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* Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
#include <stddef.h>
#include <stdint.h>
namespace webrtc {
// The function calculates the cross-correlation between two sequences
// `sequence_1` and `sequence_2`. `sequence_1` is taken as reference, with
// `sequence_1_length` as its length. `sequence_2` slides for the calculation of
// cross-correlation. The result will be saved in `cross_correlation`.
// `cross_correlation_length` correlation points are calculated.
// The corresponding lag starts from 0, and increases with a step of
// `cross_correlation_step`. The result is without normalization. To avoid
// overflow, the result will be right shifted. The amount of shifts will be
// returned.
// Input:
// - sequence_1 : First sequence (reference).
// - sequence_2 : Second sequence (sliding during calculation).
// - sequence_1_length : Length of `sequence_1`.
// - cross_correlation_length : Number of cross-correlations to calculate.
// - cross_correlation_step : Step in the lag for the cross-correlation.
// Output:
// - cross_correlation : The cross-correlation in Q(-right_shifts)
// Return:
// Number of right shifts in cross_correlation.
int CrossCorrelationWithAutoShift(const int16_t* sequence_1,
const int16_t* sequence_2,
size_t sequence_1_length,
size_t cross_correlation_length,
int cross_correlation_step,
int32_t* cross_correlation);
} // namespace webrtc