// Copyright 2013 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. // A set of utility functions to perform WSOLA. #ifndef MEDIA_FILTERS_WSOLA_INTERNALS_H_ #define MEDIA_FILTERS_WSOLA_INTERNALS_H_ #include #include "media/base/media_export.h" namespace media { class AudioBus; namespace internal { typedef std::pair Interval; // Dot-product of channels of two AudioBus. For each AudioBus an offset is // given. |dot_product[k]| is the dot-product of channel |k|. The caller should // allocate sufficient space for |dot_product|. MEDIA_EXPORT void MultiChannelDotProduct(const AudioBus* a, int frame_offset_a, const AudioBus* b, int frame_offset_b, int num_frames, float* dot_product); // Energies of sliding windows of channels are interleaved. // The number windows is |input->frames()| - (|frames_per_window| - 1), hence, // the method assumes |energy| must be, at least, of size // (|input->frames()| - (|frames_per_window| - 1)) * |input->channels()|. MEDIA_EXPORT void MultiChannelMovingBlockEnergies(const AudioBus* input, int frames_per_window, float* energy); // Fit the curve f(x) = a * x^2 + b * x + c such that // f(-1) = y[0] // f(0) = y[1] // f(1) = y[2] // and return the maximum, assuming that y[0] <= y[1] >= y[2]. MEDIA_EXPORT void QuadraticInterpolation(const float* y_values, float* extremum, float* extremum_value); // Search a subset of all candid blocks. The search is performed every // |decimation| frames. This reduces complexity by a factor of about // 1 / |decimation|. A cubic interpolation is used to have a better estimate of // the best match. MEDIA_EXPORT int DecimatedSearch(int decimation, Interval exclude_interval, const AudioBus* target_block, const AudioBus* search_segment, const float* energy_target_block, const float* energy_candid_blocks); // Search [|low_limit|, |high_limit|] of |search_segment| to find a block that // is most similar to |target_block|. |energy_target_block| is the energy of the // |target_block|. |energy_candidate_blocks| is the energy of all blocks within // |search_block|. MEDIA_EXPORT int FullSearch(int low_limit, int hight_limimit, Interval exclude_interval, const AudioBus* target_block, const AudioBus* search_block, const float* energy_target_block, const float* energy_candidate_blocks); // Find the index of the block, within |search_block|, that is most similar // to |target_block|. Obviously, the returned index is w.r.t. |search_block|. // |exclude_interval| is an interval that is excluded from the search. MEDIA_EXPORT int OptimalIndex(const AudioBus* search_block, const AudioBus* target_block, Interval exclude_interval); // Return a "periodic" Hann window. This is the first L samples of an L+1 // Hann window. It is perfect reconstruction for overlap-and-add. MEDIA_EXPORT void GetPeriodicHanningWindow(int window_length, float* window); } // namespace internal } // namespace media #endif // MEDIA_FILTERS_WSOLA_INTERNALS_H_