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/*
* Mpeg Layer-2 audio decoder
* --------------------------
* copyright (c) 1995 by Michael Hipp, All rights reserved. See also 'README'
*
*/
#include "mpg123.h"
static int grp_3tab
[32 * 3] = { 0, }; /* used: 27 */
static int grp_5tab
[128 * 3] = { 0, }; /* used: 125 */
static int grp_9tab
[1024 * 3] = { 0, }; /* used: 729 */
real muls
[27][64]; /* also used by layer 1 */
void init_layer2
(void)
{
static double mulmul
[27] = {
0.0 , -2.0/3.0 , 2.0/3.0 ,
2.0/7.0 , 2.0/15.0 , 2.0/31.0, 2.0/63.0 , 2.0/127.0 , 2.0/255.0 ,
2.0/511.0 , 2.0/1023.0 , 2.0/2047.0 , 2.0/4095.0 , 2.0/8191.0 ,
2.0/16383.0 , 2.0/32767.0 , 2.0/65535.0 ,
-4.0/5.0 , -2.0/5.0 , 2.0/5.0, 4.0/5.0 ,
-8.0/9.0 , -4.0/9.0 , -2.0/9.0 , 2.0/9.0 , 4.0/9.0 , 8.0/9.0 };
static int base
[3][9] = {
{ 1 , 0, 2 , } ,
{ 17, 18, 0 , 19, 20 , } ,
{ 21, 1, 22, 23, 0, 24, 25, 2, 26 } };
int i
,j
,k
,l
,len
;
real
*table
;
static int tablen
[3] = { 3 , 5 , 9 };
static int *itable
,*tables
[3] = { grp_3tab
, grp_5tab
, grp_9tab
};
for(i
=0;i
<3;i
++)
{
itable
= tables
[i
];
len
= tablen
[i
];
for(j
=0;j
<len
;j
++)
for(k
=0;k
<len
;k
++)
for(l
=0;l
<len
;l
++)
{
*itable
++ = base
[i
][l
];
*itable
++ = base
[i
][k
];
*itable
++ = base
[i
][j
];
}
}
for(k
=0;k
<27;k
++)
{
double m
=mulmul
[k
];
table
= muls
[k
];
for(j
=3,i
=0;i
<63;i
++,j
--)
*table
++ = m
* pow(2.0,(double) j
/ 3.0);
*table
++ = 0.0;
}
}
void II_step_one
(unsigned int *bit_alloc
,int *scale
,struct frame
*fr
)
{
int stereo
= fr
->stereo
-1;
int sblimit
= fr
->II_sblimit
;
int jsbound
= fr
->jsbound
;
int sblimit2
= fr
->II_sblimit
<<stereo
;
struct al_table
*alloc1
= fr
->alloc
;
int i
;
static unsigned int scfsi_buf
[64];
unsigned int *scfsi
,*bita
;
int sc
,step
;
bita
= bit_alloc
;
if(stereo
)
{
for (i
=jsbound
;i
;i
--,alloc1
+=(1<<step
))
{
*bita
++ = (char) getbits
(step
=alloc1
->bits
);
*bita
++ = (char) getbits
(step
);
}
for (i
=sblimit
-jsbound
;i
;i
--,alloc1
+=(1<<step
))
{
bita
[0] = (char) getbits
(step
=alloc1
->bits
);
bita
[1] = bita
[0];
bita
+=2;
}
bita
= bit_alloc
;
scfsi
=scfsi_buf
;
for (i
=sblimit2
;i
;i
--)
if (*bita
++)
*scfsi
++ = (char) getbits_fast
(2);
}
else /* mono */
{
for (i
=sblimit
;i
;i
--,alloc1
+=(1<<step
))
*bita
++ = (char) getbits
(step
=alloc1
->bits
);
bita
= bit_alloc
;
scfsi
=scfsi_buf
;
for (i
=sblimit
;i
;i
--)
if (*bita
++)
*scfsi
++ = (char) getbits_fast
(2);
}
bita
= bit_alloc
;
scfsi
=scfsi_buf
;
for (i
=sblimit2
;i
;i
--)
if (*bita
++)
switch (*scfsi
++)
{
case 0:
*scale
++ = getbits_fast
(6);
*scale
++ = getbits_fast
(6);
*scale
++ = getbits_fast
(6);
break;
case 1 :
*scale
++ = sc
= getbits_fast
(6);
*scale
++ = sc
;
*scale
++ = getbits_fast
(6);
break;
case 2:
*scale
++ = sc
= getbits_fast
(6);
*scale
++ = sc
;
*scale
++ = sc
;
break;
default: /* case 3 */
*scale
++ = getbits_fast
(6);
*scale
++ = sc
= getbits_fast
(6);
*scale
++ = sc
;
break;
}
}
void II_step_two
(unsigned int *bit_alloc
,real fraction
[2][4][SBLIMIT
],int *scale
,struct frame
*fr
,int x1
)
{
int i
,j
,k
,ba
;
int stereo
= fr
->stereo
;
int sblimit
= fr
->II_sblimit
;
int jsbound
= fr
->jsbound
;
struct al_table
*alloc2
,*alloc1
= fr
->alloc
;
unsigned int *bita
=bit_alloc
;
int d1
,step
;
for (i
=0;i
<jsbound
;i
++,alloc1
+=(1<<step
))
{
step
= alloc1
->bits
;
for (j
=0;j
<stereo
;j
++)
{
if ( (ba
=*bita
++) )
{
k
=(alloc2
= alloc1
+ba
)->bits
;
if( (d1
=alloc2
->d
) < 0)
{
real cm
=muls
[k
][scale
[x1
]];
fraction
[j
][0][i
] = ((real
) ((int)getbits
(k
) + d1
)) * cm
;
fraction
[j
][1][i
] = ((real
) ((int)getbits
(k
) + d1
)) * cm
;
fraction
[j
][2][i
] = ((real
) ((int)getbits
(k
) + d1
)) * cm
;
}
else
{
static int *table
[] = { 0,0,0,grp_3tab
,0,grp_5tab
,0,0,0,grp_9tab
};
unsigned int idx
,*tab
,m
=scale
[x1
];
idx
= (unsigned int) getbits
(k
);
tab
= (unsigned int *) (table
[d1
] + idx
+ idx
+ idx
);
fraction
[j
][0][i
] = muls
[*tab
++][m
];
fraction
[j
][1][i
] = muls
[*tab
++][m
];
fraction
[j
][2][i
] = muls
[*tab
][m
];
}
scale
+=3;
}
else
fraction
[j
][0][i
] = fraction
[j
][1][i
] = fraction
[j
][2][i
] = 0.0;
}
}
for (i
=jsbound
;i
<sblimit
;i
++,alloc1
+=(1<<step
))
{
step
= alloc1
->bits
;
bita
++; /* channel 1 and channel 2 bitalloc are the same */
if ( (ba
=*bita
++) )
{
k
=(alloc2
= alloc1
+ba
)->bits
;
if( (d1
=alloc2
->d
) < 0)
{
real cm
;
cm
=muls
[k
][scale
[x1
+3]];
fraction
[1][0][i
] = (fraction
[0][0][i
] = (real
) ((int)getbits
(k
) + d1
) ) * cm
;
fraction
[1][1][i
] = (fraction
[0][1][i
] = (real
) ((int)getbits
(k
) + d1
) ) * cm
;
fraction
[1][2][i
] = (fraction
[0][2][i
] = (real
) ((int)getbits
(k
) + d1
) ) * cm
;
cm
=muls
[k
][scale
[x1
]];
fraction
[0][0][i
] *= cm
; fraction
[0][1][i
] *= cm
; fraction
[0][2][i
] *= cm
;
}
else
{
static int *table
[] = { 0,0,0,grp_3tab
,0,grp_5tab
,0,0,0,grp_9tab
};
unsigned int idx
,*tab
,m1
,m2
;
m1
= scale
[x1
]; m2
= scale
[x1
+3];
idx
= (unsigned int) getbits
(k
);
tab
= (unsigned int *) (table
[d1
] + idx
+ idx
+ idx
);
fraction
[0][0][i
] = muls
[*tab
][m1
]; fraction
[1][0][i
] = muls
[*tab
++][m2
];
fraction
[0][1][i
] = muls
[*tab
][m1
]; fraction
[1][1][i
] = muls
[*tab
++][m2
];
fraction
[0][2][i
] = muls
[*tab
][m1
]; fraction
[1][2][i
] = muls
[*tab
][m2
];
}
scale
+=6;
}
else {
fraction
[0][0][i
] = fraction
[0][1][i
] = fraction
[0][2][i
] =
fraction
[1][0][i
] = fraction
[1][1][i
] = fraction
[1][2][i
] = 0.0;
}
/*
should we use individual scalefac for channel 2 or
is the current way the right one , where we just copy channel 1 to
channel 2 ??
The current 'strange' thing is, that we throw away the scalefac
values for the second channel ...!!
-> changed .. now we use the scalefac values of channel one !!
*/
}
if(sblimit
> (SBLIMIT
>>fr
->down_sample
) )
sblimit
= SBLIMIT
>>fr
->down_sample
;
for(i
=sblimit
;i
<SBLIMIT
;i
++)
for (j
=0;j
<stereo
;j
++)
fraction
[j
][0][i
] = fraction
[j
][1][i
] = fraction
[j
][2][i
] = 0.0;
}
int do_layer2
(struct frame
*fr
,int outmode
,struct audio_info_struct
*ai
)
{
int clip
=0;
int i
,j
;
int stereo
= fr
->stereo
;
real fraction
[2][4][SBLIMIT
]; /* pick_table clears unused subbands */
unsigned int bit_alloc
[64];
int scale
[192];
int single
= fr
->single
;
if(stereo
== 1 || single
== 3)
single
= 0;
II_step_one
(bit_alloc
, scale
, fr
);
for (i
=0;i
<SCALE_BLOCK
;i
++)
{
II_step_two
(bit_alloc
,fraction
,scale
,fr
,i
>>2);
for (j
=0;j
<3;j
++)
{
if(single
>= 0)
{
clip
+= (fr
->synth_mono
) (fraction
[single
][j
],pcm_sample
+pcm_point
);
}
else {
clip
+= (fr
->synth
) (fraction
[0][j
],0,pcm_sample
+pcm_point
);
clip
+= (fr
->synth
) (fraction
[1][j
],1,pcm_sample
+pcm_point
);
}
pcm_point
+= fr
->block_size
;
if(pcm_point
== audiobufsize
)
audio_flush
(outmode
,ai
);
}
}
return clip
;
}