FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavcodec/lpc.c
Date: 2025-10-29 00:48:36
Exec Total Coverage
Lines: 156 171 91.2%
Functions: 9 10 90.0%
Branches: 88 106 83.0%
Line Branch Exec Source
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 #include "libavutil/mem.h"
25 #include "libavutil/mem_internal.h"
26
27 #define LPC_USE_DOUBLE
28 #include "lpc.h"
29 #include "lpc_functions.h"
30 #include "libavutil/avassert.h"
31
32 /**
33 * Schur recursion.
34 * Produces reflection coefficients from autocorrelation data.
35 */
36 2145 static inline void compute_ref_coefs(const LPC_TYPE *autoc, int max_order,
37 LPC_TYPE *ref, LPC_TYPE *error)
38 {
39 LPC_TYPE err;
40 LPC_TYPE gen0[MAX_LPC_ORDER], gen1[MAX_LPC_ORDER];
41
42
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 26405 for (int i = 0; i < max_order; i++)
43 24260 gen0[i] = gen1[i] = autoc[i + 1];
44
45 2145 err = autoc[0];
46
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 2145 ref[0] = -gen1[0] / ((LPC_USE_FIXED || err) ? err : 1);
47 2145 err += gen1[0] * ref[0];
48
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 2145 if (error)
49 2145 error[0] = err;
50
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 24260 for (int i = 1; i < max_order; i++) {
51
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 150365 for (int j = 0; j < max_order - i; j++) {
52 128250 gen1[j] = gen1[j + 1] + ref[i - 1] * gen0[j];
53 128250 gen0[j] = gen1[j + 1] * ref[i - 1] + gen0[j];
54 }
55
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 22115 ref[i] = -gen1[0] / ((LPC_USE_FIXED || err) ? err : 1);
56 22115 err += gen1[0] * ref[i];
57
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 22115 if (error)
58 22115 error[i] = err;
59 }
60 2145 }
61
62
63 /**
64 * Apply Welch window function to audio block
65 */
66 4529 static void lpc_apply_welch_window_c(const int32_t *data, ptrdiff_t len,
67 double *w_data)
68 {
69 int i, n2;
70 double w;
71 double c;
72
73
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 4529 if (len == 1) {
74 ✗ w_data[0] = 0.0;
75 ✗ return;
76 }
77
78 4529 n2 = (len >> 1);
79 4529 c = 2.0 / (len - 1.0);
80
81
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 4529 if (len & 1) {
82
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 9659 for(i=0; i<n2; i++) {
83 9652 w = c - i - 1.0;
84 9652 w = 1.0 - (w * w);
85 9652 w_data[i] = data[i] * w;
86 9652 w_data[len-1-i] = data[len-1-i] * w;
87 }
88 7 w_data[n2] = 0.0;
89 7 return;
90 }
91
92 4522 w_data+=n2;
93 4522 data+=n2;
94
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 10478902 for(i=0; i<n2; i++) {
95 10474380 w = c - n2 + i;
96 10474380 w = 1.0 - (w * w);
97 10474380 w_data[-i-1] = data[-i-1] * w;
98 10474380 w_data[+i ] = data[+i ] * w;
99 }
100 }
101
102 /**
103 * Calculate autocorrelation data from audio samples
104 * A Welch window function is applied before calculation.
105 */
106 6674 static void lpc_compute_autocorr_c(const double *data, ptrdiff_t len, int lag,
107 double *autoc)
108 {
109 int i, j;
110
111
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 49287 for(j=0; j<lag; j+=2){
112 42613 double sum0 = 1.0, sum1 = 1.0;
113
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 145217245 for(i=j; i<len; i++){
114 145174632 sum0 += data[i] * data[i-j];
115 145174632 sum1 += data[i] * data[i-j-1];
116 }
117 42613 autoc[j ] = sum0;
118 42613 autoc[j+1] = sum1;
119 }
120
121
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 6674 if(j==lag){
122 6378 double sum = 1.0;
123
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 22062230 for(i=j-1; i<len; i++){
124 22055852 sum += data[i] * data[i-j];
125 }
126 6378 autoc[j] = sum;
127 }
128 6674 }
129
130 /**
131 * Quantize LPC coefficients
132 */
133 12319 static void quantize_lpc_coefs(double *lpc_in, int order, int precision,
134 int32_t *lpc_out, int *shift, int min_shift,
135 int max_shift, int zero_shift)
136 {
137 int i;
138 double cmax, error;
139 int32_t qmax;
140 int sh;
141
142 /* define maximum levels */
143 12319 qmax = (1 << (precision - 1)) - 1;
144
145 /* find maximum coefficient value */
146 12319 cmax = 0.0;
147
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 74604 for(i=0; i<order; i++) {
148
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 62285 cmax= FFMAX(cmax, fabs(lpc_in[i]));
149 }
150
151 /* if maximum value quantizes to zero, return all zeros */
152
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 12319 if(cmax * (1 << max_shift) < 1.0) {
153 ✗ *shift = zero_shift;
154 ✗ memset(lpc_out, 0, sizeof(int32_t) * order);
155 ✗ return;
156 }
157
158 /* calculate level shift which scales max coeff to available bits */
159 12319 sh = max_shift;
160
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 34228 while((cmax * (1 << sh) > qmax) && (sh > min_shift)) {
161 21909 sh--;
162 }
163
164 /* since negative shift values are unsupported in decoder, scale down
165 coefficients instead */
166
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 12319 if(sh == 0 && cmax > qmax) {
167 ✗ double scale = ((double)qmax) / cmax;
168 ✗ for(i=0; i<order; i++) {
169 ✗ lpc_in[i] *= scale;
170 }
171 }
172
173 /* output quantized coefficients and level shift */
174 12319 error=0;
175
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 74604 for(i=0; i<order; i++) {
176 62285 error -= lpc_in[i] * (1 << sh);
177 62285 lpc_out[i] = av_clip(lrintf(error), -qmax, qmax);
178 62285 error -= lpc_out[i];
179 }
180 12319 *shift = sh;
181 }
182
183 9487 static int estimate_best_order(double *ref, int min_order, int max_order)
184 {
185 int i, est;
186
187 9487 est = min_order;
188
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 65162 for(i=max_order-1; i>=min_order-1; i--) {
189
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 64988 if(ref[i] > 0.10) {
190 9313 est = i+1;
191 9313 break;
192 }
193 }
194 9487 return est;
195 }
196
197 ✗ int ff_lpc_calc_ref_coefs(LPCContext *s,
198 const int32_t *samples, int order, double *ref)
199 {
200 double autoc[MAX_LPC_ORDER + 1];
201
202 ✗ s->lpc_apply_welch_window(samples, s->blocksize, s->windowed_samples);
203 ✗ s->lpc_compute_autocorr(s->windowed_samples, s->blocksize, order, autoc);
204 ✗ compute_ref_coefs(autoc, order, ref, NULL);
205
206 ✗ return order;
207 }
208
209 2145 double ff_lpc_calc_ref_coefs_f(LPCContext *s, const float *samples, int len,
210 int order, double *ref)
211 {
212 int i;
213 2145 double signal = 0.0f, avg_err = 0.0f;
214 2145 double autoc[MAX_LPC_ORDER+1] = {0}, error[MAX_LPC_ORDER+1] = {0};
215 2145 const double a = 0.5f, b = 1.0f - a;
216
217 /* Apply windowing */
218
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 602118 for (i = 0; i <= len / 2; i++) {
219 599973 double weight = a - b*cos((2*M_PI*i)/(len - 1));
220 599973 s->windowed_samples[i] = weight*samples[i];
221 599973 s->windowed_samples[len-1-i] = weight*samples[len-1-i];
222 }
223
224 2145 s->lpc_compute_autocorr(s->windowed_samples, len, order, autoc);
225 2145 signal = autoc[0];
226 2145 compute_ref_coefs(autoc, order, ref, error);
227
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 26405 for (i = 0; i < order; i++)
228 24260 avg_err = (avg_err + error[i])/2.0f;
229
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 2145 return avg_err ? signal/avg_err : NAN;
230 }
231
232 /**
233 * Calculate LPC coefficients for multiple orders
234 *
235 * @param lpc_type LPC method for determining coefficients,
236 * see #FFLPCType for details
237 */
238 9723 int ff_lpc_calc_coefs(LPCContext *s,
239 const int32_t *samples, int blocksize, int min_order,
240 int max_order, int precision,
241 int32_t coefs[][MAX_LPC_ORDER], int *shift,
242 enum FFLPCType lpc_type, int lpc_passes,
243 int omethod, int min_shift, int max_shift, int zero_shift)
244 {
245 double autoc[MAX_LPC_ORDER+1];
246 9723 double ref[MAX_LPC_ORDER] = { 0 };
247 double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER];
248 9723 int i, j, pass = 0;
249 int opt_order;
250
251 av_assert2(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER &&
252 lpc_type > FF_LPC_TYPE_FIXED);
253
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 9723 av_assert0(lpc_type == FF_LPC_TYPE_CHOLESKY || lpc_type == FF_LPC_TYPE_LEVINSON);
254
255 /* reinit LPC context if parameters have changed */
256
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 9723 if (blocksize != s->blocksize || max_order != s->max_order ||
257
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 9655 lpc_type != s->lpc_type) {
258 69 ff_lpc_end(s);
259 69 ff_lpc_init(s, blocksize, max_order, lpc_type);
260 }
261
262
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 9723 if(lpc_passes <= 0)
263 2589 lpc_passes = 2;
264
265
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 9723 if (lpc_type == FF_LPC_TYPE_LEVINSON || (lpc_type == FF_LPC_TYPE_CHOLESKY && lpc_passes > 1)) {
266 9723 s->lpc_apply_welch_window(samples, blocksize, s->windowed_samples);
267
268 9723 s->lpc_compute_autocorr(s->windowed_samples, blocksize, max_order, autoc);
269
270 9723 compute_lpc_coefs(autoc, 0, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1, NULL);
271
272
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 111933 for(i=0; i<max_order; i++)
273 102210 ref[i] = fabs(lpc[i][i]);
274
275 9723 pass++;
276 }
277
278
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 9723 if (lpc_type == FF_LPC_TYPE_CHOLESKY) {
279 182 LLSModel *m = s->lls_models;
280 182 LOCAL_ALIGNED(32, double, var, [FFALIGN(MAX_LPC_ORDER+1,4)]);
281 182 double av_uninit(weight);
282 182 memset(var, 0, FFALIGN(MAX_LPC_ORDER+1,4)*sizeof(*var));
283
284 /* Avoids initializing with an unused value when lpc_passes == 1 */
285
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 182 if (lpc_passes > 1)
286
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 1638 for(j=0; j<max_order; j++)
287 1456 m[0].coeff[max_order-1][j] = -lpc[max_order-1][j];
288
289
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 364 for(; pass<lpc_passes; pass++){
290 182 avpriv_init_lls(&m[pass&1], max_order);
291
292 182 weight=0;
293
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 836626 for(i=max_order; i<blocksize; i++){
294
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 8364440 for(j=0; j<=max_order; j++)
295 7527996 var[j]= samples[i-j];
296
297
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 836444 if(pass){
298 double eval, inv, rinv;
299 836444 eval= m[pass&1].evaluate_lls(&m[(pass-1)&1], var+1, max_order-1);
300 836444 eval= (512>>pass) + fabs(eval - var[0]);
301 836444 inv = 1/eval;
302 836444 rinv = sqrt(inv);
303
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 8364440 for(j=0; j<=max_order; j++)
304 7527996 var[j] *= rinv;
305 836444 weight += inv;
306 }else
307 ✗ weight++;
308
309 836444 m[pass&1].update_lls(&m[pass&1], var);
310 }
311 182 avpriv_solve_lls(&m[pass&1], 0.001, 0);
312 }
313
314
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 1638 for(i=0; i<max_order; i++){
315
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 13104 for(j=0; j<max_order; j++)
316 11648 lpc[i][j]=-m[(pass-1)&1].coeff[i][j];
317 1456 ref[i]= sqrt(m[(pass-1)&1].variance[i] / weight) * (blocksize - max_order) / 4000;
318 }
319
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 1456 for(i=max_order-1; i>0; i--)
320 1274 ref[i] = ref[i-1] - ref[i];
321 }
322
323 9723 opt_order = max_order;
324
325
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 9723 if(omethod == ORDER_METHOD_EST) {
326 9487 opt_order = estimate_best_order(ref, min_order, max_order);
327 9487 i = opt_order-1;
328 9487 quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i],
329 min_shift, max_shift, zero_shift);
330 } else {
331
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 3068 for(i=min_order-1; i<max_order; i++) {
332 2832 quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i],
333 min_shift, max_shift, zero_shift);
334 }
335 }
336
337 9723 return opt_order;
338 }
339
340 214 av_cold int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
341 enum FFLPCType lpc_type)
342 {
343 214 s->blocksize = blocksize;
344 214 s->max_order = max_order;
345 214 s->lpc_type = lpc_type;
346
347 214 s->windowed_buffer = av_mallocz((blocksize + 2 + FFALIGN(max_order, 4)) *
348 sizeof(*s->windowed_samples));
349
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 214 if (!s->windowed_buffer)
350 ✗ return AVERROR(ENOMEM);
351 214 s->windowed_samples = s->windowed_buffer + FFALIGN(max_order, 4);
352
353 214 s->lpc_apply_welch_window = lpc_apply_welch_window_c;
354 214 s->lpc_compute_autocorr = lpc_compute_autocorr_c;
355
356 #if ARCH_RISCV
357 ff_lpc_init_riscv(s);
358 #elif ARCH_X86
359 214 ff_lpc_init_x86(s);
360 #endif
361
362 214 return 0;
363 }
364
365 214 av_cold void ff_lpc_end(LPCContext *s)
366 {
367 214 av_freep(&s->windowed_buffer);
368 214 }
369