convertSegment_(
      old, initSegmentKey, periodStart, periodEnd, presentationTimeOffset) {
    const timestampOffset = periodStart - presentationTimeOffset;

    return {
      startTime: periodStart + old.startTime,
      endTime: periodStart + old.endTime,
      initSegmentKey,
      appendWindowStart: periodStart,
      appendWindowEnd: periodEnd,
      timestampOffset,
      dataKey: old.dataKey,
      tilesLayout: '',
      mimeType: null,
      codecs: null,
      thumbnailSprite: null,
    };
  }
@param {shaka.extern.SegmentDBV2} old
@param {?number} initSegmentKey
@param {number} periodStart
@param {number} periodEnd
@param {number} presentationTimeOffset
@return {shaka.extern.SegmentDB}
@private