Finalization of the first version of EchoCanceller 3

webrtc/modules/audio_processing/aec3/subtractor.cc

+/*
+ *  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.
+ */
+
+#include "webrtc/modules/audio_processing/aec3/subtractor.h"
+
+#include <algorithm>
+
+#include "webrtc/base/array_view.h"
+#include "webrtc/base/checks.h"
+#include "webrtc/modules/audio_processing/logging/apm_data_dumper.h"
+
+namespace webrtc {
+
+std::vector<size_t> Subtractor::NumBlocksInRenderSums() const {
+  if (kMainFilterLength != kShadowFilterLength) {
+    std::vector<size_t> v(2);
+    v[0] = kMainFilterLength;
+    v[1] = kShadowFilterLength;
+    return v;

[aleloi, 2017/02/13 16:44:51]

return {kMainFilterLength, kShadowFilterLength};

should do the same thing. Same for the else clause below.

[peah-webrtc, 2017/02/20 07:37:19]

Done.

+  } else {
+    std::vector<size_t> v(1);
+    v[0] = kMainFilterLength;
+    return v;
+  }
+}
+
+Subtractor::Subtractor(ApmDataDumper* data_dumper)
+    : data_dumper_(data_dumper),
+      main_filter_(kMainFilterLength, true, data_dumper_),
+      shadow_filter_(kShadowFilterLength, false, data_dumper_) {
+  RTC_DCHECK(data_dumper_);
+}
+
+Subtractor::~Subtractor() {}
+
+void Subtractor::HandleEchoPathChange(
+    const EchoPathVariability& echo_path_variability) {
+  if (echo_path_variability.AudioPathChanged()) {
+    if (echo_path_variability.delay_change) {
+      main_filter_.HandleEchoPathChange();
+      shadow_filter_.HandleEchoPathChange();
+      G_main_.HandleEchoPathChange();
+    }
+  }
+}
+
+void Subtractor::Process(const FftBuffer& render_buffer,
+                         const rtc::ArrayView<const float> capture,
+                         const RenderSignalAnalyzer& render_signal_analyzer,
+                         bool saturation,
+                         SubtractorOutput* output) {
+  RTC_DCHECK_EQ(kBlockSize, capture.size());
+  const rtc::ArrayView<const float> y = capture;
+  const FftBuffer& X_buffer = render_buffer;
+  FftData& E_main = output->E_main;
+  FftData& E_shadow = output->E_shadow;
+  std::array<float, kBlockSize>& e_main = output->e_main;
+  std::array<float, kBlockSize>& e_shadow = output->e_shadow;
+
+  FftData S;
+  FftData& G = S;
+
+  std::array<float, kFftLength> s;
+  constexpr float kScale = 1.0f / kFftLengthBy2;
+
+  // Form and analyze the output of the main filter.
+  main_filter_.Filter(X_buffer, &S);
+  fft_.Ifft(S, &s);
+  std::transform(y.begin(), y.end(), s.begin() + kFftLengthBy2, e_main.begin(),
+                 [&](float a, float b) { return a - b * kScale; });

[aleloi, 2017/02/13 16:44:51]

Beginner question: why the scaling? Is it because it's missing in Ifft and FFT
composed with Ifft is not identity?

[peah-webrtc, 2017/02/20 07:37:19]

It is not included in the ifft method. My guess is that it is not desired to do
the scaling if that is not strictly needed and that therefore that scaling needs
to be explicitly done.

+  std::for_each(e_main.begin(), e_main.end(), [](float& a) {
+    a = std::max(std::min(a, 32767.0f), -32768.0f);
+  });
+  fft_.ZeroPaddedFft(e_main, &E_main);
+
+  // Form and analyze the output of the shadow filter.
+  shadow_filter_.Filter(X_buffer, &S);
+  fft_.Ifft(S, &s);
+  std::transform(y.begin(), y.end(), s.begin() + kFftLengthBy2,
+                 e_shadow.begin(),
+                 [&](float a, float b) { return a - b * kScale; });
+  std::for_each(e_shadow.begin(), e_shadow.end(), [](float& a) {
+    a = std::max(std::min(a, 32767.0f), -32768.0f);
+  });
+  fft_.ZeroPaddedFft(e_shadow, &E_shadow);
+

[aleloi, 2017/02/13 16:44:51]

I suggest putting the filtering & subtraction in a function to avoid having to
almost identical blocks.

[peah-webrtc, 2017/02/20 07:37:19]

I did a variant of that. I think it is nice to see both parts together. Very
likely this code should be changed after the tuning is done.

Done.

+  // Compute spectra for future use.
+  E_main.Spectrum(&output->E2_main);
+  E_shadow.Spectrum(&output->E2_shadow);
+
+  // Update the main filter.
+  G_main_.Compute(X_buffer, render_signal_analyzer, *output, main_filter_,
+                  saturation, &G);
+  main_filter_.Adapt(X_buffer, G);
+  data_dumper_->DumpRaw("aec3_subtractor_G_main", G.re);
+  data_dumper_->DumpRaw("aec3_subtractor_G_main", G.im);
+
+  // Update the shadow filter.
+  G_shadow_.Compute(X_buffer, render_signal_analyzer, E_shadow,
+                    shadow_filter_.SizePartitions(), saturation, &G);
+  shadow_filter_.Adapt(X_buffer, G);
+  data_dumper_->DumpRaw("aec3_subtractor_G_shadow", G.re);
+  data_dumper_->DumpRaw("aec3_subtractor_G_shadow", G.im);
+}
+
+}  // namespace webrtc