1// Copyright 2013 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5// A set of utility functions to perform WSOLA.
6
7#ifndef MEDIA_FILTERS_WSOLA_INTERNALS_H_
8#define MEDIA_FILTERS_WSOLA_INTERNALS_H_
9
10#include <utility>
11
12#include "media/base/media_export.h"
13
14namespace media {
15
16class AudioBus;
17
18namespace internal {
19
20typedef std::pair<int, int> Interval;
21
22// Dot-product of channels of two AudioBus. For each AudioBus an offset is
23// given. |dot_product[k]| is the dot-product of channel |k|. The caller should
24// allocate sufficient space for |dot_product|.
25MEDIA_EXPORT void MultiChannelDotProduct(const AudioBus* a,
26                                         int frame_offset_a,
27                                         const AudioBus* b,
28                                         int frame_offset_b,
29                                         int num_frames,
30                                         float* dot_product);
31
32// Energies of sliding windows of channels are interleaved.
33// The number windows is |input->frames()| - (|frames_per_window| - 1), hence,
34// the method assumes |energy| must be, at least, of size
35// (|input->frames()| - (|frames_per_window| - 1)) * |input->channels()|.
36MEDIA_EXPORT void MultiChannelMovingBlockEnergies(const AudioBus* input,
37                                                  int frames_per_window,
38                                                  float* energy);
39
40// Fit the curve f(x) = a * x^2 + b * x + c such that
41//   f(-1) = y[0]
42//   f(0) = y[1]
43//   f(1) = y[2]
44// and return the maximum, assuming that y[0] <= y[1] >= y[2].
45MEDIA_EXPORT void QuadraticInterpolation(const float* y_values,
46                                         float* extremum,
47                                         float* extremum_value);
48
49// Search a subset of all candid blocks. The search is performed every
50// |decimation| frames. This reduces complexity by a factor of about
51// 1 / |decimation|. A cubic interpolation is used to have a better estimate of
52// the best match.
53MEDIA_EXPORT int DecimatedSearch(int decimation,
54                                 Interval exclude_interval,
55                                 const AudioBus* target_block,
56                                 const AudioBus* search_segment,
57                                 const float* energy_target_block,
58                                 const float* energy_candid_blocks);
59
60// Search [|low_limit|, |high_limit|] of |search_segment| to find a block that
61// is most similar to |target_block|. |energy_target_block| is the energy of the
62// |target_block|. |energy_candidate_blocks| is the energy of all blocks within
63// |search_block|.
64MEDIA_EXPORT int FullSearch(int low_limit,
65                            int hight_limimit,
66                            Interval exclude_interval,
67                            const AudioBus* target_block,
68                            const AudioBus* search_block,
69                            const float* energy_target_block,
70                            const float* energy_candidate_blocks);
71
72// Find the index of the block, within |search_block|, that is most similar
73// to |target_block|. Obviously, the returned index is w.r.t. |search_block|.
74// |exclude_interval| is an interval that is excluded from the search.
75MEDIA_EXPORT int OptimalIndex(const AudioBus* search_block,
76                              const AudioBus* target_block,
77                              Interval exclude_interval);
78
79// Return a "periodic" Hann window. This is the first L samples of an L+1
80// Hann window. It is perfect reconstruction for overlap-and-add.
81MEDIA_EXPORT void GetSymmetricHanningWindow(int window_length, float* window);
82
83}  // namespace internal
84
85}  // namespace media
86
87#endif  // MEDIA_FILTERS_WSOLA_INTERNALS_H_
88