==== AC3_descriptor

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

Because of the presence of an ATSC version of the `AC3_descriptor`,
the XML name for the DVB version is `<DVB_AC3_descriptor>`.
For compatibility, `<AC3_descriptor>` is still accepted.

[source,xml]
----
<DVB_AC3_descriptor
    component_type="uint8, optional"
    bsid="uint8, optional"
    mainid="uint8, optional"
    asvc="uint8, optional">
  <additional_info>
    Hexadecimal content, optional
  </additional_info>
</DVB_AC3_descriptor>
----
