Category:Recompression
From Just Solve the File Format Problem
Recompression involves a special-purpose algorithm that losslessly compresses a specific standard (typically already compressed) format, to an incompatible format, taking advantage of the properties of the standard format to improve the compression.
Decompressing such a file restores the original format. The decompressed file will be at least functionally identical to the original, and for some recompression formats is guaranteed to be byte-for-byte identical.