media/filters/wsola_internals.h

   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 //   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].
  45 MEDIA_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.
  53 MEDIA_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|.
  64 MEDIA_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.
  75 MEDIA_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.
  81 MEDIA_EXPORT void GetSymmetricHanningWindow(int window_length, float* window);
  82
  83 }  // namespace internal
  84
  85 }  // namespace media
  86
  87 #endif  // MEDIA_FILTERS_WSOLA_INTERNALS_H_