155 lines
3.6 KiB
C
155 lines
3.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* SpanDSP - a series of DSP components for telephony
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*
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* fir.h - General telephony FIR routines
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*
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* Written by Steve Underwood <steveu@coppice.org>
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*
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* Copyright (C) 2002 Steve Underwood
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*
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* All rights reserved.
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*/
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#if !defined(_FIR_H_)
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#define _FIR_H_
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/*
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Ideas for improvement:
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1/ Rewrite filter for dual MAC inner loop. The issue here is handling
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history sample offsets that are 16 bit aligned - the dual MAC needs
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32 bit aligmnent. There are some good examples in libbfdsp.
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2/ Use the hardware circular buffer facility tohalve memory usage.
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3/ Consider using internal memory.
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Using less memory might also improve speed as cache misses will be
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reduced. A drop in MIPs and memory approaching 50% should be
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possible.
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The foreground and background filters currenlty use a total of
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about 10 MIPs/ch as measured with speedtest.c on a 256 TAP echo
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can.
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*/
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/*
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* 16 bit integer FIR descriptor. This defines the working state for a single
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* instance of an FIR filter using 16 bit integer coefficients.
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*/
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struct fir16_state_t {
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int taps;
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int curr_pos;
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const int16_t *coeffs;
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int16_t *history;
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};
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/*
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* 32 bit integer FIR descriptor. This defines the working state for a single
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* instance of an FIR filter using 32 bit integer coefficients, and filtering
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* 16 bit integer data.
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*/
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struct fir32_state_t {
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int taps;
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int curr_pos;
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const int32_t *coeffs;
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int16_t *history;
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};
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/*
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* Floating point FIR descriptor. This defines the working state for a single
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* instance of an FIR filter using floating point coefficients and data.
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*/
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struct fir_float_state_t {
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int taps;
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int curr_pos;
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const float *coeffs;
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float *history;
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};
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static inline const int16_t *fir16_create(struct fir16_state_t *fir,
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const int16_t *coeffs, int taps)
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{
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fir->taps = taps;
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fir->curr_pos = taps - 1;
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fir->coeffs = coeffs;
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fir->history = kcalloc(taps, sizeof(int16_t), GFP_KERNEL);
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return fir->history;
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}
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static inline void fir16_flush(struct fir16_state_t *fir)
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{
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memset(fir->history, 0, fir->taps * sizeof(int16_t));
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}
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static inline void fir16_free(struct fir16_state_t *fir)
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{
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kfree(fir->history);
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}
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static inline int16_t fir16(struct fir16_state_t *fir, int16_t sample)
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{
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int32_t y;
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int i;
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int offset1;
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int offset2;
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fir->history[fir->curr_pos] = sample;
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offset2 = fir->curr_pos;
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offset1 = fir->taps - offset2;
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y = 0;
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for (i = fir->taps - 1; i >= offset1; i--)
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y += fir->coeffs[i] * fir->history[i - offset1];
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for (; i >= 0; i--)
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y += fir->coeffs[i] * fir->history[i + offset2];
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if (fir->curr_pos <= 0)
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fir->curr_pos = fir->taps;
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fir->curr_pos--;
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return (int16_t) (y >> 15);
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}
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static inline const int16_t *fir32_create(struct fir32_state_t *fir,
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const int32_t *coeffs, int taps)
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{
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fir->taps = taps;
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fir->curr_pos = taps - 1;
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fir->coeffs = coeffs;
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fir->history = kcalloc(taps, sizeof(int16_t), GFP_KERNEL);
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return fir->history;
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}
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static inline void fir32_flush(struct fir32_state_t *fir)
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{
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memset(fir->history, 0, fir->taps * sizeof(int16_t));
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}
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static inline void fir32_free(struct fir32_state_t *fir)
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{
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kfree(fir->history);
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}
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static inline int16_t fir32(struct fir32_state_t *fir, int16_t sample)
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{
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int i;
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int32_t y;
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int offset1;
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int offset2;
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fir->history[fir->curr_pos] = sample;
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offset2 = fir->curr_pos;
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offset1 = fir->taps - offset2;
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y = 0;
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for (i = fir->taps - 1; i >= offset1; i--)
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y += fir->coeffs[i] * fir->history[i - offset1];
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for (; i >= 0; i--)
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y += fir->coeffs[i] * fir->history[i + offset2];
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if (fir->curr_pos <= 0)
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fir->curr_pos = fir->taps;
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fir->curr_pos--;
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return (int16_t) (y >> 15);
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}
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#endif
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