From 1fad94f50252092f901e8e2a9893748ee35c2114 Mon Sep 17 00:00:00 2001
From: Gustaf Ullberg <gustaf@webrtc.org>
Date: Tue, 13 Apr 2021 14:05:34 +0200
Subject: [PATCH] Remove ErleUncertainty

Erle Uncertainty changes the residual echo computation during saturated
echo. However, the case of saturated echo is already handled by the
residual echo estimator causing the ErleUncertainty to be a no-op.

The change has been tested for bit-exactness.

Bug: webrtc:8671
Change-Id: I779ba67f99f29d4475a0465d05da03d42d50e075
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/215072
Reviewed-by: Jesus de Vicente Pena <devicentepena@webrtc.org>
Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33719}
---
 modules/audio_processing/aec3/aec_state.cc    |  8 -------
 modules/audio_processing/aec3/aec_state.h     |  6 -----
 .../aec3/residual_echo_estimator.cc           | 23 +------------------
 3 files changed, 1 insertion(+), 36 deletions(-)

diff --git a/modules/audio_processing/aec3/aec_state.cc b/modules/audio_processing/aec3/aec_state.cc
index 5b31e3cb9f..15f3e17801 100644
--- a/modules/audio_processing/aec3/aec_state.cc
+++ b/modules/audio_processing/aec3/aec_state.cc
@@ -113,14 +113,6 @@ void AecState::GetResidualEchoScaling(
                                           residual_scaling);
 }
 
-absl::optional<float> AecState::ErleUncertainty() const {
-  if (SaturatedEcho()) {
-    return 1.f;
-  }
-
-  return absl::nullopt;
-}
-
 AecState::AecState(const EchoCanceller3Config& config,
                    size_t num_capture_channels)
     : data_dumper_(
diff --git a/modules/audio_processing/aec3/aec_state.h b/modules/audio_processing/aec3/aec_state.h
index 5b40e9513a..22b4fed4a2 100644
--- a/modules/audio_processing/aec3/aec_state.h
+++ b/modules/audio_processing/aec3/aec_state.h
@@ -74,12 +74,6 @@ class AecState {
     return erle_estimator_.Erle();
   }
 
-  // Returns an offset to apply to the estimation of the residual echo
-  // computation. Returning nullopt means that no offset should be used, while
-  // any other value will be applied as a multiplier to the estimated residual
-  // echo.
-  absl::optional<float> ErleUncertainty() const;
-
   // Returns the fullband ERLE estimate in log2 units.
   float FullBandErleLog2() const { return erle_estimator_.FullbandErleLog2(); }
 
diff --git a/modules/audio_processing/aec3/residual_echo_estimator.cc b/modules/audio_processing/aec3/residual_echo_estimator.cc
index e352cf5552..0567b546c9 100644
--- a/modules/audio_processing/aec3/residual_echo_estimator.cc
+++ b/modules/audio_processing/aec3/residual_echo_estimator.cc
@@ -84,22 +84,6 @@ void LinearEstimate(
   }
 }
 
-// Estimates the residual echo power based on an uncertainty estimate of the
-// echo return loss enhancement (ERLE) and the linear power estimate.
-void LinearEstimate(
-    rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>> S2_linear,
-    float erle_uncertainty,
-    rtc::ArrayView<std::array<float, kFftLengthBy2Plus1>> R2) {
-  RTC_DCHECK_EQ(S2_linear.size(), R2.size());
-
-  const size_t num_capture_channels = R2.size();
-  for (size_t ch = 0; ch < num_capture_channels; ++ch) {
-    for (size_t k = 0; k < kFftLengthBy2Plus1; ++k) {
-      R2[ch][k] = S2_linear[ch][k] * erle_uncertainty;
-    }
-  }
-}
-
 // Estimates the residual echo power based on the estimate of the echo path
 // gain.
 void NonLinearEstimate(
@@ -201,12 +185,7 @@ void ResidualEchoEstimator::Estimate(
         std::copy(Y2[ch].begin(), Y2[ch].end(), R2[ch].begin());
       }
     } else {
-      absl::optional<float> erle_uncertainty = aec_state.ErleUncertainty();
-      if (erle_uncertainty) {
-        LinearEstimate(S2_linear, *erle_uncertainty, R2);
-      } else {
-        LinearEstimate(S2_linear, aec_state.Erle(), R2);
-      }
+      LinearEstimate(S2_linear, aec_state.Erle(), R2);
     }
 
     AddReverb(ReverbType::kLinear, aec_state, render_buffer, R2);