/* this file is a part of amp software, (C) tomislav uzelac 1996,1997
*/
/* getdata.c scalefactor & huffman data extraction
*
* Created by: tomislav uzelac Apr 1996
* Last modified by: tomislav uzelac Feb 27 1997
*/
#include "amp.h"
#include "audio.h"
#include "getbits.h"
#include "huffman.h"
#define GETDATA
#include "getdata.h"
/* layer3 scalefactor decoding. should we check for the number
* of bits read, just in case?
*/
int decode_scalefactors(struct SIDE_INFO *info,struct AUDIO_HEADER *header,int gr,int ch)
{
int sfb,window;
int slen1,slen2;
int i1,i2,i=0;
int j,k;
if (header->ID==1) {
/* this is MPEG-1 scalefactors format, quite different than
* the MPEG-2 format.
*/
slen1=t_slen1[info->scalefac_compress[gr][ch]];
slen2=t_slen2[info->scalefac_compress[gr][ch]];
i1=3*slen1;
i2=3*slen2;
if (info->window_switching_flag[gr][ch] && info->block_type[gr][ch]==2) {
if (info->mixed_block_flag[gr][ch]) {
for (sfb=0;sfb<8;sfb++) {
scalefac_l[gr][ch][sfb]=getbits(slen1);
i+=slen1;
}
for (sfb=3;sfb<6;sfb++) {
for (window=0;window<3;window++)
scalefac_s[gr][ch][sfb][window]=getbits(slen1);
i+=i1;
}
for (;sfb<12;sfb++) {
for (window=0;window<3;window++)
scalefac_s[gr][ch][sfb][window]=getbits(slen2);
i+=i2;
}
} else { /* !mixed_block_flag */
for (sfb=0;sfb<6;sfb++) {
for (window=0;window<3;window++)
scalefac_s[gr][ch][sfb][window]=getbits(slen1);
i+=i1;
}
for (;sfb<12;sfb++) {
for (window=0;window<3;window++)
scalefac_s[gr][ch][sfb][window]=getbits(slen2);
i+=i2;
}
}
for (window=0;window<3;window++)
scalefac_s[gr][ch][12][window]=0;
} else { /* block_type!=2 */
if ( !info->scfsi[ch][0] || !gr )
for (sfb=0;sfb<6;sfb++) {
scalefac_l[gr][ch][sfb]=getbits(slen1);
i+=slen1;
}
else for (sfb=0;sfb<6;sfb++) {
scalefac_l[1][ch][sfb]=scalefac_l[0][ch][sfb];
}
if ( !info->scfsi[ch][1] || !gr )
for (sfb=6;sfb<11;sfb++) {
scalefac_l[gr][ch][sfb]=getbits(slen1);
i+=slen1;
}
else for (sfb=6;sfb<11;sfb++) {
scalefac_l[1][ch][sfb]=scalefac_l[0][ch][sfb];
}
if ( !info->scfsi[ch][2] || !gr )
for (sfb=11;sfb<16;sfb++) {
scalefac_l[gr][ch][sfb]=getbits(slen2);
i+=slen2;
}
else for (sfb=11;sfb<16;sfb++) {
scalefac_l[1][ch][sfb]=scalefac_l[0][ch][sfb];
}
if ( !info->scfsi[ch][3] || !gr )
for (sfb=16;sfb<21;sfb++) {
scalefac_l[gr][ch][sfb]=getbits(slen2);
i+=slen2;
}
else for (sfb=16;sfb<21;sfb++) {
scalefac_l[1][ch][sfb]=scalefac_l[0][ch][sfb];
}
scalefac_l[gr][ch][21]=0;
}
} else { /* ID==0 */
int index=0,index2,spooky_index;
int slen[6],nr_of_sfb[6]; /* actually, there's four of each, not five, labelled 1 through 4, but
* what's a word of storage compared to one's sanity. so [0] is irellevant.
*/
/* ok, so we got 3 indexes.
* spooky_index - indicates whether we use the normal set of slen eqs and nr_of_sfb tables
* or the one for the right channel of intensity stereo coded frame
* index - corresponds to the value of scalefac_compress, as listed in the standard
* index2 - 0 for long blocks, 1 for short wo/ mixed_block_flag, 2 for short with it
*/
if ( (header->mode_extension==1 || header->mode_extension==3) && ch==1) { /* right ch... */
int int_scalefac_compress=info->scalefac_compress[0][ch]>>1;
intensity_scale=info->scalefac_compress[0][1]&1;
spooky_index=1;
if (int_scalefac_compress < 180) {
slen[1]=int_scalefac_compress/36;
slen[2]=(int_scalefac_compress%36)/6;
slen[3]=(int_scalefac_compress%36)%6;
slen[4]=0;
info->preflag[0][ch]=0;
index=0;
}
if ( 180 <= int_scalefac_compress && int_scalefac_compress < 244) {
slen[1]=((int_scalefac_compress-180)%64)>>4;
slen[2]=((int_scalefac_compress-180)%16)>>2;
slen[3]=(int_scalefac_compress-180)%4;
slen[4]=0;
info->preflag[0][ch]=0;
index=1;
}
if ( 244 <= int_scalefac_compress && int_scalefac_compress < 255) {
slen[1]=(int_scalefac_compress-244)/3;
slen[2]=(int_scalefac_compress-244)%3;
slen[3]=0;
slen[4]=0;
info->preflag[0][ch]=0;
index=2;
}
} else { /* the usual */
spooky_index=0;
if (info->scalefac_compress[0][ch] < 400) {
slen[1]=(info->scalefac_compress[0][ch]>>4)/5;
slen[2]=(info->scalefac_compress[0][ch]>>4)%5;
slen[3]=(info->scalefac_compress[0][ch]%16)>>2;
slen[4]=info->scalefac_compress[0][ch]%4;
info->preflag[0][ch]=0;
index=0;
}
if (info->scalefac_compress[0][ch] >= 400 && info->scalefac_compress[0][ch] < 500) {
slen[1]=((info->scalefac_compress[0][ch]-400)>>2)/5;
slen[2]=((info->scalefac_compress[0][ch]-400)>>2)%5;
slen[3]=(info->scalefac_compress[0][ch]-400)%4;
slen[4]=0;
info->preflag[0][ch]=0;
index=1;
}
if (info->scalefac_compress[0][ch] >= 500 && info->scalefac_compress[0][ch] < 512) {
slen[1]=(info->scalefac_compress[0][ch]-500)/3;
slen[2]=(info->scalefac_compress[0][ch]-500)%3;
slen[3]=0;
slen[4]=0;
info->preflag[0][ch]=1;
index=2;
}
}
if (info->window_switching_flag[0][ch] && info->block_type[0][ch]==2)
if (info->mixed_block_flag[0][ch]) index2=2;
else index2=1;
else index2=0;
for (j=1;j<=4;j++) nr_of_sfb[j]=spooky_table[spooky_index][index][index2][j-1];
/* now we'll do some actual scalefactor extraction, and a little more.
* for each scalefactor band we'll set the value of is_max to indicate
* illegal is_pos, since with MPEG2 it's not 'hardcoded' to 7.
*/
if (!info->window_switching_flag[0][ch] || (info->window_switching_flag[0][ch] && info->block_type[0][ch]!=2)) {
sfb=0;
for (j=1;j<=4;j++)
for (k=0;k<nr_of_sfb[j];k++) {
scalefac_l[0][ch][sfb]=getbits(slen[j]);
i+=slen[j];
if (ch) is_max[sfb]=(1<<slen[j])-1;
sfb++;
}
} else if (info->block_type[0][ch]==2)
{
if (!info->mixed_block_flag[0][ch]) {
sfb=0;
for (j=1;j<=4;j++)
for (k=0;k<nr_of_sfb[j];k+=3) {
/* we assume here that nr_of_sfb is divisible by 3. it is.
*/
scalefac_s[0][ch][sfb][0]=getbits(slen[j]);
scalefac_s[0][ch][sfb][1]=getbits(slen[j]);
scalefac_s[0][ch][sfb][2]=getbits(slen[j]);
i+=3*slen[j];
if (ch) is_max[sfb+6]=(1<<slen[j])-1;
sfb++;
}
} else {
/* what we do here is:
* 1. assume that for every fs, the two lowest subbands are equal to the
* six lowest scalefactor bands for long blocks/MPEG2. they are.
* 2. assume that for every fs, the two lowest subbands are equal to the
* three lowest scalefactor bands for short blocks. they are.
*/
sfb=0;
for (k=0;k<6;k++) {
scalefac_l[0][ch][sfb]=getbits(slen[1]);
i+=slen[j];
if (ch) is_max[sfb]=(1<<slen[1])-1;
sfb++;
}
nr_of_sfb[1]-=6;
sfb=3;
for (j=1;j<=4;j++)
for (k=0;k<nr_of_sfb[j];k+=3) {
scalefac_s[0][ch][sfb][0]=getbits(slen[j]);
scalefac_s[0][ch][sfb][1]=getbits(slen[j]);
scalefac_s[0][ch][sfb][2]=getbits(slen[j]);
i+=3*slen[j];
if (ch) is_max[sfb+6]=(1<<slen[j])-1;
sfb++;
}
}
}
}
return i;
}