mirror of https://github.com/saitohirga/WSJT-X.git
177 lines
4.8 KiB
Fortran
177 lines
4.8 KiB
Fortran
subroutine decode24(dat,npts,dtx,dfx,flip,mode,mode4,decoded,ncount, &
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deepbest,qbest,submode)
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! Decodes JT65 data, assuming that DT and DF have already been determined.
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parameter (MAXAVE=120)
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real dat(npts) !Raw data
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character decoded*22,deepmsg*22,deepbest*22
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character*12 mycall,hiscall
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character*6 hisgrid
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character*72 c72
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character submode*1
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real*8 dt,df,phi,f0,dphi,twopi,phi1,dphi1
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complex*16 cz,cz1,c0,c1
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integer*1 symbol(207)
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real*4 rsymbol(207,7)
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real*4 sym(207)
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integer nsum(7)
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integer*1 data1(13) !Decoded data (8-bit bytes)
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integer data4a(9) !Decoded data (8-bit bytes)
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integer data4(12) !Decoded data (6-bit bytes)
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integer amp,delta
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integer mettab(0:255,0:1) !Metric table
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integer nch(7)
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integer npr2(207)
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common/ave/ppsave(207,7,MAXAVE),nflag(MAXAVE),nsave,iseg(MAXAVE)
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data mode0/-999/
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data nsum/7*0/,rsymbol/1449*0.0/
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data npr2/ &
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0,0,0,0,1,1,0,0,0,1,1,0,1,1,0,0,1,0,1,0,0,0,0,0,0,0,1,1,0,0, &
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0,0,0,0,0,0,0,0,0,0,1,0,1,1,0,1,1,0,1,0,1,1,1,1,1,0,1,0,0,0, &
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1,0,0,1,0,0,1,1,1,1,1,0,0,0,1,0,1,0,0,0,1,1,1,1,0,1,1,0,0,1, &
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0,0,0,1,1,0,1,0,1,0,1,0,1,0,1,1,1,1,1,0,1,0,1,0,1,1,0,1,0,1, &
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0,1,1,1,0,0,1,0,1,1,0,1,1,1,1,0,0,0,0,1,1,0,1,1,0,0,0,1,1,1, &
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0,1,1,1,0,1,1,1,0,0,1,0,0,0,1,1,0,1,1,0,0,1,0,0,0,1,1,1,1,1, &
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1,0,0,1,1,0,0,0,0,1,1,0,0,0,1,0,1,1,0,1,1,1,1,0,1,0,1/
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data nch/1,2,4,9,18,36,72/
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save mettab,mode0,nsum,rsymbol
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if(mode.ne.mode0) call getmet24(mode,mettab)
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mode0=mode
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twopi=8*atan(1.d0)
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dt=2.d0/11025 !Sample interval (2x downsampled data)
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df=11025.d0/2520.d0
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nsym=206
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amp=15
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istart=nint(dtx/dt) !Start index for synced FFTs
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if(istart.lt.0) istart=0
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nchips=0
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ich=0
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qbest=0.
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deepmsg=' '
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ichbest=-1
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! Should amp be adjusted according to signal strength?
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! Compute soft symbols using differential BPSK demodulation
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c0=0. !### C0=amp ???
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k=istart
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phi=0.d0
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phi1=0.d0
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40 ich=ich+1
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nchips=nch(ich)
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nspchip=1260/nchips
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k=istart
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phi=0.d0
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phi1=0.d0
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fac2=1.e-8 * sqrt(float(mode4))
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do j=1,nsym+1
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if(flip.gt.0.0) then
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f0=1270.46 + dfx + (npr2(j)-1.5)*mode4*df
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f1=1270.46 + dfx + (2+npr2(j)-1.5)*mode4*df
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else
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f0=1270.46 + dfx + (1-npr2(j)-1.5)*mode4*df
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f1=1270.46 + dfx + (3-npr2(j)-1.5)*mode4*df
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endif
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dphi=twopi*dt*f0
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dphi1=twopi*dt*f1
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sq0=0.
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sq1=0.
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do nc=1,nchips
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phi=0.d0
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phi1=0.d0
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c0=0.
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c1=0.
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do i=1,nspchip
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k=k+1
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phi=phi+dphi
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phi1=phi1+dphi1
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cz=dcmplx(cos(phi),-sin(phi))
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cz1=dcmplx(cos(phi1),-sin(phi1))
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if(k.le.npts) then
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c0=c0 + dat(k)*cz
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c1=c1 + dat(k)*cz1
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endif
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enddo
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sq0=sq0 + real(c0)**2 + aimag(c0)**2
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sq1=sq1 + real(c1)**2 + aimag(c1)**2
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enddo
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sq0=fac2*sq0
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sq1=fac2*sq1
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rsym=amp*(sq1-sq0)
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r=rsym+128.
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if(r.gt.255.0) r=255.0
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if(r.lt.0.0) r=0.0
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i4=nint(r)
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if(i4.gt.127) i4=i4-256
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if(j.ge.1) then
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symbol(j)=i4
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! rsymbol(j,ich)=rsymbol(j,ich) + rsym
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rsymbol(j,ich)=rsym
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sym(j)=rsym
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endif
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enddo
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!### The following does simple message averaging:
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! nsum(ich)=nsum(ich)+1
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! do j=1,207
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! sym(j)=rsymbol(j,ich)/nsum(ich)
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! r=sym(j) + 128.
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! if(r.gt.255.0) r=255.0
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! if(r.lt.0.0) r=0.0
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! i4=nint(r)
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! if(i4.gt.127) i4=i4-256
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! symbol(j)=i4
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! enddo
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!###
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call extract4(sym,nadd,ncount,decoded) !Do the KV decode
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qual=0. !Now try deep search
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neme=1
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mycall='VK7MO'
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hiscall='W5LUA'
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hisgrid='EM13'
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call deep24(sym(2),neme,flip,mycall,hiscall,hisgrid,deepmsg,qual)
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if(qual.gt.qbest) then
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qbest=qual
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deepbest=deepmsg
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ichbest=ich
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endif
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if(ncount.ge.0) go to 100
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if(mode.eq.7 .and. nchips.lt.mode4) go to 40
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100 continue
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!100 do i=1,9
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! i4=data1(i)
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! if(i4.lt.0) i4=i4+256
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! data4a(i)=i4
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! enddo
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! write(c72,1100) (data4a(i),i=1,9)
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!1100 format(9b8.8)
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! read(c72,1102) data4
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!1102 format(12b6)
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! decoded=' '
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! submode=' '
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if(ncount.lt.0) then
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decoded=deepbest
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submode=char(ichar('A')+ichbest-1)
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qual=qbest
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endif
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! if(decoded(1:6).eq.'000AAA') then
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! decoded='***WRONG MODE?***'
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! ncount=-1
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! endif
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! Save symbol spectra for possible decoding of average.
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ppsave(1:207,1:7,nsave)=rsymbol(1:207,1:7)
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return
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end subroutine decode24
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