Finalization of the first version of EchoCanceller 3

webrtc/modules/audio_processing/aec3/fft_buffer.h

Index: webrtc/modules/audio_processing/aec3/fft_buffer.h
diff --git a/webrtc/modules/audio_processing/aec3/fft_buffer.h b/webrtc/modules/audio_processing/aec3/fft_buffer.h
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+/*
+ *  Copyright (c) 2017 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.
+ */
+
+#ifndef WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_FFT_BUFFER_H_
+#define WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_FFT_BUFFER_H_
+
+#include <memory>
+#include <vector>
+
+#include "webrtc/base/array_view.h"
+#include "webrtc/base/constructormagic.h"
+#include "webrtc/modules/audio_processing/aec3/fft_data.h"
+
+namespace webrtc {
+
+// Provides a circular buffer for 128 point real-valued FFT data.
+class FftBuffer {
+ public:
+  // The constructor takes as parameters the size of the buffer, as well as a
+  // vector containing the number of FFTs that will be included in the spectral
+  // sums in the call to SpectralSum.

[aleloi, 2017/02/23 15:16:00]

Comment about the vector seemed unclear to me. Suggested rewording: "vector
contains values |num_ffts| that the SpectralSum method of the created instance
will support."

That didn't sound perfect either. 

+  FftBuffer(Aec3Optimization optimization,
+            size_t size,
+            const std::vector<size_t> num_ffts_for_spectral_sums);
+  ~FftBuffer();
+
+  // Insert an FFT into the buffer.
+  void Insert(const FftData& fft);
+
+  // Get the spectrum from one of the FFTs in the buffer
+  const std::array<float, kFftLengthBy2Plus1>& Spectrum(
+      size_t buffer_offset_ffts) const {
+    return spectrum_buffer_[(position_ + buffer_offset_ffts) %
+                            fft_buffer_.size()];
+  }
+
+  // Returns the sum of the spectrums for a certain number of FFTs.

[aleloi, 2017/02/23 15:16:00]

Suggestion: change comment to "Returns the sum of the spectrums of the
|num_ffts| most recent FFTs."

+  const std::array<float, kFftLengthBy2Plus1>& SpectralSum(
+      size_t num_ffts) const {
+    RTC_DCHECK_EQ(spectral_sums_length_, num_ffts);
+    return spectral_sums_[0];
+  }
+
+  // Returns the circular buffer.
+  rtc::ArrayView<const FftData> Buffer() const { return fft_buffer_; }
+
+  // Returns the current position in the circular buffer
+  size_t Position() const { return position_; }
+
+ private:
+  const Aec3Optimization optimization_;
+  std::vector<FftData> fft_buffer_;
+  std::vector<std::array<float, kFftLengthBy2Plus1>> spectrum_buffer_;
+  size_t spectral_sums_length_;
+  std::vector<std::array<float, kFftLengthBy2Plus1>> spectral_sums_;
+  size_t position_ = 0;
+
+  RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(FftBuffer);
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_FFT_BUFFER_H_