Data is compressed, which includes first through sixth patterns having respective first through sixth values, where the first pattern precedes the second pattern in the data, the third pattern precedes the fourth pattern in the data, and the fifth pattern precedes the sixth pattern in the data. Compression includes outputting a first code and the second value if the second value exceeds the first value by more than a predetermined amount, outputting a second code and a difference between the third and fourth values if the fourth value does not exceed the third value by more than the predetermined amount, and outputting the fifth value and the sixth value if the sixth value exceeds the fifth value by a predefined number.