From 2711027dcfc70bd72a2d6e476854049c20c318d0 Mon Sep 17 00:00:00 2001
From: Emile Clark-Boman <eclarkboman@gmail.com>
Date: Thu, 4 Sep 2025 11:23:07 +1000
Subject: [PATCH] separate frequency from accumulator

---
 lib/main.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/lib/main.c b/lib/main.c
index b834c43..a9a59dc 100644
--- a/lib/main.c
+++ b/lib/main.c
@@ -11,6 +11,8 @@
 #define DEFAULT_VOLUME 0.7
 #define DEFAULT_FREQ 200
 
+#define DEFAULT_ACCUMULATOR -1
+
 #define PWSTREAM_NAME "Dorne"
 
 struct data {
@@ -43,9 +45,9 @@ 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 >= M_PI_M2) {
-      data->accumulator -= M_PI_M2;
+    // data->accumulator += M_PI_M2 * DEFAULT_FREQ / DEFAULT_RATE; // * 440
+    if (data->accumulator++ == DEFAULT_RATE) {
+      data->accumulator = DEFAULT_ACCUMULATOR;
       data->cycle++;
     }
 
@@ -55,7 +57,7 @@ static void on_process(void *userdata) {
      * 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) * DEFAULT_VOLUME * 32767.0;
+    val = sin(data->accumulator * M_PI_M2 * DEFAULT_FREQ / DEFAULT_RATE) * DEFAULT_VOLUME * 32767.0;
     for (c = 0; c < DEFAULT_CHANNELS; c++)
       *dst++ = val;
   }
@@ -75,7 +77,8 @@ static const struct pw_stream_events stream_events = {
 
 int main(int argc, char *argv[]) {
   struct data data = {
-      0,
+      .accumulator = DEFAULT_ACCUMULATOR,
+      .cycle = 0,
   };
   const struct spa_pod *params[1];
   uint8_t buffer[1024];