132 lines
3.1 KiB
C
132 lines
3.1 KiB
C
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/* Copyright (C) 2002 Jean-Marc Valin
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File: math_approx.c
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Various math approximation functions for Speex
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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- Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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- Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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- Neither the name of the Xiph.org Foundation nor the names of its
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contributors may be used to endorse or promote products derived from
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this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR
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CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include "math_approx.h"
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#include "misc.h"
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#ifdef FIXED_POINT
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/* sqrt(x) ~= 0.22178 + 1.29227*x - 0.77070*x^2 + 0.25723*x^3 (for .25 < x < 1) */
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#define C0 3634
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#define C1 21173
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#define C2 -12627
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#define C3 4215
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spx_word16_t spx_sqrt(spx_word32_t x)
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{
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int k=0;
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spx_word32_t rt;
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if (x==0)
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return 0;
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#if 1
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if (x>16777216)
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{
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x>>=10;
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k+=5;
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}
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if (x>1048576)
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{
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x>>=6;
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k+=3;
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}
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if (x>262144)
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{
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x>>=4;
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k+=2;
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}
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if (x>32768)
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{
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x>>=2;
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k+=1;
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}
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if (x>16384)
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{
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x>>=2;
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k+=1;
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}
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#else
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while (x>16384)
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{
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x>>=2;
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k++;
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}
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#endif
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while (x<4096)
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{
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x<<=2;
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k--;
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}
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rt = ADD16(C0, MULT16_16_Q14(x, ADD16(C1, MULT16_16_Q14(x, ADD16(C2, MULT16_16_Q14(x, (C3)))))));
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if (k>0)
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rt <<= k;
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else
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rt >>= -k;
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rt >>=7;
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return rt;
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}
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/* log(x) ~= -2.18151 + 4.20592*x - 2.88938*x^2 + 0.86535*x^3 (for .5 < x < 1) */
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#define A1 16469
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#define A2 2242
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#define A3 1486
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spx_word16_t spx_acos(spx_word16_t x)
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{
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int s=0;
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spx_word16_t ret;
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spx_word16_t sq;
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if (x<0)
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{
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s=1;
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x = NEG16(x);
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}
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x = SUB16(16384,x);
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x = x >> 1;
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sq = MULT16_16_Q13(x, ADD16(A1, MULT16_16_Q13(x, ADD16(A2, MULT16_16_Q13(x, (A3))))));
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ret = spx_sqrt(SHL32(EXTEND32(sq),13));
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/*ret = spx_sqrt(67108864*(-1.6129e-04 + 2.0104e+00*f + 2.7373e-01*f*f + 1.8136e-01*f*f*f));*/
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if (s)
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ret = SUB16(25736,ret);
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return ret;
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}
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#endif
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