==== announcement_support_descriptor

Defined by DVB in <<ETSI-300-468>>.

Note that the 16-bit field named `announcement_support_indicator` is automatically built as
a bit-mask from all `announcement_type` values.

[source,xml]
----
<announcement_support_descriptor>
  <!-- One per announcement type -->
  <announcement
      announcement_type="uint4, required"
      reference_type="uint3, required"
      original_network_id="uint16, optional"
      transport_stream_id="uint16, optional"
      service_id="uint16, optional"
      component_tag="uint8, optional"/>
</announcement_support_descriptor>
----
