2014-12-02 19:06:54 -05:00
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subroutine extract(s3,nadd,ncount,nhist,decoded,ltext,nbmkv)
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!subroutine extract(s3,nadd,nbirdie,afac1,xlambda,ncount,nhist,decoded, &
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! ltext,nbmkv,ntest)
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! Input:
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! s3 64-point spectra for each of 63 data symbols
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! nadd number of spectra summed into s3
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! Output:
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! ncount number of symbols requiring correction
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! nhist maximum number of identical symbol values
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! decoded decoded message (if ncount >=0)
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! ltext true if decoded message is free text
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! nbmkv 0=no decode; 1=BM decode; 2=KV decode
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use prog_args !shm_key, exe_dir, data_dir
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real s3(64,63)
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character decoded*22
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integer dat4(12)
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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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nbirdie=7
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npct=40
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afac1=10.1
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xlambda=8.0
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nbmkv=0
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nfail=0
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decoded=' '
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call pctile(s3,4032,npct,base)
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s3=s3/base
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! Get most reliable and second-most-reliable symbol values, and their
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! probabilities
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1 call demod64a(s3,nadd,afac1,mrsym,mrprob,mr2sym,mr2prob,ntest,nlow)
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if(ntest.lt.100) then
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ncount=-999 !Flag and reject bad data
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go to 900
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endif
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call chkhist(mrsym,nhist,ipk) !Test for birdies and QRM
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if(nhist.ge.nbirdie) then
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nfail=nfail+1
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call pctile(s3,4032,npct,base)
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s3(ipk,1:63)=base
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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) !Remove gray code and interleaving
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call interleave63(mrsym,-1) !from most reliable symbols
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call interleave63(mrprob,-1)
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! Decode using Berlekamp-Massey algorithm
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call timer('rs_decod',0)
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call rs_decode(mrsym,0,0,dat4,ncount)
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call timer('rs_decod',1)
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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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! 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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call graycode65(mr2sym,63,-1) !Remove gray code and interleaving
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call interleave63(mr2sym,-1) !from second-most-reliable symbols
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call interleave63(mr2prob,-1)
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nsec1=nsec1+1
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dat4=0
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write(22,rec=1) nsec1,xlambda,maxe,200,mrsym,mrprob,mr2sym,mr2prob
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write(22,rec=2) -1,-1,dat4
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call flush(22)
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call timer('kvasd ',0)
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#ifdef WIN32
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iret=system('""'//trim(exe_dir)//'/kvasd" "'//trim(temp_dir)//'/kvasd.dat" >"'//trim(temp_dir)//'/dev_null""')
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#else
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iret=system('"'//trim(exe_dir)//'/kvasd" "'//trim(temp_dir)//'/kvasd.dat" >/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) iret
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1000 format('Error in KV decoder, or no KV decoder present.',i12)
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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(index(decoded,'...... ').gt.0) then
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ncount=-1
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go to 900
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endif
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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 return
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end subroutine extract
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