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Diffstat (limited to 'src/libfaad/pns.c')
| -rw-r--r-- | src/libfaad/pns.c | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/src/libfaad/pns.c b/src/libfaad/pns.c new file mode 100644 index 000000000..8df56cb9c --- /dev/null +++ b/src/libfaad/pns.c @@ -0,0 +1,120 @@ +/* +** FAAD - Freeware Advanced Audio Decoder +** Copyright (C) 2002 M. Bakker +** +** This program is free software; you can redistribute it and/or modify +** it under the terms of the GNU General Public License as published by +** the Free Software Foundation; either version 2 of the License, or +** (at your option) any later version. +** +** This program is distributed in the hope that it will be useful, +** but WITHOUT ANY WARRANTY; without even the implied warranty of +** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +** GNU General Public License for more details. +** +** You should have received a copy of the GNU General Public License +** along with this program; if not, write to the Free Software +** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. +** +** $Id: pns.c,v 1.1 2002/07/14 23:43:01 miguelfreitas Exp $ +**/ + +#include "common.h" + +#include "pns.h" + + +/* Needs some more work */ +/* From the spec: + If the same scalefactor band and group is coded by perceptual noise + substitution in both channels of a channel pair, the correlation of + the noise signal can be controlled by means of the ms_used field: While + the default noise generation process works independently for each channel + (separate generation of random vectors), the same random vector is used + for both channels if ms_used[] is set for a particular scalefactor band + and group. In this case, no M/S stereo coding is carried out (because M/S + stereo coding and noise substitution coding are mutually exclusive). + If the same scalefactor band and group is coded by perceptual noise + substitution in only one channel of a channel pair the setting of ms_used[] + is not evaluated. +*/ + + + +static INLINE int32_t random2() +{ + static int32_t state = 1; + + state = (1664525L * state) + 1013904223L; /* Numerical recipes */ + + return state; +} + +/* The function gen_rand_vector(addr, size) generates a vector of length + <size> with signed random values of average energy MEAN_NRG per random + value. A suitable random number generator can be realized using one + multiplication/accumulation per random value. +*/ +static INLINE void gen_rand_vector(real_t *spec, uint16_t scale_factor, uint16_t size) +{ + uint16_t i; + real_t scale; + + for (i = 0; i < size; i++) + { + spec[i] = (real_t)random2(); + } + + /* 14496-3 says: + scale = 1.0f/(size * (real_t)sqrt(MEAN_NRG)); + */ + scale = 1.0f/(real_t)sqrt(size * MEAN_NRG); + scale = MUL(scale, (real_t)exp(LN2 * 0.25 * scale_factor)); + + /* Scale random vector to desired target energy */ + for (i = 0; i < size; i++) + spec[i] = MUL(spec[i], scale); +} + +void pns_decode(ic_stream *ics, real_t *spec, uint16_t frame_len) +{ + uint8_t g, sfb, b; + uint16_t size, offs; + + uint8_t group = 0; + uint16_t nshort = frame_len/8; + + for (g = 0; g < ics->num_window_groups; g++) + { + /* Do perceptual noise substitution decoding */ + for (b = 0; b < ics->window_group_length[g]; b++) + { + for (sfb = 0; sfb < ics->max_sfb; sfb++) + { + if (is_noise(ics, g, sfb)) + { + /* Simultaneous use of LTP and PNS is not prevented in the + syntax. If both LTP, and PNS are enabled on the same + scalefactor band, PNS takes precedence, and no prediction + is applied to this band. + */ + ics->ltp.long_used[sfb] = 0; + ics->ltp2.long_used[sfb] = 0; + + /* For scalefactor bands coded using PNS the corresponding + predictors are switched to "off". + */ + ics->pred.prediction_used[sfb] = 0; + + offs = ics->swb_offset[sfb]; + size = ics->swb_offset[sfb+1] - offs; + + /* Generate random vector */ + gen_rand_vector(&spec[(group*nshort)+offs], + ics->scale_factors[g][sfb], size); + } + } + group++; + } + } +} |