www.pudn.com > mp3decoder.rar > Decode.c
/***********************************************
copyright by Haia Tech
www.haia2004.com
************************************************/
#include
//#include
#include "common.h"
#include "decode.h"
extern struct Granule grle[2][2];
extern Bit_stream_struc bs;
extern frame_params fr_ps;
struct BandIndex sfBandIndex[3]=
{
{{0,4,8,12,16,20,24,30,36,44,52,62,74,90,110,134,162,196,238,288,342,418,576},
{0,4,8,12,16,22,30,40,52,66,84,106,136,192}},
{{0,4,8,12,16,20,24,30,36,42,50,60,72,88,106,128,156,190,230,276,330,384,576},
{0,4,8,12,16,22,28,38,50,64,80,100,126,192}},
{{0,4,8,12,16,20,24,30,36,44,54,66,82,102,126,156,194,240,296,364,448,550,576},
{0,4,8,12,16,22,30,42,58,78,104,138,180,192}}
};
void decode_info()
{
layer *hdr = fr_ps.header;
int x;
hdr->version = getbit(1);
hdr->lay = 4-getbit(2);
hdr->error_protection = !getbit(1); /* error protect. TRUE/FALSE */
hdr->bitrate_index = getbit(4);
hdr->sampling_frequency = getbit(2);
hdr->padding = getbit(1);
hdr->extension = getbit(1);
hdr->mode = getbit(2);
hdr->mode_ext = getbit(2);
hdr->copyright = getbit(1);
hdr->original = getbit(1);
hdr->emphasis = getbit(2);
}
void III_get_side_info(III_side_info_t *si)
{
int ch, gr, i;
int stereo = fr_ps.stereo;
si->main_data_begin = getbit(9); //SI 边信息结构
if (stereo == 1)
si->private_bits = getbit(5);
else
si->private_bits = getbit(3);
for (ch=0; chscfsi[ch][i] = getbit(1);
for (gr=0; gr<2; gr++) {
for (ch=0; chwindow_switching_flag && (gr_info->block_type == 2)) {
if (gr_info->mixed_block_flag) { /* MIXED */ /* NEW - ag 11/25 */
for (sfb = 0; sfb < 8; sfb++)
(*scalefac)[ch].l[sfb] = hgetbits(
slen[0][gr_info->scalefac_compress]); //用 slen[0]
for (sfb = 3; sfb < 6; sfb++)
for (window=0; window<3; window++)
(*scalefac)[ch].s[window][sfb] = hgetbits(
slen[0][gr_info->scalefac_compress]); //用 slen[0]
for (sfb = 6; sfb < 12; sfb++)
for (window=0; window<3; window++)
(*scalefac)[ch].s[window][sfb] = hgetbits(
slen[1][gr_info->scalefac_compress]); //6-11用 slen[1]
for (sfb=12,window=0; window<3; window++)
(*scalefac)[ch].s[window][sfb] = 0;
}
else { /* SHORT*/
for (i=0; i<2; i++)
for (sfb = sfbtable.s[i]; sfb < sfbtable.s[i+1]; sfb++)
for (window=0; window<3; window++)
(*scalefac)[ch].s[window][sfb] = hgetbits(
slen[i][gr_info->scalefac_compress]);
for (sfb=12,window=0; window<3; window++)
(*scalefac)[ch].s[window][sfb] = 0;
}
}
else { /* LONG types 0,1,3 */
for (i=0; i<4; i++) {
if ((si->scfsi[ch][i] == 0) || (gr == 0))
for (sfb = sfbtable.l[i]; sfb < sfbtable.l[i+1]; sfb++)
(*scalefac)[ch].l[sfb] = hgetbits(
slen[(i<2)?0:1][gr_info->scalefac_compress]);
}
(*scalefac)[ch].l[22] = 0;
}
}
int pretab[22] = {0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,2,2,3,3,3,2,0};
void III_dequantize_sample(int is[SBLIMIT][SSLIMIT], double xr[SBLIMIT][SSLIMIT], III_scalefac_t *scalefac, struct Granule *gr_info, int ch)
{
int ss,sb,cb=0,sfreq=fr_ps.header->sampling_frequency;
int next_cb_boundary, cb_begin, cb_width, sign;
double is43_table[1024],temp;
static int init=1;
if(init)
{
for(init=0;init<1024;init++)
is43_table[init]=1.33333333333*log(init);
init=0;
}
/* choose correct scalefactor band per block type, initalize boundary */
if (gr_info->window_switching_flag && (gr_info->block_type == 2) )
if (gr_info->mixed_block_flag)
next_cb_boundary=sfBandIndex[sfreq].l[1]; /* LONG blocks: 0,1,3 */
else
{
next_cb_boundary=sfBandIndex[sfreq].s[1]*3; /* pure SHORT block */
cb_width = sfBandIndex[sfreq].s[1];
cb_begin = 0;
}
else
next_cb_boundary=sfBandIndex[sfreq].l[1]; /* LONG blocks: 0,1,3 */
/* apply formula per block type */
for (sb=0 ; sb < SBLIMIT ; sb++) { //0-31
for (ss=0 ; ss < SSLIMIT ; ss++) { //0-17
/********* 由sb和ss计算cb(比例因子带)和cb_width(比例因子带宽) **************/
if ( (sb*18)+ss == next_cb_boundary)
{ /* Adjust critical band boundary */
if (gr_info->window_switching_flag && (gr_info->block_type == 2))
{
if (gr_info->mixed_block_flag)
{
if (((sb*18)+ss) == sfBandIndex[sfreq].l[8])
{
next_cb_boundary=sfBandIndex[sfreq].s[4]*3;
cb = 3;
cb_width = sfBandIndex[sfreq].s[cb+1] -
sfBandIndex[sfreq].s[cb];
cb_begin = sfBandIndex[sfreq].s[cb]*3;
}
else if (((sb*18)+ss) < sfBandIndex[sfreq].l[8])
next_cb_boundary = sfBandIndex[sfreq].l[(++cb)+1];
else {
next_cb_boundary = sfBandIndex[sfreq].s[(++cb)+1]*3;
cb_width = sfBandIndex[sfreq].s[cb+1] -
sfBandIndex[sfreq].s[cb];
cb_begin = sfBandIndex[sfreq].s[cb]*3;
}
}
else
{
next_cb_boundary = sfBandIndex[sfreq].s[(++cb)+1]*3;
cb_width = sfBandIndex[sfreq].s[cb+1] -
sfBandIndex[sfreq].s[cb];
cb_begin = sfBandIndex[sfreq].s[cb]*3;
}
}
else /* long blocks */
next_cb_boundary = sfBandIndex[sfreq].l[(++cb)+1];
}
/***************************************************************************************/
if(is[sb][ss]!=0)
{
/* Compute overall (global) scaling. */
xr[sb][ss] = (0.25 * (gr_info->global_gain - 210.0));
/* Do long/short dependent scaling operations. */
if (gr_info->window_switching_flag && (
((gr_info->block_type == 2) && (gr_info->mixed_block_flag == 0)) ||
((gr_info->block_type == 2) && gr_info->mixed_block_flag && (sb >= 2)) ))
{
xr[sb][ss] += (0.25 * -8.0 *gr_info->subblock_gain[(((sb*18)+ss) - cb_begin)/cb_width]);
xr[sb][ss] += (0.25 * -2.0 * (1.0+gr_info->scalefac_scale)
* (*scalefac)[ch].s[(((sb*18)+ss) - cb_begin)/cb_width][cb]);
}
else /* LONG block types 0,1,3 & 1st 2 subbands of switched blocks */
{
xr[sb][ss] += (-0.5 * (1.0+gr_info->scalefac_scale)
* ((*scalefac)[ch].l[cb]
+ gr_info->preflag * pretab[cb]));
}
/* Scale quantized value. */
//求出符号
sign=0;
if(is[sb][ss]<0)
{
sign=1;
is[sb][ss]=-is[sb][ss];
}
if(is[sb][ss]>1023)
temp=is43_table[(unsigned)is[sb][ss]>>3]+2.7725887;// 4/3*ln8
else
temp=is43_table[is[sb][ss]];
xr[sb][ss] *=0.69314318; //log(2);
xr[sb][ss] +=temp;
xr[sb][ss] =exp(xr[sb][ss]);
if (sign) xr[sb][ss] = -xr[sb][ss];
}
else
xr[sb][ss] =0;
}
}
}
void III_reorder(SS xr , struct Granule *gr_info)
{
int sfreq=fr_ps.header->sampling_frequency;
int sfb, sfb_start, sfb_lines;
int sb, ss, window, freq, src_line, des_line;
SS ro ;
if (gr_info->window_switching_flag && (gr_info->block_type == 2))
{
if (gr_info->mixed_block_flag)
{
/* NO REORDER FOR LOW 2 SUBBANDS */
for (sb=0 ; sb < 2 ; sb++)
for (ss=0 ; ss < SSLIMIT ; ss++)
ro[sb][ss] = xr[sb][ss];
/* REORDERING FOR REST SWITCHED SHORT */
for(sfb=3,sfb_start=sfBandIndex[sfreq].s[3],
sfb_lines=sfBandIndex[sfreq].s[4] - sfb_start;
sfb < 13; sfb++,sfb_start=sfBandIndex[sfreq].s[sfb],
(sfb_lines=sfBandIndex[sfreq].s[sfb+1] - sfb_start))
for(window=0; window<3; window++)
for(freq=0;freqsampling_frequency;
int stereo = fr_ps.stereo;
int ms_stereo = (fr_ps.header->mode == MPG_MD_JOINT_STEREO) &&
(fr_ps.header->mode_ext & 0x2);
int i_stereo = (fr_ps.header->mode == MPG_MD_JOINT_STEREO) &&
(fr_ps.header->mode_ext & 0x1);
int sfb;
int i,j,sb,ss,is_pos[576];
double is_ratio[576];
/* intialization */
for ( i=0; i<576; i++ )
is_pos[i] = 7;
if ((stereo == 2) && i_stereo )
{ if (gr_info->window_switching_flag && (gr_info->block_type == 2))
{ if( gr_info->mixed_block_flag )
{ int max_sfb = 0;
for ( j=0; j<3; j++ )
{ int sfbcnt;
sfbcnt = 2;
for( sfb=12; sfb >=3; sfb-- )
{ int lines;
lines = sfBandIndex[sfreq].s[sfb+1]-sfBandIndex[sfreq].s[sfb];
i = 3*sfBandIndex[sfreq].s[sfb] + (j+1) * lines - 1;
while ( lines > 0 )
{ if ( xr[1][i/SSLIMIT][i%SSLIMIT] != 0.0 )
{ sfbcnt = sfb;
sfb = -10;
lines = -10;
}
lines--;
i--;
}
}
sfb = sfbcnt + 1;
if ( sfb > max_sfb )
max_sfb = sfb;
while( sfb<12 )
{ sb = sfBandIndex[sfreq].s[sfb+1]-sfBandIndex[sfreq].s[sfb];
i = 3*sfBandIndex[sfreq].s[sfb] + j * sb;
for ( ; sb > 0; sb--)
{ is_pos[i] = (*scalefac)[1].s[j][sfb];
if ( is_pos[i] != 7 )
is_ratio[i] = tan( is_pos[i] * (PI / 12));
i++;
}
sfb++;
}
sb = sfBandIndex[sfreq].s[11]-sfBandIndex[sfreq].s[10];
sfb = 3*sfBandIndex[sfreq].s[10] + j * sb;
sb = sfBandIndex[sfreq].s[12]-sfBandIndex[sfreq].s[11];
i = 3*sfBandIndex[sfreq].s[11] + j * sb;
for ( ; sb > 0; sb-- )
{ is_pos[i] = is_pos[sfb];
is_ratio[i] = is_ratio[sfb];
i++;
}
}
if ( max_sfb <= 3 )
{ i = 2;
ss = 17;
sb = -1;
while ( i >= 0 )
{ if ( xr[1][i][ss] != 0.0 )
{ sb = i*18+ss;
i = -1;
} else
{ ss--;
if ( ss < 0 )
{ i--;
ss = 17;
}
}
}
i = 0;
while ( sfBandIndex[sfreq].l[i] <= sb )
i++;
sfb = i;
i = sfBandIndex[sfreq].l[i];
for ( ; sfb<8; sfb++ )
{ sb = sfBandIndex[sfreq].l[sfb+1]-sfBandIndex[sfreq].l[sfb];
for ( ; sb > 0; sb--)
{ is_pos[i] = (*scalefac)[1].l[sfb];
if ( is_pos[i] != 7 )
is_ratio[i] = tan( is_pos[i] * (PI / 12));
i++;
}
}
}
} else
{ for ( j=0; j<3; j++ )
{ int sfbcnt;
sfbcnt = -1;
for( sfb=12; sfb >=0; sfb-- )
{ int lines;
lines = sfBandIndex[sfreq].s[sfb+1]-sfBandIndex[sfreq].s[sfb];
i = 3*sfBandIndex[sfreq].s[sfb] + (j+1) * lines - 1;
while ( lines > 0 )
{ if ( xr[1][i/SSLIMIT][i%SSLIMIT] != 0.0 )
{ sfbcnt = sfb;
sfb = -10;
lines = -10;
}
lines--;
i--;
}
}
sfb = sfbcnt + 1;
while( sfb<12 )
{ sb = sfBandIndex[sfreq].s[sfb+1]-sfBandIndex[sfreq].s[sfb];
i = 3*sfBandIndex[sfreq].s[sfb] + j * sb;
for ( ; sb > 0; sb--)
{ is_pos[i] = (*scalefac)[1].s[j][sfb];
if ( is_pos[i] != 7 )
is_ratio[i] = tan( is_pos[i] * (PI / 12));
i++;
}
sfb++;
}
sb = sfBandIndex[sfreq].s[11]-sfBandIndex[sfreq].s[10];
sfb = 3*sfBandIndex[sfreq].s[10] + j * sb;
sb = sfBandIndex[sfreq].s[12]-sfBandIndex[sfreq].s[11];
i = 3*sfBandIndex[sfreq].s[11] + j * sb;
for ( ; sb > 0; sb-- )
{ is_pos[i] = is_pos[sfb];
is_ratio[i] = is_ratio[sfb];
i++;
}
}
}
} else
{ i = 31;
ss = 17;
sb = 0;
while ( i >= 0 )
{ if ( xr[1][i][ss] != 0.0 )
{ sb = i*18+ss;
i = -1;
} else
{ ss--;
if ( ss < 0 )
{ i--;
ss = 17;
}
}
}
i = 0;
while ( sfBandIndex[sfreq].l[i] <= sb )
i++;
sfb = i;
i = sfBandIndex[sfreq].l[i];
for ( ; sfb<21; sfb++ )
{ sb = sfBandIndex[sfreq].l[sfb+1] - sfBandIndex[sfreq].l[sfb];
for ( ; sb > 0; sb--)
{ is_pos[i] = (*scalefac)[1].l[sfb];
if ( is_pos[i] != 7 )
is_ratio[i] = tan( is_pos[i] * (PI / 12));
i++;
}
}
sfb = sfBandIndex[sfreq].l[20];
for ( sb = 576 - sfBandIndex[sfreq].l[21]; sb > 0; sb-- )
{ is_pos[i] = is_pos[sfb];
is_ratio[i] = is_ratio[sfb];
i++;
}
}
}
if (stereo==2)
for(sb=0;sbwindow_switching_flag && (gr_info->block_type == 2) &&
!gr_info->mixed_block_flag ) return;
if ( gr_info->window_switching_flag && gr_info->mixed_block_flag &&
(gr_info->block_type == 2))
sblim = 1;
else
sblim = SBLIMIT-1;
/* 31 alias-reduction operations between each pair of sub-bands */
/* with 8 butterflies between each pair */
for(sb=0;sbbitrate_index])
/ s_freq[fr_ps.header->sampling_frequency]);
if (fr_ps.header->padding) nSlots++;
nSlots -= 4; //减去4字节的头
if (fr_ps.header->error_protection) //如有CRC 则减2字节
nSlots -= 2;
if (fr_ps.stereo == 1) //单声道-17字节的side 信息
nSlots -= 17;
else
nSlots -=32; //单声道-32字节的side 信息
return(nSlots);
}