getH264Codec_(qualityLevel, codecPrivateData) {
    // Extract from the CodecPrivateData field the hexadecimal representation
    // of the following three bytes in the sequence parameter set NAL unit.
    // => Find the SPS nal header
    const nalHeader = /00000001[0-9]7/.exec(codecPrivateData);
    if (!nalHeader.length) {
      return '';
    }
    if (!codecPrivateData) {
      return '';
    }
    // => Find the 6 characters after the SPS nalHeader (if it exists)
    const avcOti = codecPrivateData.substr(
        codecPrivateData.indexOf(nalHeader[0]) + 10, 6);

    return 'avc1.' + avcOti;
  }
@param {!shaka.extern.xml.Node} qualityLevel
@param {?string} codecPrivateData
@return {string}
@private