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iir_df1_generic.c
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109 lines (96 loc) · 3.35 KB
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// SPDX-License-Identifier: BSD-3-Clause
//
// Copyright(c) 2022 Intel Corporation. All rights reserved.
//
// Author: Andrula Song <andrula.song@intel.com>
#include <stdint.h>
#include <stddef.h>
#include <errno.h>
#include <sof/audio/format.h>
#include <sof/math/iir_df1.h>
#include <user/eq.h>
#if IIR_DF1_GENERIC
/*
* Direct form I second order filter block (biquad)
*
* +----+ +---+ +-------+
* X(z) ---o--->| b0 |---> + --+-------------o--->| g |--->| shift |---> Y(z)
* | +----+ ^ ^ | +---+ +-------+
* | | | |
* +------+ | | +------+
* | z^-1 | | | | z^-1 |
* +------+ | | +------+
* | +----+ | | +----+ |
* o--->| b1 |---> + + <---| a1 |---o
* | +----+ ^ ^ +----+ |
* | | | |
* +------+ | | +------+
* | z^-1 | | | | z^-1 |
* +------+ | | +------+
* | ^ ^ |
* | +----+ | | +----+ |
* o--->| b2 |---> + +<--- | a2 |---o
* +----+ +----+
*
* y[n] = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
* the a1 a2 has been negated during calculation
*/
/* Series DF1 IIR */
/* 32 bit data, 32 bit coefficients and 32 bit state variables */
int32_t iir_df1(struct iir_state_df1 *iir, int32_t x)
{
int32_t in;
int32_t tmp;
int64_t out = 0;
int64_t acc;
int i;
int j;
int d = 0; /* Index to state */
int c = 0; /* Index to coefficient a2 */
int32_t *coefp = iir->coef;
int32_t *delay = iir->delay;
int nseries = iir->biquads_in_series;
/* Bypass is set with number of biquads set to zero. */
if (!iir->biquads)
return x;
/* Coefficients order in coef[] is {a2, a1, b2, b1, b0, shift, gain} */
/* Delay order in state[] is {y(n - 2), y(n - 1), x(n - 2), x(n - 1)} */
for (j = 0; j < iir->biquads; j += nseries) {
in = x;
for (i = 0; i < nseries; i++) {
/* Compute output: Delay is Q3.61
* Q2.30 x Q1.31 -> Q3.61
* Shift Q3.61 to Q3.31 with rounding, saturate to Q1.31
*/
acc = ((int64_t)coefp[c]) * delay[d]; /* a2 * y(n - 2) */
acc += ((int64_t)coefp[c + 1]) * delay[d + 1]; /* a1 * y(n - 1) */
acc += ((int64_t)coefp[c + 2]) * delay[d + 2]; /* b2 * x(n - 2) */
acc += ((int64_t)coefp[c + 3]) * delay[d + 3]; /* b1 * x(n - 1) */
acc += ((int64_t)coefp[c + 4]) * in; /* b0 * x */
tmp = (int32_t)sat_int32(Q_SHIFT_RND(acc, 61, 31));
/* update the delay value */
delay[d] = delay[d + 1];
delay[d + 1] = tmp;
delay[d + 2] = delay[d + 3];
delay[d + 3] = in;
/* Apply gain Q2.14 x Q1.31 -> Q3.45 */
acc = ((int64_t)coefp[c + 6]) * tmp; /* Gain */
/* Apply biquad output shift right parameter
* simultaneously with Q3.45 to Q3.31 conversion. Then
* saturate to 32 bits Q1.31 and prepare for next
* biquad.
*/
acc = Q_SHIFT_RND(acc, 45 + coefp[c + 5], 31);
in = sat_int32(acc);
/* Proceed to next biquad coefficients and delay
* lines.
*/
c += SOF_EQ_IIR_NBIQUAD;
d += IIR_DF1_NUM_STATE;
}
/* Output of previous section is in variable in */
out += (int64_t)in;
}
return sat_int32(out);
}
#endif