// the symbol set is reduced. The symbols used are stored as a
	// two-level, 16x16 bitmap.
	symbolRangeUsedBitmap := br.ReadBits(16)
	symbolPresent := make([]bool, 256)
	numSymbols := 0
	for symRange := uint(0); symRange < 16; symRange++ {
		if symbolRangeUsedBitmap&(1<<(15-symRange)) != 0 {
			bits := br.ReadBits(16)
			for symbol := uint(0); symbol < 16; symbol++ {