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put all integer init code to compute n^(4/3) - memory alloc and header fixes 

Originally committed as revision 518 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Fabrice Bellard 2002-05-18 22:58:08 +00:00
parent 5bd12d1277
commit f9ed4f8894
1 changed files with 88 additions and 6 deletions
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94
libavcodec/mpegaudiodec.c
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@ -18,7 +18,6 @@
*/
//#define DEBUG
#include "avcodec.h"
#include <math.h>
#include "mpegaudio.h"
/*
@ -221,6 +220,72 @@ static inline int l3_unscale(int value, int exponent)
#endif
}
/* all integer n^(4/3) computation code */
#define DEV_ORDER 13
#define POW_FRAC_BITS 24
#define POW_FRAC_ONE (1 << POW_FRAC_BITS)
#define POW_FIX(a) ((int)((a) * POW_FRAC_ONE))
#define POW_MULL(a,b) (((INT64)(a) * (INT64)(b)) >> POW_FRAC_BITS)
static int dev_4_3_coefs[DEV_ORDER];
static int pow_mult3[3] = {
POW_FIX(1.0),
POW_FIX(1.25992104989487316476),
POW_FIX(1.58740105196819947474),
};
static void int_pow_init(void)
{
int i, a;
a = POW_FIX(1.0);
for(i=0;i<DEV_ORDER;i++) {
a = POW_MULL(a, POW_FIX(4.0 / 3.0) - i * POW_FIX(1.0)) / (i + 1);
dev_4_3_coefs[i] = a;
}
}
/* return the mantissa and the binary exponent */
static int int_pow(int i, int *exp_ptr)
{
int e, er, eq, j;
int a, a1;
/* renormalize */
a = i;
e = POW_FRAC_BITS;
while (a < (1 << (POW_FRAC_BITS - 1))) {
a = a << 1;
e--;
}
a -= (1 << POW_FRAC_BITS);
a1 = 0;
for(j = DEV_ORDER - 1; j >= 0; j--)
a1 = POW_MULL(a, dev_4_3_coefs[j] + a1);
a = (1 << POW_FRAC_BITS) + a1;
/* exponent compute (exact) */
e = e * 4;
er = e % 3;
eq = e / 3;
a = POW_MULL(a, pow_mult3[er]);
while (a >= 2 * POW_FRAC_ONE) {
a = a >> 1;
eq++;
}
/* convert to float */
while (a < POW_FRAC_ONE) {
a = a << 1;
eq--;
}
*exp_ptr = eq;
#if POW_FRAC_BITS == FRAC_BITS
return a;
#else
return (a + (1 << (POW_FRAC_BITS - FRAC_BITS - 1))) >> (POW_FRAC_BITS - FRAC_BITS);
#endif
}
static int decode_init(AVCodecContext * avctx)
{
@ -315,19 +380,36 @@ static int decode_init(AVCodecContext * avctx)
table_4_3_value = av_mallocz(TABLE_4_3_SIZE *
sizeof(table_4_3_value[0]));
if (!table_4_3_value) {
free(table_4_3_exp);
av_free(table_4_3_exp);
return -1;
}
int_pow_init();
for(i=1;i<TABLE_4_3_SIZE;i++) {
double f, fm;
int e, m;
f = pow((double)i, 4.0 / 3.0);
fm = frexp(f, &e);
m = FIXR(2 * fm);
m = int_pow(i, &e);
#if FRAC_BITS <= 15
if ((unsigned short)m != m)
m = 65535;
#endif
#if 0
/* test code */
{
double f, fm;
int e1, m1;
f = pow((double)i, 4.0 / 3.0);
fm = frexp(f, &e1);
m1 = FIXR(2 * fm);
#if FRAC_BITS <= 15
if ((unsigned short)m1 != m1)
m1 = 65535;
#endif
e1--;
if (m != m1 || e != e1) {
printf("%4d: m=%x m1=%x e=%d e1=%d\n",
i, m, m1, e, e1);
}
}
#endif
/* normalized to FRAC_BITS */
table_4_3_value[i] = m;