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