parseInbandPssh(contentType, mediaSegment) {
    if (!this.config_.parseInbandPsshEnabled || this.manifestInitData_) {
      return Promise.resolve();
    }

    const ContentType = shaka.util.ManifestParserUtils.ContentType;
    if (![ContentType.AUDIO, ContentType.VIDEO].includes(contentType)) {
      return Promise.resolve();
    }

    const pssh = new shaka.util.Pssh(
        shaka.util.BufferUtils.toUint8(mediaSegment));

    let totalLength = 0;
    for (const data of pssh.data) {
      totalLength += data.length;
    }
    if (totalLength == 0) {
      return Promise.resolve();
    }
    const combinedData = new Uint8Array(totalLength);
    let pos = 0;
    for (const data of pssh.data) {
      combinedData.set(data, pos);
      pos += data.length;
    }
    this.newInitData('cenc', combinedData);
    return this.allSessionsLoaded_;
  }
Parse  pssh from a media segment and announce new initData

@param {shaka.util.ManifestParserUtils.ContentType} contentType
@param {!BufferSource} mediaSegment
@return {!Promise<void>}