2012-10-02 20:41:07 -04:00
|
|
|
subroutine decode9(i1SoftSymbols,msg)
|
|
|
|
|
|
|
|
|
|
! Decoder for JT9
|
|
|
|
|
! Input: i1SoftSymbols(207) - Single-bit soft symbols
|
|
|
|
|
! Output: msg - decoded message (blank if erasure)
|
|
|
|
|
|
|
|
|
|
character*22 msg
|
|
|
|
|
integer*4 i4DecodedBytes(9)
|
|
|
|
|
integer*4 i4Decoded6BitWords(12)
|
|
|
|
|
integer*1 i1DecodedBytes(13) !72 bits and zero tail as 8-bit bytes
|
|
|
|
|
integer*1 i1SoftSymbols(207)
|
|
|
|
|
integer*1 i1DecodedBits(72)
|
|
|
|
|
|
|
|
|
|
integer*1 i1
|
|
|
|
|
logical first
|
|
|
|
|
integer*4 mettab(0:255,0:1)
|
|
|
|
|
equivalence (i1,i4)
|
|
|
|
|
data first/.true./
|
|
|
|
|
save
|
|
|
|
|
|
|
|
|
|
if(first) then
|
|
|
|
|
! Get the metric table
|
2012-10-06 11:38:06 -04:00
|
|
|
! bias=0.37 !To be optimized, in decoder program
|
|
|
|
|
bias=0.0 !Seems better, in jt9.exe ???
|
2012-10-02 20:41:07 -04:00
|
|
|
scale=10 ! ... ditto ...
|
|
|
|
|
open(19,file='met8.21',status='old')
|
|
|
|
|
do i=0,255
|
|
|
|
|
read(19,*) x00,x0,x1
|
|
|
|
|
mettab(i,0)=nint(scale*(x0-bias))
|
|
|
|
|
mettab(i,1)=nint(scale*(x1-bias)) !### Check range, etc. ###
|
|
|
|
|
enddo
|
|
|
|
|
close(19)
|
|
|
|
|
first=.false.
|
|
|
|
|
endif
|
|
|
|
|
|
|
|
|
|
msg=' '
|
|
|
|
|
nbits=72
|
|
|
|
|
ndelta=17
|
2012-10-03 09:26:52 -04:00
|
|
|
limit=10000
|
2012-10-02 20:41:07 -04:00
|
|
|
call fano232(i1SoftSymbols,nbits+31,mettab,ndelta,limit,i1DecodedBytes, &
|
2012-10-20 12:37:01 -04:00
|
|
|
ncycles,metric,ierr)
|
2012-10-02 20:41:07 -04:00
|
|
|
|
|
|
|
|
if(ncycles.lt.(nbits*limit)) then
|
|
|
|
|
nbytes=(nbits+7)/8
|
|
|
|
|
do i=1,nbytes
|
|
|
|
|
n=i1DecodedBytes(i)
|
|
|
|
|
i4DecodedBytes(i)=iand(n,255)
|
|
|
|
|
enddo
|
|
|
|
|
call unpackbits(i4DecodedBytes,nbytes,8,i1DecodedBits)
|
|
|
|
|
call packbits(i1DecodedBits,12,6,i4Decoded6BitWords)
|
|
|
|
|
call unpackmsg(i4Decoded6BitWords,msg) !Unpack decoded msg
|
|
|
|
|
endif
|
|
|
|
|
|
|
|
|
|
return
|
|
|
|
|
end subroutine decode9
|
