NetEQ: BackgroundNoise::Update returns true when the filter is updated

Bug: webrtc:10690
Change-Id: I17ff7dc1cffc8c46987d0a9ff8c6633ce9dcc8d3
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/144040
Commit-Queue: Alessio Bazzica <alessiob@webrtc.org>
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28411}

modules/audio_coding/neteq/background_noise.cc

@@ -45,12 +45,13 @@ void BackgroundNoise::Reset() {
   }
 }
 
-void BackgroundNoise::Update(const AudioMultiVector& input,
+bool BackgroundNoise::Update(const AudioMultiVector& input,
                              const PostDecodeVad& vad) {
+  bool filter_params_saved = false;
   if (vad.running() && vad.active_speech()) {
     // Do not update the background noise parameters if we know that the signal
     // is active speech.
-    return;
+    return filter_params_saved;
   }
 
   int32_t auto_correlation[kMaxLpcOrder + 1];
@@ -62,6 +63,7 @@ void BackgroundNoise::Update(const AudioMultiVector& input,
     ChannelParameters& parameters = channel_parameters_[channel_ix];
     int16_t temp_signal_array[kVecLen + kMaxLpcOrder] = {0};
     int16_t* temp_signal = &temp_signal_array[kMaxLpcOrder];
+    RTC_DCHECK_GE(input.Size(), kVecLen);
     input[channel_ix].CopyTo(kVecLen, input.Size() - kVecLen, temp_signal);
     int32_t sample_energy =
         CalculateAutoCorrelation(temp_signal, kVecLen, auto_correlation);
@@ -70,7 +72,11 @@ void BackgroundNoise::Update(const AudioMultiVector& input,
          sample_energy < parameters.energy_update_threshold) ||
         (vad.running() && !vad.active_speech())) {
       // Generate LPC coefficients.
-      if (auto_correlation[0] > 0) {
+      if (auto_correlation[0] <= 0) {
+        // Center value in auto-correlation is not positive. Do not update.
+        return filter_params_saved;
+      }
+
       // Regardless of whether the filter is actually updated or not,
       // update energy threshold levels, since we have in fact observed
       // a low energy signal.
@@ -85,11 +91,7 @@ void BackgroundNoise::Update(const AudioMultiVector& input,
       if (WebRtcSpl_LevinsonDurbin(auto_correlation, lpc_coefficients,
                                    reflection_coefficients,
                                    kMaxLpcOrder) != 1) {
-          return;
+        return filter_params_saved;
-        }
-      } else {
-        // Center value in auto-correlation is not positive. Do not update.
-        return;
       }
 
       // Generate the CNG gain factor by looking at the energy of the residual.
@@ -113,6 +115,7 @@ void BackgroundNoise::Update(const AudioMultiVector& input,
         SaveParameters(channel_ix, lpc_coefficients,
                        temp_signal + kVecLen - kMaxLpcOrder, sample_energy,
                        residual_energy);
+        filter_params_saved = true;
       }
     } else {
       // Will only happen if post-decode VAD is disabled and |sample_energy| is
@@ -121,7 +124,7 @@ void BackgroundNoise::Update(const AudioMultiVector& input,
       IncrementEnergyThreshold(channel_ix, sample_energy);
     }
   }
-  return;
+  return filter_params_saved;
 }
 
 void BackgroundNoise::GenerateBackgroundNoise(

modules/audio_coding/neteq/background_noise.h

@@ -37,7 +37,8 @@ class BackgroundNoise {
 
   // Updates the parameter estimates based on the signal currently in the
   // |sync_buffer|, and on the latest decision in |vad| if it is running.
-  void Update(const AudioMultiVector& sync_buffer, const PostDecodeVad& vad);
+  // Returns true if the filter parameters are updated.
+  bool Update(const AudioMultiVector& sync_buffer, const PostDecodeVad& vad);
 
   // Generates background noise given a random vector and writes the output to
   // |buffer|.