Initial commit

git-svn-id: file:///home/lennart/svn/public/vfax/trunk@3 541b366f-4dd8-0310-ae39-b2612fd50714

1 files changed, 206 insertions, 0 deletions

diff --git a/v17mod.c b/v17mod.c
new file mode 100644
index 0000000..3c604ef
--- /dev/null
+++ b/v17mod.c
@@ -0,0 +1,206 @@
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <math.h>
+
+#include "v17mod.h"
+
+#define SAMPLE_RATE 8000
+#define CARRIER_FREQ 1800
+#define BAUD_RATE 2400
+#define SYMBOL_INTERVAL ((float) SAMPLE_RATE/BAUD_RATE)
+#define SINC_RADIUS 5
+#define SYMBOLS_MAX 1024
+
+static const float v17_7k2_x[] = {
+    0.6, -0.2, 0.6, -0.6,
+    -0.6, 0.2, -0.6, 0.6,
+    -0.2, 0.6, -0.2, 0.2,
+    0.2, -0.6, 0.2, -0.2
+};
+
+static const float v17_7k2_y[] = {
+    -0.6, 0.6, 0.2, -0.6,
+    0.6, -0.6, -0.2, 0.6,
+    0.2, -0.2, -0.6, 0.2,
+    -0.2, 0.2, 0.6, -0.2
+};
+
+void v17mod_init(struct v17mod_state *s) {
+    size_t l;
+    int i;
+    
+    assert(s);
+    memset(s, 0, sizeof(*s));
+
+    s->xsymbols = malloc(l = (sizeof(float)*SYMBOLS_MAX));
+    s->ysymbols = malloc(l);
+
+    s->n_symbols = SINC_RADIUS*2;
+
+    for (i = 0; i < s->n_symbols; i++)
+        s->xsymbols[i] = s->ysymbols[i] = 0.0;
+}
+
+void v17mod_done(struct v17mod_state *s) {
+    assert(s);
+    free(s->xsymbols);
+    free(s->ysymbols);
+}
+
+static const float sinc_table[] = {
+    0.0000, -0.0000, -0.0002, -0.0005, -0.0009,
+   -0.0014, -0.0018, -0.0020, -0.0019, -0.0013,
+    0.0000,  0.0019,  0.0042,  0.0068,  0.0093,
+    0.0113,  0.0124,  0.0120,  0.0098,  0.0058,
+   -0.0000, -0.0073, -0.0153, -0.0234, -0.0303,
+   -0.0350, -0.0365, -0.0340, -0.0270, -0.0155,
+    0.0000,  0.0183,  0.0377,  0.0562,  0.0716,
+    0.0815,  0.0838,  0.0771,  0.0605,  0.0344,
+   -0.0000, -0.0403, -0.0832, -0.1243, -0.1589,
+   -0.1821, -0.1893, -0.1767, -0.1415, -0.0824,
+    0.0000,  0.1035,  0.2241,  0.3561,  0.4926,
+    0.6261,  0.7488,  0.8533,  0.9330,  0.9830,
+    1.0000,  0.9830,  0.9330,  0.8533,  0.7488,
+    0.6261,  0.4926,  0.3561,  0.2241,  0.1035,
+    0.0000, -0.0824, -0.1415, -0.1767, -0.1893,
+   -0.1821, -0.1589, -0.1243, -0.0832, -0.0403,
+   -0.0000,  0.0344,  0.0605,  0.0771,  0.0838,
+    0.0815,  0.0716,  0.0562,  0.0377,  0.0183,
+    0.0000, -0.0155, -0.0270, -0.0340, -0.0365,
+   -0.0350, -0.0303, -0.0234, -0.0153, -0.0073,
+   -0.0000,  0.0058,  0.0098,  0.0120,  0.0124,
+    0.0113,  0.0093,  0.0068,  0.0042,  0.0019,
+    0.0000, -0.0013, -0.0019, -0.0020, -0.0018,
+   -0.0014, -0.0009, -0.0005, -0.0002, -0.0000,
+   -0.0000
+};
+
+static float sinc(float x) {
+    int i;
+    assert(sizeof(sinc_table)/sizeof(float) == 121);
+
+    i = (int) (60+x*10+.5);
+
+    if (i < 0)
+        return 0;
+    if (i > 120)
+        return 0;
+
+    return sinc_table[i];
+}
+
+
+void v17mod_push(struct v17mod_state *s, const uint8_t *p, int l) {
+    int i, j;
+
+    assert(s && p && l);
+    assert(s->n_symbols+l <= SYMBOLS_MAX);
+
+    for (i = 0, j = (s->i_symbols+s->n_symbols) % SYMBOLS_MAX; i < l; i++, j = (j+1) % SYMBOLS_MAX) {
+        assert(p[i] < 16);
+        s->xsymbols[j] = v17_7k2_x[p[i]];
+        s->ysymbols[j] = v17_7k2_y[p[i]];
+    }
+
+    s->n_symbols += l;
+}
+
+inline static float symbol_at(struct v17mod_state *s, float *a, int i) {
+    int j = s->i_symbols+i;
+
+    assert(i >= 0);
+    assert(i < s->n_symbols);
+
+    while(j >= SYMBOLS_MAX)
+        j -= SYMBOLS_MAX;
+
+    assert(j>=0);
+    assert(j<SYMBOLS_MAX);
+    
+    return a[j];
+}
+
+static float fsignal(struct v17mod_state *s, int i) {
+    float sum, d;
+    int n;
+    float *symbols;
+    
+    assert(s && i >= 0 && i <= 1);
+
+    symbols = (i == 0) ? s->xsymbols : s->ysymbols;
+    sum = 0;
+    d = s->sample - s->symbol_index*SAMPLE_RATE/BAUD_RATE;
+    
+    for (n = -SINC_RADIUS; n < SINC_RADIUS; n++) {
+        float a,b;
+        a = symbol_at(s, symbols, n+SINC_RADIUS);
+        b = sinc(-n + d*BAUD_RATE/SAMPLE_RATE);
+        sum +=  a*b; 
+    }
+    assert(sum<=10);
+    assert(sum >=-10);
+    
+    return sum;
+}
+
+int v17mod_pull(struct v17mod_state *s, float *p, int l) {
+    assert(s && p && l && p && l);
+
+    int n_samples = 0;
+    
+    for (;;) {
+        float x;
+        int nsi;
+
+        if (s->sample % 800 == 0) 
+             fprintf(stderr, "seconds: %i; samples: %i; symbols: %i          \r", s->seconds, s->sample, s->symbol_index); 
+        
+        if (!l) {
+            fprintf(stderr, "v17_mod(): destination buffer too short\n");
+            return -1;
+        }
+
+        nsi = (int) ((float) s->sample*BAUD_RATE/SAMPLE_RATE);
+        if (nsi != s->symbol_index) {
+            s->i_symbols++;
+            s->n_symbols--;
+
+            while (s->i_symbols >= SYMBOLS_MAX)
+                s->i_symbols -= SYMBOLS_MAX;
+            
+            s->symbol_index = nsi;
+        }
+
+        if (s->n_symbols < SINC_RADIUS*2)
+            return n_samples;
+
+        if (s->sample == SAMPLE_RATE) {
+            assert(s->symbol_index == BAUD_RATE);
+
+            s->symbol_index = s->sample = 0;
+            s->seconds++;
+        }
+        
+        
+        x = (s->sample % SAMPLE_RATE) * M_PI*2 * CARRIER_FREQ / SAMPLE_RATE;
+        
+        *(p++) = fsignal(s, 0)*sin(x) + fsignal(s, 1)*cos(x);
+        l--;
+
+        s->sample++;
+        n_samples++;
+    }
+}
+
+
+#if (TEST == 3)
+
+int main() {
+    fprintf(stderr, "%f\n", sinc(1.0/3));
+
+    return 0;
+}
+
+#endif