Fix normalization of noise estimate in NoiseSuppressor

webrtc/modules/audio_processing/noise_suppression_impl.cc

Index: webrtc/modules/audio_processing/noise_suppression_impl.cc
diff --git a/webrtc/modules/audio_processing/noise_suppression_impl.cc b/webrtc/modules/audio_processing/noise_suppression_impl.cc
index a9d9f4a93bbf8086105ea4cb28fc0ee181be644b..d0c5f9ffee2c76bf77e8448cacfc365e4a52c2d3 100644
--- a/webrtc/modules/audio_processing/noise_suppression_impl.cc
+++ b/webrtc/modules/audio_processing/noise_suppression_impl.cc
@@ -177,20 +177,20 @@ 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();