commit 504bd59422283ebfa6275108804197edeeef908e
author Alessio Bazzica <alessiob@webrtc.org> Thu Dec 01 13:26:26 2022 +0100
committer WebRTC LUCI CQ <webrtc-scoped@luci-project-accounts.iam.gserviceaccount.com> Thu Dec 01 15:30:13 2022 +0000
tree ff813f009d6d5582c2b9b0e73a8da870d243f8b4
parent 8754a3c9451bbcc31eb1a3d581d2e7755f9b813e

Expose APM pipeline parameter to select downmixing method

Bug: b/257289030
Change-Id: I03a666a15752d7a1125af2f8d3edae530493618c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/285473
Reviewed-by: Jesus de Vicente Pena <devicentepena@webrtc.org>
Commit-Queue: Alessio Bazzica <alessiob@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#38789}

modules/audio_processing/audio_processing_impl.cc

diff --git a/modules/audio_processing/audio_processing_impl.cc b/modules/audio_processing/audio_processing_impl.cc
index 52f2fcb..2cb4858 100644
--- a/modules/audio_processing/audio_processing_impl.cc
+++ b/modules/audio_processing/audio_processing_impl.cc
@@ -442,6 +442,19 @@
   return adjusted_config;
 }
 
+using DownmixMethod = AudioProcessing::Config::Pipeline::DownmixMethod;
+
+void SetDownmixMethod(AudioBuffer& buffer, DownmixMethod method) {
+  switch (method) {
+    case DownmixMethod::kAverageChannels:
+      buffer.set_downmixing_by_averaging();
+      break;
+    case DownmixMethod::kUseFirstChannel:
+      buffer.set_downmixing_to_specific_channel(/*channel=*/0);
+      break;
+  }
+}
+
 constexpr int kUnspecifiedDataDumpInputVolume = -100;
 
 }  // namespace
@@ -689,6 +702,8 @@
       formats_.api_format.output_stream().num_channels(),
       formats_.api_format.output_stream().sample_rate_hz(),
       formats_.api_format.output_stream().num_channels()));
+  SetDownmixMethod(*capture_.capture_audio,
+                   config_.pipeline.capture_downmix_method);
 
   if (capture_nonlocked_.capture_processing_format.sample_rate_hz() <
           formats_.api_format.output_stream().sample_rate_hz() &&
@@ -700,6 +715,8 @@
                         formats_.api_format.output_stream().num_channels(),
                         formats_.api_format.output_stream().sample_rate_hz(),
                         formats_.api_format.output_stream().num_channels()));
+    SetDownmixMethod(*capture_.capture_fullband_audio,
+                     config_.pipeline.capture_downmix_method);
   } else {
     capture_.capture_fullband_audio.reset();
   }
@@ -821,7 +838,9 @@
       config_.pipeline.multi_channel_capture !=
           adjusted_config.pipeline.multi_channel_capture ||
       config_.pipeline.maximum_internal_processing_rate !=
-          adjusted_config.pipeline.maximum_internal_processing_rate;
+          adjusted_config.pipeline.maximum_internal_processing_rate ||
+      config_.pipeline.capture_downmix_method !=
+          adjusted_config.pipeline.capture_downmix_method;
 
   const bool aec_config_changed =
       config_.echo_canceller.enabled !=

modules/audio_processing/include/audio_processing.h

diff --git a/modules/audio_processing/include/audio_processing.h b/modules/audio_processing/include/audio_processing.h
index f3600b3..9935167 100644
--- a/modules/audio_processing/include/audio_processing.h
+++ b/modules/audio_processing/include/audio_processing.h
@@ -146,6 +146,12 @@
   struct RTC_EXPORT Config {
     // Sets the properties of the audio processing pipeline.
     struct RTC_EXPORT Pipeline {
+      // Ways to downmix a multi-channel track to mono.
+      enum class DownmixMethod {
+        kAverageChannels,  // Average across channels.
+        kUseFirstChannel   // Use the first channel.
+      };
+
       // Maximum allowed processing rate used internally. May only be set to
       // 32000 or 48000 and any differing values will be treated as 48000.
       int maximum_internal_processing_rate = 48000;
@@ -154,6 +160,9 @@
       // Allow multi-channel processing of capture audio when AEC3 is active
       // or a custom AEC is injected..
       bool multi_channel_capture = false;
+      // Indicates how to downmix multi-channel capture audio to mono (when
+      // needed).
+      DownmixMethod capture_downmix_method = DownmixMethod::kAverageChannels;
     } pipeline;
 
     // Enabled the pre-amplifier. It amplifies the capture signal