 Track Encryption Box ('tenc') and
        the sample group with grouping type 'seig' (CencSampleEncryption group),
        if any, associated with the sample.  The default encryption state of a
        sample is defined by the IsEncrypted flag in the associated track
        encryption box ('tenc'). This default state may be modified by the
        IsEncrypted flag in the SampleGroupDescriptionBox ('sgpd'), pointed to
        by an index in the SampleToGroupBox ('sbgp').
      </p>
      <p>
        Sample