Source/ThirdParty/libwebrtc/Source/webrtc/modules/audio_processing/aec3/adaptive_fir_filter.cc - WebKit - Git at Google

 /*
  *  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 "modules/audio_processing/aec3/adaptive_fir_filter.h"

 // Defines WEBRTC_ARCH_X86_FAMILY, used below.
 #include "rtc_base/system/arch.h"

 #if defined(WEBRTC_HAS_NEON)
 #include <arm_neon.h>
 #endif
 #if defined(WEBRTC_ARCH_X86_FAMILY)
 #include <emmintrin.h>
 #endif
 #include <algorithm>
 #include <functional>

 #include "modules/audio_processing/aec3/fft_data.h"
 #include "rtc_base/checks.h"

 namespace webrtc {

 namespace aec3 {

 // Computes and stores the frequency response of the filter.
 void UpdateFrequencyResponse(
     rtc::ArrayView<const FftData> H,
     std::vector<std::array<float, kFftLengthBy2Plus1>>* H2) {
   RTC_DCHECK_EQ(H.size(), H2->size());
   for (size_t k = 0; k < H.size(); ++k) {
     std::transform(H[k].re.begin(), H[k].re.end(), H[k].im.begin(),
                    (*H2)[k].begin(),
                    [](float a, float b) { return a * a + b * b; });
   }
 }

 #if defined(WEBRTC_HAS_NEON)
 // Computes and stores the frequency response of the filter.
 void UpdateFrequencyResponse_NEON(
     rtc::ArrayView<const FftData> H,
     std::vector<std::array<float, kFftLengthBy2Plus1>>* H2) {
   RTC_DCHECK_EQ(H.size(), H2->size());
   for (size_t k = 0; k < H.size(); ++k) {
     for (size_t j = 0; j < kFftLengthBy2; j += 4) {
       const float32x4_t re = vld1q_f32(&H[k].re[j]);
       const float32x4_t im = vld1q_f32(&H[k].im[j]);
       float32x4_t H2_k_j = vmulq_f32(re, re);
       H2_k_j = vmlaq_f32(H2_k_j, im, im);
       vst1q_f32(&(*H2)[k][j], H2_k_j);
     }
     (*H2)[k][kFftLengthBy2] = H[k].re[kFftLengthBy2] * H[k].re[kFftLengthBy2] +
                               H[k].im[kFftLengthBy2] * H[k].im[kFftLengthBy2];
   }
 }
 #endif

 #if defined(WEBRTC_ARCH_X86_FAMILY)
 // Computes and stores the frequency response of the filter.
 void UpdateFrequencyResponse_SSE2(
     rtc::ArrayView<const FftData> H,
     std::vector<std::array<float, kFftLengthBy2Plus1>>* H2) {
   RTC_DCHECK_EQ(H.size(), H2->size());
   for (size_t k = 0; k < H.size(); ++k) {
     for (size_t j = 0; j < kFftLengthBy2; j += 4) {
       const __m128 re = _mm_loadu_ps(&H[k].re[j]);
       const __m128 re2 = _mm_mul_ps(re, re);
       const __m128 im = _mm_loadu_ps(&H[k].im[j]);
       const __m128 im2 = _mm_mul_ps(im, im);
       const __m128 H2_k_j = _mm_add_ps(re2, im2);
       _mm_storeu_ps(&(*H2)[k][j], H2_k_j);
     }
     (*H2)[k][kFftLengthBy2] = H[k].re[kFftLengthBy2] * H[k].re[kFftLengthBy2] +
                               H[k].im[kFftLengthBy2] * H[k].im[kFftLengthBy2];
   }
 }
 #endif


 // Adapts the filter partitions as H(t+1)=H(t)+G(t)*conj(X(t)).
 void AdaptPartitions(const RenderBuffer& render_buffer,
                      const FftData& G,
                      rtc::ArrayView<FftData> H) {
   rtc::ArrayView<const std::vector<FftData>> render_buffer_data =
       render_buffer.GetFftBuffer();
   size_t index = render_buffer.Position();
   for (auto& H_j : H) {
     const FftData& X = render_buffer_data[index][/*channel=*/0];
     for (size_t k = 0; k < kFftLengthBy2Plus1; ++k) {
       H_j.re[k] += X.re[k] * G.re[k] + X.im[k] * G.im[k];
       H_j.im[k] += X.re[k] * G.im[k] - X.im[k] * G.re[k];
     }

     index = index < (render_buffer_data.size() - 1) ? index + 1 : 0;
   }
 }

 #if defined(WEBRTC_HAS_NEON)
 // Adapts the filter partitions. (NEON variant)
 void AdaptPartitions_NEON(const RenderBuffer& render_buffer,
                           const FftData& G,
                           rtc::ArrayView<FftData> H) {
   rtc::ArrayView<const std::vector<FftData>> render_buffer_data =
       render_buffer.GetFftBuffer();
   const int lim1 =
       std::min(render_buffer_data.size() - render_buffer.Position(), H.size());
   const int lim2 = H.size();
   constexpr int kNumFourBinBands = kFftLengthBy2 / 4;
   FftData* H_j = &H[0];
   const std::vector<FftData>* X_channels =
       &render_buffer_data[render_buffer.Position()];
   int limit = lim1;
   int j = 0;
   do {
     for (; j < limit; ++j, ++H_j, ++X_channels) {
       const FftData& X = (*X_channels)[/*channel=*/0];
       for (int k = 0, n = 0; n < kNumFourBinBands; ++n, k += 4) {
         const float32x4_t G_re = vld1q_f32(&G.re[k]);
         const float32x4_t G_im = vld1q_f32(&G.im[k]);
         const float32x4_t X_re = vld1q_f32(&X.re[k]);
         const float32x4_t X_im = vld1q_f32(&X.im[k]);
         const float32x4_t H_re = vld1q_f32(&H_j->re[k]);
         const float32x4_t H_im = vld1q_f32(&H_j->im[k]);
         const float32x4_t a = vmulq_f32(X_re, G_re);
         const float32x4_t e = vmlaq_f32(a, X_im, G_im);
         const float32x4_t c = vmulq_f32(X_re, G_im);
         const float32x4_t f = vmlsq_f32(c, X_im, G_re);
         const float32x4_t g = vaddq_f32(H_re, e);
         const float32x4_t h = vaddq_f32(H_im, f);

         vst1q_f32(&H_j->re[k], g);
         vst1q_f32(&H_j->im[k], h);
       }
     }

     X_channels = &render_buffer_data[0];
     limit = lim2;
   } while (j < lim2);

   H_j = &H[0];
   X_channels = &render_buffer_data[render_buffer.Position()];
   limit = lim1;
   j = 0;
   do {
     for (; j < limit; ++j, ++H_j, ++X_channels) {
       const FftData& X = (*X_channels)[/*channel=*/0];
       H_j->re[kFftLengthBy2] += X.re[kFftLengthBy2] * G.re[kFftLengthBy2] +
                                 X.im[kFftLengthBy2] * G.im[kFftLengthBy2];
       H_j->im[kFftLengthBy2] += X.re[kFftLengthBy2] * G.im[kFftLengthBy2] -
                                 X.im[kFftLengthBy2] * G.re[kFftLengthBy2];
     }

     X_channels = &render_buffer_data[0];
     limit = lim2;
   } while (j < lim2);
 }
 #endif

 #if defined(WEBRTC_ARCH_X86_FAMILY)
 // Adapts the filter partitions. (SSE2 variant)
 void AdaptPartitions_SSE2(const RenderBuffer& render_buffer,
                           const FftData& G,
                           rtc::ArrayView<FftData> H) {
   rtc::ArrayView<const std::vector<FftData>> render_buffer_data =
       render_buffer.GetFftBuffer();
   const int lim1 =
       std::min(render_buffer_data.size() - render_buffer.Position(), H.size());
   const int lim2 = H.size();
   constexpr int kNumFourBinBands = kFftLengthBy2 / 4;
   FftData* H_j;
   const std::vector<FftData>* X_channels;
   int limit;
   int j;
   for (int k = 0, n = 0; n < kNumFourBinBands; ++n, k += 4) {
     const __m128 G_re = _mm_loadu_ps(&G.re[k]);
     const __m128 G_im = _mm_loadu_ps(&G.im[k]);

     H_j = &H[0];
     X_channels = &render_buffer_data[render_buffer.Position()];
     limit = lim1;
     j = 0;
     do {
       for (; j < limit; ++j, ++H_j, ++X_channels) {
         const FftData& X = (*X_channels)[/*channel=*/0];
         const __m128 X_re = _mm_loadu_ps(&X.re[k]);
         const __m128 X_im = _mm_loadu_ps(&X.im[k]);
         const __m128 H_re = _mm_loadu_ps(&H_j->re[k]);
         const __m128 H_im = _mm_loadu_ps(&H_j->im[k]);
         const __m128 a = _mm_mul_ps(X_re, G_re);
         const __m128 b = _mm_mul_ps(X_im, G_im);
         const __m128 c = _mm_mul_ps(X_re, G_im);
         const __m128 d = _mm_mul_ps(X_im, G_re);
         const __m128 e = _mm_add_ps(a, b);
         const __m128 f = _mm_sub_ps(c, d);
         const __m128 g = _mm_add_ps(H_re, e);
         const __m128 h = _mm_add_ps(H_im, f);
         _mm_storeu_ps(&H_j->re[k], g);
         _mm_storeu_ps(&H_j->im[k], h);
       }

       X_channels = &render_buffer_data[0];
       limit = lim2;
     } while (j < lim2);
   }

   H_j = &H[0];
   X_channels = &render_buffer_data[render_buffer.Position()];
   limit = lim1;
   j = 0;
   do {
     for (; j < limit; ++j, ++H_j, ++X_channels) {
       const FftData& X = (*X_channels)[/*channel=*/0];
       H_j->re[kFftLengthBy2] += X.re[kFftLengthBy2] * G.re[kFftLengthBy2] +
                                 X.im[kFftLengthBy2] * G.im[kFftLengthBy2];
       H_j->im[kFftLengthBy2] += X.re[kFftLengthBy2] * G.im[kFftLengthBy2] -
                                 X.im[kFftLengthBy2] * G.re[kFftLengthBy2];
     }

     X_channels = &render_buffer_data[0];
     limit = lim2;
   } while (j < lim2);
 }
 #endif

 // Produces the filter output.
 void ApplyFilter(const RenderBuffer& render_buffer,
                  rtc::ArrayView<const FftData> H,
                  FftData* S) {
   S->re.fill(0.f);
   S->im.fill(0.f);

   rtc::ArrayView<const std::vector<FftData>> render_buffer_data =
       render_buffer.GetFftBuffer();
   size_t index = render_buffer.Position();
   for (auto& H_j : H) {
     const FftData& X = render_buffer_data[index][0];
     for (size_t k = 0; k < kFftLengthBy2Plus1; ++k) {
       S->re[k] += X.re[k] * H_j.re[k] - X.im[k] * H_j.im[k];
       S->im[k] += X.re[k] * H_j.im[k] + X.im[k] * H_j.re[k];
     }
     index = index < (render_buffer_data.size() - 1) ? index + 1 : 0;
   }
 }

 #if defined(WEBRTC_HAS_NEON)
 // Produces the filter output (NEON variant).
 void ApplyFilter_NEON(const RenderBuffer& render_buffer,
                       rtc::ArrayView<const FftData> H,
                       FftData* S) {
   RTC_DCHECK_GE(H.size(), H.size() - 1);
   S->Clear();

   rtc::ArrayView<const std::vector<FftData>> render_buffer_data =
       render_buffer.GetFftBuffer();
   const int lim1 =
       std::min(render_buffer_data.size() - render_buffer.Position(), H.size());
   const int lim2 = H.size();
   constexpr int kNumFourBinBands = kFftLengthBy2 / 4;
   const FftData* H_j = &H[0];
   const std::vector<FftData>* X_channels =
       &render_buffer_data[render_buffer.Position()];

   int j = 0;
   int limit = lim1;
   do {
     for (; j < limit; ++j, ++H_j, ++X_channels) {
       const FftData& X = (*X_channels)[/*channel=*/0];
       for (int k = 0, n = 0; n < kNumFourBinBands; ++n, k += 4) {
         const float32x4_t X_re = vld1q_f32(&X.re[k]);
         const float32x4_t X_im = vld1q_f32(&X.im[k]);
         const float32x4_t H_re = vld1q_f32(&H_j->re[k]);
         const float32x4_t H_im = vld1q_f32(&H_j->im[k]);
         const float32x4_t S_re = vld1q_f32(&S->re[k]);
         const float32x4_t S_im = vld1q_f32(&S->im[k]);
         const float32x4_t a = vmulq_f32(X_re, H_re);
         const float32x4_t e = vmlsq_f32(a, X_im, H_im);
         const float32x4_t c = vmulq_f32(X_re, H_im);
         const float32x4_t f = vmlaq_f32(c, X_im, H_re);
         const float32x4_t g = vaddq_f32(S_re, e);
         const float32x4_t h = vaddq_f32(S_im, f);
         vst1q_f32(&S->re[k], g);
         vst1q_f32(&S->im[k], h);
       }
     }
     limit = lim2;
     X_channels = &render_buffer_data[0];
   } while (j < lim2);

   H_j = &H[0];
   X_channels = &render_buffer_data[render_buffer.Position()];
   j = 0;
   limit = lim1;
   do {
     for (; j < limit; ++j, ++H_j, ++X_channels) {
       const FftData& X = (*X_channels)[/*channel=*/0];
       S->re[kFftLengthBy2] += X.re[kFftLengthBy2] * H_j->re[kFftLengthBy2] -
                               X.im[kFftLengthBy2] * H_j->im[kFftLengthBy2];
       S->im[kFftLengthBy2] += X.re[kFftLengthBy2] * H_j->im[kFftLengthBy2] +
                               X.im[kFftLengthBy2] * H_j->re[kFftLengthBy2];
     }
     limit = lim2;
     X_channels = &render_buffer_data[0];
   } while (j < lim2);
 }
 #endif

 #if defined(WEBRTC_ARCH_X86_FAMILY)
 // Produces the filter output (SSE2 variant).
 void ApplyFilter_SSE2(const RenderBuffer& render_buffer,
                       rtc::ArrayView<const FftData> H,
                       FftData* S) {
   RTC_DCHECK_GE(H.size(), H.size() - 1);
   S->re.fill(0.f);
   S->im.fill(0.f);

   rtc::ArrayView<const std::vector<FftData>> render_buffer_data =
       render_buffer.GetFftBuffer();
   const int lim1 =
       std::min(render_buffer_data.size() - render_buffer.Position(), H.size());
   const int lim2 = H.size();
   constexpr int kNumFourBinBands = kFftLengthBy2 / 4;
   const FftData* H_j = &H[0];
   const std::vector<FftData>* X_channels =
       &render_buffer_data[render_buffer.Position()];

   int j = 0;
   int limit = lim1;
   do {
     for (; j < limit; ++j, ++H_j, ++X_channels) {
       const FftData& X = (*X_channels)[/*channel=*/0];
       for (int k = 0, n = 0; n < kNumFourBinBands; ++n, k += 4) {
         const __m128 X_re = _mm_loadu_ps(&X.re[k]);
         const __m128 X_im = _mm_loadu_ps(&X.im[k]);
         const __m128 H_re = _mm_loadu_ps(&H_j->re[k]);
         const __m128 H_im = _mm_loadu_ps(&H_j->im[k]);
         const __m128 S_re = _mm_loadu_ps(&S->re[k]);
         const __m128 S_im = _mm_loadu_ps(&S->im[k]);
         const __m128 a = _mm_mul_ps(X_re, H_re);
         const __m128 b = _mm_mul_ps(X_im, H_im);
         const __m128 c = _mm_mul_ps(X_re, H_im);
         const __m128 d = _mm_mul_ps(X_im, H_re);
         const __m128 e = _mm_sub_ps(a, b);
         const __m128 f = _mm_add_ps(c, d);
         const __m128 g = _mm_add_ps(S_re, e);
         const __m128 h = _mm_add_ps(S_im, f);
         _mm_storeu_ps(&S->re[k], g);
         _mm_storeu_ps(&S->im[k], h);
       }
     }
     limit = lim2;
     X_channels = &render_buffer_data[0];
   } while (j < lim2);

   H_j = &H[0];
   X_channels = &render_buffer_data[render_buffer.Position()];
   j = 0;
   limit = lim1;
   do {
     for (; j < limit; ++j, ++H_j, ++X_channels) {
       const FftData& X = (*X_channels)[/*channel=*/0];
       S->re[kFftLengthBy2] += X.re[kFftLengthBy2] * H_j->re[kFftLengthBy2] -
                               X.im[kFftLengthBy2] * H_j->im[kFftLengthBy2];
       S->im[kFftLengthBy2] += X.re[kFftLengthBy2] * H_j->im[kFftLengthBy2] +
                               X.im[kFftLengthBy2] * H_j->re[kFftLengthBy2];
     }
     limit = lim2;
     X_channels = &render_buffer_data[0];
   } while (j < lim2);
 }
 #endif

 }  // namespace aec3

 AdaptiveFirFilter::AdaptiveFirFilter(size_t max_size_partitions,
                                      size_t initial_size_partitions,
                                      size_t size_change_duration_blocks,
                                      size_t num_render_channels,
                                      size_t num_capture_channels,
                                      Aec3Optimization optimization,
                                      ApmDataDumper* data_dumper)
     : data_dumper_(data_dumper),
       fft_(),
       optimization_(optimization),
       max_size_partitions_(max_size_partitions),
       size_change_duration_blocks_(
           static_cast<int>(size_change_duration_blocks)),
       current_size_partitions_(initial_size_partitions),
       target_size_partitions_(initial_size_partitions),
       old_target_size_partitions_(initial_size_partitions),
       H_(max_size_partitions_) {
   RTC_DCHECK(data_dumper_);
   RTC_DCHECK_GE(max_size_partitions, initial_size_partitions);

   RTC_DCHECK_LT(0, size_change_duration_blocks_);
   one_by_size_change_duration_blocks_ = 1.f / size_change_duration_blocks_;

   for (auto& H_j : H_) {
     H_j.Clear();
   }
   SetSizePartitions(current_size_partitions_, true);
 }

 AdaptiveFirFilter::~AdaptiveFirFilter() = default;

 void AdaptiveFirFilter::HandleEchoPathChange() {
   size_t current_size_partitions = H_.size();
   H_.resize(max_size_partitions_);

   for (size_t k = current_size_partitions; k < max_size_partitions_; ++k) {
     H_[k].Clear();
   }
   H_.resize(current_size_partitions);
 }

 void AdaptiveFirFilter::SetSizePartitions(size_t size, bool immediate_effect) {
   RTC_DCHECK_EQ(max_size_partitions_, H_.capacity());
   RTC_DCHECK_LE(size, max_size_partitions_);

   target_size_partitions_ = std::min(max_size_partitions_, size);
   if (immediate_effect) {
     current_size_partitions_ = old_target_size_partitions_ =
         target_size_partitions_;
     ResetFilterBuffersToCurrentSize();
     size_change_counter_ = 0;
   } else {
     size_change_counter_ = size_change_duration_blocks_;
   }
 }

 void AdaptiveFirFilter::ResetFilterBuffersToCurrentSize() {
   H_.resize(current_size_partitions_);
   RTC_DCHECK_LT(0, current_size_partitions_);
   partition_to_constrain_ =
       std::min(partition_to_constrain_, current_size_partitions_ - 1);
 }

 void AdaptiveFirFilter::UpdateSize() {
   RTC_DCHECK_GE(size_change_duration_blocks_, size_change_counter_);
   if (size_change_counter_ > 0) {
     --size_change_counter_;

     auto average = [](float from, float to, float from_weight) {
       return from * from_weight + to * (1.f - from_weight);
     };

     float change_factor =
         size_change_counter_ * one_by_size_change_duration_blocks_;

     current_size_partitions_ = average(old_target_size_partitions_,
                                        target_size_partitions_, change_factor);

     ResetFilterBuffersToCurrentSize();
   } else {
     current_size_partitions_ = old_target_size_partitions_ =
         target_size_partitions_;
   }
   RTC_DCHECK_LE(0, size_change_counter_);
 }

 void AdaptiveFirFilter::Filter(const RenderBuffer& render_buffer,
                                FftData* S) const {
   RTC_DCHECK(S);
   switch (optimization_) {
 #if defined(WEBRTC_ARCH_X86_FAMILY)
     case Aec3Optimization::kSse2:
       aec3::ApplyFilter_SSE2(render_buffer, H_, S);
       break;
 #endif
 #if defined(WEBRTC_HAS_NEON)
     case Aec3Optimization::kNeon:
       aec3::ApplyFilter_NEON(render_buffer, H_, S);
       break;
 #endif
     default:
       aec3::ApplyFilter(render_buffer, H_, S);
   }
 }

 void AdaptiveFirFilter::Adapt(const RenderBuffer& render_buffer,
                               const FftData& G) {
   // Adapt the filter and update the filter size.
   AdaptAndUpdateSize(render_buffer, G);

   // Constrain the filter partitions in a cyclic manner.
   Constrain();
 }

 void AdaptiveFirFilter::Adapt(const RenderBuffer& render_buffer,
                               const FftData& G,
                               std::vector<float>* impulse_response) {
   // Adapt the filter and update the filter size.
   AdaptAndUpdateSize(render_buffer, G);

   // Constrain the filter partitions in a cyclic manner.
   ConstrainAndUpdateImpulseResponse(impulse_response);
 }

 void AdaptiveFirFilter::ComputeFrequencyResponse(
     std::vector<std::array<float, kFftLengthBy2Plus1>>* H2) const {
   RTC_DCHECK_EQ(max_size_partitions_, H2->capacity());

   if (H2->size() > H_.size()) {
     for (size_t k = H_.size(); k < H2->size(); ++k) {
       (*H2)[k].fill(0.f);
     }
   }
   H2->resize(H_.size());

   switch (optimization_) {
 #if defined(WEBRTC_ARCH_X86_FAMILY)
     case Aec3Optimization::kSse2:
       aec3::UpdateFrequencyResponse_SSE2(H_, H2);
       break;
 #endif
 #if defined(WEBRTC_HAS_NEON)
     case Aec3Optimization::kNeon:
       aec3::UpdateFrequencyResponse_NEON(H_, H2);
       break;
 #endif
     default:
       aec3::UpdateFrequencyResponse(H_, H2);
   }
 }

 void AdaptiveFirFilter::AdaptAndUpdateSize(const RenderBuffer& render_buffer,
                                            const FftData& G) {
   // Update the filter size if needed.
   UpdateSize();

   // Adapt the filter.
   switch (optimization_) {
 #if defined(WEBRTC_ARCH_X86_FAMILY)
     case Aec3Optimization::kSse2:
       aec3::AdaptPartitions_SSE2(render_buffer, G, H_);
       break;
 #endif
 #if defined(WEBRTC_HAS_NEON)
     case Aec3Optimization::kNeon:
       aec3::AdaptPartitions_NEON(render_buffer, G, H_);
       break;
 #endif
     default:
       aec3::AdaptPartitions(render_buffer, G, H_);
   }
 }

 // Constrains the partition of the frequency domain filter to be limited in
 // time via setting the relevant time-domain coefficients to zero and updates
 // the corresponding values in an externally stored impulse response estimate.
 void AdaptiveFirFilter::ConstrainAndUpdateImpulseResponse(
     std::vector<float>* impulse_response) {
   RTC_DCHECK_EQ(GetTimeDomainLength(max_size_partitions_),
                 impulse_response->capacity());

   impulse_response->resize(GetTimeDomainLength(current_size_partitions_));
   std::array<float, kFftLength> h;
   fft_.Ifft(H_[partition_to_constrain_], &h);

   static constexpr float kScale = 1.0f / kFftLengthBy2;
   std::for_each(h.begin(), h.begin() + kFftLengthBy2,
                 [](float& a) { a *= kScale; });
   std::fill(h.begin() + kFftLengthBy2, h.end(), 0.f);

   std::copy(
       h.begin(), h.begin() + kFftLengthBy2,
       impulse_response->begin() + partition_to_constrain_ * kFftLengthBy2);

   fft_.Fft(&h, &H_[partition_to_constrain_]);

   partition_to_constrain_ = partition_to_constrain_ < (H_.size() - 1)
                                 ? partition_to_constrain_ + 1
                                 : 0;
 }

 // Constrains the a partiton of the frequency domain filter to be limited in
 // time via setting the relevant time-domain coefficients to zero.
 void AdaptiveFirFilter::Constrain() {
   std::array<float, kFftLength> h;
   fft_.Ifft(H_[partition_to_constrain_], &h);

   static constexpr float kScale = 1.0f / kFftLengthBy2;
   std::for_each(h.begin(), h.begin() + kFftLengthBy2,
                 [](float& a) { a *= kScale; });
   std::fill(h.begin() + kFftLengthBy2, h.end(), 0.f);

   fft_.Fft(&h, &H_[partition_to_constrain_]);

   partition_to_constrain_ = partition_to_constrain_ < (H_.size() - 1)
                                 ? partition_to_constrain_ + 1
                                 : 0;
 }

 void AdaptiveFirFilter::ScaleFilter(float factor) {
   for (auto& H : H_) {
     for (auto& re : H.re) {
       re *= factor;
     }
     for (auto& im : H.im) {
       im *= factor;
     }
   }
 }

 // Set the filter coefficients.
 void AdaptiveFirFilter::SetFilter(const std::vector<FftData>& H) {
   const size_t num_partitions = std::min(H_.size(), H.size());
   for (size_t k = 0; k < num_partitions; ++k) {
     std::copy(H[k].re.begin(), H[k].re.end(), H_[k].re.begin());
     std::copy(H[k].im.begin(), H[k].im.end(), H_[k].im.begin());
   }
 }

 }  // namespace webrtc
	/*
	* 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 "modules/audio_processing/aec3/adaptive_fir_filter.h"

	// Defines WEBRTC_ARCH_X86_FAMILY, used below.
	#include "rtc_base/system/arch.h"

	#if defined(WEBRTC_HAS_NEON)
	#include <arm_neon.h>
	#endif
	#if defined(WEBRTC_ARCH_X86_FAMILY)
	#include <emmintrin.h>
	#endif
	#include <algorithm>
	#include <functional>

	#include "modules/audio_processing/aec3/fft_data.h"
	#include "rtc_base/checks.h"

	namespace webrtc {

	namespace aec3 {

	// Computes and stores the frequency response of the filter.
	void UpdateFrequencyResponse(
	rtc::ArrayView<const FftData> H,
	std::vector<std::array<float, kFftLengthBy2Plus1>>* H2) {
	RTC_DCHECK_EQ(H.size(), H2->size());
	for (size_t k = 0; k < H.size(); ++k) {
	std::transform(H[k].re.begin(), H[k].re.end(), H[k].im.begin(),
	(*H2)[k].begin(),
	[](float a, float b) { return a * a + b * b; });
	}
	}

	#if defined(WEBRTC_HAS_NEON)
	// Computes and stores the frequency response of the filter.
	void UpdateFrequencyResponse_NEON(
	rtc::ArrayView<const FftData> H,
	std::vector<std::array<float, kFftLengthBy2Plus1>>* H2) {
	RTC_DCHECK_EQ(H.size(), H2->size());
	for (size_t k = 0; k < H.size(); ++k) {
	for (size_t j = 0; j < kFftLengthBy2; j += 4) {
	const float32x4_t re = vld1q_f32(&H[k].re[j]);
	const float32x4_t im = vld1q_f32(&H[k].im[j]);
	float32x4_t H2_k_j = vmulq_f32(re, re);
	H2_k_j = vmlaq_f32(H2_k_j, im, im);
	vst1q_f32(&(*H2)[k][j], H2_k_j);
	}
	(H2)[k][kFftLengthBy2] = H[k].re[kFftLengthBy2] H[k].re[kFftLengthBy2] +
	H[k].im[kFftLengthBy2] * H[k].im[kFftLengthBy2];
	}
	}
	#endif

	#if defined(WEBRTC_ARCH_X86_FAMILY)
	// Computes and stores the frequency response of the filter.
	void UpdateFrequencyResponse_SSE2(
	rtc::ArrayView<const FftData> H,
	std::vector<std::array<float, kFftLengthBy2Plus1>>* H2) {
	RTC_DCHECK_EQ(H.size(), H2->size());
	for (size_t k = 0; k < H.size(); ++k) {
	for (size_t j = 0; j < kFftLengthBy2; j += 4) {
	const __m128 re = _mm_loadu_ps(&H[k].re[j]);
	const __m128 re2 = _mm_mul_ps(re, re);
	const __m128 im = _mm_loadu_ps(&H[k].im[j]);
	const __m128 im2 = _mm_mul_ps(im, im);
	const __m128 H2_k_j = _mm_add_ps(re2, im2);
	_mm_storeu_ps(&(*H2)[k][j], H2_k_j);
	}
	(H2)[k][kFftLengthBy2] = H[k].re[kFftLengthBy2] H[k].re[kFftLengthBy2] +
	H[k].im[kFftLengthBy2] * H[k].im[kFftLengthBy2];
	}
	}
	#endif


	// Adapts the filter partitions as H(t+1)=H(t)+G(t)*conj(X(t)).
	void AdaptPartitions(const RenderBuffer& render_buffer,
	const FftData& G,
	rtc::ArrayView<FftData> H) {
	rtc::ArrayView<const std::vector<FftData>> render_buffer_data =
	render_buffer.GetFftBuffer();
	size_t index = render_buffer.Position();
	for (auto& H_j : H) {
	const FftData& X = render_buffer_data[index][/channel=/0];
	for (size_t k = 0; k < kFftLengthBy2Plus1; ++k) {
	H_j.re[k] += X.re[k] * G.re[k] + X.im[k] * G.im[k];
	H_j.im[k] += X.re[k] * G.im[k] - X.im[k] * G.re[k];
	}

	index = index < (render_buffer_data.size() - 1) ? index + 1 : 0;
	}
	}

	#if defined(WEBRTC_HAS_NEON)
	// Adapts the filter partitions. (NEON variant)
	void AdaptPartitions_NEON(const RenderBuffer& render_buffer,
	const FftData& G,
	rtc::ArrayView<FftData> H) {
	rtc::ArrayView<const std::vector<FftData>> render_buffer_data =
	render_buffer.GetFftBuffer();
	const int lim1 =
	std::min(render_buffer_data.size() - render_buffer.Position(), H.size());
	const int lim2 = H.size();
	constexpr int kNumFourBinBands = kFftLengthBy2 / 4;
	FftData* H_j = &H[0];
	const std::vector<FftData>* X_channels =
	&render_buffer_data[render_buffer.Position()];
	int limit = lim1;
	int j = 0;
	do {
	for (; j < limit; ++j, ++H_j, ++X_channels) {
	const FftData& X = (X_channels)[/channel=*/0];
	for (int k = 0, n = 0; n < kNumFourBinBands; ++n, k += 4) {
	const float32x4_t G_re = vld1q_f32(&G.re[k]);
	const float32x4_t G_im = vld1q_f32(&G.im[k]);
	const float32x4_t X_re = vld1q_f32(&X.re[k]);
	const float32x4_t X_im = vld1q_f32(&X.im[k]);
	const float32x4_t H_re = vld1q_f32(&H_j->re[k]);
	const float32x4_t H_im = vld1q_f32(&H_j->im[k]);
	const float32x4_t a = vmulq_f32(X_re, G_re);
	const float32x4_t e = vmlaq_f32(a, X_im, G_im);
	const float32x4_t c = vmulq_f32(X_re, G_im);
	const float32x4_t f = vmlsq_f32(c, X_im, G_re);
	const float32x4_t g = vaddq_f32(H_re, e);
	const float32x4_t h = vaddq_f32(H_im, f);

	vst1q_f32(&H_j->re[k], g);
	vst1q_f32(&H_j->im[k], h);
	}
	}

	X_channels = &render_buffer_data[0];
	limit = lim2;
	} while (j < lim2);

	H_j = &H[0];
	X_channels = &render_buffer_data[render_buffer.Position()];
	limit = lim1;
	j = 0;
	do {
	for (; j < limit; ++j, ++H_j, ++X_channels) {
	const FftData& X = (X_channels)[/channel=*/0];
	H_j->re[kFftLengthBy2] += X.re[kFftLengthBy2] * G.re[kFftLengthBy2] +
	X.im[kFftLengthBy2] * G.im[kFftLengthBy2];
	H_j->im[kFftLengthBy2] += X.re[kFftLengthBy2] * G.im[kFftLengthBy2] -
	X.im[kFftLengthBy2] * G.re[kFftLengthBy2];
	}

	X_channels = &render_buffer_data[0];
	limit = lim2;
	} while (j < lim2);
	}
	#endif

	#if defined(WEBRTC_ARCH_X86_FAMILY)
	// Adapts the filter partitions. (SSE2 variant)
	void AdaptPartitions_SSE2(const RenderBuffer& render_buffer,
	const FftData& G,
	rtc::ArrayView<FftData> H) {
	rtc::ArrayView<const std::vector<FftData>> render_buffer_data =
	render_buffer.GetFftBuffer();
	const int lim1 =
	std::min(render_buffer_data.size() - render_buffer.Position(), H.size());
	const int lim2 = H.size();
	constexpr int kNumFourBinBands = kFftLengthBy2 / 4;
	FftData* H_j;
	const std::vector<FftData>* X_channels;
	int limit;
	int j;
	for (int k = 0, n = 0; n < kNumFourBinBands; ++n, k += 4) {
	const __m128 G_re = _mm_loadu_ps(&G.re[k]);
	const __m128 G_im = _mm_loadu_ps(&G.im[k]);

	H_j = &H[0];
	X_channels = &render_buffer_data[render_buffer.Position()];
	limit = lim1;
	j = 0;
	do {
	for (; j < limit; ++j, ++H_j, ++X_channels) {
	const FftData& X = (X_channels)[/channel=*/0];
	const __m128 X_re = _mm_loadu_ps(&X.re[k]);
	const __m128 X_im = _mm_loadu_ps(&X.im[k]);
	const __m128 H_re = _mm_loadu_ps(&H_j->re[k]);
	const __m128 H_im = _mm_loadu_ps(&H_j->im[k]);
	const __m128 a = _mm_mul_ps(X_re, G_re);
	const __m128 b = _mm_mul_ps(X_im, G_im);
	const __m128 c = _mm_mul_ps(X_re, G_im);
	const __m128 d = _mm_mul_ps(X_im, G_re);
	const __m128 e = _mm_add_ps(a, b);
	const __m128 f = _mm_sub_ps(c, d);
	const __m128 g = _mm_add_ps(H_re, e);
	const __m128 h = _mm_add_ps(H_im, f);
	_mm_storeu_ps(&H_j->re[k], g);
	_mm_storeu_ps(&H_j->im[k], h);
	}

	X_channels = &render_buffer_data[0];
	limit = lim2;
	} while (j < lim2);
	}

	H_j = &H[0];
	X_channels = &render_buffer_data[render_buffer.Position()];
	limit = lim1;
	j = 0;
	do {
	for (; j < limit; ++j, ++H_j, ++X_channels) {
	const FftData& X = (X_channels)[/channel=*/0];
	H_j->re[kFftLengthBy2] += X.re[kFftLengthBy2] * G.re[kFftLengthBy2] +
	X.im[kFftLengthBy2] * G.im[kFftLengthBy2];
	H_j->im[kFftLengthBy2] += X.re[kFftLengthBy2] * G.im[kFftLengthBy2] -
	X.im[kFftLengthBy2] * G.re[kFftLengthBy2];
	}

	X_channels = &render_buffer_data[0];
	limit = lim2;
	} while (j < lim2);
	}
	#endif

	// Produces the filter output.
	void ApplyFilter(const RenderBuffer& render_buffer,
	rtc::ArrayView<const FftData> H,
	FftData* S) {
	S->re.fill(0.f);
	S->im.fill(0.f);

	rtc::ArrayView<const std::vector<FftData>> render_buffer_data =
	render_buffer.GetFftBuffer();
	size_t index = render_buffer.Position();
	for (auto& H_j : H) {
	const FftData& X = render_buffer_data[index][0];
	for (size_t k = 0; k < kFftLengthBy2Plus1; ++k) {
	S->re[k] += X.re[k] * H_j.re[k] - X.im[k] * H_j.im[k];
	S->im[k] += X.re[k] * H_j.im[k] + X.im[k] * H_j.re[k];
	}
	index = index < (render_buffer_data.size() - 1) ? index + 1 : 0;
	}
	}

	#if defined(WEBRTC_HAS_NEON)
	// Produces the filter output (NEON variant).
	void ApplyFilter_NEON(const RenderBuffer& render_buffer,
	rtc::ArrayView<const FftData> H,
	FftData* S) {
	RTC_DCHECK_GE(H.size(), H.size() - 1);
	S->Clear();

	rtc::ArrayView<const std::vector<FftData>> render_buffer_data =
	render_buffer.GetFftBuffer();
	const int lim1 =
	std::min(render_buffer_data.size() - render_buffer.Position(), H.size());
	const int lim2 = H.size();
	constexpr int kNumFourBinBands = kFftLengthBy2 / 4;
	const FftData* H_j = &H[0];
	const std::vector<FftData>* X_channels =
	&render_buffer_data[render_buffer.Position()];

	int j = 0;
	int limit = lim1;
	do {
	for (; j < limit; ++j, ++H_j, ++X_channels) {
	const FftData& X = (X_channels)[/channel=*/0];
	for (int k = 0, n = 0; n < kNumFourBinBands; ++n, k += 4) {
	const float32x4_t X_re = vld1q_f32(&X.re[k]);
	const float32x4_t X_im = vld1q_f32(&X.im[k]);
	const float32x4_t H_re = vld1q_f32(&H_j->re[k]);
	const float32x4_t H_im = vld1q_f32(&H_j->im[k]);
	const float32x4_t S_re = vld1q_f32(&S->re[k]);
	const float32x4_t S_im = vld1q_f32(&S->im[k]);
	const float32x4_t a = vmulq_f32(X_re, H_re);
	const float32x4_t e = vmlsq_f32(a, X_im, H_im);
	const float32x4_t c = vmulq_f32(X_re, H_im);
	const float32x4_t f = vmlaq_f32(c, X_im, H_re);
	const float32x4_t g = vaddq_f32(S_re, e);
	const float32x4_t h = vaddq_f32(S_im, f);
	vst1q_f32(&S->re[k], g);
	vst1q_f32(&S->im[k], h);
	}
	}
	limit = lim2;
	X_channels = &render_buffer_data[0];
	} while (j < lim2);

	H_j = &H[0];
	X_channels = &render_buffer_data[render_buffer.Position()];
	j = 0;
	limit = lim1;
	do {
	for (; j < limit; ++j, ++H_j, ++X_channels) {
	const FftData& X = (X_channels)[/channel=*/0];
	S->re[kFftLengthBy2] += X.re[kFftLengthBy2] * H_j->re[kFftLengthBy2] -
	X.im[kFftLengthBy2] * H_j->im[kFftLengthBy2];
	S->im[kFftLengthBy2] += X.re[kFftLengthBy2] * H_j->im[kFftLengthBy2] +
	X.im[kFftLengthBy2] * H_j->re[kFftLengthBy2];
	}
	limit = lim2;
	X_channels = &render_buffer_data[0];
	} while (j < lim2);
	}
	#endif

	#if defined(WEBRTC_ARCH_X86_FAMILY)
	// Produces the filter output (SSE2 variant).
	void ApplyFilter_SSE2(const RenderBuffer& render_buffer,
	rtc::ArrayView<const FftData> H,
	FftData* S) {
	RTC_DCHECK_GE(H.size(), H.size() - 1);
	S->re.fill(0.f);
	S->im.fill(0.f);

	rtc::ArrayView<const std::vector<FftData>> render_buffer_data =
	render_buffer.GetFftBuffer();
	const int lim1 =
	std::min(render_buffer_data.size() - render_buffer.Position(), H.size());
	const int lim2 = H.size();
	constexpr int kNumFourBinBands = kFftLengthBy2 / 4;
	const FftData* H_j = &H[0];
	const std::vector<FftData>* X_channels =
	&render_buffer_data[render_buffer.Position()];

	int j = 0;
	int limit = lim1;
	do {
	for (; j < limit; ++j, ++H_j, ++X_channels) {
	const FftData& X = (X_channels)[/channel=*/0];
	for (int k = 0, n = 0; n < kNumFourBinBands; ++n, k += 4) {
	const __m128 X_re = _mm_loadu_ps(&X.re[k]);
	const __m128 X_im = _mm_loadu_ps(&X.im[k]);
	const __m128 H_re = _mm_loadu_ps(&H_j->re[k]);
	const __m128 H_im = _mm_loadu_ps(&H_j->im[k]);
	const __m128 S_re = _mm_loadu_ps(&S->re[k]);
	const __m128 S_im = _mm_loadu_ps(&S->im[k]);
	const __m128 a = _mm_mul_ps(X_re, H_re);
	const __m128 b = _mm_mul_ps(X_im, H_im);
	const __m128 c = _mm_mul_ps(X_re, H_im);
	const __m128 d = _mm_mul_ps(X_im, H_re);
	const __m128 e = _mm_sub_ps(a, b);
	const __m128 f = _mm_add_ps(c, d);
	const __m128 g = _mm_add_ps(S_re, e);
	const __m128 h = _mm_add_ps(S_im, f);
	_mm_storeu_ps(&S->re[k], g);
	_mm_storeu_ps(&S->im[k], h);
	}
	}
	limit = lim2;
	X_channels = &render_buffer_data[0];
	} while (j < lim2);

	H_j = &H[0];
	X_channels = &render_buffer_data[render_buffer.Position()];
	j = 0;
	limit = lim1;
	do {
	for (; j < limit; ++j, ++H_j, ++X_channels) {
	const FftData& X = (X_channels)[/channel=*/0];
	S->re[kFftLengthBy2] += X.re[kFftLengthBy2] * H_j->re[kFftLengthBy2] -
	X.im[kFftLengthBy2] * H_j->im[kFftLengthBy2];
	S->im[kFftLengthBy2] += X.re[kFftLengthBy2] * H_j->im[kFftLengthBy2] +
	X.im[kFftLengthBy2] * H_j->re[kFftLengthBy2];
	}
	limit = lim2;
	X_channels = &render_buffer_data[0];
	} while (j < lim2);
	}
	#endif

	} // namespace aec3

	AdaptiveFirFilter::AdaptiveFirFilter(size_t max_size_partitions,
	size_t initial_size_partitions,
	size_t size_change_duration_blocks,
	size_t num_render_channels,
	size_t num_capture_channels,
	Aec3Optimization optimization,
	ApmDataDumper* data_dumper)
	: data_dumper_(data_dumper),
	fft_(),
	optimization_(optimization),
	max_size_partitions_(max_size_partitions),
	size_change_duration_blocks_(
	static_cast<int>(size_change_duration_blocks)),
	current_size_partitions_(initial_size_partitions),
	target_size_partitions_(initial_size_partitions),
	old_target_size_partitions_(initial_size_partitions),
	H_(max_size_partitions_) {
	RTC_DCHECK(data_dumper_);
	RTC_DCHECK_GE(max_size_partitions, initial_size_partitions);

	RTC_DCHECK_LT(0, size_change_duration_blocks_);
	one_by_size_change_duration_blocks_ = 1.f / size_change_duration_blocks_;

	for (auto& H_j : H_) {
	H_j.Clear();
	}
	SetSizePartitions(current_size_partitions_, true);
	}

	AdaptiveFirFilter::~AdaptiveFirFilter() = default;

	void AdaptiveFirFilter::HandleEchoPathChange() {
	size_t current_size_partitions = H_.size();
	H_.resize(max_size_partitions_);

	for (size_t k = current_size_partitions; k < max_size_partitions_; ++k) {
	H_[k].Clear();
	}
	H_.resize(current_size_partitions);
	}

	void AdaptiveFirFilter::SetSizePartitions(size_t size, bool immediate_effect) {
	RTC_DCHECK_EQ(max_size_partitions_, H_.capacity());
	RTC_DCHECK_LE(size, max_size_partitions_);

	target_size_partitions_ = std::min(max_size_partitions_, size);
	if (immediate_effect) {
	current_size_partitions_ = old_target_size_partitions_ =
	target_size_partitions_;
	ResetFilterBuffersToCurrentSize();
	size_change_counter_ = 0;
	} else {
	size_change_counter_ = size_change_duration_blocks_;
	}
	}

	void AdaptiveFirFilter::ResetFilterBuffersToCurrentSize() {
	H_.resize(current_size_partitions_);
	RTC_DCHECK_LT(0, current_size_partitions_);
	partition_to_constrain_ =
	std::min(partition_to_constrain_, current_size_partitions_ - 1);
	}

	void AdaptiveFirFilter::UpdateSize() {
	RTC_DCHECK_GE(size_change_duration_blocks_, size_change_counter_);
	if (size_change_counter_ > 0) {
	--size_change_counter_;

	auto average = [](float from, float to, float from_weight) {
	return from * from_weight + to * (1.f - from_weight);
	};

	float change_factor =
	size_change_counter_ * one_by_size_change_duration_blocks_;

	current_size_partitions_ = average(old_target_size_partitions_,
	target_size_partitions_, change_factor);

	ResetFilterBuffersToCurrentSize();
	} else {
	current_size_partitions_ = old_target_size_partitions_ =
	target_size_partitions_;
	}
	RTC_DCHECK_LE(0, size_change_counter_);
	}

	void AdaptiveFirFilter::Filter(const RenderBuffer& render_buffer,
	FftData* S) const {
	RTC_DCHECK(S);
	switch (optimization_) {
	#if defined(WEBRTC_ARCH_X86_FAMILY)
	case Aec3Optimization::kSse2:
	aec3::ApplyFilter_SSE2(render_buffer, H_, S);
	break;
	#endif
	#if defined(WEBRTC_HAS_NEON)
	case Aec3Optimization::kNeon:
	aec3::ApplyFilter_NEON(render_buffer, H_, S);
	break;
	#endif
	default:
	aec3::ApplyFilter(render_buffer, H_, S);
	}
	}

	void AdaptiveFirFilter::Adapt(const RenderBuffer& render_buffer,
	const FftData& G) {
	// Adapt the filter and update the filter size.
	AdaptAndUpdateSize(render_buffer, G);

	// Constrain the filter partitions in a cyclic manner.
	Constrain();
	}

	void AdaptiveFirFilter::Adapt(const RenderBuffer& render_buffer,
	const FftData& G,
	std::vector<float>* impulse_response) {
	// Adapt the filter and update the filter size.
	AdaptAndUpdateSize(render_buffer, G);

	// Constrain the filter partitions in a cyclic manner.
	ConstrainAndUpdateImpulseResponse(impulse_response);
	}

	void AdaptiveFirFilter::ComputeFrequencyResponse(
	std::vector<std::array<float, kFftLengthBy2Plus1>>* H2) const {
	RTC_DCHECK_EQ(max_size_partitions_, H2->capacity());

	if (H2->size() > H_.size()) {
	for (size_t k = H_.size(); k < H2->size(); ++k) {
	(*H2)[k].fill(0.f);
	}
	}
	H2->resize(H_.size());

	switch (optimization_) {
	#if defined(WEBRTC_ARCH_X86_FAMILY)
	case Aec3Optimization::kSse2:
	aec3::UpdateFrequencyResponse_SSE2(H_, H2);
	break;
	#endif
	#if defined(WEBRTC_HAS_NEON)
	case Aec3Optimization::kNeon:
	aec3::UpdateFrequencyResponse_NEON(H_, H2);
	break;
	#endif
	default:
	aec3::UpdateFrequencyResponse(H_, H2);
	}
	}

	void AdaptiveFirFilter::AdaptAndUpdateSize(const RenderBuffer& render_buffer,
	const FftData& G) {
	// Update the filter size if needed.
	UpdateSize();

	// Adapt the filter.
	switch (optimization_) {
	#if defined(WEBRTC_ARCH_X86_FAMILY)
	case Aec3Optimization::kSse2:
	aec3::AdaptPartitions_SSE2(render_buffer, G, H_);
	break;
	#endif
	#if defined(WEBRTC_HAS_NEON)
	case Aec3Optimization::kNeon:
	aec3::AdaptPartitions_NEON(render_buffer, G, H_);
	break;
	#endif
	default:
	aec3::AdaptPartitions(render_buffer, G, H_);
	}
	}

	// Constrains the partition of the frequency domain filter to be limited in
	// time via setting the relevant time-domain coefficients to zero and updates
	// the corresponding values in an externally stored impulse response estimate.
	void AdaptiveFirFilter::ConstrainAndUpdateImpulseResponse(
	std::vector<float>* impulse_response) {
	RTC_DCHECK_EQ(GetTimeDomainLength(max_size_partitions_),
	impulse_response->capacity());

	impulse_response->resize(GetTimeDomainLength(current_size_partitions_));
	std::array<float, kFftLength> h;
	fft_.Ifft(H_[partition_to_constrain_], &h);

	static constexpr float kScale = 1.0f / kFftLengthBy2;
	std::for_each(h.begin(), h.begin() + kFftLengthBy2,
	[](float& a) { a *= kScale; });
	std::fill(h.begin() + kFftLengthBy2, h.end(), 0.f);

	std::copy(
	h.begin(), h.begin() + kFftLengthBy2,
	impulse_response->begin() + partition_to_constrain_ * kFftLengthBy2);

	fft_.Fft(&h, &H_[partition_to_constrain_]);

	partition_to_constrain_ = partition_to_constrain_ < (H_.size() - 1)
	? partition_to_constrain_ + 1
	: 0;
	}

	// Constrains the a partiton of the frequency domain filter to be limited in
	// time via setting the relevant time-domain coefficients to zero.
	void AdaptiveFirFilter::Constrain() {
	std::array<float, kFftLength> h;
	fft_.Ifft(H_[partition_to_constrain_], &h);

	static constexpr float kScale = 1.0f / kFftLengthBy2;
	std::for_each(h.begin(), h.begin() + kFftLengthBy2,
	[](float& a) { a *= kScale; });
	std::fill(h.begin() + kFftLengthBy2, h.end(), 0.f);

	fft_.Fft(&h, &H_[partition_to_constrain_]);

	partition_to_constrain_ = partition_to_constrain_ < (H_.size() - 1)
	? partition_to_constrain_ + 1
	: 0;
	}

	void AdaptiveFirFilter::ScaleFilter(float factor) {
	for (auto& H : H_) {
	for (auto& re : H.re) {
	re *= factor;
	}
	for (auto& im : H.im) {
	im *= factor;
	}
	}
	}

	// Set the filter coefficients.
	void AdaptiveFirFilter::SetFilter(const std::vector<FftData>& H) {
	const size_t num_partitions = std::min(H_.size(), H.size());
	for (size_t k = 0; k < num_partitions; ++k) {
	std::copy(H[k].re.begin(), H[k].re.end(), H_[k].re.begin());
	std::copy(H[k].im.begin(), H[k].im.end(), H_[k].im.begin());
	}
	}

	} // namespace webrtc