Fix normalization of noise estimate in NoiseSuppressor

webrtc/modules/audio_processing/noise_suppression_impl.cc

 /*
  *  Copyright (c) 2012 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 159 matching lines @@
   // TODO(peah): Returning error code as a float! Remove this.
   // Currently not available for the fixed point implementation.
   return AudioProcessing::kUnsupportedFunctionError;
 #endif
 }
 
 std::vector<float> NoiseSuppressionImpl::NoiseEstimate() {
   rtc::CritScope cs(crit_);
   std::vector<float> noise_estimate;
 #if defined(WEBRTC_NS_FLOAT)
-  const float kNormalizationFactor = 1.f / (1 << 15);
   noise_estimate.assign(WebRtcNs_num_freq(), 0.f);
   for (auto& suppressor : suppressors_) {
     const float* noise = WebRtcNs_noise_estimate(suppressor->state());
     for (size_t i = 0; i < noise_estimate.size(); ++i) {
-      noise_estimate[i] +=
-          kNormalizationFactor * noise[i] / suppressors_.size();
+      noise_estimate[i] += noise[i] / suppressors_.size();

[peah-webrtc, 2016/03/31 20:50:57]

In order to avoid the divisions, please precompute 1/suppressors_.size() and use
that to multiply with.

[aluebs-webrtc, 2016/04/01 01:52:42]

Good point. Done.

     }
   }
 #elif defined(WEBRTC_NS_FIXED)
-  const float kNormalizationFactor = 1.f / (1 << 23);
   noise_estimate.assign(WebRtcNsx_num_freq(), 0.f);
   for (auto& suppressor : suppressors_) {
-    const uint32_t* noise = WebRtcNsx_noise_estimate(suppressor->state());
+    int domain;
+    const uint32_t* noise = WebRtcNsx_noise_estimate(suppressor->state(),
+                                                     &domain);
+    const float kNormalizationFactor = 1.f / (1 << domain);
     for (size_t i = 0; i < noise_estimate.size(); ++i) {
       noise_estimate[i] += kNormalizationFactor *

[peah-webrtc, 2016/03/31 20:50:57]

In order to avoid the divisions, 1/suppressors_.size() should be included in
normalization factor, which would also eliminate the need for the cast.

[aluebs-webrtc, 2016/04/01 01:52:42]

Good point. Done.

           static_cast<float>(noise[i]) / suppressors_.size();
     }
   }
 #endif
   return noise_estimate;
 }
 
 size_t NoiseSuppressionImpl::num_noise_bins() {
 #if defined(WEBRTC_NS_FLOAT)
   return WebRtcNs_num_freq();
 #elif defined(WEBRTC_NS_FIXED)
   return WebRtcNsx_num_freq();
 #endif
 }
 
 }  // namespace webrtc