Each second block portion is {HEAD ~ transform} processed to generate a plurality of {TAIL ~ transformed block portions}, and it is determined which transformed block portion is most similar to a preselected first block portion 
Each second block portion is { HEAD ~ transform } processed to generate a plurality of { TAIL ~ transformed block portions } , and it is determined which transformed block portion is most similar to a preselected first block portion
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH