_packData(size, arg) {
    return [
      new Uint8Array([arg, arg >> 8]),
      new Uint8Array([arg, arg >> 8, arg >> 16, arg >> 24]),
    ][size];
  }
Packs data into an Int16 format
@private
@param {number} size 0 = 1x Int16, 1 = 2x Int16
@param {number} arg value to pack
@returns