delay estimator: Look for early reverberation

Look for first echo (and not only the strongest one) on the same matched
filter.

This change is bit exact with previous version when `pre_echo` is false.

Author: Jesús de Vicente Peña <devicentepena@webrtc.org>

Bug: webrtc:14205
Change-Id: I6782eaa1d690b0df78d00f6d425a85c951b2ca9d
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/266321
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Commit-Queue: Lionel Koenig <lionelk@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37360}

12 files changed, 950 insertions, 392 deletions

diff --git a/modules/audio_processing/aec3/BUILD.gn b/modules/audio_processing/aec3/BUILD.gn
index 70d049549a..4de2d00f3e 100644
--- a/modules/audio_processing/aec3/BUILD.gn
+++ b/modules/audio_processing/aec3/BUILD.gn
@@ -226,6 +226,7 @@ rtc_source_set("matched_filter") {
     "../../../api:array_view",
     "../../../rtc_base/system:arch",
   ]
+  absl_deps = [ "//third_party/abseil-cpp/absl/types:optional" ]
 }
 
 rtc_source_set("vector_math") {
diff --git a/modules/audio_processing/aec3/echo_canceller3.cc b/modules/audio_processing/aec3/echo_canceller3.cc
index 8e306aca56..1404a9987d 100644
--- a/modules/audio_processing/aec3/echo_canceller3.cc
+++ b/modules/audio_processing/aec3/echo_canceller3.cc
@@ -377,6 +377,14 @@ EchoCanceller3Config AdjustConfig(const EchoCanceller3Config& config) {
         false;
   }
 
+  if (field_trial::IsEnabled("WebRTC-Aec3DelayEstimatorDetectPreEcho")) {
+    adjusted_cfg.delay.detect_pre_echo = true;
+  }
+
+  if (field_trial::IsDisabled("WebRTC-Aec3DelayEstimatorDetectPreEcho")) {
+    adjusted_cfg.delay.detect_pre_echo = false;
+  }
+
   if (field_trial::IsEnabled("WebRTC-Aec3SensitiveDominantNearendActivation")) {
     adjusted_cfg.suppressor.dominant_nearend_detection.enr_threshold = 0.5f;
   } else if (field_trial::IsEnabled(
diff --git a/modules/audio_processing/aec3/echo_path_delay_estimator.cc b/modules/audio_processing/aec3/echo_path_delay_estimator.cc
index e64c4493f6..fc83ca2f89 100644
--- a/modules/audio_processing/aec3/echo_path_delay_estimator.cc
+++ b/modules/audio_processing/aec3/echo_path_delay_estimator.cc
@@ -43,10 +43,11 @@ EchoPathDelayEstimator::EchoPathDelayEstimator(
               : config.render_levels.poor_excitation_render_limit,
           config.delay.delay_estimate_smoothing,
           config.delay.delay_estimate_smoothing_delay_found,
-          config.delay.delay_candidate_detection_threshold),
+          config.delay.delay_candidate_detection_threshold,
+          config.delay.detect_pre_echo),
       matched_filter_lag_aggregator_(data_dumper_,
                                      matched_filter_.GetMaxFilterLag(),
-                                     config.delay.delay_selection_thresholds) {
+                                     config.delay) {
   RTC_DCHECK(data_dumper);
   RTC_DCHECK(down_sampling_factor_ > 0);
 }
@@ -75,13 +76,14 @@ absl::optional<DelayEstimate> EchoPathDelayEstimator::EstimateDelay(
 
   absl::optional<DelayEstimate> aggregated_matched_filter_lag =
       matched_filter_lag_aggregator_.Aggregate(
-          matched_filter_.GetLagEstimates());
+          matched_filter_.GetBestLagEstimate());
 
   // Run clockdrift detection.
   if (aggregated_matched_filter_lag &&
       (*aggregated_matched_filter_lag).quality ==
           DelayEstimate::Quality::kRefined)
-    clockdrift_detector_.Update((*aggregated_matched_filter_lag).delay);
+    clockdrift_detector_.Update(
+        matched_filter_lag_aggregator_.GetDelayAtHighestPeak());
 
   // TODO(peah): Move this logging outside of this class once EchoCanceller3
   // development is done.
diff --git a/modules/audio_processing/aec3/echo_path_delay_estimator_unittest.cc b/modules/audio_processing/aec3/echo_path_delay_estimator_unittest.cc
index 13c9c1122e..810b0ae185 100644
--- a/modules/audio_processing/aec3/echo_path_delay_estimator_unittest.cc
+++ b/modules/audio_processing/aec3/echo_path_delay_estimator_unittest.cc
@@ -78,6 +78,7 @@ TEST(EchoPathDelayEstimator, DelayEstimation) {
   constexpr size_t kDownSamplingFactors[] = {2, 4, 8};
   for (auto down_sampling_factor : kDownSamplingFactors) {
     EchoCanceller3Config config;
+    config.delay.delay_headroom_samples = 0;
     config.delay.down_sampling_factor = down_sampling_factor;
     config.delay.num_filters = 10;
     for (size_t delay_samples : {30, 64, 150, 200, 800, 4000}) {
@@ -111,12 +112,13 @@ TEST(EchoPathDelayEstimator, DelayEstimation) {
       }
 
       if (estimated_delay_samples) {
-        // Allow estimated delay to be off by one sample in the down-sampled
-        // domain.
+        // Allow estimated delay to be off by a block as internally the delay is
+        // quantized with an error up to a block.
         size_t delay_ds = delay_samples / down_sampling_factor;
         size_t estimated_delay_ds =
             estimated_delay_samples->delay / down_sampling_factor;
-        EXPECT_NEAR(delay_ds, estimated_delay_ds, 1);
+        EXPECT_NEAR(delay_ds, estimated_delay_ds,
+                    kBlockSize / down_sampling_factor);
       } else {
         ADD_FAILURE();
       }
diff --git a/modules/audio_processing/aec3/matched_filter.cc b/modules/audio_processing/aec3/matched_filter.cc
index faca933856..c5e394ad2f 100644
--- a/modules/audio_processing/aec3/matched_filter.cc
+++ b/modules/audio_processing/aec3/matched_filter.cc
@@ -24,16 +24,147 @@
 #include <iterator>
 #include <numeric>
 
+#include "absl/types/optional.h"
+#include "api/array_view.h"
 #include "modules/audio_processing/aec3/downsampled_render_buffer.h"
 #include "modules/audio_processing/logging/apm_data_dumper.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
 
+namespace {
+
+// Subsample rate used for computing the accumulated error.
+// The implementation of some core functions depends on this constant being
+// equal to 4.
+constexpr int kAccumulatedErrorSubSampleRate = 4;
+
+void UpdateAccumulatedError(
+    const rtc::ArrayView<const float> instantaneous_accumulated_error,
+    const rtc::ArrayView<float> accumulated_error,
+    float one_over_error_sum_anchor) {
+  for (size_t k = 0; k < instantaneous_accumulated_error.size(); ++k) {
+    float error_norm =
+        instantaneous_accumulated_error[k] * one_over_error_sum_anchor;
+    if (error_norm < accumulated_error[k]) {
+      accumulated_error[k] = error_norm;
+    } else {
+      accumulated_error[k] += 0.01f * (error_norm - accumulated_error[k]);
+    }
+  }
+}
+
+size_t ComputePreEchoLag(const rtc::ArrayView<float> accumulated_error,
+                         size_t lag,
+                         size_t alignment_shift_winner) {
+  size_t pre_echo_lag_estimate = lag - alignment_shift_winner;
+  size_t maximum_pre_echo_lag =
+      std::min(pre_echo_lag_estimate / kAccumulatedErrorSubSampleRate,
+               accumulated_error.size());
+  for (size_t k = 1; k < maximum_pre_echo_lag; ++k) {
+    if (accumulated_error[k] < 0.5f * accumulated_error[k - 1] &&
+        accumulated_error[k] < 0.5f) {
+      pre_echo_lag_estimate = (k + 1) * kAccumulatedErrorSubSampleRate - 1;
+      break;
+    }
+  }
+  return pre_echo_lag_estimate + alignment_shift_winner;
+}
+
+}  // namespace
+
 namespace webrtc {
 namespace aec3 {
 
 #if defined(WEBRTC_HAS_NEON)
 
+inline float SumAllElements(float32x4_t elements) {
+  float32x2_t sum = vpadd_f32(vget_low_f32(elements), vget_high_f32(elements));
+  sum = vpadd_f32(sum, sum);
+  return vget_lane_f32(sum, 0);
+}
+
+void MatchedFilterCoreWithAccumulatedError_NEON(
+    size_t x_start_index,
+    float x2_sum_threshold,
+    float smoothing,
+    rtc::ArrayView<const float> x,
+    rtc::ArrayView<const float> y,
+    rtc::ArrayView<float> h,
+    bool* filters_updated,
+    float* error_sum,
+    rtc::ArrayView<float> accumulated_error,
+    rtc::ArrayView<float> scratch_memory) {
+  const int h_size = static_cast<int>(h.size());
+  const int x_size = static_cast<int>(x.size());
+  RTC_DCHECK_EQ(0, h_size % 4);
+  std::fill(accumulated_error.begin(), accumulated_error.end(), 0.0f);
+  // Process for all samples in the sub-block.
+  for (size_t i = 0; i < y.size(); ++i) {
+    // Apply the matched filter as filter * x, and compute x * x.
+    RTC_DCHECK_GT(x_size, x_start_index);
+    // Compute loop chunk sizes until, and after, the wraparound of the circular
+    // buffer for x.
+    const int chunk1 =
+        std::min(h_size, static_cast<int>(x_size - x_start_index));
+    if (chunk1 != h_size) {
+      const int chunk2 = h_size - chunk1;
+      std::copy(x.begin() + x_start_index, x.end(), scratch_memory.begin());
+      std::copy(x.begin(), x.begin() + chunk2, scratch_memory.begin() + chunk1);
+    }
+    const float* x_p =
+        chunk1 != h_size ? scratch_memory.data() : &x[x_start_index];
+    const float* h_p = &h[0];
+    float* accumulated_error_p = &accumulated_error[0];
+    // Initialize values for the accumulation.
+    float32x4_t x2_sum_128 = vdupq_n_f32(0);
+    float x2_sum = 0.f;
+    float s = 0;
+    // Perform 128 bit vector operations.
+    const int limit_by_4 = h_size >> 2;
+    for (int k = limit_by_4; k > 0;
+         --k, h_p += 4, x_p += 4, accumulated_error_p++) {
+      // Load the data into 128 bit vectors.
+      const float32x4_t x_k = vld1q_f32(x_p);
+      const float32x4_t h_k = vld1q_f32(h_p);
+      // Compute and accumulate x * x.
+      x2_sum_128 = vmlaq_f32(x2_sum_128, x_k, x_k);
+      // Compute x * h
+      float32x4_t hk_xk_128 = vmulq_f32(h_k, x_k);
+      s += SumAllElements(hk_xk_128);
+      const float e = s - y[i];
+      accumulated_error_p[0] += e * e;
+    }
+    // Combine the accumulated vector and scalar values.
+    x2_sum += SumAllElements(x2_sum_128);
+    // Compute the matched filter error.
+    float e = y[i] - s;
+    const bool saturation = y[i] >= 32000.f || y[i] <= -32000.f;
+    (*error_sum) += e * e;
+    // Update the matched filter estimate in an NLMS manner.
+    if (x2_sum > x2_sum_threshold && !saturation) {
+      RTC_DCHECK_LT(0.f, x2_sum);
+      const float alpha = smoothing * e / x2_sum;
+      const float32x4_t alpha_128 = vmovq_n_f32(alpha);
+      // filter = filter + smoothing * (y - filter * x) * x / x * x.
+      float* h_p = &h[0];
+      x_p = chunk1 != h_size ? scratch_memory.data() : &x[x_start_index];
+      // Perform 128 bit vector operations.
+      const int limit_by_4 = h_size >> 2;
+      for (int k = limit_by_4; k > 0; --k, h_p += 4, x_p += 4) {
+        // Load the data into 128 bit vectors.
+        float32x4_t h_k = vld1q_f32(h_p);
+        const float32x4_t x_k = vld1q_f32(x_p);
+        // Compute h = h + alpha * x.
+        h_k = vmlaq_f32(h_k, alpha_128, x_k);
+        // Store the result.
+        vst1q_f32(h_p, h_k);
+      }
+      *filters_updated = true;
+    }
+    x_start_index = x_start_index > 0 ? x_start_index - 1 : x_size - 1;
+  }
+}
+
 void MatchedFilterCore_NEON(size_t x_start_index,
                             float x2_sum_threshold,
                             float smoothing,
@@ -41,11 +172,20 @@ void MatchedFilterCore_NEON(size_t x_start_index,
                             rtc::ArrayView<const float> y,
                             rtc::ArrayView<float> h,
                             bool* filters_updated,
-                            float* error_sum) {
+                            float* error_sum,
+                            bool compute_accumulated_error,
+                            rtc::ArrayView<float> accumulated_error,
+                            rtc::ArrayView<float> scratch_memory) {
   const int h_size = static_cast<int>(h.size());
   const int x_size = static_cast<int>(x.size());
   RTC_DCHECK_EQ(0, h_size % 4);
 
+  if (compute_accumulated_error) {
+    return MatchedFilterCoreWithAccumulatedError_NEON(
+        x_start_index, x2_sum_threshold, smoothing, x, y, h, filters_updated,
+        error_sum, accumulated_error, scratch_memory);
+  }
+
   // Process for all samples in the sub-block.
   for (size_t i = 0; i < y.size(); ++i) {
     // Apply the matched filter as filter * x, and compute x * x.
@@ -90,10 +230,8 @@ void MatchedFilterCore_NEON(size_t x_start_index,
     }
 
     // Combine the accumulated vector and scalar values.
-    float* v = reinterpret_cast<float*>(&x2_sum_128);
-    x2_sum += v[0] + v[1] + v[2] + v[3];
-    v = reinterpret_cast<float*>(&s_128);
-    s += v[0] + v[1] + v[2] + v[3];
+    s += SumAllElements(s_128);
+    x2_sum += SumAllElements(x2_sum_128);
 
     // Compute the matched filter error.
     float e = y[i] - s;
@@ -144,6 +282,103 @@ void MatchedFilterCore_NEON(size_t x_start_index,
 
 #if defined(WEBRTC_ARCH_X86_FAMILY)
 
+void MatchedFilterCore_AccumulatedError_SSE2(
+    size_t x_start_index,
+    float x2_sum_threshold,
+    float smoothing,
+    rtc::ArrayView<const float> x,
+    rtc::ArrayView<const float> y,
+    rtc::ArrayView<float> h,
+    bool* filters_updated,
+    float* error_sum,
+    rtc::ArrayView<float> accumulated_error,
+    rtc::ArrayView<float> scratch_memory) {
+  const int h_size = static_cast<int>(h.size());
+  const int x_size = static_cast<int>(x.size());
+  RTC_DCHECK_EQ(0, h_size % 8);
+  std::fill(accumulated_error.begin(), accumulated_error.end(), 0.0f);
+  // Process for all samples in the sub-block.
+  for (size_t i = 0; i < y.size(); ++i) {
+    // Apply the matched filter as filter * x, and compute x * x.
+    RTC_DCHECK_GT(x_size, x_start_index);
+    const int chunk1 =
+        std::min(h_size, static_cast<int>(x_size - x_start_index));
+    if (chunk1 != h_size) {
+      const int chunk2 = h_size - chunk1;
+      std::copy(x.begin() + x_start_index, x.end(), scratch_memory.begin());
+      std::copy(x.begin(), x.begin() + chunk2, scratch_memory.begin() + chunk1);
+    }
+    const float* x_p =
+        chunk1 != h_size ? scratch_memory.data() : &x[x_start_index];
+    const float* h_p = &h[0];
+    float* a_p = &accumulated_error[0];
+    __m128 s_inst_128;
+    __m128 s_inst_128_4;
+    __m128 x2_sum_128 = _mm_set1_ps(0);
+    __m128 x2_sum_128_4 = _mm_set1_ps(0);
+    __m128 e_128;
+    float* const s_p = reinterpret_cast<float*>(&s_inst_128);
+    float* const s_4_p = reinterpret_cast<float*>(&s_inst_128_4);
+    float* const e_p = reinterpret_cast<float*>(&e_128);
+    float x2_sum = 0.0f;
+    float s_acum = 0;
+    // Perform 128 bit vector operations.
+    const int limit_by_8 = h_size >> 3;
+    for (int k = limit_by_8; k > 0; --k, h_p += 8, x_p += 8, a_p += 2) {
+      // Load the data into 128 bit vectors.
+      const __m128 x_k = _mm_loadu_ps(x_p);
+      const __m128 h_k = _mm_loadu_ps(h_p);
+      const __m128 x_k_4 = _mm_loadu_ps(x_p + 4);
+      const __m128 h_k_4 = _mm_loadu_ps(h_p + 4);
+      const __m128 xx = _mm_mul_ps(x_k, x_k);
+      const __m128 xx_4 = _mm_mul_ps(x_k_4, x_k_4);
+      // Compute and accumulate x * x and h * x.
+      x2_sum_128 = _mm_add_ps(x2_sum_128, xx);
+      x2_sum_128_4 = _mm_add_ps(x2_sum_128_4, xx_4);
+      s_inst_128 = _mm_mul_ps(h_k, x_k);
+      s_inst_128_4 = _mm_mul_ps(h_k_4, x_k_4);
+      s_acum += s_p[0] + s_p[1] + s_p[2] + s_p[3];
+      e_p[0] = s_acum - y[i];
+      s_acum += s_4_p[0] + s_4_p[1] + s_4_p[2] + s_4_p[3];
+      e_p[1] = s_acum - y[i];
+      a_p[0] += e_p[0] * e_p[0];
+      a_p[1] += e_p[1] * e_p[1];
+    }
+    // Combine the accumulated vector and scalar values.
+    x2_sum_128 = _mm_add_ps(x2_sum_128, x2_sum_128_4);
+    float* v = reinterpret_cast<float*>(&x2_sum_128);
+    x2_sum += v[0] + v[1] + v[2] + v[3];
+    // Compute the matched filter error.
+    float e = y[i] - s_acum;
+    const bool saturation = y[i] >= 32000.f || y[i] <= -32000.f;
+    (*error_sum) += e * e;
+    // Update the matched filter estimate in an NLMS manner.
+    if (x2_sum > x2_sum_threshold && !saturation) {
+      RTC_DCHECK_LT(0.f, x2_sum);
+      const float alpha = smoothing * e / x2_sum;
+      const __m128 alpha_128 = _mm_set1_ps(alpha);
+      // filter = filter + smoothing * (y - filter * x) * x / x * x.
+      float* h_p = &h[0];
+      const float* x_p =
+          chunk1 != h_size ? scratch_memory.data() : &x[x_start_index];
+      // Perform 128 bit vector operations.
+      const int limit_by_4 = h_size >> 2;
+      for (int k = limit_by_4; k > 0; --k, h_p += 4, x_p += 4) {
+        // Load the data into 128 bit vectors.
+        __m128 h_k = _mm_loadu_ps(h_p);
+        const __m128 x_k = _mm_loadu_ps(x_p);
+        // Compute h = h + alpha * x.
+        const __m128 alpha_x = _mm_mul_ps(alpha_128, x_k);
+        h_k = _mm_add_ps(h_k, alpha_x);
+        // Store the result.
+        _mm_storeu_ps(h_p, h_k);
+      }
+      *filters_updated = true;
+    }
+    x_start_index = x_start_index > 0 ? x_start_index - 1 : x_size - 1;
+  }
+}
+
 void MatchedFilterCore_SSE2(size_t x_start_index,
                             float x2_sum_threshold,
                             float smoothing,
@@ -151,19 +386,24 @@ void MatchedFilterCore_SSE2(size_t x_start_index,
                             rtc::ArrayView<const float> y,
                             rtc::ArrayView<float> h,
                             bool* filters_updated,
-                            float* error_sum) {
+                            float* error_sum,
+                            bool compute_accumulated_error,
+                            rtc::ArrayView<float> accumulated_error,
+                            rtc::ArrayView<float> scratch_memory) {
+  if (compute_accumulated_error) {
+    return MatchedFilterCore_AccumulatedError_SSE2(
+        x_start_index, x2_sum_threshold, smoothing, x, y, h, filters_updated,
+        error_sum, accumulated_error, scratch_memory);
+  }
   const int h_size = static_cast<int>(h.size());
   const int x_size = static_cast<int>(x.size());
   RTC_DCHECK_EQ(0, h_size % 4);
-
   // Process for all samples in the sub-block.
   for (size_t i = 0; i < y.size(); ++i) {
     // Apply the matched filter as filter * x, and compute x * x.
-
     RTC_DCHECK_GT(x_size, x_start_index);
     const float* x_p = &x[x_start_index];
     const float* h_p = &h[0];
-
     // Initialize values for the accumulation.
     __m128 s_128 = _mm_set1_ps(0);
     __m128 s_128_4 = _mm_set1_ps(0);
@@ -171,12 +411,10 @@ void MatchedFilterCore_SSE2(size_t x_start_index,
     __m128 x2_sum_128_4 = _mm_set1_ps(0);
     float x2_sum = 0.f;
     float s = 0;
-
     // Compute loop chunk sizes until, and after, the wraparound of the circular
     // buffer for x.
     const int chunk1 =
         std::min(h_size, static_cast<int>(x_size - x_start_index));
-
     // Perform the loop in two chunks.
     const int chunk2 = h_size - chunk1;
     for (int limit : {chunk1, chunk2}) {
@@ -198,17 +436,14 @@ void MatchedFilterCore_SSE2(size_t x_start_index,
         s_128 = _mm_add_ps(s_128, hx);
         s_128_4 = _mm_add_ps(s_128_4, hx_4);
       }
-
       // Perform non-vector operations for any remaining items.
       for (int k = limit - limit_by_8 * 8; k > 0; --k, ++h_p, ++x_p) {
         const float x_k = *x_p;
         x2_sum += x_k * x_k;
         s += *h_p * x_k;
       }
-
       x_p = &x[0];
     }
-
     // Combine the accumulated vector and scalar values.
     x2_sum_128 = _mm_add_ps(x2_sum_128, x2_sum_128_4);
     float* v = reinterpret_cast<float*>(&x2_sum_128);
@@ -216,22 +451,18 @@ void MatchedFilterCore_SSE2(size_t x_start_index,
     s_128 = _mm_add_ps(s_128, s_128_4);
     v = reinterpret_cast<float*>(&s_128);
     s += v[0] + v[1] + v[2] + v[3];
-
     // Compute the matched filter error.
     float e = y[i] - s;
     const bool saturation = y[i] >= 32000.f || y[i] <= -32000.f;
     (*error_sum) += e * e;
-
     // Update the matched filter estimate in an NLMS manner.
     if (x2_sum > x2_sum_threshold && !saturation) {
       RTC_DCHECK_LT(0.f, x2_sum);
       const float alpha = smoothing * e / x2_sum;
       const __m128 alpha_128 = _mm_set1_ps(alpha);
-
       // filter = filter + smoothing * (y - filter * x) * x / x * x.
       float* h_p = &h[0];
       x_p = &x[x_start_index];
-
       // Perform the loop in two chunks.
       for (int limit : {chunk1, chunk2}) {
         // Perform 128 bit vector operations.
@@ -244,22 +475,17 @@ void MatchedFilterCore_SSE2(size_t x_start_index,
           // Compute h = h + alpha * x.
           const __m128 alpha_x = _mm_mul_ps(alpha_128, x_k);
           h_k = _mm_add_ps(h_k, alpha_x);
-
           // Store the result.
           _mm_storeu_ps(h_p, h_k);
         }
-
         // Perform non-vector operations for any remaining items.
         for (int k = limit - limit_by_4 * 4; k > 0; --k, ++h_p, ++x_p) {
           *h_p += alpha * *x_p;
         }
-
         x_p = &x[0];
       }
-
       *filters_updated = true;
     }
-
     x_start_index = x_start_index > 0 ? x_start_index - 1 : x_size - 1;
   }
 }
@@ -272,17 +498,35 @@ void MatchedFilterCore(size_t x_start_index,
                        rtc::ArrayView<const float> y,
                        rtc::ArrayView<float> h,
                        bool* filters_updated,
-                       float* error_sum) {
+                       float* error_sum,
+                       bool compute_accumulated_error,
+                       rtc::ArrayView<float> accumulated_error) {
+  if (compute_accumulated_error) {
+    std::fill(accumulated_error.begin(), accumulated_error.end(), 0.0f);
+  }
+
   // Process for all samples in the sub-block.
   for (size_t i = 0; i < y.size(); ++i) {
     // Apply the matched filter as filter * x, and compute x * x.
     float x2_sum = 0.f;
     float s = 0;
     size_t x_index = x_start_index;
-    for (size_t k = 0; k < h.size(); ++k) {
-      x2_sum += x[x_index] * x[x_index];
-      s += h[k] * x[x_index];
-      x_index = x_index < (x.size() - 1) ? x_index + 1 : 0;
+    if (compute_accumulated_error) {
+      for (size_t k = 0; k < h.size(); ++k) {
+        x2_sum += x[x_index] * x[x_index];
+        s += h[k] * x[x_index];
+        x_index = x_index < (x.size() - 1) ? x_index + 1 : 0;
+        if ((k + 1 & 0b11) == 0) {
+          int idx = k >> 2;
+          accumulated_error[idx] += (y[i] - s) * (y[i] - s);
+        }
+      }
+    } else {
+      for (size_t k = 0; k < h.size(); ++k) {
+        x2_sum += x[x_index] * x[x_index];
+        s += h[k] * x[x_index];
+        x_index = x_index < (x.size() - 1) ? x_index + 1 : 0;
+      }
     }
 
     // Compute the matched filter error.
@@ -354,7 +598,8 @@ MatchedFilter::MatchedFilter(ApmDataDumper* data_dumper,
                              float excitation_limit,
                              float smoothing_fast,
                              float smoothing_slow,
-                             float matching_filter_threshold)
+                             float matching_filter_threshold,
+                             bool detect_pre_echo)
     : data_dumper_(data_dumper),
       optimization_(optimization),
       sub_block_size_(sub_block_size),
@@ -362,16 +607,31 @@ MatchedFilter::MatchedFilter(ApmDataDumper* data_dumper,
       filters_(
           num_matched_filters,
           std::vector<float>(window_size_sub_blocks * sub_block_size_, 0.f)),
-      lag_estimates_(num_matched_filters),
       filters_offsets_(num_matched_filters, 0),
       excitation_limit_(excitation_limit),
       smoothing_fast_(smoothing_fast),
       smoothing_slow_(smoothing_slow),
-      matching_filter_threshold_(matching_filter_threshold) {
+      matching_filter_threshold_(matching_filter_threshold),
+      detect_pre_echo_(detect_pre_echo) {
   RTC_DCHECK(data_dumper);
   RTC_DCHECK_LT(0, window_size_sub_blocks);
   RTC_DCHECK((kBlockSize % sub_block_size) == 0);
   RTC_DCHECK((sub_block_size % 4) == 0);
+  static_assert(kAccumulatedErrorSubSampleRate == 4);
+  if (detect_pre_echo_) {
+    accumulated_error_ = std::vector<std::vector<float>>(
+        num_matched_filters,
+        std::vector<float>(window_size_sub_blocks * sub_block_size_ /
+                               kAccumulatedErrorSubSampleRate,
+                           1.0f));
+
+    instantaneous_accumulated_error_ =
+        std::vector<float>(window_size_sub_blocks * sub_block_size_ /
+                               kAccumulatedErrorSubSampleRate,
+                           0.0f);
+    scratch_memory_ =
+        std::vector<float>(window_size_sub_blocks * sub_block_size_);
+  }
 }
 
 MatchedFilter::~MatchedFilter() = default;
@@ -381,9 +641,12 @@ void MatchedFilter::Reset() {
     std::fill(f.begin(), f.end(), 0.f);
   }
 
-  for (auto& l : lag_estimates_) {
-    l = MatchedFilter::LagEstimate();
+  for (auto& e : accumulated_error_) {
+    std::fill(e.begin(), e.end(), 1.0f);
   }
+
+  winner_lag_ = absl::nullopt;
+  reported_lag_estimate_ = absl::nullopt;
 }
 
 void MatchedFilter::Update(const DownsampledRenderBuffer& render_buffer,
@@ -398,11 +661,25 @@ void MatchedFilter::Update(const DownsampledRenderBuffer& render_buffer,
   const float x2_sum_threshold =
       filters_[0].size() * excitation_limit_ * excitation_limit_;
 
+  // Compute anchor for the matched filter error.
+  float error_sum_anchor = 0.0f;
+  for (size_t k = 0; k < y.size(); ++k) {
+    error_sum_anchor += y[k] * y[k];
+  }
+
   // Apply all matched filters.
+  float winner_error_sum = error_sum_anchor;
+  winner_lag_ = absl::nullopt;
+  reported_lag_estimate_ = absl::nullopt;
   size_t alignment_shift = 0;
-  for (size_t n = 0; n < filters_.size(); ++n) {
+  absl::optional<size_t> previous_lag_estimate;
+  const int num_filters = static_cast<int>(filters_.size());
+  int winner_index = -1;
+  for (int n = 0; n < num_filters; ++n) {
     float error_sum = 0.f;
     bool filters_updated = false;
+    const bool compute_pre_echo =
+        detect_pre_echo_ && n == last_detected_best_lag_filter_;
 
     size_t x_start_index =
         (render_buffer.read + alignment_shift + sub_block_size_ - 1) %
@@ -411,85 +688,79 @@ void MatchedFilter::Update(const DownsampledRenderBuffer& render_buffer,
     switch (optimization_) {
 #if defined(WEBRTC_ARCH_X86_FAMILY)
       case Aec3Optimization::kSse2:
-        aec3::MatchedFilterCore_SSE2(x_start_index, x2_sum_threshold, smoothing,
-                                     render_buffer.buffer, y, filters_[n],
-                                     &filters_updated, &error_sum);
+        aec3::MatchedFilterCore_SSE2(
+            x_start_index, x2_sum_threshold, smoothing, render_buffer.buffer, y,
+            filters_[n], &filters_updated, &error_sum, compute_pre_echo,
+            instantaneous_accumulated_error_, scratch_memory_);
         break;
       case Aec3Optimization::kAvx2:
-        aec3::MatchedFilterCore_AVX2(x_start_index, x2_sum_threshold, smoothing,
-                                     render_buffer.buffer, y, filters_[n],
-                                     &filters_updated, &error_sum);
+        aec3::MatchedFilterCore_AVX2(
+            x_start_index, x2_sum_threshold, smoothing, render_buffer.buffer, y,
+            filters_[n], &filters_updated, &error_sum, compute_pre_echo,
+            instantaneous_accumulated_error_, scratch_memory_);
         break;
 #endif
 #if defined(WEBRTC_HAS_NEON)
       case Aec3Optimization::kNeon:
-        aec3::MatchedFilterCore_NEON(x_start_index, x2_sum_threshold, smoothing,
-                                     render_buffer.buffer, y, filters_[n],
-                                     &filters_updated, &error_sum);
+        aec3::MatchedFilterCore_NEON(
+            x_start_index, x2_sum_threshold, smoothing, render_buffer.buffer, y,
+            filters_[n], &filters_updated, &error_sum, compute_pre_echo,
+            instantaneous_accumulated_error_, scratch_memory_);
         break;
 #endif
       default:
         aec3::MatchedFilterCore(x_start_index, x2_sum_threshold, smoothing,
                                 render_buffer.buffer, y, filters_[n],
-                                &filters_updated, &error_sum);
-    }
-
-    // Compute anchor for the matched filter error.
-    float error_sum_anchor = 0.0f;
-    for (size_t k = 0; k < y.size(); ++k) {
-      error_sum_anchor += y[k] * y[k];
+                                &filters_updated, &error_sum, compute_pre_echo,
+                                instantaneous_accumulated_error_);
     }
 
     // Estimate the lag in the matched filter as the distance to the portion in
     // the filter that contributes the most to the matched filter output. This
     // is detected as the peak of the matched filter.
     const size_t lag_estimate = aec3::MaxSquarePeakIndex(filters_[n]);
-
-    // Update the lag estimates for the matched filter.
-    lag_estimates_[n] = LagEstimate(
-        error_sum_anchor - error_sum,
-        (lag_estimate > 2 && lag_estimate < (filters_[n].size() - 10) &&
-         error_sum < matching_filter_threshold_ * error_sum_anchor),
-        lag_estimate + alignment_shift, filters_updated);
-
-    RTC_DCHECK_GE(10, filters_.size());
-    switch (n) {
-      case 0:
-        data_dumper_->DumpRaw("aec3_correlator_0_h", filters_[0]);
-        break;
-      case 1:
-        data_dumper_->DumpRaw("aec3_correlator_1_h", filters_[1]);
-        break;
-      case 2:
-        data_dumper_->DumpRaw("aec3_correlator_2_h", filters_[2]);
-        break;
-      case 3:
-        data_dumper_->DumpRaw("aec3_correlator_3_h", filters_[3]);
-        break;
-      case 4:
-        data_dumper_->DumpRaw("aec3_correlator_4_h", filters_[4]);
-        break;
-      case 5:
-        data_dumper_->DumpRaw("aec3_correlator_5_h", filters_[5]);
-        break;
-      case 6:
-        data_dumper_->DumpRaw("aec3_correlator_6_h", filters_[6]);
-        break;
-      case 7:
-        data_dumper_->DumpRaw("aec3_correlator_7_h", filters_[7]);
-        break;
-      case 8:
-        data_dumper_->DumpRaw("aec3_correlator_8_h", filters_[8]);
-        break;
-      case 9:
-        data_dumper_->DumpRaw("aec3_correlator_9_h", filters_[9]);
-        break;
-      default:
-        RTC_DCHECK_NOTREACHED();
+    const bool reliable =
+        lag_estimate > 2 && lag_estimate < (filters_[n].size() - 10) &&
+        error_sum < matching_filter_threshold_ * error_sum_anchor;
+
+    // Find the best estimate
+    const size_t lag = lag_estimate + alignment_shift;
+    if (filters_updated && reliable && error_sum < winner_error_sum) {
+      winner_error_sum = error_sum;
+      winner_index = n;
+      // In case that 2 matched filters return the same winner candidate
+      // (overlap region), the one with the smaller index is chosen in order
+      // to search for pre-echoes.
+      if (previous_lag_estimate && previous_lag_estimate == lag) {
+        winner_lag_ = previous_lag_estimate;
+        winner_index = n - 1;
+      } else {
+        winner_lag_ = lag;
+      }
     }
-
+    previous_lag_estimate = lag;
     alignment_shift += filter_intra_lag_shift_;
   }
+
+  if (winner_index != -1) {
+    RTC_DCHECK(winner_lag_.has_value());
+    reported_lag_estimate_ =
+        LagEstimate(winner_lag_.value(), /*pre_echo_lag=*/winner_lag_.value());
+    if (detect_pre_echo_ && last_detected_best_lag_filter_ == winner_index) {
+      if (error_sum_anchor > 30.0f * 30.0f * y.size()) {
+        UpdateAccumulatedError(instantaneous_accumulated_error_,
+                               accumulated_error_[winner_index],
+                               1.0f / error_sum_anchor);
+      }
+      reported_lag_estimate_->pre_echo_lag = ComputePreEchoLag(
+          accumulated_error_[winner_index], winner_lag_.value(),
+          winner_index * filter_intra_lag_shift_ /*alignment_shift_winner*/);
+    }
+    last_detected_best_lag_filter_ = winner_index;
+  }
+  if (ApmDataDumper::IsAvailable()) {
+    Dump();
+  }
 }
 
 void MatchedFilter::LogFilterProperties(int sample_rate_hz,
@@ -510,4 +781,27 @@ void MatchedFilter::LogFilterProperties(int sample_rate_hz,
   }
 }
 
+void MatchedFilter::Dump() {
+  for (size_t n = 0; n < filters_.size(); ++n) {
+    const size_t lag_estimate = aec3::MaxSquarePeakIndex(filters_[n]);
+    std::string dumper_filter = "aec3_correlator_" + std::to_string(n) + "_h";
+    data_dumper_->DumpRaw(dumper_filter.c_str(), filters_[n]);
+    std::string dumper_lag = "aec3_correlator_lag_" + std::to_string(n);
+    data_dumper_->DumpRaw(dumper_lag.c_str(),
+                          lag_estimate + n * filter_intra_lag_shift_);
+    if (detect_pre_echo_) {
+      std::string dumper_error =
+          "aec3_correlator_error_" + std::to_string(n) + "_h";
+      data_dumper_->DumpRaw(dumper_error.c_str(), accumulated_error_[n]);
+
+      size_t pre_echo_lag = ComputePreEchoLag(
+          accumulated_error_[n], lag_estimate + n * filter_intra_lag_shift_,
+          n * filter_intra_lag_shift_);
+      std::string dumper_pre_lag =
+          "aec3_correlator_pre_echo_lag_" + std::to_string(n);
+      data_dumper_->DumpRaw(dumper_pre_lag.c_str(), pre_echo_lag);
+    }
+  }
+}
+
 }  // namespace webrtc
diff --git a/modules/audio_processing/aec3/matched_filter.h b/modules/audio_processing/aec3/matched_filter.h
index dd4a678394..760d5e39fd 100644
--- a/modules/audio_processing/aec3/matched_filter.h
+++ b/modules/audio_processing/aec3/matched_filter.h
@@ -15,6 +15,7 @@
 
 #include <vector>
 
+#include "absl/types/optional.h"
 #include "api/array_view.h"
 #include "modules/audio_processing/aec3/aec3_common.h"
 #include "rtc_base/system/arch.h"
@@ -36,7 +37,10 @@ void MatchedFilterCore_NEON(size_t x_start_index,
                             rtc::ArrayView<const float> y,
                             rtc::ArrayView<float> h,
                             bool* filters_updated,
-                            float* error_sum);
+                            float* error_sum,
+                            bool compute_accumulation_error,
+                            rtc::ArrayView<float> accumulated_error,
+                            rtc::ArrayView<float> scratch_memory);
 
 #endif
 
@@ -50,7 +54,10 @@ void MatchedFilterCore_SSE2(size_t x_start_index,
                             rtc::ArrayView<const float> y,
                             rtc::ArrayView<float> h,
                             bool* filters_updated,
-                            float* error_sum);
+                            float* error_sum,
+                            bool compute_accumulated_error,
+                            rtc::ArrayView<float> accumulated_error,
+                            rtc::ArrayView<float> scratch_memory);
 
 // Filter core for the matched filter that is optimized for AVX2.
 void MatchedFilterCore_AVX2(size_t x_start_index,
@@ -60,7 +67,10 @@ void MatchedFilterCore_AVX2(size_t x_start_index,
                             rtc::ArrayView<const float> y,
                             rtc::ArrayView<float> h,
                             bool* filters_updated,
-                            float* error_sum);
+                            float* error_sum,
+                            bool compute_accumulated_error,
+                            rtc::ArrayView<float> accumulated_error,
+                            rtc::ArrayView<float> scratch_memory);
 
 #endif
 
@@ -72,7 +82,9 @@ void MatchedFilterCore(size_t x_start_index,
                        rtc::ArrayView<const float> y,
                        rtc::ArrayView<float> h,
                        bool* filters_updated,
-                       float* error_sum);
+                       float* error_sum,
+                       bool compute_accumulation_error,
+                       rtc::ArrayView<float> accumulated_error);
 
 // Find largest peak of squared values in array.
 size_t MaxSquarePeakIndex(rtc::ArrayView<const float> h);
@@ -87,13 +99,10 @@ class MatchedFilter {
   // shift.
   struct LagEstimate {
     LagEstimate() = default;
-    LagEstimate(float accuracy, bool reliable, size_t lag, bool updated)
-        : accuracy(accuracy), reliable(reliable), lag(lag), updated(updated) {}
-
-    float accuracy = 0.f;
-    bool reliable = false;
+    LagEstimate(size_t lag, size_t pre_echo_lag)
+        : lag(lag), pre_echo_lag(pre_echo_lag) {}
     size_t lag = 0;
-    bool updated = false;
+    size_t pre_echo_lag = 0;
   };
 
   MatchedFilter(ApmDataDumper* data_dumper,
@@ -105,7 +114,8 @@ class MatchedFilter {
                 float excitation_limit,
                 float smoothing_fast,
                 float smoothing_slow,
-                float matching_filter_threshold);
+                float matching_filter_threshold,
+                bool detect_pre_echo);
 
   MatchedFilter() = delete;
   MatchedFilter(const MatchedFilter&) = delete;
@@ -122,8 +132,8 @@ class MatchedFilter {
   void Reset();
 
   // Returns the current lag estimates.
-  rtc::ArrayView<const MatchedFilter::LagEstimate> GetLagEstimates() const {
-    return lag_estimates_;
+  absl::optional<const MatchedFilter::LagEstimate> GetBestLagEstimate() const {
+    return reported_lag_estimate_;
   }
 
   // Returns the maximum filter lag.
@@ -137,17 +147,25 @@ class MatchedFilter {
                            size_t downsampling_factor) const;
 
  private:
+  void Dump();
+
   ApmDataDumper* const data_dumper_;
   const Aec3Optimization optimization_;
   const size_t sub_block_size_;
   const size_t filter_intra_lag_shift_;
   std::vector<std::vector<float>> filters_;
-  std::vector<LagEstimate> lag_estimates_;
+  std::vector<std::vector<float>> accumulated_error_;
+  std::vector<float> instantaneous_accumulated_error_;
+  std::vector<float> scratch_memory_;
+  absl::optional<MatchedFilter::LagEstimate> reported_lag_estimate_;
+  absl::optional<size_t> winner_lag_;
+  int last_detected_best_lag_filter_ = -1;
   std::vector<size_t> filters_offsets_;
   const float excitation_limit_;
   const float smoothing_fast_;
   const float smoothing_slow_;
   const float matching_filter_threshold_;
+  const bool detect_pre_echo_;
 };
 
 }  // namespace webrtc
diff --git a/modules/audio_processing/aec3/matched_filter_avx2.cc b/modules/audio_processing/aec3/matched_filter_avx2.cc
index 8b7010f1dc..8c2ffcbd1e 100644
--- a/modules/audio_processing/aec3/matched_filter_avx2.cc
+++ b/modules/audio_processing/aec3/matched_filter_avx2.cc
@@ -8,15 +8,134 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include "modules/audio_processing/aec3/matched_filter.h"
-
 #include <immintrin.h>
 
+#include "modules/audio_processing/aec3/matched_filter.h"
 #include "rtc_base/checks.h"
 
 namespace webrtc {
 namespace aec3 {
 
+// Let ha denote the horizontal of a, and hb the horizontal sum of b
+// returns [ha, hb, ha, hb]
+inline __m128 hsum_ab(__m256 a, __m256 b) {
+  __m256 s_256 = _mm256_hadd_ps(a, b);
+  const __m256i mask = _mm256_set_epi32(7, 6, 3, 2, 5, 4, 1, 0);
+  s_256 = _mm256_permutevar8x32_ps(s_256, mask);
+  __m128 s = _mm_hadd_ps(_mm256_extractf128_ps(s_256, 0),
+                         _mm256_extractf128_ps(s_256, 1));
+  s = _mm_hadd_ps(s, s);
+  return s;
+}
+
+void MatchedFilterCore_AccumulatedError_AVX2(
+    size_t x_start_index,
+    float x2_sum_threshold,
+    float smoothing,
+    rtc::ArrayView<const float> x,
+    rtc::ArrayView<const float> y,
+    rtc::ArrayView<float> h,
+    bool* filters_updated,
+    float* error_sum,
+    rtc::ArrayView<float> accumulated_error,
+    rtc::ArrayView<float> scratch_memory) {
+  const int h_size = static_cast<int>(h.size());
+  const int x_size = static_cast<int>(x.size());
+  RTC_DCHECK_EQ(0, h_size % 16);
+  std::fill(accumulated_error.begin(), accumulated_error.end(), 0.0f);
+
+  // Process for all samples in the sub-block.
+  for (size_t i = 0; i < y.size(); ++i) {
+    // Apply the matched filter as filter * x, and compute x * x.
+    RTC_DCHECK_GT(x_size, x_start_index);
+    const int chunk1 =
+        std::min(h_size, static_cast<int>(x_size - x_start_index));
+    if (chunk1 != h_size) {
+      const int chunk2 = h_size - chunk1;
+      std::copy(x.begin() + x_start_index, x.end(), scratch_memory.begin());
+      std::copy(x.begin(), x.begin() + chunk2, scratch_memory.begin() + chunk1);
+    }
+    const float* x_p =
+        chunk1 != h_size ? scratch_memory.data() : &x[x_start_index];
+    const float* h_p = &h[0];
+    float* a_p = &accumulated_error[0];
+    __m256 s_inst_hadd_256;
+    __m256 s_inst_256;
+    __m256 s_inst_256_8;
+    __m256 x2_sum_256 = _mm256_set1_ps(0);
+    __m256 x2_sum_256_8 = _mm256_set1_ps(0);
+    __m128 e_128;
+    float x2_sum = 0.0f;
+    float s_acum = 0;
+    const int limit_by_16 = h_size >> 4;
+    for (int k = limit_by_16; k > 0; --k, h_p += 16, x_p += 16, a_p += 4) {
+      // Load the data into 256 bit vectors.
+      __m256 x_k = _mm256_loadu_ps(x_p);
+      __m256 h_k = _mm256_loadu_ps(h_p);
+      __m256 x_k_8 = _mm256_loadu_ps(x_p + 8);
+      __m256 h_k_8 = _mm256_loadu_ps(h_p + 8);
+      // Compute and accumulate x * x and h * x.
+      x2_sum_256 = _mm256_fmadd_ps(x_k, x_k, x2_sum_256);
+      x2_sum_256_8 = _mm256_fmadd_ps(x_k_8, x_k_8, x2_sum_256_8);
+      s_inst_256 = _mm256_mul_ps(h_k, x_k);
+      s_inst_256_8 = _mm256_mul_ps(h_k_8, x_k_8);
+      s_inst_hadd_256 = _mm256_hadd_ps(s_inst_256, s_inst_256_8);
+      s_inst_hadd_256 = _mm256_hadd_ps(s_inst_hadd_256, s_inst_hadd_256);
+      s_acum += s_inst_hadd_256[0];
+      e_128[0] = s_acum - y[i];
+      s_acum += s_inst_hadd_256[4];
+      e_128[1] = s_acum - y[i];
+      s_acum += s_inst_hadd_256[1];
+      e_128[2] = s_acum - y[i];
+      s_acum += s_inst_hadd_256[5];
+      e_128[3] = s_acum - y[i];
+
+      __m128 accumulated_error = _mm_load_ps(a_p);
+      accumulated_error = _mm_fmadd_ps(e_128, e_128, accumulated_error);
+      _mm_storeu_ps(a_p, accumulated_error);
+    }
+    // Sum components together.
+    x2_sum_256 = _mm256_add_ps(x2_sum_256, x2_sum_256_8);
+    __m128 x2_sum_128 = _mm_add_ps(_mm256_extractf128_ps(x2_sum_256, 0),
+                                   _mm256_extractf128_ps(x2_sum_256, 1));
+    // Combine the accumulated vector and scalar values.
+    float* v = reinterpret_cast<float*>(&x2_sum_128);
+    x2_sum += v[0] + v[1] + v[2] + v[3];
+
+    // Compute the matched filter error.
+    float e = y[i] - s_acum;
+    const bool saturation = y[i] >= 32000.f || y[i] <= -32000.f;
+    (*error_sum) += e * e;
+
+    // Update the matched filter estimate in an NLMS manner.
+    if (x2_sum > x2_sum_threshold && !saturation) {
+      RTC_DCHECK_LT(0.f, x2_sum);
+      const float alpha = smoothing * e / x2_sum;
+      const __m256 alpha_256 = _mm256_set1_ps(alpha);
+
+      // filter = filter + smoothing * (y - filter * x) * x / x * x.
+      float* h_p = &h[0];
+      const float* x_p =
+          chunk1 != h_size ? scratch_memory.data() : &x[x_start_index];
+      // Perform 256 bit vector operations.
+      const int limit_by_8 = h_size >> 3;
+      for (int k = limit_by_8; k > 0; --k, h_p += 8, x_p += 8) {
+        // Load the data into 256 bit vectors.
+        __m256 h_k = _mm256_loadu_ps(h_p);
+        __m256 x_k = _mm256_loadu_ps(x_p);
+        // Compute h = h + alpha * x.
+        h_k = _mm256_fmadd_ps(x_k, alpha_256, h_k);
+
+        // Store the result.
+        _mm256_storeu_ps(h_p, h_k);
+      }
+      *filters_updated = true;
+    }
+
+    x_start_index = x_start_index > 0 ? x_start_index - 1 : x_size - 1;
+  }
+}
+
 void MatchedFilterCore_AVX2(size_t x_start_index,
                             float x2_sum_threshold,
                             float smoothing,
@@ -24,7 +143,15 @@ void MatchedFilterCore_AVX2(size_t x_start_index,
                             rtc::ArrayView<const float> y,
                             rtc::ArrayView<float> h,
                             bool* filters_updated,
-                            float* error_sum) {
+                            float* error_sum,
+                            bool compute_accumulated_error,
+                            rtc::ArrayView<float> accumulated_error,
+                            rtc::ArrayView<float> scratch_memory) {
+  if (compute_accumulated_error) {
+    return MatchedFilterCore_AccumulatedError_AVX2(
+        x_start_index, x2_sum_threshold, smoothing, x, y, h, filters_updated,
+        error_sum, accumulated_error, scratch_memory);
+  }
   const int h_size = static_cast<int>(h.size());
   const int x_size = static_cast<int>(x.size());
   RTC_DCHECK_EQ(0, h_size % 8);
@@ -81,15 +208,9 @@ void MatchedFilterCore_AVX2(size_t x_start_index,
     // Sum components together.
     x2_sum_256 = _mm256_add_ps(x2_sum_256, x2_sum_256_8);
     s_256 = _mm256_add_ps(s_256, s_256_8);
-    __m128 x2_sum_128 = _mm_add_ps(_mm256_extractf128_ps(x2_sum_256, 0),
-                                   _mm256_extractf128_ps(x2_sum_256, 1));
-    __m128 s_128 = _mm_add_ps(_mm256_extractf128_ps(s_256, 0),
-                              _mm256_extractf128_ps(s_256, 1));
-    // Combine the accumulated vector and scalar values.
-    float* v = reinterpret_cast<float*>(&x2_sum_128);
-    x2_sum += v[0] + v[1] + v[2] + v[3];
-    v = reinterpret_cast<float*>(&s_128);
-    s += v[0] + v[1] + v[2] + v[3];
+    __m128 sum = hsum_ab(x2_sum_256, s_256);
+    x2_sum += sum[0];
+    s += sum[1];
 
     // Compute the matched filter error.
     float e = y[i] - s;
diff --git a/modules/audio_processing/aec3/matched_filter_lag_aggregator.cc b/modules/audio_processing/aec3/matched_filter_lag_aggregator.cc
index 603a864b34..17f517a001 100644
--- a/modules/audio_processing/aec3/matched_filter_lag_aggregator.cc
+++ b/modules/audio_processing/aec3/matched_filter_lag_aggregator.cc
@@ -14,84 +14,148 @@
 
 #include "modules/audio_processing/logging/apm_data_dumper.h"
 #include "rtc_base/checks.h"
+#include "rtc_base/numerics/safe_minmax.h"
 
 namespace webrtc {
+namespace {
+int GetDownSamplingBlockSizeLog2(int down_sampling_factor) {
+  int down_sampling_factor_log2 = 0;
+  down_sampling_factor >>= 1;
+  while (down_sampling_factor > 0) {
+    down_sampling_factor_log2++;
+    down_sampling_factor >>= 1;
+  }
+  return static_cast<int>(kBlockSizeLog2) > down_sampling_factor_log2
+             ? static_cast<int>(kBlockSizeLog2) - down_sampling_factor_log2
+             : 0;
+}
+}  // namespace
 
 MatchedFilterLagAggregator::MatchedFilterLagAggregator(
     ApmDataDumper* data_dumper,
     size_t max_filter_lag,
-    const EchoCanceller3Config::Delay::DelaySelectionThresholds& thresholds)
+    const EchoCanceller3Config::Delay& delay_config)
     : data_dumper_(data_dumper),
-      histogram_(max_filter_lag + 1, 0),
-      thresholds_(thresholds) {
+      thresholds_(delay_config.delay_selection_thresholds),
+      headroom_(static_cast<int>(delay_config.delay_headroom_samples /
+                                 delay_config.down_sampling_factor)),
+      highest_peak_aggregator_(max_filter_lag) {
+  if (delay_config.detect_pre_echo) {
+    pre_echo_lag_aggregator_ = std::make_unique<PreEchoLagAggregator>(
+        max_filter_lag, delay_config.down_sampling_factor);
+  }
   RTC_DCHECK(data_dumper);
   RTC_DCHECK_LE(thresholds_.initial, thresholds_.converged);
-  histogram_data_.fill(0);
 }
 
 MatchedFilterLagAggregator::~MatchedFilterLagAggregator() = default;
 
 void MatchedFilterLagAggregator::Reset(bool hard_reset) {
-  std::fill(histogram_.begin(), histogram_.end(), 0);
-  histogram_data_.fill(0);
-  histogram_data_index_ = 0;
+  highest_peak_aggregator_.Reset();
+  if (pre_echo_lag_aggregator_ != nullptr) {
+    pre_echo_lag_aggregator_->Reset();
+  }
   if (hard_reset) {
     significant_candidate_found_ = false;
   }
 }
 
 absl::optional<DelayEstimate> MatchedFilterLagAggregator::Aggregate(
-    rtc::ArrayView<const MatchedFilter::LagEstimate> lag_estimates) {
-  // Choose the strongest lag estimate as the best one.
-  float best_accuracy = 0.f;
-  int best_lag_estimate_index = -1;
-  for (size_t k = 0; k < lag_estimates.size(); ++k) {
-    if (lag_estimates[k].updated && lag_estimates[k].reliable) {
-      if (lag_estimates[k].accuracy > best_accuracy) {
-        best_accuracy = lag_estimates[k].accuracy;
-        best_lag_estimate_index = static_cast<int>(k);
-      }
+    const absl::optional<const MatchedFilter::LagEstimate>& lag_estimate) {
+  if (lag_estimate && pre_echo_lag_aggregator_) {
+    pre_echo_lag_aggregator_->Dump(data_dumper_);
+    pre_echo_lag_aggregator_->Aggregate(
+        std::max(0, static_cast<int>(lag_estimate->pre_echo_lag) - headroom_));
+  }
+
+  if (lag_estimate) {
+    highest_peak_aggregator_.Aggregate(
+        std::max(0, static_cast<int>(lag_estimate->lag) - headroom_));
+    rtc::ArrayView<const int> histogram = highest_peak_aggregator_.histogram();
+    int candidate = highest_peak_aggregator_.candidate();
+    significant_candidate_found_ = significant_candidate_found_ ||
+                                   histogram[candidate] > thresholds_.converged;
+    if (histogram[candidate] > thresholds_.converged ||
+        (histogram[candidate] > thresholds_.initial &&
+         !significant_candidate_found_)) {
+      DelayEstimate::Quality quality = significant_candidate_found_
+                                           ? DelayEstimate::Quality::kRefined
+                                           : DelayEstimate::Quality::kCoarse;
+      int reported_delay = pre_echo_lag_aggregator_ != nullptr
+                               ? pre_echo_lag_aggregator_->pre_echo_candidate()
+                               : candidate;
+      return DelayEstimate(quality, reported_delay);
     }
   }
 
-  // TODO(peah): Remove this logging once all development is done.
-  data_dumper_->DumpRaw("aec3_echo_path_delay_estimator_best_index",
-                        best_lag_estimate_index);
-  data_dumper_->DumpRaw("aec3_echo_path_delay_estimator_histogram", histogram_);
+  return absl::nullopt;
+}
 
-  if (best_lag_estimate_index != -1) {
-    RTC_DCHECK_GT(histogram_.size(), histogram_data_[histogram_data_index_]);
-    RTC_DCHECK_LE(0, histogram_data_[histogram_data_index_]);
-    --histogram_[histogram_data_[histogram_data_index_]];
+MatchedFilterLagAggregator::HighestPeakAggregator::HighestPeakAggregator(
+    size_t max_filter_lag)
+    : histogram_(max_filter_lag + 1, 0) {
+  histogram_data_.fill(0);
+}
 
-    histogram_data_[histogram_data_index_] =
-        lag_estimates[best_lag_estimate_index].lag;
+void MatchedFilterLagAggregator::HighestPeakAggregator::Reset() {
+  std::fill(histogram_.begin(), histogram_.end(), 0);
+  histogram_data_.fill(0);
+  histogram_data_index_ = 0;
+}
 
-    RTC_DCHECK_GT(histogram_.size(), histogram_data_[histogram_data_index_]);
-    RTC_DCHECK_LE(0, histogram_data_[histogram_data_index_]);
-    ++histogram_[histogram_data_[histogram_data_index_]];
+void MatchedFilterLagAggregator::HighestPeakAggregator::Aggregate(int lag) {
+  RTC_DCHECK_GT(histogram_.size(), histogram_data_[histogram_data_index_]);
+  RTC_DCHECK_LE(0, histogram_data_[histogram_data_index_]);
+  --histogram_[histogram_data_[histogram_data_index_]];
+  histogram_data_[histogram_data_index_] = lag;
+  RTC_DCHECK_GT(histogram_.size(), histogram_data_[histogram_data_index_]);
+  RTC_DCHECK_LE(0, histogram_data_[histogram_data_index_]);
+  ++histogram_[histogram_data_[histogram_data_index_]];
+  histogram_data_index_ = (histogram_data_index_ + 1) % histogram_data_.size();
+  candidate_ =
+      std::distance(histogram_.begin(),
+                    std::max_element(histogram_.begin(), histogram_.end()));
+}
 
-    histogram_data_index_ =
-        (histogram_data_index_ + 1) % histogram_data_.size();
+MatchedFilterLagAggregator::PreEchoLagAggregator::PreEchoLagAggregator(
+    size_t max_filter_lag,
+    size_t down_sampling_factor)
+    : block_size_log2_(GetDownSamplingBlockSizeLog2(down_sampling_factor)),
+      histogram_(
+          ((max_filter_lag + 1) * down_sampling_factor) >> kBlockSizeLog2,
+          0) {
+  Reset();
+}
 
-    const int candidate =
-        std::distance(histogram_.begin(),
-                      std::max_element(histogram_.begin(), histogram_.end()));
+void MatchedFilterLagAggregator::PreEchoLagAggregator::Reset() {
+  std::fill(histogram_.begin(), histogram_.end(), 0);
+  histogram_data_.fill(0);
+  histogram_data_index_ = 0;
+  pre_echo_candidate_ = 0;
+}
 
-    significant_candidate_found_ =
-        significant_candidate_found_ ||
-        histogram_[candidate] > thresholds_.converged;
-    if (histogram_[candidate] > thresholds_.converged ||
-        (histogram_[candidate] > thresholds_.initial &&
-         !significant_candidate_found_)) {
-      DelayEstimate::Quality quality = significant_candidate_found_
-                                           ? DelayEstimate::Quality::kRefined
-                                           : DelayEstimate::Quality::kCoarse;
-      return DelayEstimate(quality, candidate);
-    }
+void MatchedFilterLagAggregator::PreEchoLagAggregator::Aggregate(
+    int pre_echo_lag) {
+  int pre_echo_block_size = pre_echo_lag >> block_size_log2_;
+  RTC_DCHECK(pre_echo_block_size >= 0 &&
+             pre_echo_block_size < static_cast<int>(histogram_.size()));
+  pre_echo_block_size =
+      rtc::SafeClamp(pre_echo_block_size, 0, histogram_.size() - 1);
+  if (histogram_[histogram_data_[histogram_data_index_]] > 0) {
+    --histogram_[histogram_data_[histogram_data_index_]];
   }
+  histogram_data_[histogram_data_index_] = pre_echo_block_size;
+  ++histogram_[histogram_data_[histogram_data_index_]];
+  histogram_data_index_ = (histogram_data_index_ + 1) % histogram_data_.size();
+  int pre_echo_candidate_block_size =
+      std::distance(histogram_.begin(),
+                    std::max_element(histogram_.begin(), histogram_.end()));
+  pre_echo_candidate_ = (pre_echo_candidate_block_size << block_size_log2_);
+}
 
-  return absl::nullopt;
+void MatchedFilterLagAggregator::PreEchoLagAggregator::Dump(
+    ApmDataDumper* const data_dumper) {
+  data_dumper->DumpRaw("aec3_pre_echo_delay_candidate", pre_echo_candidate_);
 }
 
 }  // namespace webrtc
diff --git a/modules/audio_processing/aec3/matched_filter_lag_aggregator.h b/modules/audio_processing/aec3/matched_filter_lag_aggregator.h
index 612bd5d942..c0598bf226 100644
--- a/modules/audio_processing/aec3/matched_filter_lag_aggregator.h
+++ b/modules/audio_processing/aec3/matched_filter_lag_aggregator.h
@@ -26,10 +26,9 @@ class ApmDataDumper;
 // reliable combined lag estimate.
 class MatchedFilterLagAggregator {
  public:
-  MatchedFilterLagAggregator(
-      ApmDataDumper* data_dumper,
-      size_t max_filter_lag,
-      const EchoCanceller3Config::Delay::DelaySelectionThresholds& thresholds);
+  MatchedFilterLagAggregator(ApmDataDumper* data_dumper,
+                             size_t max_filter_lag,
+                             const EchoCanceller3Config::Delay& delay_config);
 
   MatchedFilterLagAggregator() = delete;
   MatchedFilterLagAggregator(const MatchedFilterLagAggregator&) = delete;
@@ -43,18 +42,55 @@ class MatchedFilterLagAggregator {
 
   // Aggregates the provided lag estimates.
   absl::optional<DelayEstimate> Aggregate(
-      rtc::ArrayView<const MatchedFilter::LagEstimate> lag_estimates);
+      const absl::optional<const MatchedFilter::LagEstimate>& lag_estimate);
 
   // Returns whether a reliable delay estimate has been found.
   bool ReliableDelayFound() const { return significant_candidate_found_; }
 
+  // Returns the delay candidate that is computed by looking at the highest peak
+  // on the matched filters.
+  int GetDelayAtHighestPeak() const {
+    return highest_peak_aggregator_.candidate();
+  }
+
  private:
+  class PreEchoLagAggregator {
+   public:
+    PreEchoLagAggregator(size_t max_filter_lag, size_t down_sampling_factor);
+    void Reset();
+    void Aggregate(int pre_echo_lag);
+    int pre_echo_candidate() const { return pre_echo_candidate_; }
+    void Dump(ApmDataDumper* const data_dumper);
+
+   private:
+    const int block_size_log2_;
+    std::array<int, 250> histogram_data_;
+    std::vector<int> histogram_;
+    int histogram_data_index_ = 0;
+    int pre_echo_candidate_ = 0;
+  };
+
+  class HighestPeakAggregator {
+   public:
+    explicit HighestPeakAggregator(size_t max_filter_lag);
+    void Reset();
+    void Aggregate(int lag);
+    int candidate() const { return candidate_; }
+    rtc::ArrayView<const int> histogram() const { return histogram_; }
+
+   private:
+    std::vector<int> histogram_;
+    std::array<int, 250> histogram_data_;
+    int histogram_data_index_ = 0;
+    int candidate_ = -1;
+  };
+
   ApmDataDumper* const data_dumper_;
-  std::vector<int> histogram_;
-  std::array<int, 250> histogram_data_;
-  int histogram_data_index_ = 0;
   bool significant_candidate_found_ = false;
   const EchoCanceller3Config::Delay::DelaySelectionThresholds thresholds_;
+  const int headroom_;
+  HighestPeakAggregator highest_peak_aggregator_;
+  std::unique_ptr<PreEchoLagAggregator> pre_echo_lag_aggregator_;
 };
 }  // namespace webrtc
 
diff --git a/modules/audio_processing/aec3/matched_filter_lag_aggregator_unittest.cc b/modules/audio_processing/aec3/matched_filter_lag_aggregator_unittest.cc
index 8e2a12e6c5..6804102584 100644
--- a/modules/audio_processing/aec3/matched_filter_lag_aggregator_unittest.cc
+++ b/modules/audio_processing/aec3/matched_filter_lag_aggregator_unittest.cc
@@ -27,69 +27,31 @@ constexpr size_t kNumLagsBeforeDetection = 26;
 
 }  // namespace
 
-// Verifies that the most accurate lag estimate is chosen.
-TEST(MatchedFilterLagAggregator, MostAccurateLagChosen) {
-  constexpr size_t kLag1 = 5;
-  constexpr size_t kLag2 = 10;
-  ApmDataDumper data_dumper(0);
-  EchoCanceller3Config config;
-  std::vector<MatchedFilter::LagEstimate> lag_estimates(2);
-  MatchedFilterLagAggregator aggregator(
-      &data_dumper, std::max(kLag1, kLag2),
-      config.delay.delay_selection_thresholds);
-  lag_estimates[0] = MatchedFilter::LagEstimate(1.f, true, kLag1, true);
-  lag_estimates[1] = MatchedFilter::LagEstimate(0.5f, true, kLag2, true);
-
-  for (size_t k = 0; k < kNumLagsBeforeDetection; ++k) {
-    aggregator.Aggregate(lag_estimates);
-  }
-
-  absl::optional<DelayEstimate> aggregated_lag =
-      aggregator.Aggregate(lag_estimates);
-  EXPECT_TRUE(aggregated_lag);
-  EXPECT_EQ(kLag1, aggregated_lag->delay);
-
-  lag_estimates[0] = MatchedFilter::LagEstimate(0.5f, true, kLag1, true);
-  lag_estimates[1] = MatchedFilter::LagEstimate(1.f, true, kLag2, true);
-
-  for (size_t k = 0; k < kNumLagsBeforeDetection; ++k) {
-    aggregated_lag = aggregator.Aggregate(lag_estimates);
-    EXPECT_TRUE(aggregated_lag);
-    EXPECT_EQ(kLag1, aggregated_lag->delay);
-  }
-
-  aggregated_lag = aggregator.Aggregate(lag_estimates);
-  aggregated_lag = aggregator.Aggregate(lag_estimates);
-  EXPECT_TRUE(aggregated_lag);
-  EXPECT_EQ(kLag2, aggregated_lag->delay);
-}
-
 // Verifies that varying lag estimates causes lag estimates to not be deemed
 // reliable.
 TEST(MatchedFilterLagAggregator,
      LagEstimateInvarianceRequiredForAggregatedLag) {
   ApmDataDumper data_dumper(0);
   EchoCanceller3Config config;
-  std::vector<MatchedFilter::LagEstimate> lag_estimates(1);
-  MatchedFilterLagAggregator aggregator(
-      &data_dumper, 100, config.delay.delay_selection_thresholds);
+  MatchedFilterLagAggregator aggregator(&data_dumper, /*max_filter_lag=*/100,
+                                        config.delay);
 
   absl::optional<DelayEstimate> aggregated_lag;
   for (size_t k = 0; k < kNumLagsBeforeDetection; ++k) {
-    lag_estimates[0] = MatchedFilter::LagEstimate(1.f, true, 10, true);
-    aggregated_lag = aggregator.Aggregate(lag_estimates);
+    aggregated_lag = aggregator.Aggregate(
+        MatchedFilter::LagEstimate(/*lag=*/10, /*pre_echo_lag=*/10));
   }
   EXPECT_TRUE(aggregated_lag);
 
   for (size_t k = 0; k < kNumLagsBeforeDetection * 100; ++k) {
-    lag_estimates[0] = MatchedFilter::LagEstimate(1.f, true, k % 100, true);
-    aggregated_lag = aggregator.Aggregate(lag_estimates);
+    aggregated_lag = aggregator.Aggregate(
+        MatchedFilter::LagEstimate(/*lag=*/k % 100, /*pre_echo_lag=*/k % 100));
   }
   EXPECT_FALSE(aggregated_lag);
 
   for (size_t k = 0; k < kNumLagsBeforeDetection * 100; ++k) {
-    lag_estimates[0] = MatchedFilter::LagEstimate(1.f, true, k % 100, true);
-    aggregated_lag = aggregator.Aggregate(lag_estimates);
+    aggregated_lag = aggregator.Aggregate(
+        MatchedFilter::LagEstimate(/*lag=*/k % 100, /*pre_echo_lag=*/k % 100));
     EXPECT_FALSE(aggregated_lag);
   }
 }
@@ -101,13 +63,11 @@ TEST(MatchedFilterLagAggregator,
   constexpr size_t kLag = 5;
   ApmDataDumper data_dumper(0);
   EchoCanceller3Config config;
-  std::vector<MatchedFilter::LagEstimate> lag_estimates(1);
-  MatchedFilterLagAggregator aggregator(
-      &data_dumper, kLag, config.delay.delay_selection_thresholds);
+  MatchedFilterLagAggregator aggregator(&data_dumper, /*max_filter_lag=*/kLag,
+                                        config.delay);
   for (size_t k = 0; k < kNumLagsBeforeDetection * 10; ++k) {
-    lag_estimates[0] = MatchedFilter::LagEstimate(1.f, true, kLag, false);
-    absl::optional<DelayEstimate> aggregated_lag =
-        aggregator.Aggregate(lag_estimates);
+    absl::optional<DelayEstimate> aggregated_lag = aggregator.Aggregate(
+        MatchedFilter::LagEstimate(/*lag=*/kLag, /*pre_echo_lag=*/kLag));
     EXPECT_FALSE(aggregated_lag);
     EXPECT_EQ(kLag, aggregated_lag->delay);
   }
@@ -122,20 +82,19 @@ TEST(MatchedFilterLagAggregator, DISABLED_PersistentAggregatedLag) {
   ApmDataDumper data_dumper(0);
   EchoCanceller3Config config;
   std::vector<MatchedFilter::LagEstimate> lag_estimates(1);
-  MatchedFilterLagAggregator aggregator(
-      &data_dumper, std::max(kLag1, kLag2),
-      config.delay.delay_selection_thresholds);
+  MatchedFilterLagAggregator aggregator(&data_dumper, std::max(kLag1, kLag2),
+                                        config.delay);
   absl::optional<DelayEstimate> aggregated_lag;
   for (size_t k = 0; k < kNumLagsBeforeDetection; ++k) {
-    lag_estimates[0] = MatchedFilter::LagEstimate(1.f, true, kLag1, true);
-    aggregated_lag = aggregator.Aggregate(lag_estimates);
+    aggregated_lag = aggregator.Aggregate(
+        MatchedFilter::LagEstimate(/*lag=*/kLag1, /*pre_echo_lag=*/kLag1));
   }
   EXPECT_TRUE(aggregated_lag);
   EXPECT_EQ(kLag1, aggregated_lag->delay);
 
   for (size_t k = 0; k < kNumLagsBeforeDetection * 40; ++k) {
-    lag_estimates[0] = MatchedFilter::LagEstimate(1.f, false, kLag2, true);
-    aggregated_lag = aggregator.Aggregate(lag_estimates);
+    aggregated_lag = aggregator.Aggregate(
+        MatchedFilter::LagEstimate(/*lag=*/kLag2, /*pre_echo_lag=*/kLag2));
     EXPECT_TRUE(aggregated_lag);
     EXPECT_EQ(kLag1, aggregated_lag->delay);
   }
@@ -146,9 +105,7 @@ TEST(MatchedFilterLagAggregator, DISABLED_PersistentAggregatedLag) {
 // Verifies the check for non-null data dumper.
 TEST(MatchedFilterLagAggregatorDeathTest, NullDataDumper) {
   EchoCanceller3Config config;
-  EXPECT_DEATH(MatchedFilterLagAggregator(
-                   nullptr, 10, config.delay.delay_selection_thresholds),
-               "");
+  EXPECT_DEATH(MatchedFilterLagAggregator(nullptr, 10, config.delay), "");
 }
 
 #endif
diff --git a/modules/audio_processing/aec3/matched_filter_unittest.cc b/modules/audio_processing/aec3/matched_filter_unittest.cc
index 9924256f0c..b080308191 100644
--- a/modules/audio_processing/aec3/matched_filter_unittest.cc
+++ b/modules/audio_processing/aec3/matched_filter_unittest.cc
@@ -47,12 +47,15 @@ constexpr size_t kAlignmentShiftSubBlocks = kWindowSizeSubBlocks * 3 / 4;
 
 }  // namespace
 
+class MatchedFilterTest : public ::testing::TestWithParam<bool> {};
+
 #if defined(WEBRTC_HAS_NEON)
 // Verifies that the optimized methods for NEON are similar to their reference
 // counterparts.
-TEST(MatchedFilter, TestNeonOptimizations) {
+TEST_P(MatchedFilterTest, TestNeonOptimizations) {
   Random random_generator(42U);
   constexpr float kSmoothing = 0.7f;
+  const bool kComputeAccumulatederror = GetParam();
   for (auto down_sampling_factor : kDownSamplingFactors) {
     const size_t sub_block_size = kBlockSize / down_sampling_factor;
 
@@ -61,6 +64,10 @@ TEST(MatchedFilter, TestNeonOptimizations) {
     std::vector<float> y(sub_block_size);
     std::vector<float> h_NEON(512);
     std::vector<float> h(512);
+    std::vector<float> accumulated_error(512);
+    std::vector<float> accumulated_error_NEON(512);
+    std::vector<float> scratch_memory(512);
+
     int x_index = 0;
     for (int k = 0; k < 1000; ++k) {
       RandomizeSampleVector(&random_generator, y);
@@ -71,10 +78,13 @@ TEST(MatchedFilter, TestNeonOptimizations) {
       float error_sum_NEON = 0.f;
 
       MatchedFilterCore_NEON(x_index, h.size() * 150.f * 150.f, kSmoothing, x,
-                             y, h_NEON, &filters_updated_NEON, &error_sum_NEON);
+                             y, h_NEON, &filters_updated_NEON, &error_sum_NEON,
+                             kComputeAccumulatederror, accumulated_error_NEON,
+                             scratch_memory);
 
       MatchedFilterCore(x_index, h.size() * 150.f * 150.f, kSmoothing, x, y, h,
-                        &filters_updated, &error_sum);
+                        &filters_updated, &error_sum, kComputeAccumulatederror,
+                        accumulated_error);
 
       EXPECT_EQ(filters_updated, filters_updated_NEON);
       EXPECT_NEAR(error_sum, error_sum_NEON, error_sum / 100000.f);
@@ -83,6 +93,17 @@ TEST(MatchedFilter, TestNeonOptimizations) {
         EXPECT_NEAR(h[j], h_NEON[j], 0.00001f);
       }
 
+      if (kComputeAccumulatederror) {
+        for (size_t j = 0; j < accumulated_error.size(); ++j) {
+          float difference =
+              std::abs(accumulated_error[j] - accumulated_error_NEON[j]);
+          float relative_difference = accumulated_error[j] > 0
+                                          ? difference / accumulated_error[j]
+                                          : difference;
+          EXPECT_NEAR(relative_difference, 0.0f, 0.02f);
+        }
+      }
+
       x_index = (x_index + sub_block_size) % x.size();
     }
   }
@@ -92,7 +113,8 @@ TEST(MatchedFilter, TestNeonOptimizations) {
 #if defined(WEBRTC_ARCH_X86_FAMILY)
 // Verifies that the optimized methods for SSE2 are bitexact to their reference
 // counterparts.
-TEST(MatchedFilter, TestSse2Optimizations) {
+TEST_P(MatchedFilterTest, TestSse2Optimizations) {
+  const bool kComputeAccumulatederror = GetParam();
   bool use_sse2 = (GetCPUInfo(kSSE2) != 0);
   if (use_sse2) {
     Random random_generator(42U);
@@ -104,6 +126,9 @@ TEST(MatchedFilter, TestSse2Optimizations) {
       std::vector<float> y(sub_block_size);
       std::vector<float> h_SSE2(512);
       std::vector<float> h(512);
+      std::vector<float> accumulated_error(512 / 4);
+      std::vector<float> accumulated_error_SSE2(512 / 4);
+      std::vector<float> scratch_memory(512);
       int x_index = 0;
       for (int k = 0; k < 1000; ++k) {
         RandomizeSampleVector(&random_generator, y);
@@ -115,10 +140,12 @@ TEST(MatchedFilter, TestSse2Optimizations) {
 
         MatchedFilterCore_SSE2(x_index, h.size() * 150.f * 150.f, kSmoothing, x,
                                y, h_SSE2, &filters_updated_SSE2,
-                               &error_sum_SSE2);
+                               &error_sum_SSE2, kComputeAccumulatederror,
+                               accumulated_error_SSE2, scratch_memory);
 
         MatchedFilterCore(x_index, h.size() * 150.f * 150.f, kSmoothing, x, y,
-                          h, &filters_updated, &error_sum);
+                          h, &filters_updated, &error_sum,
+                          kComputeAccumulatederror, accumulated_error);
 
         EXPECT_EQ(filters_updated, filters_updated_SSE2);
         EXPECT_NEAR(error_sum, error_sum_SSE2, error_sum / 100000.f);
@@ -127,14 +154,24 @@ TEST(MatchedFilter, TestSse2Optimizations) {
           EXPECT_NEAR(h[j], h_SSE2[j], 0.00001f);
         }
 
+        for (size_t j = 0; j < accumulated_error.size(); ++j) {
+          float difference =
+              std::abs(accumulated_error[j] - accumulated_error_SSE2[j]);
+          float relative_difference = accumulated_error[j] > 0
+                                          ? difference / accumulated_error[j]
+                                          : difference;
+          EXPECT_NEAR(relative_difference, 0.0f, 0.00001f);
+        }
+
         x_index = (x_index + sub_block_size) % x.size();
       }
     }
   }
 }
 
-TEST(MatchedFilter, TestAvx2Optimizations) {
+TEST_P(MatchedFilterTest, TestAvx2Optimizations) {
   bool use_avx2 = (GetCPUInfo(kAVX2) != 0);
+  const bool kComputeAccumulatederror = GetParam();
   if (use_avx2) {
     Random random_generator(42U);
     constexpr float kSmoothing = 0.7f;
@@ -145,29 +182,36 @@ TEST(MatchedFilter, TestAvx2Optimizations) {
       std::vector<float> y(sub_block_size);
       std::vector<float> h_AVX2(512);
       std::vector<float> h(512);
+      std::vector<float> accumulated_error(512 / 4);
+      std::vector<float> accumulated_error_AVX2(512 / 4);
+      std::vector<float> scratch_memory(512);
       int x_index = 0;
       for (int k = 0; k < 1000; ++k) {
         RandomizeSampleVector(&random_generator, y);
-
         bool filters_updated = false;
         float error_sum = 0.f;
         bool filters_updated_AVX2 = false;
         float error_sum_AVX2 = 0.f;
-
         MatchedFilterCore_AVX2(x_index, h.size() * 150.f * 150.f, kSmoothing, x,
                                y, h_AVX2, &filters_updated_AVX2,
-                               &error_sum_AVX2);
-
+                               &error_sum_AVX2, kComputeAccumulatederror,
+                               accumulated_error_AVX2, scratch_memory);
         MatchedFilterCore(x_index, h.size() * 150.f * 150.f, kSmoothing, x, y,
-                          h, &filters_updated, &error_sum);
-
+                          h, &filters_updated, &error_sum,
+                          kComputeAccumulatederror, accumulated_error);
         EXPECT_EQ(filters_updated, filters_updated_AVX2);
         EXPECT_NEAR(error_sum, error_sum_AVX2, error_sum / 100000.f);
-
         for (size_t j = 0; j < h.size(); ++j) {
           EXPECT_NEAR(h[j], h_AVX2[j], 0.00001f);
         }
-
+        for (size_t j = 0; j < accumulated_error.size(); j += 4) {
+          float difference =
+              std::abs(accumulated_error[j] - accumulated_error_AVX2[j]);
+          float relative_difference = accumulated_error[j] > 0
+                                          ? difference / accumulated_error[j]
+                                          : difference;
+          EXPECT_NEAR(relative_difference, 0.0f, 0.00001f);
+        }
         x_index = (x_index + sub_block_size) % x.size();
       }
     }
@@ -199,9 +243,9 @@ TEST(MatchedFilter, MaxSquarePeakIndex) {
 }
 
 // Verifies that the matched filter produces proper lag estimates for
-// artificially
-// delayed signals.
-TEST(MatchedFilter, LagEstimation) {
+// artificially delayed signals.
+TEST_P(MatchedFilterTest, LagEstimation) {
+  const bool kDetectPreEcho = GetParam();
   Random random_generator(42U);
   constexpr size_t kNumChannels = 1;
   constexpr int kSampleRateHz = 48000;
@@ -222,12 +266,12 @@ TEST(MatchedFilter, LagEstimation) {
       Decimator capture_decimator(down_sampling_factor);
       DelayBuffer<float> signal_delay_buffer(down_sampling_factor *
                                              delay_samples);
-      MatchedFilter filter(&data_dumper, DetectOptimization(), sub_block_size,
-                           kWindowSizeSubBlocks, kNumMatchedFilters,
-                           kAlignmentShiftSubBlocks, 150,
-                           config.delay.delay_estimate_smoothing,
-                           config.delay.delay_estimate_smoothing_delay_found,
-                           config.delay.delay_candidate_detection_threshold);
+      MatchedFilter filter(
+          &data_dumper, DetectOptimization(), sub_block_size,
+          kWindowSizeSubBlocks, kNumMatchedFilters, kAlignmentShiftSubBlocks,
+          150, config.delay.delay_estimate_smoothing,
+          config.delay.delay_estimate_smoothing_delay_found,
+          config.delay.delay_candidate_detection_threshold, kDetectPreEcho);
 
       std::unique_ptr<RenderDelayBuffer> render_delay_buffer(
           RenderDelayBuffer::Create(config, kSampleRateHz, kNumChannels));
@@ -254,62 +298,97 @@ TEST(MatchedFilter, LagEstimation) {
             downsampled_capture_data.data(), sub_block_size);
         capture_decimator.Decimate(capture[0], downsampled_capture);
         filter.Update(render_delay_buffer->GetDownsampledRenderBuffer(),
-                      downsampled_capture, false);
+                      downsampled_capture, /*use_slow_smoothing=*/false);
       }
 
       // Obtain the lag estimates.
-      auto lag_estimates = filter.GetLagEstimates();
-
-      // Find which lag estimate should be the most accurate.
-      absl::optional<size_t> expected_most_accurate_lag_estimate;
-      size_t alignment_shift_sub_blocks = 0;
-      for (size_t k = 0; k < config.delay.num_filters; ++k) {
-        if ((alignment_shift_sub_blocks + 3 * kWindowSizeSubBlocks / 4) *
-                sub_block_size >
-            delay_samples) {
-          expected_most_accurate_lag_estimate = k > 0 ? k - 1 : 0;
-          break;
-        }
-        alignment_shift_sub_blocks += kAlignmentShiftSubBlocks;
-      }
-      ASSERT_TRUE(expected_most_accurate_lag_estimate);
-
-      // Verify that the expected most accurate lag estimate is the most
-      // accurate estimate.
-      for (size_t k = 0; k < kNumMatchedFilters; ++k) {
-        if (k != *expected_most_accurate_lag_estimate &&
-            k != (*expected_most_accurate_lag_estimate + 1)) {
-          EXPECT_TRUE(
-              lag_estimates[*expected_most_accurate_lag_estimate].accuracy >
-                  lag_estimates[k].accuracy ||
-              !lag_estimates[k].reliable ||
-              !lag_estimates[*expected_most_accurate_lag_estimate].reliable);
-        }
-      }
+      auto lag_estimate = filter.GetBestLagEstimate();
+      EXPECT_TRUE(lag_estimate.has_value());
 
-      // Verify that all lag estimates are updated as expected for signals
-      // containing strong noise.
-      for (auto& le : lag_estimates) {
-        EXPECT_TRUE(le.updated);
+      // Verify that the expected most accurate lag estimate is correct.
+      if (lag_estimate.has_value()) {
+        EXPECT_EQ(delay_samples, lag_estimate->lag);
+        EXPECT_EQ(delay_samples, lag_estimate->pre_echo_lag);
       }
+    }
+  }
+}
 
-      // Verify that the expected most accurate lag estimate is reliable.
-      EXPECT_TRUE(
-          lag_estimates[*expected_most_accurate_lag_estimate].reliable ||
-          lag_estimates[std::min(*expected_most_accurate_lag_estimate + 1,
-                                 lag_estimates.size() - 1)]
-              .reliable);
+// Test the pre echo estimation.
+TEST_P(MatchedFilterTest, PreEchoEstimation) {
+  const bool kDetectPreEcho = GetParam();
+  Random random_generator(42U);
+  constexpr size_t kNumChannels = 1;
+  constexpr int kSampleRateHz = 48000;
+  constexpr size_t kNumBands = NumBandsForRate(kSampleRateHz);
 
-      // Verify that the expected most accurate lag estimate is correct.
-      if (lag_estimates[*expected_most_accurate_lag_estimate].reliable) {
-        EXPECT_TRUE(delay_samples ==
-                    lag_estimates[*expected_most_accurate_lag_estimate].lag);
+  for (auto down_sampling_factor : kDownSamplingFactors) {
+    const size_t sub_block_size = kBlockSize / down_sampling_factor;
+
+    Block render(kNumBands, kNumChannels);
+    std::vector<std::vector<float>> capture(
+        1, std::vector<float>(kBlockSize, 0.f));
+    std::vector<float> capture_with_pre_echo(kBlockSize, 0.f);
+    ApmDataDumper data_dumper(0);
+    // data_dumper.SetActivated(true);
+    size_t pre_echo_delay_samples = 20e-3 * 16000 / down_sampling_factor;
+    size_t echo_delay_samples = 50e-3 * 16000 / down_sampling_factor;
+    EchoCanceller3Config config;
+    config.delay.down_sampling_factor = down_sampling_factor;
+    config.delay.num_filters = kNumMatchedFilters;
+    Decimator capture_decimator(down_sampling_factor);
+    DelayBuffer<float> signal_echo_delay_buffer(down_sampling_factor *
+                                                echo_delay_samples);
+    DelayBuffer<float> signal_pre_echo_delay_buffer(down_sampling_factor *
+                                                    pre_echo_delay_samples);
+    MatchedFilter filter(
+        &data_dumper, DetectOptimization(), sub_block_size,
+        kWindowSizeSubBlocks, kNumMatchedFilters, kAlignmentShiftSubBlocks, 150,
+        config.delay.delay_estimate_smoothing,
+        config.delay.delay_estimate_smoothing_delay_found,
+        config.delay.delay_candidate_detection_threshold, kDetectPreEcho);
+    std::unique_ptr<RenderDelayBuffer> render_delay_buffer(
+        RenderDelayBuffer::Create(config, kSampleRateHz, kNumChannels));
+    // Analyze the correlation between render and capture.
+    for (size_t k = 0; k < (600 + echo_delay_samples / sub_block_size); ++k) {
+      for (size_t band = 0; band < kNumBands; ++band) {
+        for (size_t channel = 0; channel < kNumChannels; ++channel) {
+          RandomizeSampleVector(&random_generator, render.View(band, channel));
+        }
+      }
+      signal_echo_delay_buffer.Delay(render.View(0, 0), capture[0]);
+      signal_pre_echo_delay_buffer.Delay(render.View(0, 0),
+                                         capture_with_pre_echo);
+      for (size_t k = 0; k < capture[0].size(); ++k) {
+        constexpr float gain_pre_echo = 0.8f;
+        capture[0][k] += gain_pre_echo * capture_with_pre_echo[k];
+      }
+      render_delay_buffer->Insert(render);
+      if (k == 0) {
+        render_delay_buffer->Reset();
+      }
+      render_delay_buffer->PrepareCaptureProcessing();
+      std::array<float, kBlockSize> downsampled_capture_data;
+      rtc::ArrayView<float> downsampled_capture(downsampled_capture_data.data(),
+                                                sub_block_size);
+      capture_decimator.Decimate(capture[0], downsampled_capture);
+      filter.Update(render_delay_buffer->GetDownsampledRenderBuffer(),
+                    downsampled_capture, /*use_slow_smoothing=*/false);
+    }
+    // Obtain the lag estimates.
+    auto lag_estimate = filter.GetBestLagEstimate();
+    EXPECT_TRUE(lag_estimate.has_value());
+    // Verify that the expected most accurate lag estimate is correct.
+    if (lag_estimate.has_value()) {
+      EXPECT_EQ(echo_delay_samples, lag_estimate->lag);
+      if (kDetectPreEcho) {
+        // The pre echo delay is estimated in a subsampled domain and a larger
+        // error is allowed.
+        EXPECT_NEAR(pre_echo_delay_samples, lag_estimate->pre_echo_lag, 4);
       } else {
-        EXPECT_TRUE(
-            delay_samples ==
-            lag_estimates[std::min(*expected_most_accurate_lag_estimate + 1,
-                                   lag_estimates.size() - 1)]
-                .lag);
+        // The pre echo delay fallback to the highest mached filter peak when
+        // its detection is disabled.
+        EXPECT_EQ(echo_delay_samples, lag_estimate->pre_echo_lag);
       }
     }
   }
@@ -317,7 +396,8 @@ TEST(MatchedFilter, LagEstimation) {
 
 // Verifies that the matched filter does not produce reliable and accurate
 // estimates for uncorrelated render and capture signals.
-TEST(MatchedFilter, LagNotReliableForUncorrelatedRenderAndCapture) {
+TEST_P(MatchedFilterTest, LagNotReliableForUncorrelatedRenderAndCapture) {
+  const bool kDetectPreEcho = GetParam();
   constexpr size_t kNumChannels = 1;
   constexpr int kSampleRateHz = 48000;
   constexpr size_t kNumBands = NumBandsForRate(kSampleRateHz);
@@ -335,12 +415,12 @@ TEST(MatchedFilter, LagNotReliableForUncorrelatedRenderAndCapture) {
     ApmDataDumper data_dumper(0);
     std::unique_ptr<RenderDelayBuffer> render_delay_buffer(
         RenderDelayBuffer::Create(config, kSampleRateHz, kNumChannels));
-    MatchedFilter filter(&data_dumper, DetectOptimization(), sub_block_size,
-                         kWindowSizeSubBlocks, kNumMatchedFilters,
-                         kAlignmentShiftSubBlocks, 150,
-                         config.delay.delay_estimate_smoothing,
-                         config.delay.delay_estimate_smoothing_delay_found,
-                         config.delay.delay_candidate_detection_threshold);
+    MatchedFilter filter(
+        &data_dumper, DetectOptimization(), sub_block_size,
+        kWindowSizeSubBlocks, kNumMatchedFilters, kAlignmentShiftSubBlocks, 150,
+        config.delay.delay_estimate_smoothing,
+        config.delay.delay_estimate_smoothing_delay_found,
+        config.delay.delay_candidate_detection_threshold, kDetectPreEcho);
 
     // Analyze the correlation between render and capture.
     for (size_t k = 0; k < 100; ++k) {
@@ -352,20 +432,17 @@ TEST(MatchedFilter, LagNotReliableForUncorrelatedRenderAndCapture) {
                     false);
     }
 
-    // Obtain the lag estimates.
-    auto lag_estimates = filter.GetLagEstimates();
-    EXPECT_EQ(kNumMatchedFilters, lag_estimates.size());
-
-    // Verify that no lag estimates are reliable.
-    for (auto& le : lag_estimates) {
-      EXPECT_FALSE(le.reliable);
-    }
+    // Obtain the best lag estimate and Verify that no lag estimates are
+    // reliable.
+    auto best_lag_estimates = filter.GetBestLagEstimate();
+    EXPECT_FALSE(best_lag_estimates.has_value());
   }
 }
 
 // Verifies that the matched filter does not produce updated lag estimates for
 // render signals of low level.
-TEST(MatchedFilter, LagNotUpdatedForLowLevelRender) {
+TEST_P(MatchedFilterTest, LagNotUpdatedForLowLevelRender) {
+  const bool kDetectPreEcho = GetParam();
   Random random_generator(42U);
   constexpr size_t kNumChannels = 1;
   constexpr int kSampleRateHz = 48000;
@@ -374,19 +451,17 @@ TEST(MatchedFilter, LagNotUpdatedForLowLevelRender) {
   for (auto down_sampling_factor : kDownSamplingFactors) {
     const size_t sub_block_size = kBlockSize / down_sampling_factor;
 
-    std::vector<std::vector<std::vector<float>>> render(
-        kNumBands, std::vector<std::vector<float>>(
-                       kNumChannels, std::vector<float>(kBlockSize, 0.f)));
+    Block render(kNumBands, kNumChannels);
     std::vector<std::vector<float>> capture(
         1, std::vector<float>(kBlockSize, 0.f));
     ApmDataDumper data_dumper(0);
     EchoCanceller3Config config;
-    MatchedFilter filter(&data_dumper, DetectOptimization(), sub_block_size,
-                         kWindowSizeSubBlocks, kNumMatchedFilters,
-                         kAlignmentShiftSubBlocks, 150,
-                         config.delay.delay_estimate_smoothing,
-                         config.delay.delay_estimate_smoothing_delay_found,
-                         config.delay.delay_candidate_detection_threshold);
+    MatchedFilter filter(
+        &data_dumper, DetectOptimization(), sub_block_size,
+        kWindowSizeSubBlocks, kNumMatchedFilters, kAlignmentShiftSubBlocks, 150,
+        config.delay.delay_estimate_smoothing,
+        config.delay.delay_estimate_smoothing_delay_found,
+        config.delay.delay_candidate_detection_threshold, kDetectPreEcho);
     std::unique_ptr<RenderDelayBuffer> render_delay_buffer(
         RenderDelayBuffer::Create(EchoCanceller3Config(), kSampleRateHz,
                                   kNumChannels));
@@ -394,11 +469,11 @@ TEST(MatchedFilter, LagNotUpdatedForLowLevelRender) {
 
     // Analyze the correlation between render and capture.
     for (size_t k = 0; k < 100; ++k) {
-      RandomizeSampleVector(&random_generator, render[0][0]);
-      for (auto& render_k : render[0][0]) {
+      RandomizeSampleVector(&random_generator, render.View(0, 0));
+      for (auto& render_k : render.View(0, 0)) {
         render_k *= 149.f / 32767.f;
       }
-      std::copy(render[0][0].begin(), render[0][0].end(), capture[0].begin());
+      std::copy(render.begin(0, 0), render.end(0, 0), capture[0].begin());
       std::array<float, kBlockSize> downsampled_capture_data;
       rtc::ArrayView<float> downsampled_capture(downsampled_capture_data.data(),
                                                 sub_block_size);
@@ -407,86 +482,76 @@ TEST(MatchedFilter, LagNotUpdatedForLowLevelRender) {
                     downsampled_capture, false);
     }
 
-    // Obtain the lag estimates.
-    auto lag_estimates = filter.GetLagEstimates();
-    EXPECT_EQ(kNumMatchedFilters, lag_estimates.size());
-
-    // Verify that no lag estimates are updated and that no lag estimates are
-    // reliable.
-    for (auto& le : lag_estimates) {
-      EXPECT_FALSE(le.updated);
-      EXPECT_FALSE(le.reliable);
-    }
+    // Verify that no lag estimate has been produced.
+    auto lag_estimate = filter.GetBestLagEstimate();
+    EXPECT_FALSE(lag_estimate.has_value());
   }
 }
 
-// Verifies that the correct number of lag estimates are produced for a certain
-// number of alignment shifts.
-TEST(MatchedFilter, NumberOfLagEstimates) {
-  ApmDataDumper data_dumper(0);
-  EchoCanceller3Config config;
-  for (auto down_sampling_factor : kDownSamplingFactors) {
-    const size_t sub_block_size = kBlockSize / down_sampling_factor;
-    for (size_t num_matched_filters = 0; num_matched_filters < 10;
-         ++num_matched_filters) {
-      MatchedFilter filter(&data_dumper, DetectOptimization(), sub_block_size,
-                           32, num_matched_filters, 1, 150,
-                           config.delay.delay_estimate_smoothing,
-                           config.delay.delay_estimate_smoothing_delay_found,
-                           config.delay.delay_candidate_detection_threshold);
-      EXPECT_EQ(num_matched_filters, filter.GetLagEstimates().size());
-    }
-  }
-}
+INSTANTIATE_TEST_SUITE_P(_, MatchedFilterTest, testing::Values(true, false));
 
 #if RTC_DCHECK_IS_ON && GTEST_HAS_DEATH_TEST && !defined(WEBRTC_ANDROID)
 
+class MatchedFilterDeathTest : public ::testing::TestWithParam<bool> {};
+
 // Verifies the check for non-zero windows size.
-TEST(MatchedFilterDeathTest, ZeroWindowSize) {
+TEST_P(MatchedFilterDeathTest, ZeroWindowSize) {
+  const bool kDetectPreEcho = GetParam();
   ApmDataDumper data_dumper(0);
   EchoCanceller3Config config;
   EXPECT_DEATH(MatchedFilter(&data_dumper, DetectOptimization(), 16, 0, 1, 1,
                              150, config.delay.delay_estimate_smoothing,
                              config.delay.delay_estimate_smoothing_delay_found,
-                             config.delay.delay_candidate_detection_threshold),
+                             config.delay.delay_candidate_detection_threshold,
+                             kDetectPreEcho),
                "");
 }
 
 // Verifies the check for non-null data dumper.
-TEST(MatchedFilterDeathTest, NullDataDumper) {
+TEST_P(MatchedFilterDeathTest, NullDataDumper) {
+  const bool kDetectPreEcho = GetParam();
   EchoCanceller3Config config;
   EXPECT_DEATH(MatchedFilter(nullptr, DetectOptimization(), 16, 1, 1, 1, 150,
                              config.delay.delay_estimate_smoothing,
                              config.delay.delay_estimate_smoothing_delay_found,
-                             config.delay.delay_candidate_detection_threshold),
+                             config.delay.delay_candidate_detection_threshold,
+                             kDetectPreEcho),
                "");
 }
 
 // Verifies the check for that the sub block size is a multiple of 4.
 // TODO(peah): Activate the unittest once the required code has been landed.
-TEST(MatchedFilterDeathTest, DISABLED_BlockSizeMultipleOf4) {
+TEST_P(MatchedFilterDeathTest, DISABLED_BlockSizeMultipleOf4) {
+  const bool kDetectPreEcho = GetParam();
   ApmDataDumper data_dumper(0);
   EchoCanceller3Config config;
   EXPECT_DEATH(MatchedFilter(&data_dumper, DetectOptimization(), 15, 1, 1, 1,
                              150, config.delay.delay_estimate_smoothing,
                              config.delay.delay_estimate_smoothing_delay_found,
-                             config.delay.delay_candidate_detection_threshold),
+                             config.delay.delay_candidate_detection_threshold,
+                             kDetectPreEcho),
                "");
 }
 
 // Verifies the check for that there is an integer number of sub blocks that add
 // up to a block size.
 // TODO(peah): Activate the unittest once the required code has been landed.
-TEST(MatchedFilterDeathTest, DISABLED_SubBlockSizeAddsUpToBlockSize) {
+TEST_P(MatchedFilterDeathTest, DISABLED_SubBlockSizeAddsUpToBlockSize) {
+  const bool kDetectPreEcho = GetParam();
   ApmDataDumper data_dumper(0);
   EchoCanceller3Config config;
   EXPECT_DEATH(MatchedFilter(&data_dumper, DetectOptimization(), 12, 1, 1, 1,
                              150, config.delay.delay_estimate_smoothing,
                              config.delay.delay_estimate_smoothing_delay_found,
-                             config.delay.delay_candidate_detection_threshold),
+                             config.delay.delay_candidate_detection_threshold,
+                             kDetectPreEcho),
                "");
 }
 
+INSTANTIATE_TEST_SUITE_P(_,
+                         MatchedFilterDeathTest,
+                         testing::Values(true, false));
+
 #endif
 
 }  // namespace aec3
diff --git a/modules/audio_processing/aec3/render_delay_controller.cc b/modules/audio_processing/aec3/render_delay_controller.cc
index aa3d440c33..826c38a1e9 100644
--- a/modules/audio_processing/aec3/render_delay_controller.cc
+++ b/modules/audio_processing/aec3/render_delay_controller.cc
@@ -53,7 +53,6 @@ class RenderDelayControllerImpl final : public RenderDelayController {
   static std::atomic<int> instance_count_;
   std::unique_ptr<ApmDataDumper> data_dumper_;
   const int hysteresis_limit_blocks_;
-  const int delay_headroom_samples_;
   absl::optional<DelayEstimate> delay_;
   EchoPathDelayEstimator delay_estimator_;
   RenderDelayControllerMetrics metrics_;
@@ -66,15 +65,9 @@ class RenderDelayControllerImpl final : public RenderDelayController {
 DelayEstimate ComputeBufferDelay(
     const absl::optional<DelayEstimate>& current_delay,
     int hysteresis_limit_blocks,
-    int delay_headroom_samples,
     DelayEstimate estimated_delay) {
-  // Subtract delay headroom.
-  const int delay_with_headroom_samples = std::max(
-      static_cast<int>(estimated_delay.delay) - delay_headroom_samples, 0);
-
   // Compute the buffer delay increase required to achieve the desired latency.
-  size_t new_delay_blocks = delay_with_headroom_samples >> kBlockSizeLog2;
-
+  size_t new_delay_blocks = estimated_delay.delay >> kBlockSizeLog2;
   // Add hysteresis.
   if (current_delay) {
     size_t current_delay_blocks = current_delay->delay;
@@ -83,7 +76,6 @@ DelayEstimate ComputeBufferDelay(
       new_delay_blocks = current_delay_blocks;
     }
   }
-
   DelayEstimate new_delay = estimated_delay;
   new_delay.delay = new_delay_blocks;
   return new_delay;
@@ -98,7 +90,6 @@ RenderDelayControllerImpl::RenderDelayControllerImpl(
     : data_dumper_(new ApmDataDumper(instance_count_.fetch_add(1) + 1)),
       hysteresis_limit_blocks_(
           static_cast<int>(config.delay.hysteresis_limit_blocks)),
-      delay_headroom_samples_(config.delay.delay_headroom_samples),
       delay_estimator_(data_dumper_.get(), config, num_capture_channels),
       last_delay_estimate_quality_(DelayEstimate::Quality::kCoarse) {
   RTC_DCHECK(ValidFullBandRate(sample_rate_hz));
@@ -158,9 +149,8 @@ absl::optional<DelayEstimate> RenderDelayControllerImpl::GetDelay(
     const bool use_hysteresis =
         last_delay_estimate_quality_ == DelayEstimate::Quality::kRefined &&
         delay_samples_->quality == DelayEstimate::Quality::kRefined;
-    delay_ = ComputeBufferDelay(delay_,
-                                use_hysteresis ? hysteresis_limit_blocks_ : 0,
-                                delay_headroom_samples_, *delay_samples_);
+    delay_ = ComputeBufferDelay(
+        delay_, use_hysteresis ? hysteresis_limit_blocks_ : 0, *delay_samples_);
     last_delay_estimate_quality_ = delay_samples_->quality;
   }