WSJT-X/lib/extract.F90

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3.3 KiB
Fortran
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subroutine extract(s3,nadd,nqd,ncount,nhist,decoded,ltext,nbmkv)
! Input:
! s3 64-point spectra for each of 63 data symbols
! nadd number of spectra summed into s3
! nqd 0/1 to indicate decode attempt at QSO frequency
! Output:
! ncount number of symbols requiring correction
! nhist maximum number of identical symbol values
! decoded decoded message (if ncount >=0)
! ltext true if decoded message is free text
! nbmkv 0=no decode; 1=BM decode; 2=KV decode
use prog_args !shm_key, exe_dir, data_dir
real s3(64,63)
character decoded*22
integer dat4(12)
integer mrsym(63),mr2sym(63),mrprob(63),mr2prob(63)
logical nokv,ltext
common/decstats/num65,numbm,numkv,num9,numfano
data nokv/.false./,nsec1/0/
save
nbirdie=7
npct=40
afac1=10.1
xlambda=7.999
if(nqd.eq.1) xlambda=11.999 !Increase depth at QSO frequency
nbmkv=0
nfail=0
decoded=' '
call pctile(s3,4032,npct,base)
s3=s3/base
! Get most reliable and second-most-reliable symbol values, and their
! probabilities
1 call demod64a(s3,nadd,afac1,mrsym,mrprob,mr2sym,mr2prob,ntest,nlow)
if(ntest.lt.100) then
ncount=-999 !Flag and reject bad data
go to 900
endif
call chkhist(mrsym,nhist,ipk) !Test for birdies and QRM
if(nhist.ge.nbirdie) then
nfail=nfail+1
call pctile(s3,4032,npct,base)
s3(ipk,1:63)=base
if(nfail.gt.30) then
decoded=' '
ncount=-1
go to 900
endif
go to 1
endif
call graycode65(mrsym,63,-1) !Remove gray code and interleaving
call interleave63(mrsym,-1) !from most reliable symbols
call interleave63(mrprob,-1)
num65=num65+1
! Decode using Berlekamp-Massey algorithm
call timer('rs_decod',0)
call rs_decode(mrsym,0,0,dat4,ncount)
call timer('rs_decod',1)
if(ncount.ge.0) then
call unpackmsg(dat4,decoded)
if(iand(dat4(10),8).ne.0) ltext=.true.
nbmkv=1
go to 900
endif
! Berlekamp-Massey algorithm failed, try Koetter-Vardy
if(nokv) go to 900
maxe=8 !Max KV errors in 12 most reliable symbols
call graycode65(mr2sym,63,-1) !Remove gray code and interleaving
call interleave63(mr2sym,-1) !from second-most-reliable symbols
call interleave63(mr2prob,-1)
nsec1=nsec1+1
dat4=0
write(22,rec=1) nsec1,xlambda,maxe,200,mrsym,mrprob,mr2sym,mr2prob
write(22,rec=2) -1,-1,dat4
call flush(22)
call timer('kvasd ',0)
#ifdef WIN32
iret=system('""'//trim(exe_dir)//'/kvasd" "'//trim(temp_dir)//'/kvasd.dat" >"'//trim(temp_dir)//'/dev_null""')
#else
iret=system('"'//trim(exe_dir)//'/kvasd" "'//trim(temp_dir)//'/kvasd.dat" >/dev/null')
#endif
call timer('kvasd ',1)
if(iret.ne.0) then
if(.not.nokv) write(*,1000) iret
1000 format('Error in KV decoder, or no KV decoder present.',i12)
! nokv=.true.
go to 900
endif
read(22,rec=2,err=900) nsec2,ncount,dat4
j=nsec2 !Silence compiler warning
decoded=' '
ltext=.false.
if(ncount.ge.0) then
call unpackmsg(dat4,decoded) !Unpack the user message
if(index(decoded,'...... ').gt.0) then
ncount=-1
go to 900
endif
if(iand(dat4(10),8).ne.0) ltext=.true.
nbmkv=2
endif
900 continue
return
end subroutine extract