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| 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 |
| 14 namespace media { |
| 15 |
| 16 class AudioBus; |
| 17 |
| 18 namespace internal { |
| 19 |
| 20 typedef 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|. |
| 25 MEDIA_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()|. |
| 36 MEDIA_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 // |
| 42 // f(-1) = |y[0]| |
| 43 // f(0) = |y[1]| |
| 44 // f(1) = |y[2]|. |
| 45 // |
| 46 // Then compute the |extremum| point -b / (2*a) and |extremum_value| |
| 47 // b^2 / (4*a) - b^2 / (2*a) + c. |
| 48 // |
| 49 // It is not expected that this function is called with |
| 50 // y[0] == y[1] == y[2]. |
| 51 MEDIA_EXPORT void CubicInterpolation(const float* y_values, |
| 52 float* extremum, |
| 53 float* extremum_value); |
| 54 |
| 55 // Search a subset of all candid blocks. The search is performed every |
| 56 // |decimation| frames. This reduces complexity by a factor of about |
| 57 // 1 / |decimation|. A cubic interpolation is used to have a better estimate of |
| 58 // the best match. |
| 59 MEDIA_EXPORT int DecimatedSearch(int decimation, |
| 60 Interval exclude_interval, |
| 61 const AudioBus* target_block, |
| 62 const AudioBus* search_segment, |
| 63 const float* energy_target_block, |
| 64 const float* energy_candid_blocks); |
| 65 |
| 66 // Search [|low_limit|, |high_limit|] of |search_segment| to find a block that |
| 67 // is most similar to |target_block|. |energy_target_block| is the energy of the |
| 68 // |target_block|. |energy_candidate_blocks| is the energy of all blocks within |
| 69 // |search_block|. |
| 70 MEDIA_EXPORT int FullSearch(int low_limit, |
| 71 int hight_limimit, |
| 72 Interval exclude_interval, |
| 73 const AudioBus* target_block, |
| 74 const AudioBus* search_block, |
| 75 const float* energy_target_block, |
| 76 const float* energy_candidate_blocks); |
| 77 |
| 78 // Find the index of the block, within |search_block|, that is most similar |
| 79 // to |target_block|. Obviously, the returned index is w.r.t. |search_block|. |
| 80 // |exclude_interval| is an interval that is excluded from the search. |
| 81 MEDIA_EXPORT int OptimalIndex(const AudioBus* search_block, |
| 82 const AudioBus* target_block, |
| 83 Interval exclude_interval); |
| 84 |
| 85 // Return a "periodic" Hann window. This is the first L samples of an L+1 |
| 86 // Hann window. It is perfect reconstruction for overlap-and-add. |
| 87 MEDIA_EXPORT void GetSymmetricHanningWindow(int window_length, float* window); |
| 88 |
| 89 } // namespace internal |
| 90 |
| 91 } // namespace media |
| 92 |
| 93 #endif // MEDIA_FILTERS_WSOLA_INTERNALS_H_ |
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