2012-10-02 20:41:07 -04:00
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subroutine decode9(i1SoftSymbols,msg)
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! Decoder for JT9
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! Input: i1SoftSymbols(207) - Single-bit soft symbols
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! Output: msg - decoded message (blank if erasure)
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character*22 msg
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integer*4 i4DecodedBytes(9)
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integer*4 i4Decoded6BitWords(12)
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integer*1 i1DecodedBytes(13) !72 bits and zero tail as 8-bit bytes
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integer*1 i1SoftSymbols(207)
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integer*1 i1DecodedBits(72)
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integer*1 i1
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logical first
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integer*4 mettab(0:255,0:1)
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equivalence (i1,i4)
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data first/.true./
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save
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if(first) then
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! Get the metric table
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2012-10-06 11:38:06 -04:00
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! bias=0.37 !To be optimized, in decoder program
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bias=0.0 !Seems better, in jt9.exe ???
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2012-10-02 20:41:07 -04:00
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scale=10 ! ... ditto ...
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open(19,file='met8.21',status='old')
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do i=0,255
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read(19,*) x00,x0,x1
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mettab(i,0)=nint(scale*(x0-bias))
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mettab(i,1)=nint(scale*(x1-bias)) !### Check range, etc. ###
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enddo
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close(19)
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first=.false.
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endif
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msg=' '
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nbits=72
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ndelta=17
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2012-10-20 16:52:29 -04:00
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limit=100000
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2012-10-02 20:41:07 -04:00
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call fano232(i1SoftSymbols,nbits+31,mettab,ndelta,limit,i1DecodedBytes, &
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2012-10-20 12:37:01 -04:00
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ncycles,metric,ierr)
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2012-10-02 20:41:07 -04:00
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if(ncycles.lt.(nbits*limit)) then
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nbytes=(nbits+7)/8
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do i=1,nbytes
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n=i1DecodedBytes(i)
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i4DecodedBytes(i)=iand(n,255)
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enddo
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call unpackbits(i4DecodedBytes,nbytes,8,i1DecodedBits)
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call packbits(i1DecodedBits,12,6,i4Decoded6BitWords)
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call unpackmsg(i4Decoded6BitWords,msg) !Unpack decoded msg
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endif
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return
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end subroutine decode9
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