WSJT-X/lib/ft4/get_ft4_bitmetrics.f90
2020-03-19 13:45:13 -04:00

117 lines
3.0 KiB
Fortran

subroutine get_ft4_bitmetrics(cd,bitmetrics,badsync)
include 'ft4_params.f90'
parameter (NSS=NSPS/NDOWN,NDMAX=NMAX/NDOWN)
complex cd(0:NN*NSS-1)
complex cs(0:3,NN)
complex csymb(NSS)
integer icos4a(0:3),icos4b(0:3),icos4c(0:3),icos4d(0:3)
integer graymap(0:3)
integer ip(1)
logical one(0:255,0:7) ! 256 4-symbol sequences, 8 bits
logical first
logical badsync
real bitmetrics(2*NN,3)
real s2(0:255)
real s4(0:3,NN)
data icos4a/0,1,3,2/
data icos4b/1,0,2,3/
data icos4c/2,3,1,0/
data icos4d/3,2,0,1/
data graymap/0,1,3,2/
data first/.true./
save first,one
if(first) then
one=.false.
do i=0,255
do j=0,7
if(iand(i,2**j).ne.0) one(i,j)=.true.
enddo
enddo
first=.false.
endif
do k=1,NN
i1=(k-1)*NSS
csymb=cd(i1:i1+NSS-1)
call four2a(csymb,NSS,1,-1,1)
cs(0:3,k)=csymb(1:4)
s4(0:3,k)=abs(csymb(1:4))
enddo
! Sync quality check
is1=0
is2=0
is3=0
is4=0
badsync=.false.
ibmax=0
do k=1,4
ip=maxloc(s4(:,k))
if(icos4a(k-1).eq.(ip(1)-1)) is1=is1+1
ip=maxloc(s4(:,k+33))
if(icos4b(k-1).eq.(ip(1)-1)) is2=is2+1
ip=maxloc(s4(:,k+66))
if(icos4c(k-1).eq.(ip(1)-1)) is3=is3+1
ip=maxloc(s4(:,k+99))
if(icos4d(k-1).eq.(ip(1)-1)) is4=is4+1
enddo
nsync=is1+is2+is3+is4 !Number of correct hard sync symbols, 0-16
if(nsync .lt. 8) then
badsync=.true.
return
endif
do nseq=1,3 !Try coherent sequences of 1, 2, and 4 symbols
if(nseq.eq.1) nsym=1
if(nseq.eq.2) nsym=2
if(nseq.eq.3) nsym=4
nt=2**(2*nsym)
do ks=1,NN-nsym+1,nsym !87+16=103 symbols.
amax=-1.0
do i=0,nt-1
i1=i/64
i2=iand(i,63)/16
i3=iand(i,15)/4
i4=iand(i,3)
if(nsym.eq.1) then
s2(i)=abs(cs(graymap(i4),ks))
elseif(nsym.eq.2) then
s2(i)=abs(cs(graymap(i3),ks)+cs(graymap(i4),ks+1))
elseif(nsym.eq.4) then
s2(i)=abs(cs(graymap(i1),ks ) + &
cs(graymap(i2),ks+1) + &
cs(graymap(i3),ks+2) + &
cs(graymap(i4),ks+3) &
)
else
print*,"Error - nsym must be 1, 2, or 4."
endif
enddo
ipt=1+(ks-1)*2
if(nsym.eq.1) ibmax=1
if(nsym.eq.2) ibmax=3
if(nsym.eq.4) ibmax=7
do ib=0,ibmax
bm=maxval(s2(0:nt-1),one(0:nt-1,ibmax-ib)) - &
maxval(s2(0:nt-1),.not.one(0:nt-1,ibmax-ib))
if(ipt+ib.gt.2*NN) cycle
bitmetrics(ipt+ib,nseq)=bm
enddo
enddo
enddo
bitmetrics(205:206,2)=bitmetrics(205:206,1)
bitmetrics(201:204,3)=bitmetrics(201:204,2)
bitmetrics(205:206,3)=bitmetrics(205:206,1)
call normalizebmet(bitmetrics(:,1),2*NN)
call normalizebmet(bitmetrics(:,2),2*NN)
call normalizebmet(bitmetrics(:,3),2*NN)
return
end subroutine get_ft4_bitmetrics