From 26cc5e650f15071ca200525e7a91285c48f81163 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Per=20=C3=85hgren?= <peah@webrtc.org>
Date: Tue, 26 Nov 2019 22:58:53 +0100
Subject: [PATCH] Corrected the aggregation of AGC choices and add fallback
 solution
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This CL corrects the analog AGC code so that the levels are properly
aggregated and not only the level of the first channel is chosen.

It also adds a kill-switch to allow the aggrated level to be the maximum
level rather than the minimum level.

Bug: webrtc:10859
Change-Id: Ibf4fecb53cfaf0dc064c334112105bf26401f78d
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/160708
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29931}
---
 .../agc/agc_manager_direct.cc                 | 27 +++++++++++++++----
 .../audio_processing/agc/agc_manager_direct.h |  2 +-
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/modules/audio_processing/agc/agc_manager_direct.cc b/modules/audio_processing/agc/agc_manager_direct.cc
index 6d0bb9a8b2..8af7c2d88b 100644
--- a/modules/audio_processing/agc/agc_manager_direct.cc
+++ b/modules/audio_processing/agc/agc_manager_direct.cc
@@ -56,6 +56,12 @@ const int kMaxResidualGainChange = 15;
 // restrictions from clipping events.
 const int kSurplusCompressionGain = 6;
 
+// Returns whether a fall-back solution to choose the maximum level should be
+// chosen.
+bool UseMaxAnalogChannelLevel() {
+  return field_trial::IsEnabled("WebRTC-UseMaxAnalogAgcChannelLevel");
+}
+
 // Returns kMinMicLevel if no field trial exists or if it has been disabled.
 // Returns a value between 0 and 255 depending on the field-trial string.
 // Example: 'WebRTC-Audio-AgcMinMicLevelExperiment/Enabled-80' => returns 80.
@@ -426,6 +432,7 @@ AgcManagerDirect::AgcManagerDirect(int num_capture_channels,
                                    int sample_rate_hz)
     : data_dumper_(
           new ApmDataDumper(rtc::AtomicOps::Increment(&instance_counter_))),
+      use_min_channel_level_(!UseMaxAnalogChannelLevel()),
       sample_rate_hz_(sample_rate_hz),
       num_capture_channels_(num_capture_channels),
       disable_digital_adaptive_(disable_digital_adaptive),
@@ -579,11 +586,21 @@ void AgcManagerDirect::set_stream_analog_level(int level) {
 void AgcManagerDirect::AggregateChannelLevels() {
   stream_analog_level_ = channel_agcs_[0]->stream_analog_level();
   channel_controlling_gain_ = 0;
-  for (size_t ch = 1; ch < channel_agcs_.size(); ++ch) {
-    int level = channel_agcs_[0]->stream_analog_level();
-    if (level < stream_analog_level_) {
-      stream_analog_level_ = level;
-      channel_controlling_gain_ = static_cast<int>(ch);
+  if (use_min_channel_level_) {
+    for (size_t ch = 1; ch < channel_agcs_.size(); ++ch) {
+      int level = channel_agcs_[ch]->stream_analog_level();
+      if (level < stream_analog_level_) {
+        stream_analog_level_ = level;
+        channel_controlling_gain_ = static_cast<int>(ch);
+      }
+    }
+  } else {
+    for (size_t ch = 1; ch < channel_agcs_.size(); ++ch) {
+      int level = channel_agcs_[ch]->stream_analog_level();
+      if (level > stream_analog_level_) {
+        stream_analog_level_ = level;
+        channel_controlling_gain_ = static_cast<int>(ch);
+      }
     }
   }
 }
diff --git a/modules/audio_processing/agc/agc_manager_direct.h b/modules/audio_processing/agc/agc_manager_direct.h
index 9502a7d82f..54eb867e3e 100644
--- a/modules/audio_processing/agc/agc_manager_direct.h
+++ b/modules/audio_processing/agc/agc_manager_direct.h
@@ -87,8 +87,8 @@ class AgcManagerDirect final {
   void AggregateChannelLevels();
 
   std::unique_ptr<ApmDataDumper> data_dumper_;
-
   static int instance_counter_;
+  const bool use_min_channel_level_;
   const int sample_rate_hz_;
   const int num_capture_channels_;
   const bool disable_digital_adaptive_;