Compensate for the IntelligibilityEnhancer processing delay in high bands

webrtc/modules/audio_processing/intelligibility/intelligibility_utils.cc

 /*
  *  Copyright (c) 2014 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 48 matching lines @@
 GainApplier::~GainApplier() {}
 
 void GainApplier::Apply(const std::complex<float>* in_block,
                         std::complex<float>* out_block) {
   for (size_t i = 0; i < num_freqs_; ++i) {
     current_[i] = UpdateFactor(target_[i], current_[i], relative_change_limit_);
     out_block[i] = sqrtf(fabsf(current_[i])) * in_block[i];
   }
 }
 
+DelayBuffer::DelayBuffer(size_t delay, size_t num_channels)
+    : buffer_(num_channels, std::vector<float>(delay, 0.f)), read_index_(0u) {}
+
+DelayBuffer::~DelayBuffer() {}
+
+void DelayBuffer::Delay(float* const* data, size_t length) {
+  for (size_t i = 0u; i < buffer_.size(); ++i) {
+    size_t channel_index = read_index_;

[peah-webrtc, 2016/09/17 21:31:30]

Please consider changing this name. 
To me, a channel index would be the index of the channel rather than the sample
index in the channel which is what it is here. 
What about next_read_index, or sample_index?

[aluebs-webrtc, 2016/09/19 19:17:14]

Good point. Done.

+    for (size_t j = 0u; j < length; ++j) {
+      float swap = data[i][j];
+      data[i][j] = buffer_[i][channel_index];
+      buffer_[i][channel_index] = swap;
+      if (++channel_index == buffer_.size()) {
+        channel_index = 0u;
+      }
+    }
+  }
+  read_index_ += length;
+  while (read_index_ >= buffer_.size()) {

[peah-webrtc, 2016/09/17 21:31:30]

This part is not necessary. You have the wraparound for free if you instead do
like below:
size_t channel_index = 0;
for (size_t i = 0u; i < buffer_.size(); ++i) {
  channel_index = read_index_;
  for (size_t j = 0u; j < length; ++j) {
     ...
  }
}
read_index_ = channel_index;

[aluebs-webrtc, 2016/09/19 19:17:14]

Good point. Done.

+    read_index_ -= buffer_.size();
+  }
+}
+
 }  // namespace intelligibility
 
 }  // namespace webrtc