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fixed-point: log approximation

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This commit is contained in:
Jean-Marc Valin 2008-02-28 22:14:54 +11:00
parent 98193470ec
commit 2eaba8ac1f
2 changed files with 51 additions and 1 deletions
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18
libcelt/mathops.h
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@ -54,6 +54,11 @@
#include "entcode.h" #include "entcode.h"
static inline celt_int16_t celt_ilog2(celt_word32_t x)
{
return EC_ILOG(x)-1;
}
#define C0 3634 #define C0 3634
#define C1 21173 #define C1 21173
#define C2 -12627 #define C2 -12627
@ -116,6 +121,19 @@ static inline celt_word16_t celt_cos_norm(celt_word32_t x)
} }
} }
static inline celt_word16_t celt_log2(celt_word32_t x)
{
int i;
/*-0.41446 0.96093 -0.33981 0.15600 */
const celt_word16_t C[4] = {-6791, 7872, -1392, 319};
if (x==0)
return -32767;
i = celt_ilog2(x);
celt_word16_t n = VSHR32(x,i-15)-32768-16384;
celt_word16_t ret = ADD16(C[0], MULT16_16_Q14(n, ADD16(C[1], MULT16_16_Q14(n, ADD16(C[2], MULT16_16_Q14(n, (C[3])))))));
/*printf ("%d %d %d %d\n", x, n, ret, SHL16(i-13,8)+SHR16(ret,14-8));*/
return SHL16(i-13,8)+SHR16(ret,14-8);
}
#endif #endif

34
libcelt/quant_bands.c
View file

@ -38,6 +38,7 @@
#include <math.h> #include <math.h>
#include "os_support.h" #include "os_support.h"
#include "arch.h" #include "arch.h"
#include "mathops.h"
#ifdef FIXED_POINT #ifdef FIXED_POINT
const celt_word16_t eMeans[24] = {11520, -2048, -3072, -640, 256, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}; const celt_word16_t eMeans[24] = {11520, -2048, -3072, -640, 256, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
@ -48,6 +49,37 @@ const float eMeans[24] = {45.f, -8.f, -12.f, -2.5f, 1.f, 0.f, 0.f, 0.f, 0.f, 0.f
/*const int frac[24] = {4, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2};*/ /*const int frac[24] = {4, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2};*/
const int frac[24] = {8, 6, 5, 4, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2}; const int frac[24] = {8, 6, 5, 4, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2};
#ifdef FIXED_POINT
static inline celt_ener_t dB2Amp( dB)
{
celt_ener_t amp;
amp = pow(10, .05*dB)-.3;
if (amp < 0)
amp = 0;
}
#define DBofTWO 24661
static inline celt_word16_t amp2dB(celt_ener_t amp)
{
/* equivalent to return 6.0207*log2(.3+amp) */
return ROUND(MULT16_16(24661,celt_log2(ADD32(QCONST32(.3f,14),amp))),12);
/* return DB_SCALING*20*log10(.3+ENER_SCALING_1*amp); */
}
#else
static inline celt_ener_t dB2Amp( dB)
{
celt_ener_t amp;
amp = pow(10, .05*dB)-.3;
if (amp < 0)
amp = 0;
}
static inline celt_word16_t amp2dB(celt_ener_t amp)
{
return 20*log10(.3+amp);
}
#endif
#ifdef FIXED_POINT #ifdef FIXED_POINT
#define Q8 256.f #define Q8 256.f
#define Q8_1 (1.f/256.f) #define Q8_1 (1.f/256.f)
@ -75,7 +107,7 @@ static void quant_energy_mono(const CELTMode *m, celt_ener_t *eBands, celt_word1
celt_word16_t x; /* dB */ celt_word16_t x; /* dB */
celt_word16_t f; /* Q8 */ celt_word16_t f; /* Q8 */
celt_word16_t mean = (1-coef)*eMeans[i]; celt_word16_t mean = (1-coef)*eMeans[i];
x = DB_SCALING*20*log10(.3+ENER_SCALING_1*eBands[i]); x = amp2dB(eBands[i]);
res = DB_SCALING*6; res = DB_SCALING*6;
f = QCONST16(1.f,8)*(x-mean-coef*oldEBands[i]-prev*1.f)/res; f = QCONST16(1.f,8)*(x-mean-coef*oldEBands[i]-prev*1.f)/res;
#ifdef FIXED_POINT #ifdef FIXED_POINT