Added basic framework for AEC3 in the audio processing module

webrtc/modules/audio_processing/aec3/echo_canceller3.cc

Index: webrtc/modules/audio_processing/aec3/echo_canceller3.cc
diff --git a/webrtc/modules/audio_processing/aec3/echo_canceller3.cc b/webrtc/modules/audio_processing/aec3/echo_canceller3.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c8ba2eb72c12225a03cc32a39fba7fc95b395b1c
--- /dev/null
+++ b/webrtc/modules/audio_processing/aec3/echo_canceller3.cc
@@ -0,0 +1,56 @@
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#include "webrtc/modules/audio_processing/aec3/echo_canceller3.h"
+
+#include "webrtc/system_wrappers/include/logging.h"
+
+namespace webrtc {
+
+int EchoCanceller3::instance_count_ = 0;
+
+EchoCanceller3::EchoCanceller3(int sample_rate_hz, bool use_anti_hum_filter) {
+  int band_sample_rate_hz = (sample_rate_hz == 8000 ? sample_rate_hz : 16000);
+  frame_length_ = rtc::CheckedDivExact(band_sample_rate_hz, 100);
+
+  LOG(LS_INFO) << "AEC3 created : "
+               << "{ instance_count: " << instance_count_ << "}";
+  ++instance_count_;

[ivoc, 2016/12/09 14:11:09]

Not sure if this is a concern in practice, but this is a potential race
condition if EchoCanceller3 is constructed on multiple threads.

[peah-webrtc, 2016/12/12 19:46:45]

Great point! It is only used in offline simulation though, so it should be fine.
But the increment may be causing an issue. Furthermore, there should only be one
instance active at the same time of the AEC.

WDYT? Is it ok to keep it like this?

[ivoc, 2016/12/14 08:54:15]

Let's keep it like this.

[peah-webrtc, 2016/12/14 08:56:16]

I ended up changing it to using an atomic operation. So now it should be fine.

Done.

+}
+
+EchoCanceller3::~EchoCanceller3() = default;
+
+bool EchoCanceller3::AnalyzeRender(AudioBuffer* render) const {
+  RTC_DCHECK_EQ(1u, render->num_channels());
+  RTC_DCHECK_EQ(frame_length_, render->num_frames_per_band());
+  return true;
+}
+
+void EchoCanceller3::AnalyzeCapture(AudioBuffer* capture) {}
+
+void EchoCanceller3::ProcessCapture(AudioBuffer* capture,
+                                    bool known_echo_path_change) {
+  RTC_DCHECK_EQ(1u, capture->num_channels());
+  RTC_DCHECK_EQ(frame_length_, capture->num_frames_per_band());
+}
+
+std::string EchoCanceller3::ToString(
+    const AudioProcessing::Config::EchoCanceller3& config) {
+  std::stringstream ss;
+  ss << "{"
+     << "enabled: " << (config.enabled ? "true" : "false") << "}";
+  return ss.str();
+}
+
+bool EchoCanceller3::Validate(
+    const AudioProcessing::Config::EchoCanceller3& config) {
+  return true;
+}
+
+}  // namespace webrtc