2013-07-08 09:17:22 -04:00
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subroutine extract(s3,nadd,ncount,nhist,decoded,ltext,nbmkv)
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real s3(64,63)
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character decoded*22
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integer era(51),dat4(12),indx(64)
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integer mrsym(63),mr2sym(63),mrprob(63),mr2prob(63)
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logical nokv,ltext
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data nokv/.false./,nsec1/0/
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save
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nbmkv=0
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nfail=0
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1 continue
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call demod64a(s3,nadd,mrsym,mrprob,mr2sym,mr2prob,ntest,nlow)
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if(ntest.lt.50 .or. nlow.gt.20) then
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ncount=-999 !Flag bad data
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go to 900
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endif
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call chkhist(mrsym,nhist,ipk)
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if(nhist.ge.20) then
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nfail=nfail+1
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call pctile(s3,4032,50,base) ! ### or, use ave from demod64a
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do j=1,63
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s3(ipk,j)=base
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enddo
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if(nfail.gt.30) then
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decoded=' '
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ncount=-1
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go to 900
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endif
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go to 1
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endif
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call graycode65(mrsym,63,-1)
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call interleave63(mrsym,-1)
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call interleave63(mrprob,-1)
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! Decode using Berlekamp-Massey algorithm
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nemax=30 !Max BM erasures
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call indexx(63,mrprob,indx)
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do i=1,nemax
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j=indx(i)
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if(mrprob(j).gt.120) then
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ne2=i-1
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go to 2
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endif
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era(i)=j-1
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enddo
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ne2=nemax
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2 decoded=' '
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do nerase=0,ne2,2
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call rs_decode(mrsym,era,nerase,dat4,ncount)
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if(ncount.ge.0) then
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call unpackmsg(dat4,decoded)
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if(iand(dat4(10),8).ne.0) ltext=.true.
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nbmkv=1
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go to 900
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endif
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enddo
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! Berlekamp-Massey algorithm failed, try Koetter-Vardy
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if(nokv) go to 900
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maxe=8 !Max KV errors in 12 most reliable symbols
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2013-07-17 15:13:36 -04:00
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! xlambda=12.0
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xlambda=7.99
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2013-07-08 09:17:22 -04:00
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call graycode65(mr2sym,63,-1)
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call interleave63(mr2sym,-1)
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call interleave63(mr2prob,-1)
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nsec1=nsec1+1
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write(22,rec=1) nsec1,xlambda,maxe,200,mrsym,mrprob,mr2sym,mr2prob
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call flush(22)
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call timer('kvasd ',0)
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#ifdef UNIX
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iret=system('./kvasd -q > dev_null')
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#else
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iret=system('kvasd -q > dev_null')
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#endif
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call timer('kvasd ',1)
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if(iret.ne.0) then
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if(.not.nokv) write(*,1000)
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1000 format('Error in KV decoder, or no KV decoder present.')
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nokv=.true.
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go to 900
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endif
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read(22,rec=2,err=900) nsec2,ncount,dat4
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j=nsec2 !Silence compiler warning
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decoded=' '
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ltext=.false.
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if(ncount.ge.0) then
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call unpackmsg(dat4,decoded) !Unpack the user message
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if(iand(dat4(10),8).ne.0) ltext=.true.
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nbmkv=2
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endif
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900 continue
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return
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end subroutine extract
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