From 783b56d54788f177881d68ae2ec7a7cb4bb38ac4 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Sun, 18 Apr 2004 01:35:53 +0000
Subject: Initial commit

git-svn-id: file:///home/lennart/svn/public/vfax/trunk@3 541b366f-4dd8-0310-ae39-b2612fd50714
---
 v17dem.c | 102 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)
 create mode 100644 v17dem.c

(limited to 'v17dem.c')

diff --git a/v17dem.c b/v17dem.c
new file mode 100644
index 0000000..4fad8f3
--- /dev/null
+++ b/v17dem.c
@@ -0,0 +1,102 @@
+#include "v17dem.h"
+
+#define INITIAL_BAUD_RATE 2400
+#define INITIAL_CARRIER_FREQ 1800
+#define SAMPLE_RATE 8000
+#define SAMPLES_MAX (SAMPLES_RATE*5)           /* -> 5s buffer */
+
+#define SINC_RADIUS 10
+
+struct v17dem_state {
+    float *samples;
+    int i_samples, n_samples;
+
+    int sample_index;
+
+    int baud_rate;
+    int carrier_freq;
+
+    struct interpol_state qam_interpol;
+    struct interpol_state am_interpol;
+
+    enum { COSINUS, SINUS } current;
+    float *xam, *yam;
+    int am_index;
+};
+
+
+void v17dem_init(struct v17dem_state *s) {
+    assert(s);
+
+    memset(s, 0, sizeof(struct v17dem_state));
+    s->baud_rate = INITIAL_BAUD_RATE;
+    s->carrier_freq = INITIAL_CARRIER_FREQ;
+    s->samples = malloc(sizeof(float) * SAMPLES_MAX * 2);
+
+    interpol_init(&s->qam_interpol, 9, SINC_RADIUS);
+}
+
+void v17dem_done(struct v17dem_state *s) {
+    assert(s);
+
+    free(s->samples);
+    inertpol_done(&s->qam_interpol);
+}
+
+static void move_to_front(struct v17dem_state *s) {
+    assert(s);
+
+    if (s->i_samples < SAMPLES_MAX)
+        return;
+
+    memmove(s->samples, s->samples + s->i_samples, s->n_samples*sizeof(float));
+    s->i_samples = 0;
+}
+
+void v17dem_push(struct v17dem_state *s, const float *p, int l){
+    assert(s && p && l);
+
+    assert(l <= SAMPLES_MAX-s->n_samples);
+
+    move_to_front(s);
+
+    memcpy(s->samples + s->i_samples + s->n_samples, p, l*sizeof(float));
+    s->n_samples += l;
+}
+
+int v17dem_pull(struct v17dem_state *s, uint8_t *p, int l){
+    int alt = 0;
+
+    assert(s && p && l);
+
+    for (;;) {
+        int n;
+        
+        /* Position für AM-Abtastung im Sample-Puffer berechnen -- alle 90° */
+        float x = (SAMPLE_RATE/(4.0*s->carrier_freq) * s->am_index) - s->sample_index;
+        assert(x >= 0);
+
+        /* AM-Abtatsung druchführen */
+        if (s->current = COSINUS)
+            am = s->xam;
+        else
+            am = s->yam;
+
+        am[s->am_index] = interpol_get(s->qam_interpol, s->samples + s->i_samples, s->n_samples, x);
+
+        if (s->current == SINUS)
+            s->am_index++;
+        
+        s->current = !s->current;
+
+        /* Überflüssige Sampledaten killen */
+
+        n = (int) (x - (float) SINC_RADIUS*SAMPLE_RATE/s->carrier_freq/4);
+
+        if (n > 0) {
+            s->n_samples -= n;
+            s->i_samples += n;
+            s->sample_index += n;
+        }
+    }
+}
-- 
cgit