2 ** FAAD2 - Freeware Advanced Audio (AAC) Decoder including SBR decoding
3 ** Copyright (C) 2003-2005 M. Bakker, Nero 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 ** The "appropriate copyright message" mentioned in section 2c of the GPLv2
23 ** must read: "Code from FAAD2 is copyright (c) Nero AG, www.nero.com"
25 ** Commercial non-GPL licensing of this software is possible.
26 ** For more info contact Nero AG through Mpeg4AAClicense@nero.com.
28 ** $Id: pns.c,v 1.38 2007/11/01 12:33:32 menno Exp $
37 /* static function declarations */
38 static void gen_rand_vector(real_t *spec, int16_t scale_factor, uint16_t size,
40 /* RNG states */ uint32_t *__r1, uint32_t *__r2);
45 #define DIV(A, B) (((int64_t)A << REAL_BITS)/B)
48 if ((0x40000000l >> shift) + root <= value) \
50 value -= (0x40000000l >> shift) + root; \
51 root = (root >> 1) | (0x40000000l >> shift); \
56 /* fixed point square root approximation */
57 /* !!!! ONLY WORKS FOR EVEN %REAL_BITS% !!!! */
58 real_t fp_sqrt(real_t value)
62 step( 0); step( 2); step( 4); step( 6);
63 step( 8); step(10); step(12); step(14);
64 step(16); step(18); step(20); step(22);
65 step(24); step(26); step(28); step(30);
70 root <<= (REAL_BITS/2);
75 static real_t const pow2_table[] =
78 COEF_CONST(1.18920711500272),
79 COEF_CONST(1.41421356237310),
80 COEF_CONST(1.68179283050743)
84 /* The function gen_rand_vector(addr, size) generates a vector of length
85 <size> with signed random values of average energy MEAN_NRG per random
86 value. A suitable random number generator can be realized using one
87 multiplication/accumulation per random value.
89 static INLINE void gen_rand_vector(real_t *spec, int16_t scale_factor, uint16_t size,
91 /* RNG states */ uint32_t *__r1, uint32_t *__r2)
97 real_t scale = (real_t)1.0/(real_t)size;
99 for (i = 0; i < size; i++)
101 real_t tmp = scale*(real_t)(int32_t)ne_rng(__r1, __r2);
106 scale = (real_t)1.0/(real_t)sqrt(energy);
107 scale *= (real_t)pow(2.0, 0.25 * scale_factor);
108 for (i = 0; i < size; i++)
114 real_t energy = 0, scale;
117 for (i = 0; i < size; i++)
119 /* this can be replaced by a 16 bit random generator!!!! */
120 real_t tmp = (int32_t)ne_rng(__r1, __r2);
122 tmp = -(tmp & ((1<<(REAL_BITS-1))-1));
124 tmp = (tmp & ((1<<(REAL_BITS-1))-1));
126 energy += MUL_R(tmp,tmp);
131 energy = fp_sqrt(energy);
134 scale = DIV(REAL_CONST(1),energy);
136 exp = scale_factor >> 2;
137 frac = scale_factor & 3;
139 /* IMDCT pre-scaling */
148 scale = MUL_C(scale, pow2_table[frac]);
150 for (i = 0; i < size; i++)
152 spec[i] = MUL_R(spec[i], scale);
158 void pns_decode(ic_stream *ics_left, ic_stream *ics_right,
159 real_t *spec_left, real_t *spec_right, uint16_t frame_len,
160 uint8_t channel_pair, uint8_t object_type,
161 /* RNG states */ uint32_t *__r1, uint32_t *__r2)
167 uint16_t nshort = frame_len >> 3;
173 if (object_type == LD)
177 if (ics_left->window_sequence == EIGHT_SHORT_SEQUENCE)
184 for (g = 0; g < ics_left->num_window_groups; g++)
186 /* Do perceptual noise substitution decoding */
187 for (b = 0; b < ics_left->window_group_length[g]; b++)
189 for (sfb = 0; sfb < ics_left->max_sfb; sfb++)
191 if (is_noise(ics_left, g, sfb))
194 /* Simultaneous use of LTP and PNS is not prevented in the
195 syntax. If both LTP, and PNS are enabled on the same
196 scalefactor band, PNS takes precedence, and no prediction
197 is applied to this band.
199 ics_left->ltp.long_used[sfb] = 0;
200 ics_left->ltp2.long_used[sfb] = 0;
204 /* For scalefactor bands coded using PNS the corresponding
205 predictors are switched to "off".
207 ics_left->pred.prediction_used[sfb] = 0;
210 offs = ics_left->swb_offset[sfb];
211 size = min(ics_left->swb_offset[sfb+1], ics_left->swb_offset_max) - offs;
213 /* Generate random vector */
214 gen_rand_vector(&spec_left[(group*nshort)+offs],
215 ics_left->scale_factors[g][sfb], size, sub, __r1, __r2);
219 If the same scalefactor band and group is coded by perceptual noise
220 substitution in both channels of a channel pair, the correlation of
221 the noise signal can be controlled by means of the ms_used field: While
222 the default noise generation process works independently for each channel
223 (separate generation of random vectors), the same random vector is used
224 for both channels if ms_used[] is set for a particular scalefactor band
225 and group. In this case, no M/S stereo coding is carried out (because M/S
226 stereo coding and noise substitution coding are mutually exclusive).
227 If the same scalefactor band and group is coded by perceptual noise
228 substitution in only one channel of a channel pair the setting of ms_used[]
233 if (is_noise(ics_right, g, sfb))
235 if (((ics_left->ms_mask_present == 1) &&
236 (ics_left->ms_used[g][sfb])) ||
237 (ics_left->ms_mask_present == 2))
241 offs = ics_right->swb_offset[sfb];
242 size = min(ics_right->swb_offset[sfb+1], ics_right->swb_offset_max) - offs;
244 for (c = 0; c < size; c++)
246 spec_right[(group*nshort) + offs + c] =
247 spec_left[(group*nshort) + offs + c];
249 } else /*if (ics_left->ms_mask_present == 0)*/ {
251 ics_right->ltp.long_used[sfb] = 0;
252 ics_right->ltp2.long_used[sfb] = 0;
255 ics_right->pred.prediction_used[sfb] = 0;
258 offs = ics_right->swb_offset[sfb];
259 size = min(ics_right->swb_offset[sfb+1], ics_right->swb_offset_max) - offs;
261 /* Generate random vector */
262 gen_rand_vector(&spec_right[(group*nshort)+offs],
263 ics_right->scale_factors[g][sfb], size, sub, __r1, __r2);