static parseTFHD(reader, flags) {
    let defaultSampleDuration = null;
    let defaultSampleSize = null;
    let baseDataOffset = null;
    let sampleDescriptionIndex = null;

    const trackId = reader.readUint32(); // Read "track_ID"

    // Read "base_data_offset" if present.
    if (flags & 0x000001) {
      baseDataOffset = reader.readUint64();
    }

    // Read "sample_description_index" if present.
    if (flags & 0x000002) {
      sampleDescriptionIndex = reader.readUint32();
    }

    // Read "default_sample_duration" if present.
    if (flags & 0x000008) {
      defaultSampleDuration = reader.readUint32();
    }

    // Read "default_sample_size" if present.
    if (flags & 0x000010) {
      defaultSampleSize = reader.readUint32();
    }

    return {
      trackId,
      defaultSampleDuration,
      defaultSampleSize,
      baseDataOffset,
      sampleDescriptionIndex,
    };
  }
Parses a TFHD Box.
@param {!shaka.util.DataViewReader} reader
@param {number} flags
@return {!shaka.util.ParsedTFHDBox}