Added first layer of the echo canceller 3 functionality

webrtc/modules/audio_processing/aec3/frame_blocker.cc

Index: webrtc/modules/audio_processing/aec3/frame_blocker.cc
diff --git a/webrtc/modules/audio_processing/aec3/frame_blocker.cc b/webrtc/modules/audio_processing/aec3/frame_blocker.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c6096f8e35d0cc075d5e5b573cb1cd232b0fda9e
--- /dev/null
+++ b/webrtc/modules/audio_processing/aec3/frame_blocker.cc
@@ -0,0 +1,64 @@
+/*
+ *  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/frame_blocker.h"
+
+#include <algorithm>
+
+#include "webrtc/base/checks.h"
+#include "webrtc/modules/audio_processing/aec3/aec3_constants.h"
+
+namespace webrtc {
+
+FrameBlocker::FrameBlocker(size_t num_bands)
+    : num_bands_(num_bands),
+      buffer_(num_bands_, std::vector<float>(kBlockSize, 0.f)) {

[hlundin-webrtc, 2016/12/20 15:10:36]

Instead of setting up vectors of length kBlockSize and then resizing them to
zero, I propose the following:

buffer_(num_bands_) {
  for (auto& b : buffer_) {
    b.reserve(kBlockSize);
    RTC_DCHECK(b.empty());  // Not needed, but maybe nice?
  }
}

[peah-webrtc, 2016/12/21 23:13:53]

Nice one!
Done.

+  for (auto& b : buffer_) {
+    b.resize(0);

[aleloi, 2016/12/20 15:55:35]

I think this should be done in the member initialization list above.

[peah-webrtc, 2016/12/21 23:13:53]

I want to ensure that the reserved space is proper. I think hlundin@s suggestion
achieves that in a good way so I added that.

PTAL

+  }
+}
+
+FrameBlocker::~FrameBlocker() = default;
+
+void FrameBlocker::InsertSubFrameAndExtractBlock(
+    rtc::ArrayView<rtc::ArrayView<const float>> sub_frame,
+    std::vector<std::vector<float>>* block) {
+  RTC_DCHECK_EQ(num_bands_, block->size());
+  RTC_DCHECK_EQ(num_bands_, sub_frame.size());
+  for (size_t i = 0; i < num_bands_; ++i) {
+    RTC_DCHECK_GE(kBlockSize - 16, buffer_[i].size());
+    RTC_DCHECK_EQ(kBlockSize, (*block)[i].size());
+    RTC_DCHECK_EQ(kSubFrameLength, sub_frame[i].size());
+    const int samples_to_block = kBlockSize - buffer_[i].size();
+    std::copy(buffer_[i].begin(), buffer_[i].end(), (*block)[i].begin());

[hlundin-webrtc, 2016/12/20 15:10:36]

You can use vector::insert here too.

[peah-webrtc, 2016/12/21 23:13:53]

Done.

+    std::copy(sub_frame[i].begin(), sub_frame[i].begin() + samples_to_block,

[hlundin-webrtc, 2016/12/20 15:10:36]

And here.

[peah-webrtc, 2016/12/21 23:13:53]

Done.

+              (*block)[i].begin() + buffer_[i].size());
+    buffer_[i].resize(kSubFrameLength - samples_to_block);
+    std::copy(sub_frame[i].begin() + samples_to_block, sub_frame[i].end(),

[hlundin-webrtc, 2016/12/20 15:10:36]

And here, and skip the resize.

[peah-webrtc, 2016/12/21 23:13:53]

Nice! There is still a resize needed to zero though.
Done.

+              buffer_[i].begin());
+  }
+}
+
+bool FrameBlocker::IsBlockAvailable() {

[aleloi, 2016/12/20 15:55:35]

const

[peah-webrtc, 2016/12/21 23:13:53]

Done.

+  return kBlockSize == buffer_[0].size();
+}
+
+void FrameBlocker::ExtractBlock(std::vector<std::vector<float>>* block) {
+  RTC_DCHECK_EQ(num_bands_, block->size());
+  RTC_DCHECK(IsBlockAvailable());
+  for (size_t i = 0; i < num_bands_; ++i) {
+    RTC_DCHECK_EQ(kBlockSize, buffer_[i].size());
+    RTC_DCHECK_EQ(kBlockSize, (*block)[i].size());
+    std::copy(buffer_[i].begin(), buffer_[i].end(), (*block)[i].begin());

[hlundin-webrtc, 2016/12/20 15:10:36]

vector::insert

[peah-webrtc, 2016/12/21 23:13:53]

Done.

+    buffer_[i].resize(0);

[hlundin-webrtc, 2016/12/20 15:10:36]

clear()

[peah-webrtc, 2016/12/21 23:13:53]

This sounds a bit dangerous. Are we sure that there is no reallocation. The
documentation says there might be.

I'll keep resize(0) for now.

WDYT?

[hlundin-webrtc, 2016/12/22 10:23:56]

http://en.cppreference.com/w/cpp/container/vector/clear:
"Leaves the capacity() of the vector unchanged"

See also
http://stackoverflow.com/questions/18467624/what-does-the-standard-say-about-....

[peah-webrtc, 2017/01/02 08:45:10]

Thanks! I agree. I'll change to clear.

Done.

+  }
+}
+
+}  // namespace webrtc