2 ** FAAD2 - Freeware Advanced Audio (AAC) Decoder including SBR decoding
3 ** Copyright (C) 2003-2004 M. Bakker, Ahead Software AG, http://www.nero.com
5 ** This program is free software; you can redistribute it and/or modify
6 ** it under the terms of the GNU General Public License as published by
7 ** the Free Software Foundation; either version 2 of the License, or
8 ** (at your option) any later version.
10 ** This program is distributed in the hope that it will be useful,
11 ** but WITHOUT ANY WARRANTY; without even the implied warranty of
12 ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 ** GNU General Public License for more details.
15 ** You should have received a copy of the GNU General Public License
16 ** along with this program; if not, write to the Free Software
17 ** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
19 ** Any non-GPL usage of this software or parts of this software is strictly
22 ** Commercial non-GPL licensing of this software is possible.
23 ** For more info contact Ahead Software through Mpeg4AAClicense@nero.com.
34 /* static function declarations */
35 static void gen_rand_vector(real_t
*spec
, int16_t scale_factor
, uint16_t size
,
42 if ((0x40000000l >> shift) + root <= value) \
44 value -= (0x40000000l >> shift) + root; \
45 root = (root >> 1) | (0x40000000l >> shift); \
50 /* fixed point square root approximation */
51 /* !!!! ONLY WORKS FOR EVEN %REAL_BITS% !!!! */
52 static real_t
fp_sqrt(real_t value
)
56 step( 0); step( 2); step( 4); step( 6);
57 step( 8); step(10); step(12); step(14);
58 step(16); step(18); step(20); step(22);
59 step(24); step(26); step(28); step(30);
64 root
<<= (REAL_BITS
/2);
69 static real_t pow2_table
[] =
72 COEF_CONST(1.18920711500272),
73 COEF_CONST(1.41421356237310),
74 COEF_CONST(1.68179283050743)
78 /* The function gen_rand_vector(addr, size) generates a vector of length
79 <size> with signed random values of average energy MEAN_NRG per random
80 value. A suitable random number generator can be realized using one
81 multiplication/accumulation per random value.
83 static INLINE
void gen_rand_vector(real_t
*spec
, int16_t scale_factor
, uint16_t size
,
90 real_t scale
= (real_t
)1.0/(real_t
)size
;
92 for (i
= 0; i
< size
; i
++)
94 real_t tmp
= scale
*(real_t
)(int32_t)random_int();
99 scale
= (real_t
)1.0/(real_t
)sqrt(energy
);
100 scale
*= (real_t
)pow(2.0, 0.25 * scale_factor
);
101 for (i
= 0; i
< size
; i
++)
107 real_t energy
= 0, scale
;
110 for (i
= 0; i
< size
; i
++)
112 /* this can be replaced by a 16 bit random generator!!!! */
113 real_t tmp
= (int32_t)random_int();
115 tmp
= -(tmp
& ((1<<(REAL_BITS
-1))-1));
117 tmp
= (tmp
& ((1<<(REAL_BITS
-1))-1));
119 energy
+= MUL_R(tmp
,tmp
);
124 energy
= fp_sqrt(energy
);
127 scale
= DIV_R(REAL_CONST(1), energy
);
129 exp
= scale_factor
>> 2;
130 frac
= scale_factor
& 3;
132 /* IMDCT pre-scaling */
141 scale
= MUL_C(scale
, pow2_table
[frac
]);
143 for (i
= 0; i
< size
; i
++)
145 spec
[i
] = MUL_R(spec
[i
], scale
);
151 void pns_decode(ic_stream
*ics_left
, ic_stream
*ics_right
,
152 real_t
*spec_left
, real_t
*spec_right
, uint16_t frame_len
,
153 uint8_t channel_pair
, uint8_t object_type
)
159 uint16_t nshort
= frame_len
>> 3;
165 if (object_type
== LD
)
169 if (ics_left
->window_sequence
== EIGHT_SHORT_SEQUENCE
)
176 for (g
= 0; g
< ics_left
->num_window_groups
; g
++)
178 /* Do perceptual noise substitution decoding */
179 for (b
= 0; b
< ics_left
->window_group_length
[g
]; b
++)
181 for (sfb
= 0; sfb
< ics_left
->max_sfb
; sfb
++)
183 if (is_noise(ics_left
, g
, sfb
))
186 /* Simultaneous use of LTP and PNS is not prevented in the
187 syntax. If both LTP, and PNS are enabled on the same
188 scalefactor band, PNS takes precedence, and no prediction
189 is applied to this band.
191 ics_left
->ltp
.long_used
[sfb
] = 0;
192 ics_left
->ltp2
.long_used
[sfb
] = 0;
196 /* For scalefactor bands coded using PNS the corresponding
197 predictors are switched to "off".
199 ics_left
->pred
.prediction_used
[sfb
] = 0;
202 offs
= ics_left
->swb_offset
[sfb
];
203 size
= ics_left
->swb_offset
[sfb
+1] - offs
;
205 /* Generate random vector */
206 gen_rand_vector(&spec_left
[(group
*nshort
)+offs
],
207 ics_left
->scale_factors
[g
][sfb
], size
, sub
);
211 If the same scalefactor band and group is coded by perceptual noise
212 substitution in both channels of a channel pair, the correlation of
213 the noise signal can be controlled by means of the ms_used field: While
214 the default noise generation process works independently for each channel
215 (separate generation of random vectors), the same random vector is used
216 for both channels if ms_used[] is set for a particular scalefactor band
217 and group. In this case, no M/S stereo coding is carried out (because M/S
218 stereo coding and noise substitution coding are mutually exclusive).
219 If the same scalefactor band and group is coded by perceptual noise
220 substitution in only one channel of a channel pair the setting of ms_used[]
225 if (is_noise(ics_right
, g
, sfb
))
227 if (((ics_left
->ms_mask_present
== 1) &&
228 (ics_left
->ms_used
[g
][sfb
])) ||
229 (ics_left
->ms_mask_present
== 2))
233 offs
= ics_right
->swb_offset
[sfb
];
234 size
= ics_right
->swb_offset
[sfb
+1] - offs
;
236 for (c
= 0; c
< size
; c
++)
238 spec_right
[(group
*nshort
) + offs
+ c
] =
239 spec_left
[(group
*nshort
) + offs
+ c
];
241 } else /*if (ics_left->ms_mask_present == 0)*/ {
243 ics_right
->ltp
.long_used
[sfb
] = 0;
244 ics_right
->ltp2
.long_used
[sfb
] = 0;
247 ics_right
->pred
.prediction_used
[sfb
] = 0;
250 offs
= ics_right
->swb_offset
[sfb
];
251 size
= ics_right
->swb_offset
[sfb
+1] - offs
;
253 /* Generate random vector */
254 gen_rand_vector(&spec_right
[(group
*nshort
)+offs
],
255 ics_right
->scale_factors
[g
][sfb
], size
, sub
);