Update audio_processing module

Corresponds to upstream commit 524e9b043e7e86fd72353b987c9d5f6a1ebf83e1

Update notes:

 * Pull in third party license file

 * Replace .gypi files with BUILD.gn to keep track of what changes
   upstream

 * Bunch of new filse pulled in as dependencies

 * Won't build yet due to changes needed on top of these

webrtc/modules/audio_processing/transient/transient_detector.h

@@ -0,0 +1,87 @@
+/*
+ *  Copyright (c) 2013 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_TRANSIENT_TRANSIENT_DETECTOR_H_
+#define WEBRTC_MODULES_AUDIO_PROCESSING_TRANSIENT_TRANSIENT_DETECTOR_H_
+
+#include <deque>
+
+#include "webrtc/base/scoped_ptr.h"
+#include "webrtc/modules/audio_processing/transient/moving_moments.h"
+#include "webrtc/modules/audio_processing/transient/wpd_tree.h"
+
+namespace webrtc {
+
+// This is an implementation of the transient detector described in "Causal
+// Wavelet based transient detector".
+// Calculates the log-likelihood of a transient to happen on a signal at any
+// given time based on the previous samples; it uses a WPD tree to analyze the
+// signal.  It preserves its state, so it can be multiple-called.
+class TransientDetector {
+ public:
+  // TODO(chadan): The only supported wavelet is Daubechies 8 using a WPD tree
+  // of 3 levels. Make an overloaded constructor to allow different wavelets and
+  // depths of the tree. When needed.
+
+  // Creates a wavelet based transient detector.
+  TransientDetector(int sample_rate_hz);
+
+  ~TransientDetector();
+
+  // Calculates the log-likelihood of the existence of a transient in |data|.
+  // |data_length| has to be equal to |samples_per_chunk_|.
+  // Returns a value between 0 and 1, as a non linear representation of this
+  // likelihood.
+  // Returns a negative value on error.
+  float Detect(const float* data,
+               size_t data_length,
+               const float* reference_data,
+               size_t reference_length);
+
+  bool using_reference() { return using_reference_; }
+
+ private:
+  float ReferenceDetectionValue(const float* data, size_t length);
+
+  static const size_t kLevels = 3;
+  static const size_t kLeaves = 1 << kLevels;
+
+  size_t samples_per_chunk_;
+
+  rtc::scoped_ptr<WPDTree> wpd_tree_;
+  size_t tree_leaves_data_length_;
+
+  // A MovingMoments object is needed for each leaf in the WPD tree.
+  rtc::scoped_ptr<MovingMoments> moving_moments_[kLeaves];
+
+  rtc::scoped_ptr<float[]> first_moments_;
+  rtc::scoped_ptr<float[]> second_moments_;
+
+  // Stores the last calculated moments from the previous detection.
+  float last_first_moment_[kLeaves];
+  float last_second_moment_[kLeaves];
+
+  // We keep track of the previous results from the previous chunks, so it can
+  // be used to effectively give results according to the |transient_length|.
+  std::deque<float> previous_results_;
+
+  // Number of chunks that are going to return only zeros at the beginning of
+  // the detection. It helps to avoid infs and nans due to the lack of
+  // information.
+  int chunks_at_startup_left_to_delete_;
+
+  float reference_energy_;
+
+  bool using_reference_;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_TRANSIENT_TRANSIENT_DETECTOR_H_