==== Aggregate Extended Text Table (AETT)

Defined by ATSC in <<ATSC-A81>>.

[source,xml]
----
<AETT version="uint5, default=0"
      AETT_subtype="uint8, default=0"
      MGT_tag="uint8, required">

  <!-- When AETT_subtype == 0, any number of ETM_data -->
  <ETM_data ETM_id="uint32, required">
    <!-- Optional ATSC multiple_string_structure() containing one or more strings -->
    <extended_text_message>
      <string language="char3, required" text="string, required"/>
    </extended_text_message>
  </ETM_data>

  <!-- When AETT_subtype != 0, at most one reserved -->
  <reserved>
    Hexadecimal content
  </reserved>

</AETT>
----
