Working toward multi-decode capability.

lib/q65_decode.f90

@@ -135,18 +135,12 @@ contains
     call timer('q65_dec0',1)
 
     if(idec.ge.0) then
-       dtdec=xdt                          !We have a list-decode result
+       dtdec=xdt                        !We have a list-decode result at nfqso
        f0dec=f0
        go to 100
     endif
 
-!    if(snr1.lt.2.8) then
-!       dtdec=0.                   !No reliable sync, abandon decoding attempt
-!       f0dec=0.
-!       go to 100
-!    endif
-
-! Prepare for a single-period decode woth iaptype = 0, 1, or 2  (also 4?)
+! Prepare for a single-period decode with iaptype = 0, 1, 2, or 4
     jpk0=(xdt+1.0)*6000                      !Index of nominal start of signal
     if(ntrperiod.le.30) jpk0=(xdt+0.5)*6000  !For shortest sequences
     if(jpk0.lt.0) jpk0=0
@@ -203,7 +197,7 @@ contains
        go to 100
     endif
 
-! There was no 'q3n' decode.  Try for a 'q[012]n' decode.
+! There was no 'q3n' decode.  Try for a 'q[0124]n' decode.
 ! Call top-level routine in q65 module: establish sync and try for a q[012]n
 ! decode, this time using the cumulative 's1a' symbol spectra.
 
@@ -268,6 +262,11 @@ contains
     endif
     navg0=1000*navg(0) + navg(1)
 
+!    do icand=1,ncand
+!       write(72,3072) icand,candidates(icand,1:3)
+!3072   format(i2,3f10.3)
+!    enddo
+
     return
   end subroutine decode
 

lib/qra/q65/q65.f90

@@ -12,10 +12,11 @@ module q65
   integer codewords(63,206)
   integer ibwa,ibwb,ncw,nsps,mode_q65,nfa,nfb
   integer idf,idt,ibw
-  integer istep,nsmo,lag1,lag2,npasses,nused,iseq
+  integer istep,nsmo,lag1,lag2,npasses,nused,iseq,ncand
   integer i0,j0
   integer navg(0:1)
   logical lnewdat
+  real candidates(20,3)                    !snr, xdt, and f0 of top candidates
   real,allocatable,save :: s1a(:,:,:)      !Cumulative symbol spectra
   real sync(85)                            !sync vector
   real df,dtstep,dtdec,f0dec,ftol
@@ -394,8 +395,11 @@ subroutine q65_ccf_22(s1,iz,jz,nfqso,ipk,jpk,f0,xdt,ccf2)
   real s1(iz,jz)
   real ccf2(iz)                               !Orange sync curve
   real, allocatable :: xdt2(:)
+  integer, allocatable :: indx(:)
 
   allocate(xdt2(iz))
+  allocate(indx(iz))
+
   ccfbest=0.
   ibest=0
   lagpk=0
@@ -425,11 +429,29 @@ subroutine q65_ccf_22(s1,iz,jz,nfqso,ipk,jpk,f0,xdt,ccf2)
      endif
   enddo
 
+! Parameters for the top candidate:
   ipk=ibest - i0
   jpk=lagbest
   f0=nfqso + ipk*df
   xdt=jpk*dtstep
 
+! Save parameters for best candidates
+  i1=nfa/df
+  i2=nfb/df
+  jzz=i2-i1+1
+  call pctile(ccf2(i1:i2),jzz,40,base)
+  ccf2=ccf2/base
+  call indexx(ccf2(i1:i2),jzz,indx)
+  ncand=0
+  do j=1,20
+     i=indx(jzz-j+1)+i1-1
+     if(ccf2(i).lt.3.0) exit
+     ncand=ncand+1
+     candidates(ncand,1)=ccf2(i)
+     candidates(ncand,2)=xdt2(i)
+     candidates(ncand,3)=i*df
+  enddo
+
   return
 end subroutine q65_ccf_22