dd145ca8756a0e07987f54be4f5d85afe4217be3
[libav.git] / libavcodec / lpc.c
1 /**
2 * LPC utility code
3 * Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com>
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22 #include "libavutil/lls.h"
23 #include "dsputil.h"
24
25 #define LPC_USE_DOUBLE
26 #include "lpc.h"
27
28
29 /**
30 * Quantize LPC coefficients
31 */
32 static void quantize_lpc_coefs(double *lpc_in, int order, int precision,
33 int32_t *lpc_out, int *shift, int max_shift, int zero_shift)
34 {
35 int i;
36 double cmax, error;
37 int32_t qmax;
38 int sh;
39
40 /* define maximum levels */
41 qmax = (1 << (precision - 1)) - 1;
42
43 /* find maximum coefficient value */
44 cmax = 0.0;
45 for(i=0; i<order; i++) {
46 cmax= FFMAX(cmax, fabs(lpc_in[i]));
47 }
48
49 /* if maximum value quantizes to zero, return all zeros */
50 if(cmax * (1 << max_shift) < 1.0) {
51 *shift = zero_shift;
52 memset(lpc_out, 0, sizeof(int32_t) * order);
53 return;
54 }
55
56 /* calculate level shift which scales max coeff to available bits */
57 sh = max_shift;
58 while((cmax * (1 << sh) > qmax) && (sh > 0)) {
59 sh--;
60 }
61
62 /* since negative shift values are unsupported in decoder, scale down
63 coefficients instead */
64 if(sh == 0 && cmax > qmax) {
65 double scale = ((double)qmax) / cmax;
66 for(i=0; i<order; i++) {
67 lpc_in[i] *= scale;
68 }
69 }
70
71 /* output quantized coefficients and level shift */
72 error=0;
73 for(i=0; i<order; i++) {
74 error -= lpc_in[i] * (1 << sh);
75 lpc_out[i] = av_clip(lrintf(error), -qmax, qmax);
76 error -= lpc_out[i];
77 }
78 *shift = sh;
79 }
80
81 static int estimate_best_order(double *ref, int min_order, int max_order)
82 {
83 int i, est;
84
85 est = min_order;
86 for(i=max_order-1; i>=min_order-1; i--) {
87 if(ref[i] > 0.10) {
88 est = i+1;
89 break;
90 }
91 }
92 return est;
93 }
94
95 /**
96 * Calculate LPC coefficients for multiple orders
97 */
98 int ff_lpc_calc_coefs(DSPContext *s,
99 const int32_t *samples, int blocksize, int min_order,
100 int max_order, int precision,
101 int32_t coefs[][MAX_LPC_ORDER], int *shift, int use_lpc,
102 int omethod, int max_shift, int zero_shift)
103 {
104 double autoc[MAX_LPC_ORDER+1];
105 double ref[MAX_LPC_ORDER];
106 double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER];
107 int i, j, pass;
108 int opt_order;
109
110 assert(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER);
111
112 if(use_lpc == 1){
113 s->flac_compute_autocorr(samples, blocksize, max_order, autoc);
114
115 compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1);
116
117 for(i=0; i<max_order; i++)
118 ref[i] = fabs(lpc[i][i]);
119 }else{
120 LLSModel m[2];
121 double var[MAX_LPC_ORDER+1], weight;
122
123 for(pass=0; pass<use_lpc-1; pass++){
124 av_init_lls(&m[pass&1], max_order);
125
126 weight=0;
127 for(i=max_order; i<blocksize; i++){
128 for(j=0; j<=max_order; j++)
129 var[j]= samples[i-j];
130
131 if(pass){
132 double eval, inv, rinv;
133 eval= av_evaluate_lls(&m[(pass-1)&1], var+1, max_order-1);
134 eval= (512>>pass) + fabs(eval - var[0]);
135 inv = 1/eval;
136 rinv = sqrt(inv);
137 for(j=0; j<=max_order; j++)
138 var[j] *= rinv;
139 weight += inv;
140 }else
141 weight++;
142
143 av_update_lls(&m[pass&1], var, 1.0);
144 }
145 av_solve_lls(&m[pass&1], 0.001, 0);
146 }
147
148 for(i=0; i<max_order; i++){
149 for(j=0; j<max_order; j++)
150 lpc[i][j]=-m[(pass-1)&1].coeff[i][j];
151 ref[i]= sqrt(m[(pass-1)&1].variance[i] / weight) * (blocksize - max_order) / 4000;
152 }
153 for(i=max_order-1; i>0; i--)
154 ref[i] = ref[i-1] - ref[i];
155 }
156 opt_order = max_order;
157
158 if(omethod == ORDER_METHOD_EST) {
159 opt_order = estimate_best_order(ref, min_order, max_order);
160 i = opt_order-1;
161 quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift);
162 } else {
163 for(i=min_order-1; i<max_order; i++) {
164 quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift);
165 }
166 }
167
168 return opt_order;
169 }