<?xml version="1.0" encoding="UTF-8"?>
<tsduck>
  <_descriptors>

    <!-- note each byte of the ISO_639_langiuage_code represents an ASCII character -->
    <TTML_subtitling_descriptor
        ISO_639_language_code="char3, required"
        subtitle_purpose="uint6, required"
        TTS_suitability="uint2, required"
        qualifier="uint32, optional"
        service_name="string, optional"
        reserved_zero_future_count="uint8, default=0">

      <!-- one per dvb_ttml_profile value -->
      <dvb_ttml_profile value="uint8, required"/>

      <!-- one per font_id value -->
      <font_id value="uint7, required"/>

    </TTML_subtitling_descriptor>

  </_descriptors>
</tsduck>
