Add a trivial example to run AEC offline

Just allows for some sanity testing for now, will improve for
configurability and add some sample data in the future.

examples/meson.build

@@ -0,0 +1,8 @@
+top_incdir = include_directories('..')
+
+executable('run-offline',
+  'run-offline.cpp',
+  install: false,
+  include_directories: top_incdir,
+  dependencies: [audio_processing_dep, absl_dep]
+)

examples/run-offline.cpp

@@ -0,0 +1,67 @@
+/*
+ *  Copyright (c) 2024 Asymptotic Inc. All Rights Reserved.
+ *  Author: Arun Raghavan <arun@asymptotic.io>
+ *
+ *  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 "api/scoped_refptr.h"
+#include <cstdlib>
+#include <iostream>
+#include <fstream>
+
+#include <webrtc/modules/audio_processing/include/audio_processing.h>
+
+#define DEFAULT_BLOCK_MS 10
+#define DEFAULT_RATE 32000
+#define DEFAULT_CHANNELS 1
+
+int main(int argc, char **argv) {
+    if (argc != 4) {
+	std::cerr << "Usage: " << argv[0] << " <play_file> <rec_file> <out_file>" << std::endl;
+	return EXIT_FAILURE;
+    }
+
+    std::ifstream play_file(argv[1], std::ios::binary);
+    std::ifstream rec_file(argv[2], std::ios::binary);
+    std::ofstream aec_file(argv[3], std::ios::binary);
+
+    rtc::scoped_refptr<webrtc::AudioProcessing> apm = webrtc::AudioProcessingBuilder().Create();
+
+    webrtc::AudioProcessing::Config config;
+    config.echo_canceller.enabled = true;
+    config.echo_canceller.mobile_mode = false;
+    config.gain_controller1.enabled = true;
+    config.gain_controller1.mode = webrtc::AudioProcessing::Config::GainController1::kAdaptiveAnalog;
+
+    config.gain_controller2.enabled = true;
+
+    config.high_pass_filter.enabled = true;
+
+    apm->ApplyConfig(config);
+
+    webrtc::StreamConfig stream_config(DEFAULT_RATE, DEFAULT_CHANNELS);
+
+    while (!play_file.eof() && !rec_file.eof()) {
+	int16_t play_frame[DEFAULT_RATE * DEFAULT_BLOCK_MS / 1000 * DEFAULT_CHANNELS];
+	int16_t rec_frame[DEFAULT_RATE * DEFAULT_BLOCK_MS / 1000 * DEFAULT_CHANNELS];
+
+	play_file.read(reinterpret_cast<char *>(play_frame), sizeof(play_frame));
+	rec_file.read(reinterpret_cast<char *>(rec_frame), sizeof(rec_frame));
+
+	apm->ProcessReverseStream(play_frame, stream_config, stream_config, play_frame);
+	apm->ProcessStream(rec_frame, stream_config, stream_config, rec_frame);
+
+	aec_file.write(reinterpret_cast<char *>(rec_frame), sizeof(rec_frame));
+    }
+
+    play_file.close();
+    rec_file.close();
+    aec_file.close();
+
+    return EXIT_SUCCESS;
+}

meson.build

@@ -218,3 +218,5 @@ audio_coding_dep = declare_dependency(
 )
 
 meson.override_dependency(ac_project_name, audio_coding_dep)
+
+subdir('examples')