Surface the noise estimate of the NS to be used by other components

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 de7e856676ef14e86bebe2a53511d16f7a204943..2f1e31f363d4a61b2f4aca8a5ec436ab34af3dd0 100644
--- a/webrtc/modules/audio_processing/noise_suppression_impl.cc
+++ b/webrtc/modules/audio_processing/noise_suppression_impl.cc
@@ -65,6 +65,7 @@ void NoiseSuppressionImpl::Initialize(size_t channels, int sample_rate_hz) {
   }
   suppressors_.swap(new_suppressors);
   set_level(level_);
+  noise_estimate_updated_ = false;
 }
 
 void NoiseSuppressionImpl::AnalyzeCaptureAudio(AudioBuffer* audio) {
@@ -81,6 +82,7 @@ void NoiseSuppressionImpl::AnalyzeCaptureAudio(AudioBuffer* audio) {
     WebRtcNs_Analyze(suppressors_[i]->state(),
                      audio->split_bands_const_f(i)[kBand0To8kHz]);
   }
+  noise_estimate_updated_ = true;
 #endif
 }
 
@@ -104,6 +106,7 @@ void NoiseSuppressionImpl::ProcessCaptureAudio(AudioBuffer* audio) {
                       audio->split_bands_const(i),
                       audio->num_bands(),
                       audio->split_bands(i));
+    noise_estimate_updated_ = true;
 #endif
   }
 }
@@ -172,4 +175,32 @@ float NoiseSuppressionImpl::speech_probability() const {
   return AudioProcessing::kUnsupportedFunctionError;
 #endif
 }
+
+const std::vector<float>& NoiseSuppressionImpl::noise_estimate() {

[hlundin-webrtc, 2016/02/08 10:12:31]

I think I would prefer the following changes to this method:

1. Use a local temp std::vector<float> noise_estimate instead of the class
member noise_estimate_.

2. Return it by value, and let the compiler do return-value optimization. That
is:
std::vector<float> NoiseSuppressionImpl::noise_estimate();

Then you can get rid of the member variable noise_estimate_, which you seem to
have created just to be able to return a reference.

[aluebs-webrtc, 2016/02/09 00:01:42]

I thought about doing that, but then each call to noise_estimate() would re-do
the average, cast, normalization, etc instead of caching the noise_estimate
until it changes. This is only a problem if it is called more than once per
chunk. But I could imagine this to be the case if some components (maybe IE and
AEC) start using this noise estimate instead. Of course, we can always only call
it once in the APM and pass in the same copy to all components but that puts the
burden on the APM instead of the NS.
In any case, I implemented your suggestions, because I also see the pros and the
simplicity of this approach :)

+  rtc::CritScope cs(crit_);
+  if (noise_estimate_updated_) {

[hlundin-webrtc, 2016/02/08 10:12:31]

What if the noise estimate is not updated. How valid is the return value? What
will it contain? Empty vector?

[aluebs-webrtc, 2016/02/09 00:01:42]

Since the vector is calculated every time, I removed the flag that checked if it
was updated. So now a zero vector will be returned, which I think makes sense.
Or do you think I should keep the flag and return an empty vector?

+#if defined(WEBRTC_NS_FLOAT)
+    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] += noise[i] / suppressors_.size();
+      }
+    }
+#elif defined(WEBRTC_NS_FIXED)
+    const float kNormalizationFactor = 1.f / (1 << 17);
+    noise_estimate_.assign(WebRtcNsx_num_freq(), 0.f);
+    for (auto& suppressor : suppressors_) {
+      const uint32_t* noise = WebRtcNsx_noise_estimate(suppressor->state());
+      for (size_t i = 0; i < noise_estimate_.size(); ++i) {
+        noise_estimate_[i] += kNormalizationFactor *
+            static_cast<float>(noise[i]) / suppressors_.size();
+      }
+    }
+#endif
+    noise_estimate_updated_ = false;
+  }
+  return noise_estimate_;
+}
+
 }  // namespace webrtc