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: lt_predict.c,v 1.27 2007/11/01 12:33:31 menno Exp $
44 /* static function declarations */
45 static int16_t real_to_int16(real_t sig_in);
48 /* check if the object type is an object type that can have LTP */
49 uint8_t is_ltp_ot(uint8_t object_type)
52 if ((object_type == LTP)
53 #ifdef ERROR_RESILIENCE
54 || (object_type == ER_LTP)
57 || (object_type == LD)
68 ALIGN static const real_t codebook[8] =
80 void lt_prediction(ic_stream *ics, ltp_info *ltp, real_t *spec,
81 int16_t *lt_pred_stat, fb_info *fb, uint8_t win_shape,
82 uint8_t win_shape_prev, uint8_t sr_index,
83 uint8_t object_type, uint16_t frame_len)
86 uint16_t bin, i, num_samples;
87 ALIGN real_t x_est[2048];
88 ALIGN real_t X_est[2048];
90 if (ics->window_sequence != EIGHT_SHORT_SEQUENCE)
92 if (ltp->data_present)
94 num_samples = frame_len << 1;
96 for(i = 0; i < num_samples; i++)
98 /* The extra lookback M (N/2 for LD, 0 for LTP) is handled
99 in the buffer updating */
102 x_est[i] = MUL_R_C(lt_pred_stat[num_samples + i - ltp->lag],
103 codebook[ltp->coef]);
105 /* lt_pred_stat is a 16 bit int, multiplied with the fixed point real
106 this gives a real for x_est
108 x_est[i] = (real_t)lt_pred_stat[num_samples + i - ltp->lag] * codebook[ltp->coef];
112 filter_bank_ltp(fb, ics->window_sequence, win_shape, win_shape_prev,
113 x_est, X_est, object_type, frame_len);
115 tns_encode_frame(ics, &(ics->tns), sr_index, object_type, X_est,
118 for (sfb = 0; sfb < ltp->last_band; sfb++)
120 if (ltp->long_used[sfb])
122 uint16_t low = ics->swb_offset[sfb];
123 uint16_t high = min(ics->swb_offset[sfb+1], ics->swb_offset_max);
125 for (bin = low; bin < high; bin++)
127 spec[bin] += X_est[bin];
136 static INLINE int16_t real_to_int16(real_t sig_in)
140 sig_in += (1 << (REAL_BITS-1));
141 if (sig_in >= REAL_CONST(32768))
144 sig_in += -(1 << (REAL_BITS-1));
145 if (sig_in <= REAL_CONST(-32768))
149 return (sig_in >> REAL_BITS);
152 static INLINE int16_t real_to_int16(real_t sig_in)
159 if (sig_in >= 32768.0f)
165 if (sig_in <= -32768.0f)
169 return lrintf(sig_in);
173 void lt_update_state(int16_t *lt_pred_stat, real_t *time, real_t *overlap,
174 uint16_t frame_len, uint8_t object_type)
179 * The reference point for index i and the content of the buffer
180 * lt_pred_stat are arranged so that lt_pred_stat(0 ... N/2 - 1) contains the
181 * last aliased half window from the IMDCT, and lt_pred_stat(N/2 ... N-1)
182 * is always all zeros. The rest of lt_pred_stat (i<0) contains the previous
183 * fully reconstructed time domain samples, i.e., output of the decoder.
185 * These values are shifted up by N*2 to avoid (i<0)
187 * For the LD object type an extra 512 samples lookback is accomodated here.
190 if (object_type == LD)
192 for (i = 0; i < frame_len; i++)
194 lt_pred_stat[i] /* extra 512 */ = lt_pred_stat[i + frame_len];
195 lt_pred_stat[frame_len + i] = lt_pred_stat[i + (frame_len * 2)];
196 lt_pred_stat[(frame_len * 2) + i] = real_to_int16(time[i]);
197 lt_pred_stat[(frame_len * 3) + i] = real_to_int16(overlap[i]);
201 for (i = 0; i < frame_len; i++)
203 lt_pred_stat[i] = lt_pred_stat[i + frame_len];
204 lt_pred_stat[frame_len + i] = real_to_int16(time[i]);
205 lt_pred_stat[(frame_len * 2) + i] = real_to_int16(overlap[i]);
206 #if 0 /* set to zero once upon initialisation */
207 lt_pred_stat[(frame_len * 3) + i] = 0;