A method of encoding a block of data. A first plurality of data in the block of data is assigned a worth based on a first algorithm. A second plurality of data, which is lower in frequency than the first plurality of data, in the block of data is assigned a worth according to a second algorithm. The block of data is assigned a worth based on the worth of the first plurality of data and the second plurality of data. The worth of the block of data is then compared to a threshold value, and subsequently one or more data values of the block of data are adjusted based on the comparison.