To despeckle existing MG3, MG4 and JPEG 2000 images without reencoding:
Use the -despeckleonly/-dsonly switch. For example:
mrsidgeoencoder -i foo.sid -o foo2.sid -despeckleonly
NOTE: If you use this switch, you cannot specify any other encoding options except for tile length markers (-tlm/-tilelengthmarkers - specify zero to disable), packet length markers (-plt/-packetlengthmarkers or -noplt/-nopltmarkers), and tile parts (-tp/-tileparts - specify N to disable). (For more information see JPEG 2000 Encoding.)