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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/common.h" | |
23 | #include "libavutil/lls.h" | |
24 | ||
25 | #define LPC_USE_DOUBLE | |
26 | #include "lpc.h" | |
27 | #include "libavutil/avassert.h" | |
28 | ||
29 | ||
30 | /** | |
31 | * Apply Welch window function to audio block | |
32 | */ | |
33 | static void lpc_apply_welch_window_c(const int32_t *data, int len, | |
34 | double *w_data) | |
35 | { | |
36 | int i, n2; | |
37 | double w; | |
38 | double c; | |
39 | ||
40 | /* The optimization in commit fa4ed8c does not support odd len. | |
41 | * If someone wants odd len extend that change. */ | |
42 | av_assert2(!(len & 1)); | |
43 | ||
44 | n2 = (len >> 1); | |
45 | c = 2.0 / (len - 1.0); | |
46 | ||
47 | w_data+=n2; | |
48 | data+=n2; | |
49 | for(i=0; i<n2; i++) { | |
50 | w = c - n2 + i; | |
51 | w = 1.0 - (w * w); | |
52 | w_data[-i-1] = data[-i-1] * w; | |
53 | w_data[+i ] = data[+i ] * w; | |
54 | } | |
55 | } | |
56 | ||
57 | /** | |
58 | * Calculate autocorrelation data from audio samples | |
59 | * A Welch window function is applied before calculation. | |
60 | */ | |
61 | static void lpc_compute_autocorr_c(const double *data, int len, int lag, | |
62 | double *autoc) | |
63 | { | |
64 | int i, j; | |
65 | ||
66 | for(j=0; j<lag; j+=2){ | |
67 | double sum0 = 1.0, sum1 = 1.0; | |
68 | for(i=j; i<len; i++){ | |
69 | sum0 += data[i] * data[i-j]; | |
70 | sum1 += data[i] * data[i-j-1]; | |
71 | } | |
72 | autoc[j ] = sum0; | |
73 | autoc[j+1] = sum1; | |
74 | } | |
75 | ||
76 | if(j==lag){ | |
77 | double sum = 1.0; | |
78 | for(i=j-1; i<len; i+=2){ | |
79 | sum += data[i ] * data[i-j ] | |
80 | + data[i+1] * data[i-j+1]; | |
81 | } | |
82 | autoc[j] = sum; | |
83 | } | |
84 | } | |
85 | ||
86 | /** | |
87 | * Quantize LPC coefficients | |
88 | */ | |
89 | static void quantize_lpc_coefs(double *lpc_in, int order, int precision, | |
90 | int32_t *lpc_out, int *shift, int max_shift, int zero_shift) | |
91 | { | |
92 | int i; | |
93 | double cmax, error; | |
94 | int32_t qmax; | |
95 | int sh; | |
96 | ||
97 | /* define maximum levels */ | |
98 | qmax = (1 << (precision - 1)) - 1; | |
99 | ||
100 | /* find maximum coefficient value */ | |
101 | cmax = 0.0; | |
102 | for(i=0; i<order; i++) { | |
103 | cmax= FFMAX(cmax, fabs(lpc_in[i])); | |
104 | } | |
105 | ||
106 | /* if maximum value quantizes to zero, return all zeros */ | |
107 | if(cmax * (1 << max_shift) < 1.0) { | |
108 | *shift = zero_shift; | |
109 | memset(lpc_out, 0, sizeof(int32_t) * order); | |
110 | return; | |
111 | } | |
112 | ||
113 | /* calculate level shift which scales max coeff to available bits */ | |
114 | sh = max_shift; | |
115 | while((cmax * (1 << sh) > qmax) && (sh > 0)) { | |
116 | sh--; | |
117 | } | |
118 | ||
119 | /* since negative shift values are unsupported in decoder, scale down | |
120 | coefficients instead */ | |
121 | if(sh == 0 && cmax > qmax) { | |
122 | double scale = ((double)qmax) / cmax; | |
123 | for(i=0; i<order; i++) { | |
124 | lpc_in[i] *= scale; | |
125 | } | |
126 | } | |
127 | ||
128 | /* output quantized coefficients and level shift */ | |
129 | error=0; | |
130 | for(i=0; i<order; i++) { | |
131 | error -= lpc_in[i] * (1 << sh); | |
132 | lpc_out[i] = av_clip(lrintf(error), -qmax, qmax); | |
133 | error -= lpc_out[i]; | |
134 | } | |
135 | *shift = sh; | |
136 | } | |
137 | ||
138 | static int estimate_best_order(double *ref, int min_order, int max_order) | |
139 | { | |
140 | int i, est; | |
141 | ||
142 | est = min_order; | |
143 | for(i=max_order-1; i>=min_order-1; i--) { | |
144 | if(ref[i] > 0.10) { | |
145 | est = i+1; | |
146 | break; | |
147 | } | |
148 | } | |
149 | return est; | |
150 | } | |
151 | ||
152 | int ff_lpc_calc_ref_coefs(LPCContext *s, | |
153 | const int32_t *samples, int order, double *ref) | |
154 | { | |
155 | double autoc[MAX_LPC_ORDER + 1]; | |
156 | ||
157 | s->lpc_apply_welch_window(samples, s->blocksize, s->windowed_samples); | |
158 | s->lpc_compute_autocorr(s->windowed_samples, s->blocksize, order, autoc); | |
159 | compute_ref_coefs(autoc, order, ref, NULL); | |
160 | ||
161 | return order; | |
162 | } | |
163 | ||
164 | /** | |
165 | * Calculate LPC coefficients for multiple orders | |
166 | * | |
167 | * @param lpc_type LPC method for determining coefficients, | |
168 | * see #FFLPCType for details | |
169 | */ | |
170 | int ff_lpc_calc_coefs(LPCContext *s, | |
171 | const int32_t *samples, int blocksize, int min_order, | |
172 | int max_order, int precision, | |
173 | int32_t coefs[][MAX_LPC_ORDER], int *shift, | |
174 | enum FFLPCType lpc_type, int lpc_passes, | |
175 | int omethod, int max_shift, int zero_shift) | |
176 | { | |
177 | double autoc[MAX_LPC_ORDER+1]; | |
f6fa7814 | 178 | double ref[MAX_LPC_ORDER] = { 0 }; |
2ba45a60 DM |
179 | double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER]; |
180 | int i, j, pass = 0; | |
181 | int opt_order; | |
182 | ||
183 | av_assert2(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER && | |
184 | lpc_type > FF_LPC_TYPE_FIXED); | |
185 | av_assert0(lpc_type == FF_LPC_TYPE_CHOLESKY || lpc_type == FF_LPC_TYPE_LEVINSON); | |
186 | ||
187 | /* reinit LPC context if parameters have changed */ | |
188 | if (blocksize != s->blocksize || max_order != s->max_order || | |
189 | lpc_type != s->lpc_type) { | |
190 | ff_lpc_end(s); | |
191 | ff_lpc_init(s, blocksize, max_order, lpc_type); | |
192 | } | |
193 | ||
194 | if(lpc_passes <= 0) | |
195 | lpc_passes = 2; | |
196 | ||
197 | if (lpc_type == FF_LPC_TYPE_LEVINSON || (lpc_type == FF_LPC_TYPE_CHOLESKY && lpc_passes > 1)) { | |
198 | s->lpc_apply_welch_window(samples, blocksize, s->windowed_samples); | |
199 | ||
200 | s->lpc_compute_autocorr(s->windowed_samples, blocksize, max_order, autoc); | |
201 | ||
202 | compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1); | |
203 | ||
204 | for(i=0; i<max_order; i++) | |
205 | ref[i] = fabs(lpc[i][i]); | |
206 | ||
207 | pass++; | |
208 | } | |
209 | ||
210 | if (lpc_type == FF_LPC_TYPE_CHOLESKY) { | |
f6fa7814 | 211 | LLSModel *m = s->lls_models; |
2ba45a60 DM |
212 | LOCAL_ALIGNED(32, double, var, [FFALIGN(MAX_LPC_ORDER+1,4)]); |
213 | double av_uninit(weight); | |
214 | memset(var, 0, FFALIGN(MAX_LPC_ORDER+1,4)*sizeof(*var)); | |
215 | ||
216 | for(j=0; j<max_order; j++) | |
217 | m[0].coeff[max_order-1][j] = -lpc[max_order-1][j]; | |
218 | ||
219 | for(; pass<lpc_passes; pass++){ | |
220 | avpriv_init_lls(&m[pass&1], max_order); | |
221 | ||
222 | weight=0; | |
223 | for(i=max_order; i<blocksize; i++){ | |
224 | for(j=0; j<=max_order; j++) | |
225 | var[j]= samples[i-j]; | |
226 | ||
227 | if(pass){ | |
228 | double eval, inv, rinv; | |
229 | eval= m[pass&1].evaluate_lls(&m[(pass-1)&1], var+1, max_order-1); | |
230 | eval= (512>>pass) + fabs(eval - var[0]); | |
231 | inv = 1/eval; | |
232 | rinv = sqrt(inv); | |
233 | for(j=0; j<=max_order; j++) | |
234 | var[j] *= rinv; | |
235 | weight += inv; | |
236 | }else | |
237 | weight++; | |
238 | ||
239 | m[pass&1].update_lls(&m[pass&1], var); | |
240 | } | |
241 | avpriv_solve_lls(&m[pass&1], 0.001, 0); | |
242 | } | |
243 | ||
244 | for(i=0; i<max_order; i++){ | |
245 | for(j=0; j<max_order; j++) | |
246 | lpc[i][j]=-m[(pass-1)&1].coeff[i][j]; | |
247 | ref[i]= sqrt(m[(pass-1)&1].variance[i] / weight) * (blocksize - max_order) / 4000; | |
248 | } | |
249 | for(i=max_order-1; i>0; i--) | |
250 | ref[i] = ref[i-1] - ref[i]; | |
251 | } | |
252 | ||
253 | opt_order = max_order; | |
254 | ||
255 | if(omethod == ORDER_METHOD_EST) { | |
256 | opt_order = estimate_best_order(ref, min_order, max_order); | |
257 | i = opt_order-1; | |
258 | quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift); | |
259 | } else { | |
260 | for(i=min_order-1; i<max_order; i++) { | |
261 | quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift); | |
262 | } | |
263 | } | |
264 | ||
265 | return opt_order; | |
266 | } | |
267 | ||
268 | av_cold int ff_lpc_init(LPCContext *s, int blocksize, int max_order, | |
269 | enum FFLPCType lpc_type) | |
270 | { | |
271 | s->blocksize = blocksize; | |
272 | s->max_order = max_order; | |
273 | s->lpc_type = lpc_type; | |
274 | ||
275 | s->windowed_buffer = av_mallocz((blocksize + 2 + FFALIGN(max_order, 4)) * | |
276 | sizeof(*s->windowed_samples)); | |
277 | if (!s->windowed_buffer) | |
278 | return AVERROR(ENOMEM); | |
279 | s->windowed_samples = s->windowed_buffer + FFALIGN(max_order, 4); | |
280 | ||
281 | s->lpc_apply_welch_window = lpc_apply_welch_window_c; | |
282 | s->lpc_compute_autocorr = lpc_compute_autocorr_c; | |
283 | ||
284 | if (ARCH_X86) | |
285 | ff_lpc_init_x86(s); | |
286 | ||
287 | return 0; | |
288 | } | |
289 | ||
290 | av_cold void ff_lpc_end(LPCContext *s) | |
291 | { | |
292 | av_freep(&s->windowed_buffer); | |
293 | } |