Method for reducing data expansion during data compression

A computer program product for use in a data compression process having two or more coding schemes, the product comprising:

• a medium readable by a computer, the computer readable medium having:
• means for providing a coding window that allows analysis of the compression potential of each byte of a sequence of bytes of data therewithin, wherein the coding window has a dynamically variable size p, wherein p is an integer number of bytes in the sequence and p is not greater than a predetermined maximum size N;
• means for analyzing the data within the window, wherein analyzing the data within the window includes computing a compression potential sum Sp for p data bytes within the coding window according to the formula:
• S p = ∑ n = 1 p ⁢ ⁢ f ⁡ ( W ⁡ [ n ] )
• where ƒ(W[n]) equals the compression potential of the nth data byte within the coding window;
• and
• means for swapping the coding scheme used to encode the data leaving the window from one scheme to another if the absolute value of the compression potential sum (|Sp|) is equal to or greater than a first predetermined value T.

A coding window circuit adapted to allow the analysis of the compression potential of data, the coding window circuit comprising:

• a first calculation circuit adapted to compute the compression potential of a data byte;
• a buffer having a physical buffer size (PBS), being coupled to the first calculation circuit and adapted to store a dynamically variable number (p) of data bytes, including the data byte and the computed compression potentials of each of the p stored data bytes, wherein p is less than or equal to PBS;
• a second calculation circuit coupled to the buffer and adapted to compute a compression potential sum based on the computed compression potentials of the p data bytes stored within the buffer;
• and
• a comparison circuit coupled to the second calculation circuit and adapted to generate a signal that swaps the coding scheme used to encode data bytes leaving the buffer from one scheme to another if the absolute value of the computed compression potential sum is greater than or equal to the first predetermined value T.