82 lines
2.6 KiB
C
82 lines
2.6 KiB
C
/*
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* broadvoice - a library for the BroadVoice 16 and 32 codecs
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*
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* allzero.c -
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*
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* Adapted by Steve Underwood <steveu@coppice.org> from code which is
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* Copyright 2000-2009 Broadcom Corporation
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*
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* All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License version 2.1,
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* $Id: allzero.c,v 1.1.1.1 2009/11/19 12:10:48 steveu Exp $
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*/
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/*! \file */
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#if defined(HAVE_CONFIG_H)
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#include "config.h"
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#endif
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#include "typedef.h"
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#include "bvcommon.h"
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#define MAXDIM 160 /* maximum vector dimension */
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#define MAXORDER LPCO /* maximum filter order */
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void azfilter(
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const Float *a, /* (i) prediction coefficients */
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int m, /* (i) LPC order */
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Float *x, /* (i) input signal vector */
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Float *y, /* (o) output signal vector */
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int lg, /* (i) size of filtering */
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Float *mem, /* (i/o) filter memory before filtering */
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int16_t update) /* (i) flag for memory update */
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{
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Float buf[MAXORDER + MAXDIM]; /* buffer for filter memory & signal */
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Float a0;
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Float *fp1;
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int i;
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int n;
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/* copy filter memory to beginning part of temporary buffer */
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fp1 = &mem[m - 1];
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for (i = 0; i < m; i++)
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buf[i] = *fp1--; /* this buffer is used to avoid memory shifts */
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/* loop through every element of the current vector */
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for (n = 0; n < lg; n++)
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{
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/* perform multiply-adds along the delay line of filter */
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fp1 = &buf[n];
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a0 = 0.0F;
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for (i = m; i > 0; i--)
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a0 += *fp1++ * a[i];
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/* update the temporary buffer for filter memory */
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*fp1 = x[n];
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/* do the last multiply-add separately and get the output */
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y[n] = a0 + x[n] * a[0];
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}
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/* get the filter memory after filtering the current vector */
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if (update)
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{
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for (i = 0; i < m; i++)
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mem[i] = *fp1--;
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}
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}
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