such that decoding the second coded portion relies on {HEAD ~ an output} from decoding {TAIL ~ the first coded portion}; and 
such that decoding the second coded portion relies on { HEAD ~ an output } from decoding { TAIL ~ the first coded portion } ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH