libavcodec/acelp_math.h

   1 /*
   2  * Various fixed-point math operations
   3  *
   4  * Copyright (c) 2008 Vladimir Voroshilov
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #ifndef FFMPEG_ACELP_MATH_H
  24 #define FFMPEG_ACELP_MATH_H
  25
  26 /**
  27  * \brief fixed-point implementation of cosine in [0; PI) domain
  28  * \param arg fixed-point cosine argument, 0 <= arg < 0x4000
  29  *
  30  * \return value of (1<<15) * cos(arg * PI / (1<<14)), -0x8000 <= result <= 0x7fff
  31  */
  32 int16_t ff_cos(uint16_t arg);
  33
  34 /**
  35  * \brief fixed-point implementation of exp2(x) in [0; 1] domain
  36  * \param power argument to exp2, 0 <= power <= 0x7fff
  37  *
  38  * \return value of (1<<20) * exp2(power / (1<<15))
  39  *         0x8000c <= result <= 0xfffea
  40  */
  41 int ff_exp2(uint16_t power);
  42
  43 /**
  44  * \brief Calculates log2(x)
  45  * \param value function argument, 0 < value <= 7fff ffff
  46  *
  47  * \return value of (1<<15) * log2(value)
  48  */
  49 int ff_log2(uint32_t value);
  50
  51 /**
  52  * \brief Calculates sum of array element multiplications
  53  * \param speech input data array
  54  * \param length number of elements
  55  * \param offset offset for calculation of sum of s[i]*s[i+offset]
  56  * \param shift right shift by this value will be done before multiplication
  57  *
  58  * \return sum of multiplications
  59  *
  60  * \note array must be at least length+offset long!
  61  */
  62 static int sum_of_squares(const int16_t* speech, int length, int offset, int shift)
  63 {
  64     const int16_t* speech_end;
  65     int sum = 0;
  66
  67     for(speech_end=speech+length; speech<speech_end; speech++)
  68        sum += (speech[0] * speech[offset]) >> shift;
  69
  70     return sum;
  71 }
  72
  73 #endif // FFMPEG_ACELP_MATH_H