Further improvements to JT9 decoder.

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

lib/afc9.f90

@@ -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(1)=1.736
-  deltaa(2)=0.1
+  deltaa(2)=1.736
-  deltaa(3)=0.1
+  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)
 

lib/decjt9.f90

@@ -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)

lib/fano232.f90

@@ -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)

lib/fillcom.f90

@@ -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

lib/jt9.f90

@@ -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

lib/jt9fano.f90

@@ -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))
+        mettab(i-128,0)=nint(scale*(xx0(i)-bias))
-        if(i.ge.1) mettab(256-i,1)=mettab(i,0)
+        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)
 

lib/softsym.f90

@@ -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)

lib/symspec2.f90

@@ -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
+!        i4=i4+128
-        if(i4.le.127) i1SoftSymbolsScrambled(k)=i4
+!        if(i4.le.127) i1SoftSymbolsScrambled(k)=i4
-        if(i4.ge.128) i1SoftSymbolsScrambled(k)=i4-256
+!        if(i4.ge.128) i1SoftSymbolsScrambled(k)=i4-256
+        i1SoftSymbolsScrambled(k)=i4
      enddo
   enddo
 

lib/twkfreq.f90

@@ -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)
+     dphi=(a(1) + x*a(2) + p2*a(3)) * (twopi/fsample)
-        wstep=cmplx(cos(dphi),sin(dphi))
+     wstep=cmplx(cos(dphi),sin(dphi))
-     endif
      w=w*wstep
      c4(i)=w*c3(i)
   enddo