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/* Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef CROSSOVER2_H_
#define CROSSOVER2_H_
#ifdef __cplusplus
extern "C" {
#endif
/* "crossover2" is a two channel version of the "crossover" filter. It processes
* two channels of data at once to increase performance. */
/* An LR4 filter is two biquads with the same parameters connected in series:
*
* x -- [BIQUAD] -- y -- [BIQUAD] -- z
*
* Both biquad filter has the same parameter b[012] and a[12],
* The variable [xyz][12][LR] keep the history values.
*/
struct lr42 {
float b0, b1, b2;
float a1, a2;
float x1L, x1R, x2L, x2R;
float y1L, y1R, y2L, y2R;
float z1L, z1R, z2L, z2R;
};
/* Three bands crossover filter:
*
* INPUT --+-- lp0 --+-- lp1 --+---> LOW (0)
* | | |
* | \-- hp1 --/
* |
* \-- hp0 --+-- lp2 ------> MID (1)
* |
* \-- hp2 ------> HIGH (2)
*
* [f0] [f1]
*
* Each lp or hp is an LR4 filter, which consists of two second-order
* lowpass or highpass butterworth filters.
*/
struct crossover2 {
struct lr42 lp[3], hp[3];
};
/* Initializes a crossover2 filter
* Args:
* xo2 - The crossover2 filter we want to initialize.
* freq1 - The normalized frequency splits low and mid band.
* freq2 - The normalized frequency splits mid and high band.
*/
void crossover2_init(struct crossover2 *xo2, float freq1, float freq2);
/* Splits input samples to three bands.
* Args:
* xo2 - The crossover2 filter to use.
* count - The number of input samples.
* data0L, data0R - The input samples, also the place to store low band
* output.
* data1L, data1R - The place to store mid band output.
* data2L, data2R - The place to store high band output.
*/
void crossover2_process(struct crossover2 *xo2, int count, float *data0L,
float *data0R, float *data1L, float *data1R,
float *data2L, float *data2R);
#ifdef __cplusplus
} /* extern "C" */
#endif
#endif /* CROSSOVER2_H_ */
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