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154 lines
3.6 KiB
154 lines
3.6 KiB
/* 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 <[email protected]> |
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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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