celp_math.c File Reference

#include <inttypes.h>
#include <limits.h>
#include <assert.h>
#include "avcodec.h"
#include "celp_math.h"
#include "libavutil/common.h"

Go to the source code of this file.

Functions
int	ff_exp2 (uint16_t power)
	fixed-point implementation of exp2(x) in [0; 1] domain. More...
int	ff_log2_q15 (uint32_t value)
	Calculate log2(x). More...

Variables
static const uint16_t	exp2a []
static const uint16_t	exp2b []
static const uint16_t	tab_log2 [33]
	Table used to compute log2(x) More...

Function Documentation

int ff_exp2

(

uint16_t

power

)

fixed-point implementation of exp2(x) in [0; 1] domain.

Parameters

power

argument to exp2, 0 <= power <= 0x7fff

Returns

value of (1<<20) * exp2(power / (1<<15)) 0x8000c <= result <= 0xfffea

Definition at line 47 of file celp_math.c.

int ff_log2_q15

(

uint32_t

value

)

Calculate log2(x).

Parameters

value

function argument, 0 < value <= 7fff ffff

Returns

value of (1<<15) * log2(value)

Definition at line 70 of file celp_math.c.

Referenced by ff_acelp_update_past_gain().

Variable Documentation

const uint16_t exp2a[]

static

Initial value:

=
{
     0,  1435,  2901,  4400,  5931,  7496,  9096, 10730,
 12400, 14106, 15850, 17632, 19454, 21315, 23216, 25160,
 27146, 29175, 31249, 33368, 35534, 37747, 40009, 42320,
 44682, 47095, 49562, 52082, 54657, 57289, 59979, 62727,
}

Definition at line 31 of file celp_math.c.

Referenced by ff_exp2().

const uint16_t exp2b[]

static

Initial value:

=
{
     3,   712,  1424,  2134,  2845,  3557,  4270,  4982,
  5696,  6409,  7124,  7839,  8554,  9270,  9986, 10704,
 11421, 12138, 12857, 13576, 14295, 15014, 15734, 16455,
 17176, 17898, 18620, 19343, 20066, 20790, 21514, 22238,
}

Definition at line 39 of file celp_math.c.

const uint16_t tab_log2[33]

static

Initial value:

=
{
      4,   1459,   2870,   4240,   5572,   6867,   8127,   9355,
  10552,  11719,  12858,  13971,  15057,  16120,  17158,  18175,
  19170,  20145,  21100,  22036,  22954,  23854,  24738,  25605,
  26457,  27294,  28116,  28924,  29719,  30500,  31269,  32025,  32769,
}

Table used to compute log2(x)

tab_log2[i] = (1<<15) * log2(1 + i/32), i=0..32

Definition at line 62 of file celp_math.c.

Referenced by ff_log2_q15().