{HEAD ~ An error measure} is generated as {TAIL ~ a function} of the decoded pixels of the decoded region and the previous pixels of a previous region 
is generated as
{ HEAD ~ An error measure } is generated as { TAIL ~ a function } of the decoded pixels of the decoded region and the previous pixels of a previous region
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH