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76 lines
2.2 KiB
C
76 lines
2.2 KiB
C
/*
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* Various fixed-point math operations
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*
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* Copyright (c) 2008 Vladimir Voroshilov
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg 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 GNU
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* 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 FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef FFMPEG_ACELP_MATH_H
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#define FFMPEG_ACELP_MATH_H
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#include <stdint.h>
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/**
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* \brief fixed-point implementation of cosine in [0; PI) domain
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* \param arg fixed-point cosine argument, 0 <= arg < 0x4000
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*
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* \return value of (1<<15) * cos(arg * PI / (1<<14)), -0x8000 <= result <= 0x7fff
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*/
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int16_t ff_cos(uint16_t arg);
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/**
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* \brief fixed-point implementation of exp2(x) in [0; 1] domain
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* \param power argument to exp2, 0 <= power <= 0x7fff
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*
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* \return value of (1<<20) * exp2(power / (1<<15))
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* 0x8000c <= result <= 0xfffea
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*/
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int ff_exp2(uint16_t power);
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/**
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* \brief Calculates log2(x)
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* \param value function argument, 0 < value <= 7fff ffff
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*
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* \return value of (1<<15) * log2(value)
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*/
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int ff_log2(uint32_t value);
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/**
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* \brief Calculates sum of array element multiplications
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* \param speech input data array
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* \param length number of elements
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* \param offset offset for calculation of sum of s[i]*s[i+offset]
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* \param shift right shift by this value will be done before multiplication
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*
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* \return sum of multiplications
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*
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* \note array must be at least length+offset long!
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*/
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static int sum_of_squares(const int16_t* speech, int length, int offset, int shift)
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{
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const int16_t* speech_end;
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int sum = 0;
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for(speech_end=speech+length; speech<speech_end; speech++)
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sum += (speech[0] * speech[offset]) >> shift;
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return sum;
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}
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#endif /* FFMPEG_ACELP_MATH_H */
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