1 files changed, 96 insertions, 0 deletions
diff --git a/speaker-test/pink.c b/speaker-test/pink.c
new file mode 100644
index 0000000..ef30755
--- /dev/null
+++ b/speaker-test/pink.c
@@ -0,0 +1,96 @@
+/*
+  patest_pink.c
+
+  generate Pink Noise using Gardner method.
+  Optimization suggested by James McCartney uses a tree
+  to select which random value to replace.
+
+  x x x x x x x x x x x x x x x x 
+  x   x   x   x   x   x   x   x   
+  x       x       x       x       
+  x               x               
+  x                               
+
+  Tree is generated by counting trailing zeros in an increasing index.
+  When the index is zero, no random number is selected.
+
+  This program uses the Portable Audio library which is under development.
+  For more information see:   http://www.audiomulch.com/portaudio/
+
+  Author: Phil Burk, http://www.softsynth.com
+	
+  Revision History:
+
+  Copyleft 1999 Phil Burk - No rights reserved.
+*/
+
+#include <stdio.h>
+#include <math.h>
+#include "pink.h"
+
+/************************************************************/
+/* Calculate pseudo-random 32 bit number based on linear congruential method. */
+static unsigned long generate_random_number( void )
+{
+    static unsigned long rand_seed = 22222;  /* Change this for different random sequences. */
+    rand_seed = (rand_seed * 196314165) + 907633515;
+    return rand_seed;
+}
+
+/* Setup PinkNoise structure for N rows of generators. */
+void initialize_pink_noise( pink_noise_t *pink, int num_rows )
+{
+    int i;
+    long pmax;
+    pink->pink_index = 0;
+    pink->pink_index_mask = (1<<num_rows) - 1;
+/* Calculate maximum possible signed random value. Extra 1 for white noise always added. */
+    pmax = (num_rows + 1) * (1<<(PINK_RANDOM_BITS-1));
+    pink->pink_scalar = 1.0f / pmax;
+/* Initialize rows. */
+    for( i=0; i<num_rows; i++ ) pink->pink_rows[i] = 0;
+    pink->pink_running_sum = 0;
+}
+
+/* generate Pink noise values between -1.0 and +1.0 */
+float generate_pink_noise_sample( pink_noise_t *pink )
+{
+    long new_random;
+    long sum;
+    float output;
+
+/* Increment and mask index. */
+    pink->pink_index = (pink->pink_index + 1) & pink->pink_index_mask;
+
+/* If index is zero, don't update any random values. */
+    if( pink->pink_index != 0 )
+    {
+	/* Determine how many trailing zeros in PinkIndex. */
+	/* This algorithm will hang if n==0 so test first. */
+	int num_zeros = 0;
+	int n = pink->pink_index;
+	while( (n & 1) == 0 )
+	{
+	    n = n >> 1;
+	    num_zeros++;
+	}
+
+	/* Replace the indexed ROWS random value.
+	 * Subtract and add back to Running_sum instead of adding all the random
+	 * values together. Only one changes each time.
+	 */
+	pink->pink_running_sum -= pink->pink_rows[num_zeros];
+	new_random = ((long)generate_random_number()) >> PINK_RANDOM_SHIFT;
+	pink->pink_running_sum += new_random;
+	pink->pink_rows[num_zeros] = new_random;
+    }
+	
+/* Add extra white noise value. */
+    new_random = ((long)generate_random_number()) >> PINK_RANDOM_SHIFT;
+    sum = pink->pink_running_sum + new_random;
+
+/* Scale to range of -1.0 to 0.9999. */
+    output = pink->pink_scalar * sum;
+
+    return output;
+}