tests: FFT of a sine wave

tests/test-fft.cc

@@ -20,10 +20,14 @@
 
 #include "test.h"
 
+// FFT sizes that avfft can actually handle.
+static const int FFT_BITS_MIN = 4;
+static const int FFT_BITS_MAX = 15;
+
 static void test_const()
 {
     FFT fft;
-    for (int nbits = 4; nbits < 16; ++nbits) {
+    for (int nbits = FFT_BITS_MIN; nbits <= FFT_BITS_MAX; ++nbits) {
         auto plan = fft.create(nbits);
         test("input size", 1 << nbits, plan->get_input_size());
         test("output size", (1 << nbits) / 2 + 1, plan->get_output_size());
@@ -33,33 +37,61 @@ static void test_const()
             plan->set_input(i, 0.0f);
         }
         plan->execute();
-        bool ok = true;
+        bool silence = true;
         for (int i = 0; i < plan->get_output_size(); ++i) {
             if (plan->get_output(i) > -1e12f) {
-                ok = false;
+                silence = false;
                 break;
             }
         }
-        test("zero input", true, ok);
+        test("silence", true, silence);
 
         // Test DC input.
         for (int i = 0; i < plan->get_input_size(); ++i) {
             plan->set_input(i, 1.0f);
         }
         plan->execute();
-        ok = true;
         test("dc component", 0.0f, plan->get_output(0));
+        silence = true;
         for (int i = 1; i < plan->get_output_size(); ++i) {
             if (plan->get_output(i) > -1e12f) {
-                ok = false;
+                silence = false;
                 break;
             }
         }
-        test("dc input", true, ok);
+        test("silence", true, silence);
+    }
+}
+
+static void test_sine()
+{
+    FFT fft;
+    for (int nbits = FFT_BITS_MIN; nbits <= FFT_BITS_MAX; ++nbits) {
+        auto plan = fft.create(nbits);
+        int n = plan->get_input_size();
+        for (int k = 1; k < n / 2; k *= 2) {
+            for (int i = 0; i < n; ++i) {
+                plan->set_input(i, sin(k * i * 2.0 * M_PI / n));
+            }
+            plan->execute();
+            test("sine", -602, static_cast<int>(plan->get_output(k) * 100));
+            bool silence = true;
+            for (int i = 0; i < plan->get_output_size(); ++i) {
+                if (i == k) {
+                    continue;
+                }
+                if (plan->get_output(i) > -150.0f) {
+                    silence = false;
+                    break;
+                }
+            }
+            test("silence", true, silence);
+        }
     }
 }
 
 void test_fft()
 {
     run("fft const", test_const);
+    run("fft sine", test_sine);
 }

tests/test.h

@@ -20,6 +20,7 @@
 #define TEST_H_
 
 #include <cmath>
+#include <cstdio>
 #include <functional>
 #include <iostream>
 #include <string>