The following formula describes the approximate amount of memory used by GeoExpress to compress a single image to the MrSID Generation 2 (MG2) format:
Memory = ((8 + 4 x BlockSize + 64) x NumBands x Width x 4) + ( 0.005 x ExpectedOutputFileSize ) 
Memory is the estimated memory usage in bytes.BlockSize is set by the user on Format-Specifictab of the Advanced Job Options dialog box. For more information on block size, see Block Size for MG2.NumBands is the number of bands in the image to be encoded – typically 1 or 3 (This value is noted in the Properties tab.)Width is the width of the input image in pixels. (This value is noted in the Properties tab.)ExpectedOutputFileSize is the target file size. (This value is noted in the Properties tab.)