private ZoneRecord readZoneRecord()
{
final int numZoneData = bitStream.readUI8();
assert 2 == numZoneData;
final ZoneData zoneData0 = readZoneData();
final ZoneData zoneData1 = readZoneData();
bitStream.byteAlign();
bitStream.readUB(6); // reserved
final boolean zoneMaskY = bitStream.readBit();
final boolean zoneMaskX = bitStream.readBit();