Test filter uses a dB graph to show the response graphically

src/common/debug.c

@@ -23,6 +23,7 @@
 #include <stdlib.h>
 #include <stdint.h>
 #include <errno.h>
+#include <math.h>
 #include "sample.h"
 #include "debug.h"
 #include "display.h"
@@ -118,6 +119,26 @@ const char *debug_amplitude(double level)
 	return text;
 }
 
+#define level2db(level)         (20 * log10(level))
+
+const char *debug_db(double level_db)
+{
+	static char text[128];
+	int l;
+
+	strcpy(text, ":  .  :  .  :  .  :  .  :  .  :  .  :  .  :  .  :   ");
+	if (level_db <= 0.0)
+		return text;
+	l = (int)round(level2db(level_db));
+	if (l > 3)
+		return text;
+	if (l < -48)
+		return text;
+	text[l + 48] = '*';
+
+	return text;
+}
+
 void debug_list_cat(void)
 {
 	int i;