Adding second layer of the echo canceller 3 functionality.

webrtc/modules/audio_processing/test/echo_canceller_test_tools.h

+/*
+ *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.

[hlundin-webrtc, 2017/01/18 13:08:51]

http://whatyearisit.info/

[peah-webrtc, 2017/01/19 15:33:07]

:-D

+ *
+ *  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.
+ */
+
+#ifndef WEBRTC_MODULES_AUDIO_PROCESSING_TEST_ECHO_CANCELLER_TEST_TOOLS_H_
+#define WEBRTC_MODULES_AUDIO_PROCESSING_TEST_ECHO_CANCELLER_TEST_TOOLS_H_
+
+#include <algorithm>
+#include <vector>
+
+#include "webrtc/base/constructormagic.h"

[hlundin-webrtc, 2017/01/18 13:08:51]

Order of includes.

[peah-webrtc, 2017/01/19 15:33:07]

Done.

+#include "webrtc/base/array_view.h"
+#include "webrtc/base/random.h"
+
+namespace webrtc {
+
+// Class for delaying a signal a fixed number of samples.
+template <typename T>
+class DelayBuffer {
+ public:
+  explicit DelayBuffer(size_t delay) : buffer_(delay, 0.f) {}

[hlundin-webrtc, 2017/01/18 13:08:51]

You don't know that the vector will be of float type, so 0.f is probably not
correct. I think you can omit the value and get zero-initialization anyway.

[peah-webrtc, 2017/01/19 15:33:07]

Good find!

Done.

+  ~DelayBuffer() = default;
+
+  // Produces a delayed signal copy of x.
+  void Delay(rtc::ArrayView<const T> x, rtc::ArrayView<T> x_delayed) {

[hlundin-webrtc, 2017/01/18 13:08:51]

This is quite a big chunk of inlined code. Move to .cc file?

[peah-webrtc, 2017/01/19 15:33:07]

I don't think we can do that. This is a template and afaics we cannot move that
into the .cc file. Or have I gotten that wrong?

[hlundin-webrtc, 2017/01/20 09:31:44]

You can move it to the .cc file. But you have to do some special tricks:

The method definition must look like
template <typename T>
void DelayBuffer<T>::Delay(...) { ... }

And, you must instantiate the template for the types you will be using. At the
end of the .cc file, add

template class DelayBuffer<float>;
template class DelayBuffer<int>;
}  // namespace webrtc

[peah-webrtc, 2017/01/23 14:16:40]

Thanks! Great!
Done.

+    RTC_DCHECK_EQ(x.size(), x_delayed.size());
+    if (buffer_.size() == 0) {
+      std::copy(std::begin(x), std::end(x), std::begin(x_delayed));
+    } else {
+      for (size_t k = 0; k < x.size(); ++k) {
+        x_delayed[k] = buffer_[next_insert_index_];
+        buffer_[next_insert_index_] = x[k];
+        next_insert_index_ = (next_insert_index_ + 1) % buffer_.size();
+      }
+    }
+  }
+
+ private:
+  std::vector<T> buffer_;
+  int next_insert_index_ = 0;

[hlundin-webrtc, 2017/01/18 13:08:51]

size_t

[peah-webrtc, 2017/01/19 15:33:07]

Done.

+  RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(DelayBuffer);
+};
+
+// Randomizes the elements in a vector with values -32767.f:32767.f.
+void RandomizeSampleVector(Random* random_generator, rtc::ArrayView<float> v);
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_TEST_ECHO_CANCELLER_TEST_TOOLS_H_