Added first layer of the echo canceller 3 functionality

webrtc/modules/audio_processing/aec3/block_framer.h

Index: webrtc/modules/audio_processing/aec3/block_framer.h
diff --git a/webrtc/modules/audio_processing/aec3/block_framer.h b/webrtc/modules/audio_processing/aec3/block_framer.h
new file mode 100644
index 0000000000000000000000000000000000000000..7cef8c9b6646bc014b2db2ffa6b3b399e61a4b6e
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+++ b/webrtc/modules/audio_processing/aec3/block_framer.h
@@ -0,0 +1,41 @@
+/*
+ *  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.
+ */
+
+#ifndef WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_BLOCK_FRAMER_H_
+#define WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_BLOCK_FRAMER_H_
+
+#include <vector>
+
+#include "webrtc/base/array_view.h"
+#include "webrtc/base/constructormagic.h"
+#include "webrtc/modules/audio_processing/aec3/aec3_constants.h"
+
+namespace webrtc {
+
+/* Class for producing 10 ms second frames from 64 sample blocks */

[hlundin-webrtc, 2016/12/16 10:04:46]

Use // style comments.

[hlundin-webrtc, 2016/12/16 10:04:46]

I'd like to see a little bit more of an explanation. In particular, what is the
relationship between "block" and "frame". You insert blocks and extract frames.

[aleloi, 2016/12/16 15:04:31]

Remove 'second'

[peah-webrtc, 2016/12/20 10:10:24]

I improved it a bit.

PTAL

[peah-webrtc, 2016/12/20 10:10:24]

Done.

[peah-webrtc, 2016/12/20 10:10:24]

Done.

+class BlockFramer {
+ public:
+  BlockFramer(size_t num_bands, size_t frame_length);
+  ~BlockFramer();
+  void InsertBlock(rtc::ArrayView<const float> block);
+  void ExtractFrame(size_t sub_frame_index, float* const* frame);

[hlundin-webrtc, 2016/12/16 10:04:46]

Comment, please.

[aleloi, 2016/12/16 15:04:31]

Maybe document the threading model and use base/thread_annotations.h? Document
that Extract and Insert must accessed sequentially.

[peah-webrtc, 2016/12/20 10:10:24]

I don't think we should add thread annotations as this class is supposed not to
be used in a concurrent manner and afaics it is not used in that way either. 
But if there is any annotations available that ensure the proper call order,
that would be awesome.

Agree on the documentation. Added that.

Done.

[peah-webrtc, 2016/12/20 10:10:24]

Done.

+
+ private:
+  const size_t kMaxSize = 2 * kBlockSize;

[hlundin-webrtc, 2016/12/16 10:04:46]

constexpr

[peah-webrtc, 2016/12/20 10:10:24]

Done.

+  const size_t num_bands_;
+  const size_t frame_length_;
+  std::vector<float> buffer_;
+  size_t buffer_size_;
+
+  RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(BlockFramer);
+};
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_BLOCK_FRAMER_H_