From d84b3d1f3d8ad6b1e1f2667e2d2d48cf5ca59227 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Per=20=C3=85hgren?= <peah@webrtc.org>
Date: Fri, 12 Jan 2018 14:47:11 +0100
Subject: [PATCH] Generalized the hysteresis behavior in the AEC3 delay
 estimator
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This CL generalizes the hysteresis behavior on the AEC3 delay estimator
to be two-sided and easier to configure.


Bug: webrtc:8671
Change-Id: Ife21c1511416e32eb3618c81178deefe332ac1e8
Reviewed-on: https://webrtc-review.googlesource.com/39267
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21604}
---
 .../aec3/render_delay_controller.cc           | 34 +++++++++++++++----
 .../include/audio_processing.h                |  3 ++
 2 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/modules/audio_processing/aec3/render_delay_controller.cc b/modules/audio_processing/aec3/render_delay_controller.cc
index dfc47f4b23..16a447730d 100644
--- a/modules/audio_processing/aec3/render_delay_controller.cc
+++ b/modules/audio_processing/aec3/render_delay_controller.cc
@@ -39,6 +39,9 @@ class RenderDelayControllerImpl final : public RenderDelayController {
  private:
   static int instance_count_;
   std::unique_ptr<ApmDataDumper> data_dumper_;
+  const int delay_headroom_blocks_;
+  const int hysteresis_limit_1_blocks_;
+  const int hysteresis_limit_2_blocks_;
   rtc::Optional<size_t> delay_;
   EchoPathDelayEstimator delay_estimator_;
   size_t align_call_counter_ = 0;
@@ -48,19 +51,30 @@ class RenderDelayControllerImpl final : public RenderDelayController {
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(RenderDelayControllerImpl);
 };
 
-size_t ComputeNewBufferDelay(rtc::Optional<size_t> current_delay,
+size_t ComputeNewBufferDelay(const rtc::Optional<size_t>& current_delay,
+                             int delay_headroom_blocks,
+                             int hysteresis_limit_1_blocks,
+                             int hysteresis_limit_2_blocks,
                              size_t delay_samples) {
   // The below division is not exact and the truncation is intended.
   const int echo_path_delay_blocks = delay_samples >> kBlockSizeLog2;
-  constexpr int kDelayHeadroomBlocks = 1;
 
   // Compute the buffer delay increase required to achieve the desired latency.
-  size_t new_delay = std::max(echo_path_delay_blocks - kDelayHeadroomBlocks, 0);
+  size_t new_delay =
+      std::max(echo_path_delay_blocks - delay_headroom_blocks, 0);
 
   // Add hysteresis.
   if (current_delay) {
-    if (new_delay == *current_delay + 1) {
-      new_delay = *current_delay;
+    if (new_delay > *current_delay) {
+      if (new_delay <= *current_delay + hysteresis_limit_1_blocks) {
+        new_delay = *current_delay;
+      }
+    } else if (new_delay < *current_delay) {
+      size_t hysteresis_limit = std::max(
+          static_cast<int>(*current_delay) - hysteresis_limit_2_blocks, 0);
+      if (new_delay >= hysteresis_limit) {
+        new_delay = *current_delay;
+      }
     }
   }
 
@@ -75,6 +89,12 @@ RenderDelayControllerImpl::RenderDelayControllerImpl(
     int sample_rate_hz)
     : data_dumper_(
           new ApmDataDumper(rtc::AtomicOps::Increment(&instance_count_))),
+      delay_headroom_blocks_(
+          static_cast<int>(config.delay.delay_headroom_blocks)),
+      hysteresis_limit_1_blocks_(
+          static_cast<int>(config.delay.hysteresis_limit_1_blocks)),
+      hysteresis_limit_2_blocks_(
+          static_cast<int>(config.delay.hysteresis_limit_2_blocks)),
       delay_estimator_(data_dumper_.get(), config),
       delay_buf_(kBlockSize * non_causal_offset, 0.f) {
   RTC_DCHECK(ValidFullBandRate(sample_rate_hz));
@@ -120,7 +140,9 @@ rtc::Optional<size_t> RenderDelayControllerImpl::GetDelay(
   if (delay_samples) {
     // Compute and set new render delay buffer delay.
     if (align_call_counter_ > kNumBlocksPerSecond) {
-      delay_ = ComputeNewBufferDelay(delay_, static_cast<int>(*delay_samples));
+      delay_ = ComputeNewBufferDelay(
+          delay_, delay_headroom_blocks_, hysteresis_limit_1_blocks_,
+          hysteresis_limit_2_blocks_, static_cast<int>(*delay_samples));
     }
 
     metrics_.Update(static_cast<int>(*delay_samples), delay_ ? *delay_ : 0);
diff --git a/modules/audio_processing/include/audio_processing.h b/modules/audio_processing/include/audio_processing.h
index 8951b8cda8..6f7cda0da1 100644
--- a/modules/audio_processing/include/audio_processing.h
+++ b/modules/audio_processing/include/audio_processing.h
@@ -1238,6 +1238,9 @@ struct EchoCanceller3Config {
     size_t num_filters = 4;
     size_t api_call_jitter_blocks = 26;
     size_t min_echo_path_delay_blocks = 5;
+    size_t delay_headroom_blocks = 1;
+    size_t hysteresis_limit_1_blocks = 1;
+    size_t hysteresis_limit_2_blocks = 0;
   } delay;
 
   struct Filter {