
        where a 'pssh' box is necessary.  Content using this stream format
        SHOULD include a box containing the
        <a data-cite="eme-initdata-cenc#common-system">Common SystemID and PSSH Box Format</a>.
      </p>
      <p>
        [=Initialization data=] is always one or more concatenated
        'pssh' boxes as defined by the [[[EME-INITDATA-CENC]]]
        [[EME-INITDATA-REGISTRY]].
      </p>
      <p>
        Each time one or more 'pssh' boxes are encountered, the
        [=Initialization 