convertPeriod_(period, periodDuration) {
    const streams = [];
    for (const stream of period.streams) {
      // The v4 version of the database as written by v2.5.0 - v2.5.9 might have
      // been corrupted slightly.  A bug caused the stream metadata from all
      // periods to be written to each period.  This was corrected in v2.5.10.
      // To fix this, we can identify the extra streams by their lack of
      // variantIds and skip them.
      if (stream.variantIds.length == 0) {
        continue;
      }

      streams.push(this.convertStream_(
          stream, period.startTime, period.startTime + periodDuration));
    }
    return streams;
  }
@param {shaka.extern.PeriodDBV2} period
@param {number} periodDuration
@return {!Array<shaka.extern.StreamDB>}
@private