WSJT-X/lib/decoder.f90

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subroutine decoder(ntrSeconds,c0)
! Decoder for JT9. Can run stand-alone, reading data from *.wav files;
! or as the back end of wsjt-x, with data placed in a shared memory region.
! NB: For unknown reason, ***MUST*** be compiled by g95 with -O0 !!!
parameter (NMAX=1800*12000) !Total sample intervals per 30 minutes
parameter (NDMAX=1800*1500) !Sample intervals at 1500 Hz rate
parameter (NSMAX=22000) !Max length of saved spectra
character*22 msg
real*4 ccfred(NSMAX)
integer*1 i1SoftSymbols(207)
integer*2 id2
complex c0(NDMAX)
common/jt9com/ss(184,NSMAX),savg(NSMAX),id2(NMAX),nutc,ndiskdat, &
ntr,nfqso,nagain,newdat,npts8,nfb,ntol,kin
ntrMinutes=ntrSeconds/60
newdat=1
nsps=0
if(ntrMinutes.eq.1) then
nsps=6912
df3=1500.0/2048.0
else if(ntrMinutes.eq.2) then
nsps=15360
df3=1500.0/2048.0
else if(ntrMinutes.eq.5) then
nsps=40960
df3=1500.0/6144.0
else if(ntrMinutes.eq.10) then
nsps=82944
df3=1500.0/12288.0
else if(ntrMinutes.eq.30) then
nsps=252000
df3=1500.0/32768.0
endif
if(nsps.eq.0) stop 'Error: bad TRperiod' !Better: return an error code###
! Now do the decoding
kstep=nsps/2
tstep=kstep/12000.0
! Get sync, approx freq
call sync9(ss,tstep,df3,ntol,nfqso,sync,snr,fpk0,ccfred)
call spec9(c0,npts8,nsps,fpk0,fpk,xdt,i1SoftSymbols)
call decode9(i1SoftSymbols,msg)
open(13,file='decoded.txt',status='unknown')
rewind 13
! write(*,1010) nutc,sync,xdt,1000.0+fpk,msg
nsync=sync
nsnr=nint(snr)
width=0.0
write(13,1010) nutc,nsync,nsnr,xdt,1000.0+fpk,width,msg
1010 format(i4.4,i4,i5,f6.1,f8.2,f6.2,3x,a22)
call flush(13)
close(13)
return
end subroutine decoder