void retris(complex *data,complex *a,complex *c, complex *b,
complex endl,complex endr, int nx, complex *d)
{
int ix;
complex *e,den;
complex *f;
e=alloc1complex(nx);
f=alloc1complex(nx);
e[0]=cdiv(cneg(a[0]),endl);
f[0]=cdiv(d[0],endl);
for(ix=1;ix<nx-1;++ix){
den=cadd(b[ix],cmul(c[ix],e[ix-1]));
e[ix]=cdiv(cneg(a[ix]),den);
f[ix]=cdiv(csub(d[ix],cmul(f[ix-1],c[ix])),den);
}
data[nx-1]=cdiv(csub(d[nx-1],cmul(f[nx-2],c[nx-2])),cadd(endr,cmul(c[nx-2],e[nx-2])));
for(ix=nx-2;ix>-1;--ix)
data[ix]=cadd(cmul(data[ix+1],e[ix]),f[ix]);
free1complex(e);
free1complex(f);
return;
}
void bits_to_dqpsk_symbols(COMP tx_symbols[], COMP prev_tx_symbols[], int tx_bits[], int *pilot_bit)
{
int c, msb, lsb;
COMP j = {0.0,1.0};
/* map tx_bits to to Nc DQPSK symbols */
for(c=0; c<NC; c++) {
msb = tx_bits[2*c];
lsb = tx_bits[2*c+1];
if ((msb == 0) && (lsb == 0))
tx_symbols[c] = prev_tx_symbols[c];
if ((msb == 0) && (lsb == 1))
tx_symbols[c] = cmult(j, prev_tx_symbols[c]);
if ((msb == 1) && (lsb == 0))
tx_symbols[c] = cneg(prev_tx_symbols[c]);
if ((msb == 1) && (lsb == 1))
tx_symbols[c] = cmult(cneg(j),prev_tx_symbols[c]);
}
/* +1 -1 +1 -1 BPSK sync carrier, once filtered becomes (roughly)
two spectral lines at +/- Rs/2 */
if (*pilot_bit)
tx_symbols[NC] = cneg(prev_tx_symbols[NC]);
else
tx_symbols[NC] = prev_tx_symbols[NC];
if (*pilot_bit)
*pilot_bit = 0;
else
*pilot_bit = 1;
}
void bits_to_dqpsk_symbols(COMP tx_symbols[], int Nc, COMP prev_tx_symbols[], int tx_bits[], int *pilot_bit, int old_qpsk_mapping)
{
int c, msb, lsb;
COMP j = {0.0,1.0};
/* Map tx_bits to to Nc DQPSK symbols. Note legacy support for
old (suboptimal) V0.91 FreeDV mapping */
for(c=0; c<Nc; c++) {
msb = tx_bits[2*c];
lsb = tx_bits[2*c+1];
if ((msb == 0) && (lsb == 0))
tx_symbols[c] = prev_tx_symbols[c];
if ((msb == 0) && (lsb == 1))
tx_symbols[c] = cmult(j, prev_tx_symbols[c]);
if ((msb == 1) && (lsb == 0)) {
if (old_qpsk_mapping)
tx_symbols[c] = cneg(prev_tx_symbols[c]);
else
tx_symbols[c] = cmult(cneg(j),prev_tx_symbols[c]);
}
if ((msb == 1) && (lsb == 1)) {
if (old_qpsk_mapping)
tx_symbols[c] = cmult(cneg(j),prev_tx_symbols[c]);
else
tx_symbols[c] = cneg(prev_tx_symbols[c]);
}
}
/* +1 -1 +1 -1 BPSK sync carrier, once filtered becomes (roughly)
two spectral lines at +/- Rs/2 */
if (*pilot_bit)
tx_symbols[Nc] = cneg(prev_tx_symbols[Nc]);
else
tx_symbols[Nc] = prev_tx_symbols[Nc];
if (*pilot_bit)
*pilot_bit = 0;
else
*pilot_bit = 1;
}
/*
* Multiply a complex number by a real number.
*/
COMPLEX *
cmulq(COMPLEX *c, NUMBER *q)
{
COMPLEX *r;
if (qiszero(q))
return clink(&_czero_);
if (qisone(q))
return clink(c);
if (qisnegone(q))
return cneg(c);
r = comalloc();
qfree(r->real);
qfree(r->imag);
r->real = qmul(c->real, q);
r->imag = qmul(c->imag, q);
return r;
}
/*
* Divide a complex number by a real number.
*/
COMPLEX *
cdivq(COMPLEX *c, NUMBER *q)
{
COMPLEX *r;
if (qiszero(q)) {
math_error("Division by zero");
/*NOTREACHED*/
}
if (qisone(q))
return clink(c);
if (qisnegone(q))
return cneg(c);
r = comalloc();
qfree(r->real);
qfree(r->imag);
r->real = qqdiv(c->real, q);
r->imag = qqdiv(c->imag, q);
return r;
}
void snr_update(float sig_est[], float noise_est[], COMP phase_difference[])
{
float s[NC+1];
COMP refl_symbols[NC+1];
float n[NC+1];
COMP pi_on_4;
int c;
pi_on_4.real = cosf(PI/4.0);
pi_on_4.imag = sinf(PI/4.0);
/* mag of each symbol is distance from origin, this gives us a
vector of mags, one for each carrier. */
for(c=0; c<NC+1; c++)
s[c] = cabsolute(phase_difference[c]);
/* signal mag estimate for each carrier is a smoothed version of
instantaneous magntitude, this gives us a vector of smoothed
mag estimates, one for each carrier. */
for(c=0; c<NC+1; c++)
sig_est[c] = SNR_COEFF*sig_est[c] + (1.0 - SNR_COEFF)*s[c];
/* noise mag estimate is distance of current symbol from average
location of that symbol. We reflect all symbols into the first
quadrant for convenience. */
for(c=0; c<NC+1; c++) {
refl_symbols[c].real = fabsf(phase_difference[c].real);
refl_symbols[c].imag = fabsf(phase_difference[c].imag);
n[c] = cabsolute(cadd(fcmult(sig_est[c], pi_on_4), cneg(refl_symbols[c])));
}
/* noise mag estimate for each carrier is a smoothed version of
instantaneous noise mag, this gives us a vector of smoothed
noise power estimates, one for each carrier. */
for(c=0; c<NC+1; c++)
noise_est[c] = SNR_COEFF*noise_est[c] + (1 - SNR_COEFF)*n[c];
}
void gazdagvt (float k,
int nt, float dt, float ft,
int ntau, float dtau, float ftau,
float *vt, complex *p, complex *q, float qual, float gainceil)
/*****************************************************************************
Gazdag's phase-shift zero-offset migration for one wavenumber
adapted to v(tau) velocity profile
******************************************************************************
Input:
k wavenumber
nt number of time samples
dt time sampling interval
ft first time sample
ntau number of migrated time samples
dtau migrated time sampling interval
ftau first migrated time sample
vt velocity v[tau]
p array[nt] containing data to be migrated
Output:
q array[ntau] containing migrated data
******************************************************************************/
{
int ntfft,nw,it,itau,iw;
float dw,fw,tmax,w,tau,phase,coss, *cumgain, gain, alpha;
complex cshift,*pp;
/* determine frequency sampling */
ntfft = npfa(nt);
nw = ntfft;
dw = 2.0*PI/(ntfft*dt);
fw = -PI/dt;
/* determine maximum time */
tmax = ft+(nt-1)*dt;
/* allocate workspace */
pp = alloc1complex(nw);
cumgain = alloc1float(nw);
for (iw=0; iw<nw; iw++)
cumgain[iw] = 1.0;
/* pad with zeros and Fourier transform t to w, with w centered */
for (it=0; it<nt; it++)
pp[it] = (it%2 ? cneg(p[it]) : p[it]);
for (it=nt; it<ntfft; it++)
pp[it] = cmplx(0.0,0.0);
pfacc(1,ntfft,pp);
/* account for non-zero ft and non-zero ftau */
for (itau=0 ; itau < ftau ; itau++){
for (iw=0,w=fw; iw<nw; iw++,w+=dw) {
if (w==0.0) w = 1e-10/dt;
coss = 1.0-pow(0.5 * vt[itau] * k/w,2.0);
if (coss>=pow(ftau/tmax,2.0)) {
phase = w*(ft-ftau*sqrt(coss));
cshift = cmplx(cos(phase),sin(phase));
pp[iw] = cmul(pp[iw],cshift);
} else {
pp[iw] = cmplx(0.0,0.0);
}
}
}
/* loop over migrated times tau */
for (itau=0,tau=ftau; itau<ntau; itau++,tau+=dtau) {
/* initialize migrated sample */
q[itau] = cmplx(0.0,0.0);
/* loop over frequencies w */
for (iw=0,w=fw; iw<nw; iw++,w+=dw) {
/* accumulate image (summed over frequency) */
q[itau] = cadd(q[itau],pp[iw]);
/* compute cosine squared of propagation angle */
if (w==0.0) w = 1e-10/dt;
coss = 1.0-pow(0.5 * vt[itau] * k/w,2.0);
/* if wave could have been recorded in time */
if (coss>=pow(tau/tmax,2.0)) {
/* extrapolate down one migrated time step */
phase = -w*dtau*sqrt(coss);
cshift = cmplx(cos(phase),sin(phase));
/* apply gain until gain ceiling is reached */
if (cumgain[iw] < gainceil) {
alpha = w/(2.0*vt[itau]*qual);
gain = exp(fabs(0.5*vt[itau]*dtau*alpha));
pp[iw] = cmul(pp[iw],crmul(cshift,gain));
cumgain[iw] *= gain;
} else {
pp[iw] = cmplx(0.0,0.0);
}
/* else, if wave couldn't have been recorded in time */
} else {
/* zero the wave */
pp[iw] = cmplx(0.0,0.0);
}
}
/* scale accumulated image just as we would for an FFT */
q[itau] = crmul(q[itau],1.0/nw);
}
/* free workspace */
free1complex(pp);
free1float(cumgain);
}
int
main (int argc, char **argv)
{
int nt; /* number of time samples */
int nz; /* number of migrated depth samples */
int nx,nxshot; /* number of midpoints */
int nxshot_orig; /* first value of nxshot */
int iz,iw,ix,it,ik; /* loop counters */
int igx; /* integerized gx value */
int ntfft,nxfft; /* fft size */
int nw,truenw,nk; /* number of wave number, frequency */
int dip=45; /* dip angle */
float sx,gx; /* x source and geophone location */
float gxmin=0.0,gxmax=0.0;/* x source and geophone location */
float min_sx_gx; /* min(sx,gx) */
float oldgx; /* old gx position */
float oldgxmin; /* old gx position */
float oldgxmax; /* old gx position */
float oldsx=0.0; /* old sx position */
int oldigx=0; /* old value of integerized gx value */
int oldisx=0; /* old value of integerized sx value */
int isx=0,nxo; /* index for source and geophone */
int ix1,ix2,ix3,ixshot; /* dummy index */
int lpad,rpad;/* padding on both sides of the migrated section */
float *wl=NULL,*wtmp=NULL;
float fmax;
float f1,f2,f3,f4;
int nf1,nf2,nf3,nf4;
int ntw;
float dt=0.004,dz; /* time sampling interval */
float dw,dk; /* wave number,frequency sampling interval*/
float fw,fk; /* first wave number and frequency */
float w,k; /* wave number and frequency */
float dx; /* spatial sampling interval */
float **p=NULL; /* input, output data */
float **cresult=NULL; /* input, output data */
float v1,vmin; /* average, min velocity */
double kz1,kz2;
double phase1;
float **v=NULL,**vp=NULL;
complex cshift1,cshift2;
complex *wlsp=NULL;
complex **cp=NULL;
complex **cp1=NULL;
complex **cq=NULL;
complex **cq1=NULL; /* complex input,output */
char *vfile=""; /* name of file containing velocities */
FILE *vfp=NULL;
int verbose; /* verbose flag */
/* hook up getpar to handle the parameters */
initargs(argc,argv);
requestdoc(1);
/* get required parameters */
MUSTGETPARINT("nz",&nz);
MUSTGETPARINT("nxo",&nxo);
MUSTGETPARINT("nxshot",&nxshot);
MUSTGETPARFLOAT("dz",&dz);
MUSTGETPARSTRING("vfile", &vfile);
/* get optional parameters */
if (!getparfloat("fmax",&fmax)) fmax = 25.0;
if (!getparfloat("f1",&f1)) f1 = 10.0;
if (!getparfloat("f2",&f2)) f2 = 20.0;
if (!getparfloat("f3",&f3)) f3 = 40.0;
if (!getparfloat("f4",&f4)) f4 = 50.0;
if (!getparint("lpad",&lpad)) lpad=9999;
if (!getparint("rpad",&rpad)) rpad=9999;
if (!getparint("dip",&dip)) dip=45;
if (!getparint("verbose",&verbose)) verbose = 0;
/* allocating space */
cresult = alloc2float(nz,nxo);
vp=alloc2float(nxo,nz);
/* load velocity file */
vfp=efopen(vfile,"r");
efread(vp[0],FSIZE,nz*nxo,vfp);
efclose(vfp);
/* zero out cresult array */
memset((void *) cresult[0],0, nxo*nz*FSIZE);
/* save value of nxshot */
nxshot_orig=nxshot;
/* get info from first trace */
if (!gettr(&tr)) err("can't get first trace");
nt = tr.ns;
get_sx_gx(&sx,&gx);
min_sx_gx = MIN(sx,gx);
sx = sx - min_sx_gx;
gx = gx - min_sx_gx;
/* let user give dt and/or dx from command line */
if (!getparfloat("dt", &dt)) {
if (tr.dt) { /* is dt field set? */
dt = ((double) tr.dt)/1000000.0;
} else { /* dt not set, assume 4 ms */
dt = 0.004;
warn("tr.dt not set, assuming dt=0.004");
}
}
if (!getparfloat("dx",&dx)) {
if (tr.d2) { /* is d2 field set? */
dx = tr.d2;
} else {
dx = 1.0;
warn("tr.d2 not set, assuming d2=1.0");
}
}
checkpars();
do { /* begin loop over shots */
/* determine frequency sampling interval */
ntfft = npfar(nt);
nw = ntfft/2+1;
dw = 2.0*PI/(ntfft*dt);
/* compute the index of the frequency to be migrated */
fw=2.0*PI*f1;
nf1=fw/dw+0.5;
fw=2.0*PI*f2;
nf2=fw/dw+0.5;
fw=2.0*PI*f3;
nf3=fw/dw+0.5;
fw=2.0*PI*f4;
nf4=fw/dw+0.5;
/* the number of frequency to migrated */
truenw=nf4-nf1+1;
fw=0.0+nf1*dw;
if (verbose)
warn("nf1=%d nf2=%d nf3=%d nf4=%d nw=%d",nf1,nf2,nf3,nf4,truenw);
/* allocate space */
wl=alloc1float(ntfft);
wlsp=alloc1complex(nw);
/* generate the Ricker wavelet */
wtmp=ricker(fmax,dt,&ntw);
/* zero out wl[] array */
memset((void *) wl, 0, ntfft*FSIZE);
/* CHANGE BY CHRIS STOLK, Dec. 11, 2005 */
/* The next two lines are the old code, */
/* it is erroneous because the peak of */
/* the wavelet occurs at positive time */
/* instead of time zero. */
/*
for(it=0;it<ntw;it++)
wl[it]=wtmp[it];
*/
/* New code: we put in the wavelet in a centered fashion */
for(it=0;it<ntw;it++)
wl[(it-ntw/2+ntfft) % ntfft]=wtmp[it];
/* End of new code */
free1float(wtmp);
pfarc(-1,ntfft,wl,wlsp);
/* allocate space */
p = alloc2float(ntfft,nxo);
cq = alloc2complex(nw,nxo);
/* zero out p[][] array */
memset((void *) p[0], 0, ntfft*nxo*FSIZE);
/* initialize a number of items before looping over traces */
nx = 0;
igx=0;
oldsx=sx;
oldgx=gx;
oldgxmax=gxmax;
oldgxmin=gxmin;
do { /* begin looping over traces within a shot gather */
memcpy( (void *) p[igx], (const void *) tr.data,nt*FSIZE);
/* get sx and gx */
get_sx_gx(&sx,&gx);
sx = (sx - min_sx_gx);
gx = (gx - min_sx_gx);
igx = gx/dx;
if (igx==oldigx)
warn("repeated igx!!! check dx or scalco value!!!");
oldigx = igx;
if(gxmin>gx)gxmin=gx;
if(gxmax<gx)gxmax=gx;
if(verbose)
warn(" inside loop: min_sx_gx %f isx %d igx %d gx %f sx %f",min_sx_gx,isx,igx,gx,sx);
/* sx, gx must increase monotonically */
if (!(oldsx <= sx) )
err("sx field must be monotonically increasing!");
if (!(oldgx <= gx) )
err("gx field must be monotonically increasing!");
++nx;
} while(gettr(&tr) && sx==oldsx);
isx=oldsx/dx;
if (isx==oldisx)
warn("repeated isx!!! check dx or scalco value!!!");
oldisx=isx;
ixshot=isx;
if(verbose) {
warn("sx %f, gx %f , gxmin %f gxmax %f nx %d",sx,gx,gxmin,gxmax, nx);
warn("isx %d igx %d ixshot %d" ,isx,igx,ixshot);
}
/* transform the shot gather from time to frequency domain */
pfa2rc(1,1,ntfft,nxo,p[0],cq[0]);
/* compute the most left and right index for the migrated */
/* section */
ix1=oldsx/dx;
ix2=gxmin/dx;
ix3=gxmax/dx;
if(ix1>=ix3)ix3=ix1;
if(ix1<=ix2)ix2=ix1;
ix2-=lpad;
ix3+=rpad;
if(ix2<0)ix2=0;
if(ix3>nxo-1)ix3=nxo-1;
/* the total traces to be migrated */
nx=ix3-ix2+1;
nw=truenw;
/* determine wavenumber sampling (for complex to complex FFT) */
nxfft = npfa(nx);
nk = nxfft;
dk = 2.0*PI/(nxfft*dx);
fk = -PI/dx;
/* allocate space for velocity profile within the aperature */
v=alloc2float(nx,nz);
for(iz=0;iz<nz;iz++)
for(ix=0;ix<nx;ix++)
v[iz][ix]=vp[iz][ix+ix2];
/* allocate space */
cp = alloc2complex(nx,nw);
cp1 = alloc2complex(nx,nw);
/* transpose the frequency domain data from */
/* data[ix][iw] to data[iw][ix] and apply a */
/* Hamming at the same time */
for (ix=0; ix<nx;++ix) {
for (iw=0; iw<nw; iw++){
float tmpp=0.0,tmppp=0.0;
if(iw>=(nf1-nf1)&&iw<=(nf2-nf1)){
tmpp=PI/(nf2-nf1);
tmppp=tmpp*(iw-nf1)-PI;
tmpp=0.54+0.46*cos(tmppp);
cp[iw][ix]=crmul(cq[ix+ix2][iw+nf1],tmpp);
} else {
if(iw>=(nf3-nf1)&&iw<=(nf4-nf1)) {
tmpp=PI/(nf4-nf3);
tmppp=tmpp*(iw-nf3);
tmpp=0.54+0.46*cos(tmppp);
cp[iw][ix]=crmul(cq[ix+ix2][iw+nf1],tmpp);
} else {
cp[iw][ix]=cq[ix+ix2][iw+nf1];
}
}
cp1[iw][ix]=cmplx(0.0,0.0);
}
}
for(iw=0;iw<nw;iw++) {
cp1[iw][ixshot-ix2]=wlsp[iw+nf1];
}
if(verbose) {
warn("ixshot %d ix %d ix1 %d ix2 %d ix3 %d",ixshot,ix,ix1,ix2,ix3);
warn("oldsx %f ",oldsx);
}
free2float(p);
free2complex(cq);
free1float(wl);
free1complex(wlsp);
cq=alloc2complex(nxfft,nw);
cq1=alloc2complex(nxfft,nw);
/* loops over depth */
for(iz=0;iz<nz;++iz){
/* the imaging condition */
for(ix=0;ix<nx;ix++){
for(iw=0,w=fw;iw<nw;w+=dw,iw++){
complex tmp;
float ratio=10.0;
if(fabs(ix+ix2-ixshot)*dx<ratio*iz*dz)
tmp=cmul(cp[iw][ix],cp1[iw][ix]);
else
tmp=cmplx(0.0,0.0);
cresult[ix+ix2][iz]+=tmp.r/ntfft;
}
}
/* get the minimum velocity */
vmin=v[iz][0];
for(ix=0;ix<nx;ix++){
if(v[iz][ix]<vmin)vmin=v[iz][ix];
}
/* compute time-invariant wavefield */
for (ik=0;ik<nx;++ik) {
for (iw=0; iw<nw; ++iw) {
cq[iw][ik] = ik%2 ? cneg(cp[iw][ik]) : cp[iw][ik];
cq1[iw][ik] = ik%2 ? cneg(cp1[iw][ik]) : cp1[iw][ik];
}
}
/* zero out parts of the cq[][] and cq1[][] arrays */
for (ik=nx; ik<nk; ++ik) {
for (iw=0; iw<nw; ++iw) {
cq[iw][ik] = cmplx(0.0,0.0);
cq1[iw][ik] = cmplx(0.0,0.0);
}
}
/* FFT to W-K domain */
pfa2cc(-1,1,nk,nw,cq[0]);
pfa2cc(-1,1,nk,nw,cq1[0]);
v1=vmin;
/* apply phase shift */
for(ik=0,k=fk;ik<nk;++ik,k+=dk) {
for(iw=0,w=fw;iw<nw;++iw,w+=dw){
if(w==0.0)w=1.0e-10/dt;
kz1=1.0-pow(v1*k/w,2.0);
if(kz1>0.15){
phase1 = -w*sqrt(kz1)*dz/v1;
cshift1 = cmplx(cos(phase1), sin(phase1));
cq[iw][ik] = cmul(cq[iw][ik],cshift1);
cq1[iw][ik] = cmul(cq1[iw][ik],cshift1);
} else {
cq[iw][ik] = cq1[iw][ik] = cmplx(0.0,0.0);
}
}
}
/* fourier transform */
pfa2cc(1,1,nk,nw,cq[0]);
pfa2cc(1,1,nk,nw,cq1[0]);
for(ix=0;ix<nx;++ix) {
for(iw=0,w=fw;iw<nw;w+=dw,++iw){
float a=0.015,g=1.0;
int I=10;
if(ix<=I)
g=exp(-a*(I-ix)*(I-ix));
if(ix>=nx-I)
g=exp(-a*(-nx+I+ix)*(-nx+I+ix));
cq[iw][ix] = crmul( cq[iw][ix],1.0/nxfft);
cq[iw][ix] =ix%2 ? cneg(cq[iw][ix]) : cq[iw][ix];
kz2=(1.0/v1-1.0/v[iz][ix])*w*dz;
cshift2=cmplx(cos(kz2),sin(kz2));
cp[iw][ix]=cmul(cq[iw][ix],cshift2);
cq1[iw][ix] = crmul( cq1[iw][ix],1.0/nxfft);
cq1[iw][ix] =ix%2 ? cneg(cq1[iw][ix]) : cq1[iw][ix];
cp1[iw][ix]=cmul(cq1[iw][ix],cshift2);
}
}
/* apply fdmig algorithm */
fdmig( cp, nx, nw,v[iz],fw,dw,dz,dx,dt,v1,dip);
fdmig( cp1,nx, nw,v[iz],fw,dw,dz,dx,dt,v1,dip);
}
free2complex(cp);
free2complex(cp1);
free2complex(cq);
free2complex(cq1);
free2float(v);
--nxshot;
} while (nxshot);
/* restore header fields and write output */
for(ix=0; ix<nxo; ix++) {
tr.ns = nz;
tr.d1 = dz;
tr.d2 = dx;
tr.offset = 0;
tr.cdp = tr.tracl = ix;
memcpy( (void *) tr.data, (const void *) cresult[ix],nz*FSIZE);
puttr(&tr);
}
return(CWP_Exit());
}
