WSJT-X/lib/msk144_decode.f90

84 lines
2.3 KiB
Fortran
Raw Normal View History

subroutine msk144_decode(id2,npts,nutc,nprint,line)
! Calls the experimental decoder for JTMSK 72ms ldpc messages
parameter (NMAX=30*12000)
parameter (NFFTMAX=512*1024)
parameter (NSPM=864) !Samples per JTMSK long message
integer*2 id2(0:NMAX) !Raw i*2 data, up to T/R = 30 s
integer hist(0:32868)
real d(0:NMAX) !Raw r*4 data
real ty(NMAX/512) !Ping times
real yellow(NMAX/512)
complex c(NFFTMAX) !Complex (analytic) data
complex cdat(24000) !Short segments, up to 2 s
complex cdat2(24000)
character*22 msg,msg0 !Decoded message
character*80 line(100) !Decodes passed back to caller
equivalence (hist,d)
nsnr0=-99
nline=0
line(1:100)(1:1)=char(0)
msg0=' '
msg=msg0
hist=0
do i=0,npts-1
n=abs(id2(i))
hist(n)=hist(n)+1
enddo
ns=0
do n=0,32768
ns=ns+hist(n)
if(ns.gt.npts/2) exit
enddo
fac=1.0/(1.5*n)
d(0:npts-1)=fac*id2(0:npts-1)
! rms=sqrt(dot_product(d(0:npts-1),d(0:npts-1))/npts)
!### Would it be better to set median rms to 1.0 ?
! d(0:npts-1)=d(0:npts-1)/rms !Normalize so that rms=1.0
call mskdt(d,npts,ty,yellow,nyel)
nyel=min(nyel,100)
n=log(float(npts))/log(2.0) + 1.0
nfft=min(2**n,1024*1024)
call analytic(d,npts,nfft,c) !Convert to analytic signal and filter
nafter=2*NSPM
nbefore=NSPM
! Process ping list (sorted by S/N) from top down.
do n=1,nyel
ia=ty(n)*12000.0 - nbefore
if(ia.lt.1) ia=1
ib=ia + nbefore + nafter - 1
if(ib.gt.NFFTMAX) ib=NFFTMAX
iz=ib-ia+1
cdat2(1:iz)=c(ia:ib) !Select nlen complex samples
t0=ia/12000.0
call syncmsk144(cdat2,iz,msg,freq)
if(msg(1:1).ne.' ') then
! if(msg.ne.msg0) then
nline=nline+1
nsnr0=-99
! endif
y=10.0**(0.1*(yellow(n)-1.5))
nsnr=max(-5,nint(db(y)))
! if(nsnr.gt.nsnr0 .and. nline.gt.0) then
write(line(nline),1020) nutc,nsnr,t0,nint(freq),msg
if(nprint.ne.0) write(*,1020) nutc,nsnr,t0,nint(freq),msg
1020 format(i6.6,i4,f5.1,i5,' & ',a22)
nsnr0=nsnr
! go to 900
! endif
msg0=msg
endif
enddo
900 continue
return
end subroutine msk144_decode