Simplified the ERLE computation code in AEC3

webrtc/modules/audio_processing/aec3/erle_estimator.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.
  */
 
@@ skipping 23 matching lines @@
     const std::array<float, kFftLengthBy2Plus1>& capture_spectrum,
     const std::array<float, kFftLengthBy2Plus1>& subtractor_spectrum) {
   const auto& X2 = render_spectrum;
   const auto& Y2 = capture_spectrum;
   const auto& E2 = subtractor_spectrum;
 
   // Corresponds of WGN of power -46 dBFS.
   constexpr float kX2Min = 44015068.0f;
 
   // Update the estimates in a clamped minimum statistics manner.
-  size_t k = 1;
-  size_t band_limit = kFftLengthBy2 / 2;
-  float max_erle = kMaxLfErle;
-  for (int j = 0; j < 2; ++j) {
-    for (; k < band_limit; ++k) {
+  auto erle_update = [&](size_t start, size_t stop, float max_erle) {
+    for (size_t k = start; k < stop; ++k) {
       if (X2[k] > kX2Min && E2[k] > 0.f) {
         const float new_erle = Y2[k] / E2[k];
         if (new_erle > erle_[k]) {
           hold_counters_[k - 1] = 100;
           erle_[k] += 0.1f * (new_erle - erle_[k]);
           erle_[k] = std::max(kMinErle, std::min(erle_[k], max_erle));
         }
       }
     }
-    band_limit = kFftLengthBy2;
-    max_erle = kMaxHfErle;
-  }
+  };
+  erle_update(1, kFftLengthBy2 / 2, kMaxLfErle);
+  erle_update(kFftLengthBy2 / 2, kFftLengthBy2, kMaxHfErle);
 
   std::for_each(hold_counters_.begin(), hold_counters_.end(),
                 [](int& a) { --a; });
   std::transform(hold_counters_.begin(), hold_counters_.end(),
                  erle_.begin() + 1, erle_.begin() + 1, [](int a, float b) {
                    return a > 0 ? b : std::max(kMinErle, 0.97f * b);
                  });
 
   erle_[0] = erle_[1];
   erle_[kFftLengthBy2] = erle_[kFftLengthBy2 - 1];
 }
 
 }  // namespace webrtc