From 05d8ee1b3e39eaf7d5d31e824ada9a1611415d48 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Per=20=C3=85hgren?= <peah@webrtc.org>
Date: Thu, 7 Jun 2018 15:59:59 +0200
Subject: [PATCH] AEC3: Delay stabilization after a delay change
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This CL ensures that the linear-filter based refined delay is chosen to
match the delay that was detected by the delay estimator during the time
it takes for the linear filter to converge.

Bug: webrtc:9371,chromium:850451
Change-Id: Ib9cf532df0577ceca10a260d9d2deba5306f88bb
Reviewed-on: https://webrtc-review.googlesource.com/81682
Commit-Queue: Per Åhgren <peah@webrtc.org>
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23537}
---
 modules/audio_processing/aec3/aec_state.cc | 17 +++++++++++++++++
 modules/audio_processing/aec3/aec_state.h  |  3 +++
 2 files changed, 20 insertions(+)

diff --git a/modules/audio_processing/aec3/aec_state.cc b/modules/audio_processing/aec3/aec_state.cc
index f35818564e..516f6abc3f 100644
--- a/modules/audio_processing/aec3/aec_state.cc
+++ b/modules/audio_processing/aec3/aec_state.cc
@@ -33,6 +33,11 @@ bool EnableStationaryRenderImprovements() {
       "WebRTC-Aec3StationaryRenderImprovementsKillSwitch");
 }
 
+bool EnableEnforcingDelayAfterRealignment() {
+  return !field_trial::IsEnabled(
+      "WebRTC-Aec3EnforceDelayAfterRealignmentKillSwitch");
+}
+
 float ComputeGainRampupIncrease(const EchoCanceller3Config& config) {
   const auto& c = config.echo_removal_control.gain_rampup;
   return powf(1.f / c.first_non_zero_gain, 1.f / c.non_zero_gain_blocks);
@@ -53,6 +58,7 @@ AecState::AecState(const EchoCanceller3Config& config)
       use_stationary_properties_(
           EnableStationaryRenderImprovements() &&
           config_.echo_audibility.use_stationary_properties),
+      enforce_delay_after_realignment_(EnableEnforcingDelayAfterRealignment()),
       erle_estimator_(config.erle.min, config.erle.max_l, config.erle.max_h),
       max_render_(config_.filter.main.length_blocks, 0.f),
       reverb_decay_(fabsf(config_.ep_strength.default_len)),
@@ -122,6 +128,17 @@ void AecState::Update(
   // Analyze the filter and compute the delays.
   filter_analyzer_.Update(adaptive_filter_impulse_response, render_buffer);
   filter_delay_blocks_ = filter_analyzer_.DelayBlocks();
+  if (enforce_delay_after_realignment_) {
+    if (external_delay &&
+        (!external_delay_ || external_delay_->delay != external_delay->delay)) {
+      frames_since_external_delay_change_ = 0;
+      external_delay_ = external_delay;
+    }
+    if (blocks_with_proper_filter_adaptation_ < 2 * kNumBlocksPerSecond &&
+        external_delay_) {
+      filter_delay_blocks_ = config_.delay.delay_headroom_blocks;
+    }
+  }
 
   if (filter_analyzer_.Consistent()) {
     internal_delay_ = filter_analyzer_.DelayBlocks();
diff --git a/modules/audio_processing/aec3/aec_state.h b/modules/audio_processing/aec3/aec_state.h
index 4765e84384..d513a4084d 100644
--- a/modules/audio_processing/aec3/aec_state.h
+++ b/modules/audio_processing/aec3/aec_state.h
@@ -148,6 +148,7 @@ class AecState {
   const EchoCanceller3Config config_;
   const bool allow_transparent_mode_;
   const bool use_stationary_properties_;
+  const bool enforce_delay_after_realignment_;
   ErlEstimator erl_estimator_;
   ErleEstimator erle_estimator_;
   size_t capture_block_counter_ = 0;
@@ -187,6 +188,8 @@ class AecState {
   bool converged_filter_seen_ = false;
   bool consistent_filter_seen_ = false;
   bool external_delay_seen_ = false;
+  rtc::Optional<DelayEstimate> external_delay_;
+  size_t frames_since_external_delay_change_ = 0;
   size_t converged_filter_count_ = 0;
   bool finite_erl_ = false;
   size_t active_blocks_since_converged_filter_ = 0;