123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154 |
- /* SPDX-License-Identifier: GPL-2.0-only */
- /*
- * SpanDSP - a series of DSP components for telephony
- *
- * fir.h - General telephony FIR routines
- *
- * Written by Steve Underwood <[email protected]>
- *
- * Copyright (C) 2002 Steve Underwood
- *
- * All rights reserved.
- */
- #if !defined(_FIR_H_)
- #define _FIR_H_
- /*
- Ideas for improvement:
- 1/ Rewrite filter for dual MAC inner loop. The issue here is handling
- history sample offsets that are 16 bit aligned - the dual MAC needs
- 32 bit aligmnent. There are some good examples in libbfdsp.
- 2/ Use the hardware circular buffer facility tohalve memory usage.
- 3/ Consider using internal memory.
- Using less memory might also improve speed as cache misses will be
- reduced. A drop in MIPs and memory approaching 50% should be
- possible.
- The foreground and background filters currenlty use a total of
- about 10 MIPs/ch as measured with speedtest.c on a 256 TAP echo
- can.
- */
- /*
- * 16 bit integer FIR descriptor. This defines the working state for a single
- * instance of an FIR filter using 16 bit integer coefficients.
- */
- struct fir16_state_t {
- int taps;
- int curr_pos;
- const int16_t *coeffs;
- int16_t *history;
- };
- /*
- * 32 bit integer FIR descriptor. This defines the working state for a single
- * instance of an FIR filter using 32 bit integer coefficients, and filtering
- * 16 bit integer data.
- */
- struct fir32_state_t {
- int taps;
- int curr_pos;
- const int32_t *coeffs;
- int16_t *history;
- };
- /*
- * Floating point FIR descriptor. This defines the working state for a single
- * instance of an FIR filter using floating point coefficients and data.
- */
- struct fir_float_state_t {
- int taps;
- int curr_pos;
- const float *coeffs;
- float *history;
- };
- static inline const int16_t *fir16_create(struct fir16_state_t *fir,
- const int16_t *coeffs, int taps)
- {
- fir->taps = taps;
- fir->curr_pos = taps - 1;
- fir->coeffs = coeffs;
- fir->history = kcalloc(taps, sizeof(int16_t), GFP_KERNEL);
- return fir->history;
- }
- static inline void fir16_flush(struct fir16_state_t *fir)
- {
- memset(fir->history, 0, fir->taps * sizeof(int16_t));
- }
- static inline void fir16_free(struct fir16_state_t *fir)
- {
- kfree(fir->history);
- }
- static inline int16_t fir16(struct fir16_state_t *fir, int16_t sample)
- {
- int32_t y;
- int i;
- int offset1;
- int offset2;
- fir->history[fir->curr_pos] = sample;
- offset2 = fir->curr_pos;
- offset1 = fir->taps - offset2;
- y = 0;
- for (i = fir->taps - 1; i >= offset1; i--)
- y += fir->coeffs[i] * fir->history[i - offset1];
- for (; i >= 0; i--)
- y += fir->coeffs[i] * fir->history[i + offset2];
- if (fir->curr_pos <= 0)
- fir->curr_pos = fir->taps;
- fir->curr_pos--;
- return (int16_t) (y >> 15);
- }
- static inline const int16_t *fir32_create(struct fir32_state_t *fir,
- const int32_t *coeffs, int taps)
- {
- fir->taps = taps;
- fir->curr_pos = taps - 1;
- fir->coeffs = coeffs;
- fir->history = kcalloc(taps, sizeof(int16_t), GFP_KERNEL);
- return fir->history;
- }
- static inline void fir32_flush(struct fir32_state_t *fir)
- {
- memset(fir->history, 0, fir->taps * sizeof(int16_t));
- }
- static inline void fir32_free(struct fir32_state_t *fir)
- {
- kfree(fir->history);
- }
- static inline int16_t fir32(struct fir32_state_t *fir, int16_t sample)
- {
- int i;
- int32_t y;
- int offset1;
- int offset2;
- fir->history[fir->curr_pos] = sample;
- offset2 = fir->curr_pos;
- offset1 = fir->taps - offset2;
- y = 0;
- for (i = fir->taps - 1; i >= offset1; i--)
- y += fir->coeffs[i] * fir->history[i - offset1];
- for (; i >= 0; i--)
- y += fir->coeffs[i] * fir->history[i + offset2];
- if (fir->curr_pos <= 0)
- fir->curr_pos = fir->taps;
- fir->curr_pos--;
- return (int16_t) (y >> 15);
- }
- #endif
|