==== HEVC_hierarchy_extension_descriptor

Defined by MPEG in <<ISO-13818-1>>.

[source,xml]
----
<HEVC_hierarchy_extension_descriptor
    extension_dimension_bits="uint16, required"
    hierarchy_layer_index="uint6, required"
    temporal_id="uint3, required"
    nuh_layer_id="uint6, required"
    tref_present="bool, required"
    hierarchy_channel="uint6, required">

  <!-- One per embedded layer -->
  <embedded_layer hierarchy_layer_index="uint6, required"/>

</HEVC_hierarchy_extension_descriptor>
----
