diff options
Diffstat (limited to 'drivers/isdn/mISDN/dsp_biquad.h')
| -rw-r--r-- | drivers/isdn/mISDN/dsp_biquad.h | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/drivers/isdn/mISDN/dsp_biquad.h b/drivers/isdn/mISDN/dsp_biquad.h new file mode 100644 index 00000000000..038191bc45f --- /dev/null +++ b/drivers/isdn/mISDN/dsp_biquad.h @@ -0,0 +1,65 @@ +/* + * SpanDSP - a series of DSP components for telephony + * + * biquad.h - General telephony bi-quad section routines (currently this just + * handles canonic/type 2 form) + * + * Written by Steve Underwood <steveu@coppice.org> + * + * Copyright (C) 2001 Steve Underwood + * + * All rights reserved. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + * + */ + +struct biquad2_state { + int32_t gain; + int32_t a1; + int32_t a2; + int32_t b1; + int32_t b2; + + int32_t z1; + int32_t z2; +}; + +static inline void biquad2_init(struct biquad2_state *bq, + int32_t gain, int32_t a1, int32_t a2, int32_t b1, int32_t b2) +{ + bq->gain = gain; + bq->a1 = a1; + bq->a2 = a2; + bq->b1 = b1; + bq->b2 = b2; + + bq->z1 = 0; + bq->z2 = 0; +} + +static inline int16_t biquad2(struct biquad2_state *bq, int16_t sample) +{ + int32_t y; + int32_t z0; + + z0 = sample*bq->gain + bq->z1*bq->a1 + bq->z2*bq->a2; + y = z0 + bq->z1*bq->b1 + bq->z2*bq->b2; + + bq->z2 = bq->z1; + bq->z1 = z0 >> 15; + y >>= 15; + return y; +} |