1 files changed, 91 insertions, 0 deletions
diff --git a/third_party/libwebrtc/common_audio/real_fourier_ooura.cc b/third_party/libwebrtc/common_audio/real_fourier_ooura.cc
new file mode 100644
index 0000000000..9acda5494c
--- /dev/null
+++ b/third_party/libwebrtc/common_audio/real_fourier_ooura.cc
@@ -0,0 +1,91 @@
+/*
+ *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "common_audio/real_fourier_ooura.h"
+
+#include <algorithm>
+#include <cmath>
+
+#include "common_audio/third_party/ooura/fft_size_256/fft4g.h"
+#include "rtc_base/checks.h"
+
+namespace webrtc {
+
+using std::complex;
+
+namespace {
+
+void Conjugate(complex<float>* array, size_t complex_length) {
+  std::for_each(array, array + complex_length,
+                [=](complex<float>& v) { v = std::conj(v); });
+}
+
+size_t ComputeWorkIpSize(size_t fft_length) {
+  return static_cast<size_t>(
+      2 + std::ceil(std::sqrt(static_cast<float>(fft_length))));
+}
+
+}  // namespace
+
+RealFourierOoura::RealFourierOoura(int fft_order)
+    : order_(fft_order),
+      length_(FftLength(order_)),
+      complex_length_(ComplexLength(order_)),
+      // Zero-initializing work_ip_ will cause rdft to initialize these work
+      // arrays on the first call.
+      work_ip_(new size_t[ComputeWorkIpSize(length_)]()),
+      work_w_(new float[complex_length_]()) {
+  RTC_CHECK_GE(fft_order, 1);
+}
+
+RealFourierOoura::~RealFourierOoura() = default;
+
+void RealFourierOoura::Forward(const float* src, complex<float>* dest) const {
+  {
+    // This cast is well-defined since C++11. See "Non-static data members" at:
+    // http://en.cppreference.com/w/cpp/numeric/complex
+    auto* dest_float = reinterpret_cast<float*>(dest);
+    std::copy(src, src + length_, dest_float);
+    WebRtc_rdft(length_, 1, dest_float, work_ip_.get(), work_w_.get());
+  }
+
+  // Ooura places real[n/2] in imag[0].
+  dest[complex_length_ - 1] = complex<float>(dest[0].imag(), 0.0f);
+  dest[0] = complex<float>(dest[0].real(), 0.0f);
+  // Ooura returns the conjugate of the usual Fourier definition.
+  Conjugate(dest, complex_length_);
+}
+
+void RealFourierOoura::Inverse(const complex<float>* src, float* dest) const {
+  {
+    auto* dest_complex = reinterpret_cast<complex<float>*>(dest);
+    // The real output array is shorter than the input complex array by one
+    // complex element.
+    const size_t dest_complex_length = complex_length_ - 1;
+    std::copy(src, src + dest_complex_length, dest_complex);
+    // Restore Ooura's conjugate definition.
+    Conjugate(dest_complex, dest_complex_length);
+    // Restore real[n/2] to imag[0].
+    dest_complex[0] =
+        complex<float>(dest_complex[0].real(), src[complex_length_ - 1].real());
+  }
+
+  WebRtc_rdft(length_, -1, dest, work_ip_.get(), work_w_.get());
+
+  // Ooura returns a scaled version.
+  const float scale = 2.0f / length_;
+  std::for_each(dest, dest + length_, [scale](float& v) { v *= scale; });
+}
+
+int RealFourierOoura::order() const {
+  return order_;
+}
+
+}  // namespace webrtc