gistfile1.txt

            uint value = bb.GetBits(6);

            if ((value & 0x30) > 0)
            {
                uint a = (value >> 0x04) & 0x03;
                uint b = (uint)((a == 0x03) ? 0x10 : 0);

                value = (bb.GetBits((int)(4 * a + b)) << 4) | (value & 0xF);
            }

            return (int) (base_index + value + 1);

value == 0x10 -> a = 1, b = 0 -> reads 4
value == 0x20 -> a = 2, b = 0 -> reads 8
value == 0x30 -> a = 3, b = 1 -> reads 28

same as my code :(