 285). TTML subtitles provide a data rate efficient solution for SD, HD and even UHD resolutions.