1 files changed, 17 insertions, 0 deletions
diff --git a/src/audio/idct.cc b/src/audio/idct.cc
new file mode 100644
index 0000000..5d6bde0
--- /dev/null
+++ b/src/audio/idct.cc
@@ -0,0 +1,17 @@
+#include "dct.h"
+#include "util/math.h"
+#include <math.h>
+
+void idct_512(const float input[DCT_SIZE], float output[DCT_SIZE]) {
+  float scale_k0 = sqrtf(1.0f / DCT_SIZE);
+  float scale_kn = sqrtf(2.0f / DCT_SIZE);
+
+  for (int n = 0; n < DCT_SIZE; ++n) {
+    float sum = 0.0f;
+    for (int k = 0; k < DCT_SIZE; ++k) {
+      float scale = (k == 0) ? scale_k0 : scale_kn;
+      sum += scale * input[k] * cosf((PI / DCT_SIZE) * (n + 0.5f) * k);
+    }
+    output[n] = sum;
+  }
+}