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replace l3_unscale(1, exponents[pos]) by LUT

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Originally committed as revision 6082 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2006-08-25 10:00:30 +00:00
parent 7ca1ed0d9c
commit f8347c4167
1 changed files with 7 additions and 1 deletions
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8
libavcodec/mpegaudiodec.c
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@ -173,6 +173,7 @@ static uint16_t band_index_long[9][23];
#define TABLE_4_3_SIZE (8191 + 16)*4
static int8_t *table_4_3_exp;
static uint32_t *table_4_3_value;
static uint32_t exp_table[512];
/* intensity stereo coef table */
static int32_t is_table[2][16];
static int32_t is_table_lsf[2][2][16];
@ -428,6 +429,11 @@ static int decode_init(AVCodecContext * avctx)
// av_log(NULL, AV_LOG_DEBUG, "%d %d %f\n", i, m, pow((double)i, 4.0 / 3.0));
table_4_3_exp[i] = -e;
}
for(i=0; i<512; i++){
int exponent= i-400;
double f= pow(1, 4.0 / 3.0) * pow(2, exponent*0.25 + FRAC_BITS + 5);
exp_table[i]= lrintf(f);
}
for(i=0;i<7;i++) {
float f;
@ -1760,7 +1766,7 @@ static int huffman_decode(MPADecodeContext *s, GranuleDef *g,
const static int idxtab[16]={3,3,2,2,1,1,1,1,0,0,0,0,0,0,0,0};
int pos= s_index+idxtab[code];
code ^= 8>>idxtab[code];
v = l3_unscale(1, exponents[pos]);
v = exp_table[ exponents[pos] + 400];
if(get_bits1(&s->gb))
v = -v;
g->sb_hybrid[pos] = v;