From d7159e56d299986f6743a66a548a95d46a52bb57 Mon Sep 17 00:00:00 2001
From: EvanR <evanrinehart@gmail.com>
Date: Fri, 5 Jun 2009 19:50:15 -0400
Subject: [PATCH] Added low pass stage to additive synth.

---
 core.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/core.c b/core.c
index 66ecc64..01ebd18 100644
--- a/core.c
+++ b/core.c
@@ -32,7 +32,7 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 #define SAMPLE_COUNT 16
 #define SAMPLE_NOTE_ZERO 60
 
-#define ANTIPOP_LENGTH 64
+#define ANTIPOP_LENGTH 512
 #define WAVEFORM_LENGTH 256
 
 #define MAX_COMMANDS 256
@@ -70,6 +70,7 @@ struct orgux_state{
   //float sample_velocity[SAMPLE_COUNT];
 
   int sample_rate;
+  float lp_alpha;
 
   int command_queue[512][5]; /* sample type chan val1 val2 */
   int command_count;
@@ -83,6 +84,7 @@ struct orgux_state{
   float wave_ptr[MAX_NOTES];
   float wave_step[MAX_NOTES];
   int sample_ptr[MAX_NOTES];
+  float lp_y[MAX_NOTES];
   int note_max;
 };
 
@@ -233,6 +235,10 @@ void orgux_process(orgux_state* S, float* lbuf, float* rbuf, int len){
       float y = m*(x-x1) + y1;
 //float y = 0;
 
+      float y0 = S->lp_y[j];
+      y = y0 + S->lp_alpha * (y - y0);
+      S->lp_y[j] = y;
+
       switch(S->antipop_flag[j]){
         case -1:
           y *= S->antipop[S->antipop_ptr[j]];
@@ -387,6 +393,8 @@ orgux_state* orgux_init(int sample_rate){
   orgux_state* S = malloc(sizeof(orgux_state));
   if(!S) return NULL;
 
+  float dt = 1.0/sample_rate;
+
   /* setup oscillator states */
 
   for(int i=0; i<16; i++){
@@ -401,6 +409,7 @@ orgux_state* orgux_init(int sample_rate){
     S->antipop_flag[i] = 0;
     S->note_on[i] = 0;
     S->sample_ptr[i] = 0;
+    S->lp_y[i] = 0;
   }
 
   //for(int i=0; i<SAMPLE_COUNT; i++){
@@ -409,6 +418,7 @@ orgux_state* orgux_init(int sample_rate){
   //}
 
   S->sample_rate = sample_rate;
+  S->lp_alpha = dt/(dt+(1.0/35000));
   S->command_count = 0;
   S->note_max = 0;
 
@@ -490,7 +500,6 @@ int N = 0;
   float y_l;
   float y_h0=0;
   float y_h1=0;
-  float dt = (1.0/sample_rate);
   
 /*
 notes
-- 
2.11.4.GIT