WSJT-X/libm65/rtping.f90
Joe Taylor 5079669e49 Now have a properly functioning stand-along decoder for JTMSK.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/jtms3@2529 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2012-07-19 18:01:14 +00:00

93 lines
2.6 KiB
Fortran

subroutine rtping(dat,k,cfile6,MinSigdB,MouseDF,ntol,mycall)
! Called from datasink() every 2048 sample intervals (approx 43 ms).
! Detects pings (signal level above MinSigdB). When a ping ends, its
! MSK signal is synchronized and decoded.
parameter (NSMAX=30*48000)
parameter (NZMAX=703) !703 = NSMAX/2048
real dat(NSMAX) !Raw audio data
character*6 cfile6 !Time hhmmss at start of this Rx interval
character*12 mycall
real sig(NZMAX) !Sq-law detected signal, sampled at 43 ms
real sigdb(NZMAX) !Signal in dB, sampled at 43 ms
real tmp(NZMAX)
logical inside,pingFound
data k0/9999999/
save
if(k.lt.k0) then
inside=.false.
pingFound=.false.
j0=0
t1=0.
width=0.
peak=0.
tpk=0.
dt=1.0/48000.0
kstep=2048
sdt=dt*kstep
wmin=0.043
endif
k0=k
slim=MinSigdB
snrlim=10.0**(0.1*slim) - 1.0
sdown=10.0*log10(0.25*snrlim+1.0)
! Find signal power
j=k/kstep
sig(j)=dot_product(dat(k-kstep+1:k),dat(k-kstep+1:k))/kstep
if(j.lt.20) return
! Determine baseline noise level
if(mod(j,20).eq.0) call pctile (sig,tmp,j,50,base)
sigdb(j)=db(sig(j)/base) ! (S+N)/N in dB
! write(72,3001) j*sdt,base,sig(j),sigdb(j)
!3001 format(f10.3,3f12.6)
if(sigdb(j).ge.slim .and. .not.inside) then
j0=j !Mark the start of a ping
t1=j0*sdt
inside=.true.
peak=0.
endif
if(inside .and. sigdb(j).gt.peak) then
peak=sigdb(j) !Save peak strength
tpk=j*sdt ! and time of peak
endif
if(inside .and. (sigdb(j).lt.sdown .or. j.eq.NZMAX)) then
width=(j-j0)*sdt !Save ping width
if(width.ge.wmin) pingFound=.true.
endif
if(.not.pingFound) return
! A ping was found! Assemble a signal report:
nwidth=0
if(width.ge.0.04) nwidth=1
if(width.ge.0.12) nwidth=2
if(width.gt.1.00) nwidth=3
nstrength=6
if(peak.ge.11.0) nstrength=7
if(peak.ge.17.0) nstrength=8
if(peak.ge.23.0) nstrength=9
nrpt=10*nwidth + nstrength
mswidth=10*nint(100.0*width)
i1=(t1-0.02)/dt
if(i1.lt.1) i1=1
iz=nint((width+0.02)/dt) + 1
iz=min(iz,k+1-i1,2*48000) !Length of ping in samples
call jtmsk(dat(i1),iz,cfile6,tpk,mswidth,int(peak),nrpt, &
nfreeze,DFTolerance,MouseDF,pick,mycall)
pingFound=.false.
inside=.false.
return
end subroutine rtping