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media / filters / wsola_internals.h [blame]
// Copyright 2013 The Chromium Authors
// 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 <utility>
#include "media/base/media_export.h"
namespace media {
class AudioBus;
namespace internal {
typedef std::pair<int, int> 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_