diff --git a/lib/main.c b/lib/main.c
index a9a59dc..d875c8c 100644
--- a/lib/main.c
+++ b/lib/main.c
@@ -1,15 +1,16 @@
 #include <math.h>
 
 #include <spa/param/audio/format-utils.h>
-
 #include <pipewire/pipewire.h>
 
 #define M_PI_M2 (M_PI + M_PI)
 
 #define DEFAULT_RATE 44100
+#define DEFAULT_PERIOD 1.0 / DEFAULT_RATE
+
 #define DEFAULT_CHANNELS 2
 #define DEFAULT_VOLUME 0.7
-#define DEFAULT_FREQ 200
+#define DEFAULT_FREQ 500
 
 #define DEFAULT_ACCUMULATOR -1
 
@@ -18,17 +19,72 @@
 struct data {
   struct pw_main_loop *loop;
   struct pw_stream *stream;
-  double accumulator;
-  uint32_t cycle;
+
+  /*
+   */
+  double t, tcyc; // global time and cycle time 
+  uint32_t frame, cycle;
 };
 
+#define NEW_DATA (struct data) \
+                 {             \
+                   .t = 0,     \
+                   .tcyc = 0,  \
+                   .frame = 0, \
+                   .cycle = 0, \
+                 }
+
+typedef int16_t (*snd)(struct data*);
+
+inline void data_progress(struct data *state) {
+  state->t += DEFAULT_PERIOD / DEFAULT_FREQ;
+  state->tcyc += DEFAULT_PERIOD / DEFAULT_FREQ;
+  if (++state->frame == DEFAULT_FREQ) {
+    state->tcyc -= DEFAULT_PERIOD;
+    state->frame = 0;
+    state->cycle++;
+  } 
+}
+
+int16_t snd_sine(struct data *state) {
+  int16_t val;
+  
+  /* sin() gives a value between -1.0 and 1.0, we first apply
+   * the volume and then scale with 32767.0 to get a 16 bits value
+   * between [-32767 32767].
+   * Another common method to convert a double to
+   * 16 bits is to multiple by 32768.0 and then clamp to
+   * [-32768 32767] to get the full 16 bits range. */
+  val = sin(state->tcyc * M_PI_M2 * DEFAULT_FREQ) * 32767.0 * DEFAULT_VOLUME;
+  
+  return val;
+}
+
+int graph_snd(snd f, struct data *state, double t_max, FILE *fstream) {
+  int16_t val;
+  if (fstream == NULL)
+    return 1;
+  
+  fputs("x, sin(x)\n", fstream);
+  while (state->t < t_max) {
+    val = f(state);
+    fprintf(fstream, "%f, %d\n", state->t, val);
+    data_progress(state);
+  }
+
+  fclose(fstream);
+  return 0;
+}
+
+
 /* [on_process] */
 static void on_process(void *userdata) {
   struct data *data = userdata;
   struct pw_buffer *b;
   struct spa_buffer *buf;
-  int i, c, n_frames, stride;
+  int n_frames, stride;
   int16_t *dst, val;
+  int i, c;
 
   if ((b = pw_stream_dequeue_buffer(data->stream)) == NULL) {
     pw_log_warn("out of buffers: %m");
@@ -45,19 +101,7 @@ static void on_process(void *userdata) {
     n_frames = SPA_MIN(b->requested, n_frames);
 
   for (i = 0; i < n_frames; i++) {
-    // data->accumulator += M_PI_M2 * DEFAULT_FREQ / DEFAULT_RATE; // * 440
-    if (data->accumulator++ == DEFAULT_RATE) {
-      data->accumulator = DEFAULT_ACCUMULATOR;
-      data->cycle++;
-    }
-
-    /* sin() gives a value between -1.0 and 1.0, we first apply
-     * the volume and then scale with 32767.0 to get a 16 bits value
-     * between [-32767 32767].
-     * Another common method to convert a double to
-     * 16 bits is to multiple by 32768.0 and then clamp to
-     * [-32768 32767] to get the full 16 bits range. */
-    val = sin(data->accumulator * M_PI_M2 * DEFAULT_FREQ / DEFAULT_RATE) * DEFAULT_VOLUME * 32767.0;
+    val = snd_sine(data);
     for (c = 0; c < DEFAULT_CHANNELS; c++)
       *dst++ = val;
   }
@@ -75,16 +119,20 @@ static const struct pw_stream_events stream_events = {
     .process = on_process,
 };
 
-int main(int argc, char *argv[]) {
-  struct data data = {
-      .accumulator = DEFAULT_ACCUMULATOR,
-      .cycle = 0,
-  };
+int main(int argc, char **argv) {
+  struct data data = NEW_DATA;
   const struct spa_pod *params[1];
   uint8_t buffer[1024];
   struct spa_pod_builder b = SPA_POD_BUILDER_INIT(buffer, sizeof(buffer));
 
-  pw_init(&argc, &argv);
+  // DEBUG: check sine wave is actually a sine wave
+  FILE *fstream = fopen("sine.txt", "w");
+  graph_snd(&snd_sine, &NEW_DATA, DEFAULT_PERIOD, fstream);
+  exit(69);
+  
+  int pw_argc = 0;
+  char **pw_argv = NULL;
+  pw_init(&pw_argc, &pw_argv); // pw_init(&argc, &argv);
 
   data.loop = pw_main_loop_new(NULL);