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Further improvements to JT9 decoder.

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Better AFC (wider range of possible drifts; more accurate DT alignment).
Better definition of metric tables used by Fano decoder.
Zero-centeres soft symbols, instead of offset +128.
Tuned several empirical parameters.


git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@5004 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
Joe Taylor 2015-03-04 17:07:15 +00:00
parent 127a60be68
commit 79538977c7
9 changed files with 51 additions and 32 deletions
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26
lib/afc9.f90
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@ -1,25 +1,32 @@
subroutine afc9(c3,npts,fsample,a,syncpk)
subroutine afc9(c3a,npts,fsample,a,syncpk)
complex c3(0:npts-1)
complex c3a(0:npts-1)
complex c3(0:1360-1)
real a(3),deltaa(3)
a(1)=0. !f0
a(2)=0. !f1
a(3)=0. !f2
deltaa(1)=0.4
deltaa(2)=0.1
deltaa(3)=0.1
deltaa(1)=1.736
deltaa(2)=1.736
deltaa(3)=1.0
nterms=3
! Start the iteration
chisqr=0.
chisqr0=1.e6
do iter=1,4 !One iteration is enough?
c3=c3a
a3=a(3)
do iter=1,4
do j=1,nterms
if(a(3).ne.a3) c3=cshift(c3a,nint(a(3)))
a3=a(3)
chisq1=fchisq(c3,npts,fsample,a)
fn=0.
delta=deltaa(j)
10 a(j)=a(j)+delta
if(a(3).ne.a3) c3=cshift(c3a,nint(a(3)))
a3=a(3)
chisq2=fchisq(c3,npts,fsample,a)
if(chisq2.eq.chisq1) go to 10
if(chisq2.gt.chisq1) then
@ -31,6 +38,8 @@ subroutine afc9(c3,npts,fsample,a,syncpk)
endif
20 fn=fn+1.0
a(j)=a(j)+delta
if(a(3).ne.a3) c3=cshift(c3a,nint(a(3)))
a3=a(3)
chisq3=fchisq(c3,npts,fsample,a)
if(chisq3.lt.chisq2) then
chisq1=chisq2
@ -41,16 +50,19 @@ subroutine afc9(c3,npts,fsample,a,syncpk)
! Find minimum of parabola defined by last three points
delta=delta*(1./(1.+(chisq1-chisq2)/(chisq3-chisq2))+0.5)
a(j)=a(j)-delta
deltaa(j)=deltaa(j)*fn/3.
if(j.lt.3) deltaa(j)=deltaa(j)*fn/3.
! write(*,4000) iter,j,a,-chisq2
!4000 format(i1,i2,3f10.4,f11.3)
enddo
if(a(3).ne.a3) c3=cshift(c3a,nint(a(3)))
a3=a(3)
chisqr=fchisq(c3,npts,fsample,a)
if(chisqr/chisqr0.gt.0.99) exit
chisqr0=chisqr
enddo
syncpk=-chisqr
c3a=c3
! write(*,4001) a,-chisq2
!4001 format(3x,3f10.4,f11.3)

15
lib/decjt9.f90
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@ -4,13 +4,14 @@ subroutine decjt9(ss,id2,nutc,nfqso,newdat,npts8,nfa,nfsplit,nfb,ntol, &
include 'constants.f90'
real ss(184,NSMAX)
character*22 msg
character*500 infile
real*4 ccfred(NSMAX)
real*4 red2(NSMAX)
logical ccfok(NSMAX)
logical done(NSMAX)
integer*2 id2(NTMAX*12000)
integer*1 i1SoftSymbols(207)
common/decstats/num65,numbm,numkv,num9,numfano
common/decstats/num65,numbm,numkv,num9,numfano,infile
save ccfred,red2
nsynced=0
@ -92,14 +93,12 @@ subroutine decjt9(ss,id2,nutc,nfqso,newdat,npts8,nfa,nfsplit,nfb,ntol, &
call timer('softsym ',0)
fpk=nf0 + df3*(i-1)
call softsym(id2,npts8,nsps8,newdat,fpk,syncpk,snrdb,xdt, &
freq,drift,schk,i1SoftSymbols)
freq,drift,a3,schk,i1SoftSymbols)
call timer('softsym ',1)
sync=(syncpk+1)/4.0
! if(maxval(i1SoftSymbols).eq.0) cycle
if(nqd.eq.1 .and. ((sync.lt.0.5) .or. (schk.lt.1.0))) cycle
if(nqd.ne.1 .and. ((sync.lt.1.0) .or. (schk.lt.1.5))) cycle
! if(nqd.ne.1 .and. ((sync.lt.1.0) .or. (schk.lt.1.8))) cycle
call timer('jt9fano ',0)
call jt9fano(i1SoftSymbols,limit,nlim,msg)
@ -117,14 +116,18 @@ subroutine decjt9(ss,id2,nutc,nfqso,newdat,npts8,nfa,nfsplit,nfb,ntol, &
if(nqd.eq.0) ndecodes0=ndecodes0+1
if(nqd.eq.1) ndecodes1=ndecodes1+1
!$omp critical(decode_results) ! serialize writes - see also jt65a.f90
!$omp critical(decode_results) ! serialize writes - see also jt65a.f90
write(*,1000) nutc,nsnr,xdt,nint(freq),msg
1000 format(i4.4,i4,f5.1,i5,1x,'@',1x,a22)
! i1=index(infile,'.wav')
! write(*,1000) infile(i1-11:i1-1),nsnr,xdt,nint(freq),msg, &
! schk,drift,a3,nlim
!1000 format(a11,i4,f5.1,i5,1x,'@',1x,a22,3f6.1,i6)
write(13,1002) nutc,nsync,nsnr,xdt,freq,ndrift,msg
1002 format(i4.4,i4,i5,f6.1,f8.0,i4,3x,a22,' JT9')
call flush(6)
call flush(13)
!$omp end critical(decode_results)
!$omp end critical(decode_results)
iaa=max(1,i-1)
ibb=min(NSMAX,i+22)

4
lib/fano232.f90
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@ -9,7 +9,7 @@ subroutine fano232(symbol,nbits,mettab,ndelta,maxcycles,dat, &
parameter (MAXBYTES=(MAXBITS+7)/8)
integer*1 symbol(0:2*MAXBITS-1) !Soft symbols (as unsigned i*1)
integer*1 dat(MAXBYTES) !Decoded user data, 8 bits per byte
integer mettab(0:255,0:1) !Metric table
integer mettab(-128:127,0:1) !Metric table
! These were the "node" structure in Karn's C code:
integer nstate(0:MAXBITS-1) !Encoder state of next node
@ -31,8 +31,6 @@ subroutine fano232(symbol,nbits,mettab,ndelta,maxcycles,dat, &
j=2*np
i4a=symbol(j)
i4b=symbol(j+1)
if (i4a.lt.0) i4a=i4a+256
if (i4b.lt.0) i4b=i4b+256
metrics(0,np) = mettab(i4a,0) + mettab(i4b,0)
metrics(1,np) = mettab(i4a,0) + mettab(i4b,1)
metrics(2,np) = mettab(i4a,1) + mettab(i4b,0)

3
lib/fillcom.f90
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@ -31,6 +31,7 @@ subroutine fillcom(nutc0,ndepth0,nrxfreq,mode,tx9,flow,fsplit,fhigh)
nmode=mode
end if
datetime="2013-Apr-16 15:13"
if(mode.eq.9 .and. nfsplit.ne.2700) nfa=nfsplit
return
end subroutine fillcom

2
lib/jt9.f90
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@ -39,7 +39,7 @@ program jt9
mousefqso,newdat,nfa,nfsplit,nfb,ntol,kin,nzhsym,nsynced,ndecoded
common/tracer/limtrace,lu
common/patience/npatience,nthreads
common/decstats/num65,numbm,numkv,num9,numfano
common/decstats/num65,numbm,numkv,num9,numfano,infile
data npatience/1/,nthreads/1/
do

14
lib/jt9fano.f90
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@ -14,7 +14,7 @@ subroutine jt9fano(i1SoftSymbols,limit,nlim,msg)
real*4 xx0(0:255)
logical first
integer*4 mettab(0:255,0:1)
integer*4 mettab(-128:127,0:1)
data first/.true./
data xx0/ & !Metric table
1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, &
@ -54,17 +54,21 @@ subroutine jt9fano(i1SoftSymbols,limit,nlim,msg)
if(first) then
! Get the metric table
bias=0.5
scale=10
scale=50
ndelta=nint(3.4*scale)
ib=160 !Break point
slope=2 !Slope beyond break
do i=0,255
mettab(i,0)=nint(scale*(xx0(i)-bias))
if(i.ge.1) mettab(256-i,1)=mettab(i,0)
mettab(i-128,0)=nint(scale*(xx0(i)-bias))
if(i.gt.ib) mettab(i-128,0)=mettab(ib-128,0) - slope*(i-ib)
if(i.ge.1) mettab(128-i,1)=mettab(i-128,0)
enddo
mettab(-128,1)=mettab(-127,1)
first=.false.
endif
msg=' '
nbits=72
ndelta=17
call fano232(i1SoftSymbols,nbits+31,mettab,ndelta,limit,i1DecodedBytes, &
ncycles,metric,ierr)

4
lib/softsym.f90
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@ -1,5 +1,5 @@
subroutine softsym(id2,npts8,nsps8,newdat,fpk,syncpk,snrdb,xdt, &
freq,drift,schk,i1SoftSymbols)
freq,drift,a3,schk,i1SoftSymbols)
! Compute the soft symbols
@ -28,6 +28,8 @@ subroutine softsym(id2,npts8,nsps8,newdat,fpk,syncpk,snrdb,xdt, &
call timer('afc9 ',1)
freq=fpk - a(1)
drift=-2.0*a(2)
a3=a(3)
a(3)=0.
call timer('twkfreq ',0)
call twkfreq(c3,c5,nz3,fsample,a) !Correct for delta f, f1, f2 ==> a(1:3)

7
lib/symspec2.f90
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@ -77,9 +77,10 @@ subroutine symspec2(c5,nz3,nsps8,nspsd,fsample,freq,drift,snrdb,schk, &
i4=nint(scale*(r1-r0))
if(i4.lt.-127) i4=-127
if(i4.gt.127) i4=127
i4=i4+128
if(i4.le.127) i1SoftSymbolsScrambled(k)=i4
if(i4.ge.128) i1SoftSymbolsScrambled(k)=i4-256
! i4=i4+128
! if(i4.le.127) i1SoftSymbolsScrambled(k)=i4
! if(i4.ge.128) i1SoftSymbolsScrambled(k)=i4-256
i1SoftSymbolsScrambled(k)=i4
enddo
enddo

8
lib/twkfreq.f90
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@ -13,13 +13,11 @@ subroutine twkfreq(c3,c4,npts,fsample,a)
s=2.0/npts
do i=1,npts
x=s*(i-x0)
if(mod(i,100).eq.1) then
p2=1.5*x*x - 0.5
p2=1.5*x*x - 0.5
! p3=2.5*(x**3) - 1.5*x
! p4=4.375*(x**4) - 3.75*(x**2) + 0.375
dphi=(a(1) + x*a(2) + p2*a(3)) * (twopi/fsample)
wstep=cmplx(cos(dphi),sin(dphi))
endif
dphi=(a(1) + x*a(2) + p2*a(3)) * (twopi/fsample)
wstep=cmplx(cos(dphi),sin(dphi))
w=w*wstep
c4(i)=w*c3(i)
enddo