martin modes, and some bugfixes to get them working

martin.c

@@ -0,0 +1,78 @@
+#include "martin.h"
+#include "image.h"
+#include "sstv.h"
+#include "wav.h"
+#include <stdint.h>
+
+const martin_mode_t MARTIN_M1 = {
+  .vis_code = 0x2C, // hex (dd -> 44d)
+  .width = 320,
+  .height = 256,
+  .sync_ms = 4.862,
+  .sync_porch_ms = 0.572,
+  .separator_ms = 0.572,
+  .scan_ms = 146.432,   // per channel , per line
+};
+
+const martin_mode_t MARTIN_M2 = {
+  .vis_code = 0x28, // hex (dd -> 40d)
+  .width = 320,
+  .height = 256,
+  .sync_ms = 4.862,
+  .sync_porch_ms = 0.572,
+  .separator_ms = 0.572,
+  .scan_ms = 73.216, // half of M1
+};
+
+static void scan_line_channel(wav_t *wav, uint8_t *line, int width, int channel, double scan_ms) {
+  double px_ms = scan_ms / width;
+  for (int x = 0; x < width; x++) {
+    uint8_t val = line[x * 3 + channel];
+    double freq = 1500.0 + val * 3.1372549;
+    sstv_tone(wav, freq, px_ms);
+  }
+}
+
+void martin_encode_image(wav_t *wav, uint8_t *rgb, const martin_mode_t *mode) {
+    for (int y = 0; y < mode->height; y++) {
+        uint8_t *line = &rgb[y * mode->width * 3];
+
+        sstv_tone(wav, 1200.0, mode->sync_ms);       // sync pulse
+        sstv_tone(wav, 1500.0, mode->sync_porch_ms); // sync porch
+        scan_line_channel(wav, line, mode->width, 1, mode->scan_ms); // G
+        sstv_tone(wav, 1500.0, mode->separator_ms);
+        scan_line_channel(wav, line, mode->width, 2, mode->scan_ms); // B
+        sstv_tone(wav, 1500.0, mode->separator_ms);
+        scan_line_channel(wav, line, mode->width, 0, mode->scan_ms); // R
+        sstv_tone(wav, 1500.0, mode->separator_ms);
+    }
+}
+
+int sstv_encode_martin(const char *input_image, const char *output_wav, const martin_mode_t *mode) {
+  image_t img, resized;
+  wav_t wav;
+
+  if (!image_load(&img, input_image)) {
+    return 0;
+  }
+
+  if (!image_resize(&img, &resized, mode->width, mode->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_ex(&wav, mode->vis_code);
+  martin_encode_image(&wav, resized.data, mode);
+  wave_close(&wav);
+
+  image_free(&img);
+  image_free_raw(&resized);
+
+  return 1;
+}