1 /* Copyright (c) 2013 The Chromium OS 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 6 #ifndef CROSSOVER2_H_ 7 #define CROSSOVER2_H_ 8 9 #ifdef __cplusplus 10 extern "C" { 11 #endif 12 13 /* "crossover2" is a two channel version of the "crossover" filter. It processes 14 * two channels of data at once to increase performance. */ 15 16 /* An LR4 filter is two biquads with the same parameters connected in series: 17 * 18 * x -- [BIQUAD] -- y -- [BIQUAD] -- z 19 * 20 * Both biquad filter has the same parameter b[012] and a[12], 21 * The variable [xyz][12][LR] keep the history values. 22 */ 23 struct lr42 { 24 float b0, b1, b2; 25 float a1, a2; 26 float x1L, x1R, x2L, x2R; 27 float y1L, y1R, y2L, y2R; 28 float z1L, z1R, z2L, z2R; 29 }; 30 31 /* Three bands crossover filter: 32 * 33 * INPUT --+-- lp0 --+-- lp1 --+---> LOW (0) 34 * | | | 35 * | \-- hp1 --/ 36 * | 37 * \-- hp0 --+-- lp2 ------> MID (1) 38 * | 39 * \-- hp2 ------> HIGH (2) 40 * 41 * [f0] [f1] 42 * 43 * Each lp or hp is an LR4 filter, which consists of two second-order 44 * lowpass or highpass butterworth filters. 45 */ 46 struct crossover2 { 47 struct lr42 lp[3], hp[3]; 48 }; 49 50 /* Initializes a crossover2 filter 51 * Args: 52 * xo2 - The crossover2 filter we want to initialize. 53 * freq1 - The normalized frequency splits low and mid band. 54 * freq2 - The normalized frequency splits mid and high band. 55 */ 56 void crossover2_init(struct crossover2 *xo2, float freq1, float freq2); 57 58 /* Splits input samples to three bands. 59 * Args: 60 * xo2 - The crossover2 filter to use. 61 * count - The number of input samples. 62 * data0L, data0R - The input samples, also the place to store low band 63 * output. 64 * data1L, data1R - The place to store mid band output. 65 * data2L, data2R - The place to store high band output. 66 */ 67 void crossover2_process(struct crossover2 *xo2, int count, 68 float *data0L, float *data0R, 69 float *data1L, float *data1R, 70 float *data2L, float *data2R); 71 72 #ifdef __cplusplus 73 } /* extern "C" */ 74 #endif 75 76 #endif /* CROSSOVER2_H_ */ 77