static int cdf_erfc (lua_State *L) {
lua_Number x = luaL_checknumber(L, 1);
int ind = 0;
lua_pushnumber(L, erfc1(&ind, &x));
return 1;
}
int main(int argc,char *argv[]){
unsigned char data[FRAMEBITS/8]; // One minor frame
unsigned char symbols[2*FRAMEBITS];
unsigned char nsymbols[2*FRAMEBITS];
int i,fd;
char *filename;
struct stat statbuf;
off_t length;
short *samples;
int nsamples;
int start;
int startsync = SYNC_FAIL,endsync = SYNC_FAIL;
void *vd; // Viterbi decoder handle
int symerrors;
int firstsample;
int frame;
int begin;
int maxmetric,minmetric;
int ind;
char *locale;
double clock_tolerance = 5; // Maximum allowable clock offset, samples/frame
if((locale = getenv("LANG")) != NULL)
setlocale(LC_ALL,locale);
else
setlocale(LC_ALL,"en_US.utf8");
begin = 0;
while((i = getopt(argc,argv,"c:o:r:t:")) != EOF){
switch(i){
case 't':
clock_tolerance = atof(optarg);
break;
case 'c':
Symrate = atof(optarg);
break;
case 'r':
Samprate = atof(optarg);
break;
case 'o':
begin = atoi(optarg); // Starting sample, default 0
break;
}
}
Symbolsamples = Samprate/Symrate;
Framesamples = Symbolsamples * 2*FRAMEBITS;
// Read baseband samples, downsampled to Samprate (important!) and look for sync vector
filename = argv[optind];
if(lstat(filename,&statbuf) == -1){
fprintf(stderr,"lstat(%s) failed: %s\n",filename,strerror(errno));
exit(1);
}
if(!S_ISREG(statbuf.st_mode)){
fprintf(stderr,"%s is not an ordinary file\n",filename);
exit(1);
}
length = statbuf.st_size;
if((fd = open(filename,O_RDONLY)) == -1){
fprintf(stderr,"open(%s,readonly) failed; %s\n",filename,strerror(errno));
exit(1);
}
if((samples = mmap(NULL,length,PROT_READ,MAP_SHARED,fd,0)) == MAP_FAILED){
fprintf(stderr,"mmap(%s,%lld) failed: %s\n",filename,
(long long)length,strerror(errno));
close(fd);
exit(1);
}
nsamples = length / sizeof(*samples);
printf("%s: %'d samples, %'.3lf seconds @ %.1lf Hz\n",filename,
nsamples,nsamples/Samprate,Samprate);
generate_sync(Symrate);
vd = create_viterbi224(FRAMEBITS);
if(vd == NULL){
fprintf(stderr,"Can't create viterbi decoder\n");
exit(2);
}
for(frame=1;begin + Framesamples < nsamples;frame++){
int low,high;
// Look for starting frame sync
if(startsync == SYNC_FAIL){
// No endsync from previous frame, find initial sync
while(1){
startsync = fft_sync_search(&samples[begin],0,(int)Framesamples,begin);
if(startsync != SYNC_FAIL){
startsync += begin;
break;
}
begin += Framesamples; // Skip a frame time and try again
printf("Start sync search failure, skip to %'d\n",begin);
}
}
assert(startsync != SYNC_FAIL);
// Look for ending frame sync
// Start halfway through the frame, but actually search the middle
// of the result, which straddles the next sync. Only search in the
// allowable range to keep the clock from being driven into the weeds by noise
while(1){
start = startsync + Framesamples/2;
low = 0.5 * Framesamples - clock_tolerance; // very tight tolerance, +/- 5 samples
high = 0.5 * Framesamples + clock_tolerance;
endsync = fft_sync_search(&samples[start],low,high,-1);
if(endsync != SYNC_FAIL){
endsync += start;
break;
}
// Go back to look for another start sync
begin = startsync + Framesamples;
printf("End sync search failure, skip to %'d\n",begin);
startsync = SYNC_FAIL;
goto again;
}
// Got both start and end sync, proceed
i = startsync/Samprate;
printf("Frame %'d @ sample %'d (%'d:%02d)\n",frame,startsync,i/60,i % 60);
// Update estimate of sample clock rate et al
#if 0 // Hack - not let it change
Framesamples = endsync - startsync; // Actual samples in current frame (int)
Symbolsamples = Framesamples/(2*FRAMEBITS); // Actual samples in symbol (float)
Symrate = Samprate / Symbolsamples;
#endif
printf("Symbol rate: %'.3lf Hz; samples/sym: %'.3lf; samples/frame: %'.1lf\n",
Symrate,Symbolsamples,Framesamples);
#if 0
// If clock estimate has changed a lot, regenerate the sync vector with the new clock
if(abs(SYNCBITS*Samprate/Symrate - Synclen) > Symbolsamples/10.){
printf("Clock changed; regenerate sync\n");
generate_sync(Symrate);
}
#endif
// startsync points to the first symbol in the 34-bit sync sequence,
// so we want to skip past it to the first symbol in the new frame
firstsample = SYNCBITS*Symbolsamples + startsync;
for(i=0; i < 2*FRAMEBITS; i++){
double sum;
int midpoint,last;
ind = firstsample + i * Symbolsamples;
midpoint = firstsample + (i+0.5)*Symbolsamples;
last = firstsample + (i+1.0)*Symbolsamples;
// Integrate bit, remove manchester
sum = 0;
for(;ind < midpoint;ind++) // first half of symbol
sum -= samples[ind];
for(; ind < last;ind++)
sum += samples[ind];
sum += 128; // Offset-128 for Viterbi decoder
symbols[i] = (sum > 255) ? 255 : ((sum < 0) ? 0 : sum); // Clip to range 0-255
}
// We start with the encoder having just transmitted these five fixed bytes,
// 3 bytes of coder dump and 2 bytes of sync:
// 12 fc 81 9f be
init_viterbi224(vd,0x819fbe);
update_viterbi224_blk(vd,symbols,FRAMEBITS);
chainback_viterbi224(vd,data,FRAMEBITS,0x819fbe);
maxmetric = max_metric_viterbi224(vd);
minmetric = min_metric_viterbi224(vd);
for(i=0; i<128; i++){
printf("%02x",data[i]);
if((i % 16) == 15)
putchar('\n');
else
putchar(' ');
}
// Re-encode and compare to received symbols to count channel errors
encode(nsymbols,data,FRAMEBITS/8,0x819fbe);
symerrors = 0;
for(i=0;i<2*FRAMEBITS;i++){
if(nsymbols[i] != (symbols[i] > 128)){
symerrors++;
#if 0
printf("sym error %d: %d != %d\n",i,nsymbols[i],symbols[i]);
#endif
}
}
printf("Viterbi path metric range %'d - %'d, diff %'d\n",minmetric,maxmetric,maxmetric-minmetric);
if(symerrors){
double esn0;
esn0 = erfc1(2.*symerrors/(2*FRAMEBITS)); // Amplitude ratio
esn0 *= esn0; // square to get power ratio
// ebn0 = 2 * esn0 for rate 1/2 code
printf("re-encode symbol errors: %'d/%'d; estimated Eb/No = %.2lf dB\n",
symerrors,2*FRAMEBITS,10*log10(2*esn0));
} else {
printf("No re-encode symbol errors; estimated Eb/No > %.2lf dB\n",10.5); // hack; 7.5 dB has a BER < 1/2048
}
putchar('\n');
fflush(stdout);
startsync = endsync;
again:;
}
delete_viterbi224(vd);
exit(0);
}
void grat1(double *a,double *x,double *r,double *p,double *q,
double *eps)
{
static int K2 = 0;
static double a2n,a2nm1,am0,an,an0,b2n,b2nm1,c,cma,g,h,j,l,sum,t,tol,w,z,T1,T3;
/*
..
.. Executable Statements ..
*/
/*
-----------------------------------------------------------------------
EVALUATION OF THE INCOMPLETE GAMMA RATIO FUNCTIONS
P(A,X) AND Q(A,X)
IT IS ASSUMED THAT A .LE. 1. EPS IS THE TOLERANCE TO BE USED.
THE INPUT ARGUMENT R HAS THE VALUE E**(-X)*X**A/GAMMA(A).
-----------------------------------------------------------------------
*/
if(*a**x == 0.0e0) goto S120;
if(*a == 0.5e0) goto S100;
if(*x < 1.1e0) goto S10;
goto S60;
S10:
/*
TAYLOR SERIES FOR P(A,X)/X**A
*/
an = 3.0e0;
c = *x;
sum = *x/(*a+3.0e0);
tol = 0.1e0**eps/(*a+1.0e0);
S20:
an += 1.0e0;
c = -(c*(*x/an));
t = c/(*a+an);
sum += t;
if(fabs(t) > tol) goto S20;
j = *a**x*((sum/6.0e0-0.5e0/(*a+2.0e0))**x+1.0e0/(*a+1.0e0));
z = *a*log(*x);
h = gam1(a);
g = 1.0e0+h;
if(*x < 0.25e0) goto S30;
if(*a < *x/2.59e0) goto S50;
goto S40;
S30:
if(z > -.13394e0) goto S50;
S40:
w = exp(z);
*p = w*g*(0.5e0+(0.5e0-j));
*q = 0.5e0+(0.5e0-*p);
return;
S50:
l = rexp(&z);
w = 0.5e0+(0.5e0+l);
*q = (w*j-l)*g-h;
if(*q < 0.0e0) goto S90;
*p = 0.5e0+(0.5e0-*q);
return;
S60:
/*
CONTINUED FRACTION EXPANSION
*/
a2nm1 = a2n = 1.0e0;
b2nm1 = *x;
b2n = *x+(1.0e0-*a);
c = 1.0e0;
S70:
a2nm1 = *x*a2n+c*a2nm1;
b2nm1 = *x*b2n+c*b2nm1;
am0 = a2nm1/b2nm1;
c += 1.0e0;
cma = c-*a;
a2n = a2nm1+cma*a2n;
b2n = b2nm1+cma*b2n;
an0 = a2n/b2n;
if(fabs(an0-am0) >= *eps*an0) goto S70;
*q = *r*an0;
*p = 0.5e0+(0.5e0-*q);
return;
S80:
/*
SPECIAL CASES
*/
*p = 0.0e0;
*q = 1.0e0;
return;
S90:
*p = 1.0e0;
*q = 0.0e0;
return;
S100:
if(*x >= 0.25e0) goto S110;
T1 = sqrt(*x);
*p = erf1(&T1);
*q = 0.5e0+(0.5e0-*p);
return;
S110:
T3 = sqrt(*x);
*q = erfc1(&K2,&T3);
*p = 0.5e0+(0.5e0-*q);
return;
S120:
if(*x <= *a) goto S80;
goto S90;
}
