initial

sstv.c

@@ -0,0 +1,78 @@
+#include "sstv.h"
+#include "image.h"
+#include "robot36.h"
+#include "wav.h"
+#include <math.h>
+#include <stdint.h>
+
+#define PI 3.14159265358979
+#define AMPLITUDE 12000
+
+static double phase = 0.0;
+
+void sstv_tone(wav_t *wav, double freq, double duration_ms) {
+    uint32_t total_samples = (uint32_t)((duration_ms / 1000.0) * wav->sample_rate);
+
+    for (uint32_t i = 0; i < total_samples; i++) {
+        double step = 2.0 * PI * freq / wav->sample_rate;
+        phase += step;
+        if (phase > 2.0 * PI)
+            phase -= 2.0 * PI;
+
+        int16_t sample = (int16_t)(AMPLITUDE * sin(phase));
+        wave_write_sample(wav, sample);
+    }
+}
+
+void sstv_vis_header(wav_t *wav) {
+    uint8_t vis = 0x08;   
+    uint8_t parity = 0;
+
+    sstv_tone(wav, 1900, 300);
+    sstv_tone(wav, 1200, 10);
+    sstv_tone(wav, 1900, 300);
+
+    sstv_tone(wav, 1200, 30);
+
+    for (int i = 0; i < 7; i++) {
+        uint8_t bit = (vis >> i) & 1;  
+        if (bit) {
+            sstv_tone(wav, 1100, 30);
+            parity ^= 1;
+        } else {
+            sstv_tone(wav, 1300, 30);
+        }
+    }
+
+    sstv_tone(wav, parity ? 1100 : 1300, 30);
+
+    sstv_tone(wav, 1200, 30);
+}
+
+int sstv_encode_robot36(const char *input_image, const char *output_wav) {
+    image_t img, resized;
+    wav_t wav;
+
+    if (!image_load(&img, input_image))
+        return 0;
+
+    if (!image_resize(&img, &resized, ROBOT36_WIDTH, ROBOT36_HEIGHT)) {
+        image_free(&img);
+        return 0;
+    }
+
+    if (!wave_open(&wav, output_wav, 44100)) {
+        image_free(&img);
+        image_free_raw(&resized);
+        return 0;
+    }
+
+    sstv_vis_header(&wav);
+    robot36_encode_image(&wav, resized.data);
+    wave_close(&wav);
+
+    image_free(&img);
+    image_free_raw(&resized);
+
+    return 1;
+}