Limit the maximum and minimum gain the IntelligibilityEnhancer can apply

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.
  */
 
 #include "webrtc/modules/audio_processing/intelligibility/intelligibility_utils.h"
 
 #include <math.h>
 #include <stdlib.h>
 #include <string.h>
 #include <algorithm>
 #include <limits>

[hlundin-webrtc, 2016/04/28 06:57:14]

Is this still needed?

[turaj, 2016/04/28 17:00:21]

for std::numeric_limits<float>::epsilon(), I guess.

[aluebs-webrtc, 2016/04/28 18:10:45]

Exactly!

[hlundin-webrtc, 2016/04/28 18:54:00]

Acknowledged. My bad.

 
 namespace webrtc {
 
 namespace intelligibility {
 
 namespace {
 
+const float kMinFactor = 0.01f;
+const float kMaxFactor = 1000.f;

[peah-webrtc, 2016/04/28 18:43:24]

It is a bit weird to have a limit on the max and min which is asymmetrical, i.e.
for a maximum of 0.01 I would have expected a minimum of 0.001.

[aluebs-webrtc, 2016/04/28 20:05:23]

I don't see why they should be symmetric.

+
 // Return |current| changed towards |target|, with the relative change being at
 // most |limit|.
 float UpdateFactor(float target, float current, float limit) {
   float gain = target / (current + std::numeric_limits<float>::epsilon());
-  if (gain < 1.f - limit) {
-    gain = 1.f - limit;
-  } else if (gain > 1.f + limit) {
-    gain = 1.f + limit;
-  }
-  return current * gain + std::numeric_limits<float>::epsilon();
+  gain = std::min(std::max(gain, 1.f - limit), 1.f + limit);
+  return std::min(std::max(current * gain, kMinFactor), kMaxFactor);;
 }
 
 }  // namespace
 
 template<typename T>
 PowerEstimator<T>::PowerEstimator(size_t num_freqs, float decay)
     : power_(num_freqs, 0.f), decay_(decay) {}
 
 template<typename T>
 void PowerEstimator<T>::Step(const T* data) {
@@ skipping 16 matching lines @@
                         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];
   }
 }
 
 }  // namespace intelligibility
 
 }  // namespace webrtc