1 /*
2 * Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 #include "lpc_analysis.h"
12 #include "settings.h"
13 #include "codec.h"
14 #include "entropy_coding.h"
15
16 #include <math.h>
17 #include <string.h>
18
19 #define LEVINSON_EPS 1.0e-10
20
21
22 /* window */
23 /* Matlab generation code:
24 * t = (1:256)/257; r = 1-(1-t).^.45; w = sin(r*pi).^3; w = w/sum(w); plot((1:256)/8, w); grid;
25 * for k=1:16, fprintf(1, '%.8f, ', w(k*16 + (-15:0))); fprintf(1, '\n'); end
26 */
27 static const double kLpcCorrWindow[WINLEN] = {
28 0.00000000, 0.00000001, 0.00000004, 0.00000010, 0.00000020,
29 0.00000035, 0.00000055, 0.00000083, 0.00000118, 0.00000163,
30 0.00000218, 0.00000283, 0.00000361, 0.00000453, 0.00000558, 0.00000679,
31 0.00000817, 0.00000973, 0.00001147, 0.00001342, 0.00001558,
32 0.00001796, 0.00002058, 0.00002344, 0.00002657, 0.00002997,
33 0.00003365, 0.00003762, 0.00004190, 0.00004651, 0.00005144, 0.00005673,
34 0.00006236, 0.00006837, 0.00007476, 0.00008155, 0.00008875,
35 0.00009636, 0.00010441, 0.00011290, 0.00012186, 0.00013128,
36 0.00014119, 0.00015160, 0.00016252, 0.00017396, 0.00018594, 0.00019846,
37 0.00021155, 0.00022521, 0.00023946, 0.00025432, 0.00026978,
38 0.00028587, 0.00030260, 0.00031998, 0.00033802, 0.00035674,
39 0.00037615, 0.00039626, 0.00041708, 0.00043863, 0.00046092, 0.00048396,
40 0.00050775, 0.00053233, 0.00055768, 0.00058384, 0.00061080,
41 0.00063858, 0.00066720, 0.00069665, 0.00072696, 0.00075813,
42 0.00079017, 0.00082310, 0.00085692, 0.00089164, 0.00092728, 0.00096384,
43 0.00100133, 0.00103976, 0.00107914, 0.00111947, 0.00116077,
44 0.00120304, 0.00124630, 0.00129053, 0.00133577, 0.00138200,
45 0.00142924, 0.00147749, 0.00152676, 0.00157705, 0.00162836, 0.00168070,
46 0.00173408, 0.00178850, 0.00184395, 0.00190045, 0.00195799,
47 0.00201658, 0.00207621, 0.00213688, 0.00219860, 0.00226137,
48 0.00232518, 0.00239003, 0.00245591, 0.00252284, 0.00259079, 0.00265977,
49 0.00272977, 0.00280078, 0.00287280, 0.00294582, 0.00301984,
50 0.00309484, 0.00317081, 0.00324774, 0.00332563, 0.00340446,
51 0.00348421, 0.00356488, 0.00364644, 0.00372889, 0.00381220, 0.00389636,
52 0.00398135, 0.00406715, 0.00415374, 0.00424109, 0.00432920,
53 0.00441802, 0.00450754, 0.00459773, 0.00468857, 0.00478001,
54 0.00487205, 0.00496464, 0.00505775, 0.00515136, 0.00524542, 0.00533990,
55 0.00543476, 0.00552997, 0.00562548, 0.00572125, 0.00581725,
56 0.00591342, 0.00600973, 0.00610612, 0.00620254, 0.00629895,
57 0.00639530, 0.00649153, 0.00658758, 0.00668341, 0.00677894, 0.00687413,
58 0.00696891, 0.00706322, 0.00715699, 0.00725016, 0.00734266,
59 0.00743441, 0.00752535, 0.00761540, 0.00770449, 0.00779254,
60 0.00787947, 0.00796519, 0.00804963, 0.00813270, 0.00821431, 0.00829437,
61 0.00837280, 0.00844949, 0.00852436, 0.00859730, 0.00866822,
62 0.00873701, 0.00880358, 0.00886781, 0.00892960, 0.00898884,
63 0.00904542, 0.00909923, 0.00915014, 0.00919805, 0.00924283, 0.00928436,
64 0.00932252, 0.00935718, 0.00938821, 0.00941550, 0.00943890,
65 0.00945828, 0.00947351, 0.00948446, 0.00949098, 0.00949294,
66 0.00949020, 0.00948262, 0.00947005, 0.00945235, 0.00942938, 0.00940099,
67 0.00936704, 0.00932738, 0.00928186, 0.00923034, 0.00917268,
68 0.00910872, 0.00903832, 0.00896134, 0.00887763, 0.00878706,
69 0.00868949, 0.00858478, 0.00847280, 0.00835343, 0.00822653, 0.00809199,
70 0.00794970, 0.00779956, 0.00764145, 0.00747530, 0.00730103,
71 0.00711857, 0.00692787, 0.00672888, 0.00652158, 0.00630597,
72 0.00608208, 0.00584994, 0.00560962, 0.00536124, 0.00510493, 0.00484089,
73 0.00456935, 0.00429062, 0.00400505, 0.00371310, 0.00341532,
74 0.00311238, 0.00280511, 0.00249452, 0.00218184, 0.00186864,
75 0.00155690, 0.00124918, 0.00094895, 0.00066112, 0.00039320, 0.00015881
76 };
77
WebRtcIsac_LevDurb(double * a,double * k,double * r,size_t order)78 double WebRtcIsac_LevDurb(double *a, double *k, double *r, size_t order)
79 {
80
81 double sum, alpha;
82 size_t m, m_h, i;
83 alpha = 0; //warning -DH
84 a[0] = 1.0;
85 if (r[0] < LEVINSON_EPS) { /* if r[0] <= 0, set LPC coeff. to zero */
86 for (i = 0; i < order; i++) {
87 k[i] = 0;
88 a[i+1] = 0;
89 }
90 } else {
91 a[1] = k[0] = -r[1]/r[0];
92 alpha = r[0] + r[1] * k[0];
93 for (m = 1; m < order; m++){
94 sum = r[m + 1];
95 for (i = 0; i < m; i++){
96 sum += a[i+1] * r[m - i];
97 }
98 k[m] = -sum / alpha;
99 alpha += k[m] * sum;
100 m_h = (m + 1) >> 1;
101 for (i = 0; i < m_h; i++){
102 sum = a[i+1] + k[m] * a[m - i];
103 a[m - i] += k[m] * a[i+1];
104 a[i+1] = sum;
105 }
106 a[m+1] = k[m];
107 }
108 }
109 return alpha;
110 }
111
112
113 //was static before, but didn't work with MEX file
WebRtcIsac_GetVars(const double * input,const int16_t * pitchGains_Q12,double * oldEnergy,double * varscale)114 void WebRtcIsac_GetVars(const double *input, const int16_t *pitchGains_Q12,
115 double *oldEnergy, double *varscale)
116 {
117 double nrg[4], chng, pg;
118 int k;
119
120 double pitchGains[4]={0,0,0,0};;
121
122 /* Calculate energies of first and second frame halfs */
123 nrg[0] = 0.0001;
124 for (k = QLOOKAHEAD/2; k < (FRAMESAMPLES_QUARTER + QLOOKAHEAD) / 2; k++) {
125 nrg[0] += input[k]*input[k];
126 }
127 nrg[1] = 0.0001;
128 for ( ; k < (FRAMESAMPLES_HALF + QLOOKAHEAD) / 2; k++) {
129 nrg[1] += input[k]*input[k];
130 }
131 nrg[2] = 0.0001;
132 for ( ; k < (FRAMESAMPLES*3/4 + QLOOKAHEAD) / 2; k++) {
133 nrg[2] += input[k]*input[k];
134 }
135 nrg[3] = 0.0001;
136 for ( ; k < (FRAMESAMPLES + QLOOKAHEAD) / 2; k++) {
137 nrg[3] += input[k]*input[k];
138 }
139
140 /* Calculate average level change */
141 chng = 0.25 * (fabs(10.0 * log10(nrg[3] / nrg[2])) +
142 fabs(10.0 * log10(nrg[2] / nrg[1])) +
143 fabs(10.0 * log10(nrg[1] / nrg[0])) +
144 fabs(10.0 * log10(nrg[0] / *oldEnergy)));
145
146
147 /* Find average pitch gain */
148 pg = 0.0;
149 for (k=0; k<4; k++)
150 {
151 pitchGains[k] = ((float)pitchGains_Q12[k])/4096;
152 pg += pitchGains[k];
153 }
154 pg *= 0.25;
155
156 /* If pitch gain is low and energy constant - increase noise level*/
157 /* Matlab code:
158 pg = 0:.01:.45; plot(pg, 0.0 + 1.0 * exp( -1.0 * exp(-200.0 * pg.*pg.*pg) / (1.0 + 0.4 * 0) ))
159 */
160 *varscale = 0.0 + 1.0 * exp( -1.4 * exp(-200.0 * pg*pg*pg) / (1.0 + 0.4 * chng) );
161
162 *oldEnergy = nrg[3];
163 }
164
165 void
WebRtcIsac_GetVarsUB(const double * input,double * oldEnergy,double * varscale)166 WebRtcIsac_GetVarsUB(
167 const double* input,
168 double* oldEnergy,
169 double* varscale)
170 {
171 double nrg[4], chng;
172 int k;
173
174 /* Calculate energies of first and second frame halfs */
175 nrg[0] = 0.0001;
176 for (k = 0; k < (FRAMESAMPLES_QUARTER) / 2; k++) {
177 nrg[0] += input[k]*input[k];
178 }
179 nrg[1] = 0.0001;
180 for ( ; k < (FRAMESAMPLES_HALF) / 2; k++) {
181 nrg[1] += input[k]*input[k];
182 }
183 nrg[2] = 0.0001;
184 for ( ; k < (FRAMESAMPLES*3/4) / 2; k++) {
185 nrg[2] += input[k]*input[k];
186 }
187 nrg[3] = 0.0001;
188 for ( ; k < (FRAMESAMPLES) / 2; k++) {
189 nrg[3] += input[k]*input[k];
190 }
191
192 /* Calculate average level change */
193 chng = 0.25 * (fabs(10.0 * log10(nrg[3] / nrg[2])) +
194 fabs(10.0 * log10(nrg[2] / nrg[1])) +
195 fabs(10.0 * log10(nrg[1] / nrg[0])) +
196 fabs(10.0 * log10(nrg[0] / *oldEnergy)));
197
198
199 /* If pitch gain is low and energy constant - increase noise level*/
200 /* Matlab code:
201 pg = 0:.01:.45; plot(pg, 0.0 + 1.0 * exp( -1.0 * exp(-200.0 * pg.*pg.*pg) / (1.0 + 0.4 * 0) ))
202 */
203 *varscale = exp( -1.4 / (1.0 + 0.4 * chng) );
204
205 *oldEnergy = nrg[3];
206 }
207
WebRtcIsac_GetLpcCoefLb(double * inLo,double * inHi,MaskFiltstr * maskdata,double signal_noise_ratio,const int16_t * pitchGains_Q12,double * lo_coeff,double * hi_coeff)208 void WebRtcIsac_GetLpcCoefLb(double *inLo, double *inHi, MaskFiltstr *maskdata,
209 double signal_noise_ratio, const int16_t *pitchGains_Q12,
210 double *lo_coeff, double *hi_coeff)
211 {
212 int k, n, j, pos1, pos2;
213 double varscale;
214
215 double DataLo[WINLEN], DataHi[WINLEN];
216 double corrlo[ORDERLO+2], corrlo2[ORDERLO+1];
217 double corrhi[ORDERHI+1];
218 double k_veclo[ORDERLO], k_vechi[ORDERHI];
219
220 double a_LO[ORDERLO+1], a_HI[ORDERHI+1];
221 double tmp, res_nrg;
222
223 double FwdA, FwdB;
224
225 /* hearing threshold level in dB; higher value gives more noise */
226 const double HearThresOffset = -28.0;
227
228 /* bandwdith expansion factors for low- and high band */
229 const double gammaLo = 0.9;
230 const double gammaHi = 0.8;
231
232 /* less-noise-at-low-frequencies factor */
233 double aa;
234
235
236 /* convert from dB to signal level */
237 const double H_T_H = pow(10.0, 0.05 * HearThresOffset);
238 double S_N_R = pow(10.0, 0.05 * signal_noise_ratio) / 3.46; /* divide by sqrt(12) */
239
240 /* change quallevel depending on pitch gains and level fluctuations */
241 WebRtcIsac_GetVars(inLo, pitchGains_Q12, &(maskdata->OldEnergy), &varscale);
242
243 /* less-noise-at-low-frequencies factor */
244 aa = 0.35 * (0.5 + 0.5 * varscale);
245
246 /* replace data in buffer by new look-ahead data */
247 for (pos1 = 0; pos1 < QLOOKAHEAD; pos1++)
248 maskdata->DataBufferLo[pos1 + WINLEN - QLOOKAHEAD] = inLo[pos1];
249
250 for (k = 0; k < SUBFRAMES; k++) {
251
252 /* Update input buffer and multiply signal with window */
253 for (pos1 = 0; pos1 < WINLEN - UPDATE/2; pos1++) {
254 maskdata->DataBufferLo[pos1] = maskdata->DataBufferLo[pos1 + UPDATE/2];
255 maskdata->DataBufferHi[pos1] = maskdata->DataBufferHi[pos1 + UPDATE/2];
256 DataLo[pos1] = maskdata->DataBufferLo[pos1] * kLpcCorrWindow[pos1];
257 DataHi[pos1] = maskdata->DataBufferHi[pos1] * kLpcCorrWindow[pos1];
258 }
259 pos2 = k * UPDATE/2;
260 for (n = 0; n < UPDATE/2; n++, pos1++) {
261 maskdata->DataBufferLo[pos1] = inLo[QLOOKAHEAD + pos2];
262 maskdata->DataBufferHi[pos1] = inHi[pos2++];
263 DataLo[pos1] = maskdata->DataBufferLo[pos1] * kLpcCorrWindow[pos1];
264 DataHi[pos1] = maskdata->DataBufferHi[pos1] * kLpcCorrWindow[pos1];
265 }
266
267 /* Get correlation coefficients */
268 WebRtcIsac_AutoCorr(corrlo, DataLo, WINLEN, ORDERLO+1); /* computing autocorrelation */
269 WebRtcIsac_AutoCorr(corrhi, DataHi, WINLEN, ORDERHI);
270
271
272 /* less noise for lower frequencies, by filtering/scaling autocorrelation sequences */
273 corrlo2[0] = (1.0+aa*aa) * corrlo[0] - 2.0*aa * corrlo[1];
274 tmp = (1.0 + aa*aa);
275 for (n = 1; n <= ORDERLO; n++) {
276 corrlo2[n] = tmp * corrlo[n] - aa * (corrlo[n-1] + corrlo[n+1]);
277 }
278 tmp = (1.0+aa) * (1.0+aa);
279 for (n = 0; n <= ORDERHI; n++) {
280 corrhi[n] = tmp * corrhi[n];
281 }
282
283 /* add white noise floor */
284 corrlo2[0] += 1e-6;
285 corrhi[0] += 1e-6;
286
287
288 FwdA = 0.01;
289 FwdB = 0.01;
290
291 /* recursive filtering of correlation over subframes */
292 for (n = 0; n <= ORDERLO; n++) {
293 maskdata->CorrBufLo[n] = FwdA * maskdata->CorrBufLo[n] + corrlo2[n];
294 corrlo2[n] = ((1.0-FwdA)*FwdB) * maskdata->CorrBufLo[n] + (1.0-FwdB) * corrlo2[n];
295 }
296 for (n = 0; n <= ORDERHI; n++) {
297 maskdata->CorrBufHi[n] = FwdA * maskdata->CorrBufHi[n] + corrhi[n];
298 corrhi[n] = ((1.0-FwdA)*FwdB) * maskdata->CorrBufHi[n] + (1.0-FwdB) * corrhi[n];
299 }
300
301 /* compute prediction coefficients */
302 WebRtcIsac_LevDurb(a_LO, k_veclo, corrlo2, ORDERLO);
303 WebRtcIsac_LevDurb(a_HI, k_vechi, corrhi, ORDERHI);
304
305 /* bandwidth expansion */
306 tmp = gammaLo;
307 for (n = 1; n <= ORDERLO; n++) {
308 a_LO[n] *= tmp;
309 tmp *= gammaLo;
310 }
311
312 /* residual energy */
313 res_nrg = 0.0;
314 for (j = 0; j <= ORDERLO; j++) {
315 for (n = 0; n <= j; n++) {
316 res_nrg += a_LO[j] * corrlo2[j-n] * a_LO[n];
317 }
318 for (n = j+1; n <= ORDERLO; n++) {
319 res_nrg += a_LO[j] * corrlo2[n-j] * a_LO[n];
320 }
321 }
322
323 /* add hearing threshold and compute the gain */
324 *lo_coeff++ = S_N_R / (sqrt(res_nrg) / varscale + H_T_H);
325
326 /* copy coefficients to output array */
327 for (n = 1; n <= ORDERLO; n++) {
328 *lo_coeff++ = a_LO[n];
329 }
330
331
332 /* bandwidth expansion */
333 tmp = gammaHi;
334 for (n = 1; n <= ORDERHI; n++) {
335 a_HI[n] *= tmp;
336 tmp *= gammaHi;
337 }
338
339 /* residual energy */
340 res_nrg = 0.0;
341 for (j = 0; j <= ORDERHI; j++) {
342 for (n = 0; n <= j; n++) {
343 res_nrg += a_HI[j] * corrhi[j-n] * a_HI[n];
344 }
345 for (n = j+1; n <= ORDERHI; n++) {
346 res_nrg += a_HI[j] * corrhi[n-j] * a_HI[n];
347 }
348 }
349
350 /* add hearing threshold and compute of the gain */
351 *hi_coeff++ = S_N_R / (sqrt(res_nrg) / varscale + H_T_H);
352
353 /* copy coefficients to output array */
354 for (n = 1; n <= ORDERHI; n++) {
355 *hi_coeff++ = a_HI[n];
356 }
357 }
358 }
359
360
361
362 /******************************************************************************
363 * WebRtcIsac_GetLpcCoefUb()
364 *
365 * Compute LP coefficients and correlation coefficients. At 12 kHz LP
366 * coefficients of the first and the last sub-frame is computed. At 16 kHz
367 * LP coefficients of 4th, 8th and 12th sub-frames are computed. We always
368 * compute correlation coefficients of all sub-frames.
369 *
370 * Inputs:
371 * -inSignal : Input signal
372 * -maskdata : a structure keeping signal from previous frame.
373 * -bandwidth : specifies if the codec is in 0-16 kHz mode or
374 * 0-12 kHz mode.
375 *
376 * Outputs:
377 * -lpCoeff : pointer to a buffer where A-polynomials are
378 * written to (first coeff is 1 and it is not
379 * written)
380 * -corrMat : a matrix where correlation coefficients of each
381 * sub-frame are written to one row.
382 * -varscale : a scale used to compute LPC gains.
383 */
384 void
WebRtcIsac_GetLpcCoefUb(double * inSignal,MaskFiltstr * maskdata,double * lpCoeff,double corrMat[][UB_LPC_ORDER+1],double * varscale,int16_t bandwidth)385 WebRtcIsac_GetLpcCoefUb(
386 double* inSignal,
387 MaskFiltstr* maskdata,
388 double* lpCoeff,
389 double corrMat[][UB_LPC_ORDER + 1],
390 double* varscale,
391 int16_t bandwidth)
392 {
393 int frameCntr, activeFrameCntr, n, pos1, pos2;
394 int16_t criterion1;
395 int16_t criterion2;
396 int16_t numSubFrames = SUBFRAMES * (1 + (bandwidth == isac16kHz));
397 double data[WINLEN];
398 double corrSubFrame[UB_LPC_ORDER+2];
399 double reflecCoeff[UB_LPC_ORDER];
400
401 double aPolynom[UB_LPC_ORDER+1];
402 double tmp;
403
404 /* bandwdith expansion factors */
405 const double gamma = 0.9;
406
407 /* change quallevel depending on pitch gains and level fluctuations */
408 WebRtcIsac_GetVarsUB(inSignal, &(maskdata->OldEnergy), varscale);
409
410 /* replace data in buffer by new look-ahead data */
411 for(frameCntr = 0, activeFrameCntr = 0; frameCntr < numSubFrames;
412 frameCntr++)
413 {
414 if(frameCntr == SUBFRAMES)
415 {
416 // we are in 16 kHz
417 varscale++;
418 WebRtcIsac_GetVarsUB(&inSignal[FRAMESAMPLES_HALF],
419 &(maskdata->OldEnergy), varscale);
420 }
421 /* Update input buffer and multiply signal with window */
422 for(pos1 = 0; pos1 < WINLEN - UPDATE/2; pos1++)
423 {
424 maskdata->DataBufferLo[pos1] = maskdata->DataBufferLo[pos1 +
425 UPDATE/2];
426 data[pos1] = maskdata->DataBufferLo[pos1] * kLpcCorrWindow[pos1];
427 }
428 pos2 = frameCntr * UPDATE/2;
429 for(n = 0; n < UPDATE/2; n++, pos1++, pos2++)
430 {
431 maskdata->DataBufferLo[pos1] = inSignal[pos2];
432 data[pos1] = maskdata->DataBufferLo[pos1] * kLpcCorrWindow[pos1];
433 }
434
435 /* Get correlation coefficients */
436 /* computing autocorrelation */
437 WebRtcIsac_AutoCorr(corrSubFrame, data, WINLEN, UB_LPC_ORDER+1);
438 memcpy(corrMat[frameCntr], corrSubFrame,
439 (UB_LPC_ORDER+1)*sizeof(double));
440
441 criterion1 = ((frameCntr == 0) || (frameCntr == (SUBFRAMES - 1))) &&
442 (bandwidth == isac12kHz);
443 criterion2 = (((frameCntr+1) % 4) == 0) &&
444 (bandwidth == isac16kHz);
445 if(criterion1 || criterion2)
446 {
447 /* add noise */
448 corrSubFrame[0] += 1e-6;
449 /* compute prediction coefficients */
450 WebRtcIsac_LevDurb(aPolynom, reflecCoeff, corrSubFrame,
451 UB_LPC_ORDER);
452
453 /* bandwidth expansion */
454 tmp = gamma;
455 for (n = 1; n <= UB_LPC_ORDER; n++)
456 {
457 *lpCoeff++ = aPolynom[n] * tmp;
458 tmp *= gamma;
459 }
460 activeFrameCntr++;
461 }
462 }
463 }
464
465
466
467 /******************************************************************************
468 * WebRtcIsac_GetLpcGain()
469 *
470 * Compute the LPC gains for each sub-frame, given the LPC of each sub-frame
471 * and the corresponding correlation coefficients.
472 *
473 * Inputs:
474 * -signal_noise_ratio : the desired SNR in dB.
475 * -numVecs : number of sub-frames
476 * -corrMat : a matrix of correlation coefficients where
477 * each row is a set of correlation coefficients of
478 * one sub-frame.
479 * -varscale : a scale computed when WebRtcIsac_GetLpcCoefUb()
480 * is called.
481 *
482 * Outputs:
483 * -gain : pointer to a buffer where LP gains are written.
484 *
485 */
486 void
WebRtcIsac_GetLpcGain(double signal_noise_ratio,const double * filtCoeffVecs,int numVecs,double * gain,double corrMat[][UB_LPC_ORDER+1],const double * varscale)487 WebRtcIsac_GetLpcGain(
488 double signal_noise_ratio,
489 const double* filtCoeffVecs,
490 int numVecs,
491 double* gain,
492 double corrMat[][UB_LPC_ORDER + 1],
493 const double* varscale)
494 {
495 int16_t j, n;
496 int16_t subFrameCntr;
497 double aPolynom[ORDERLO + 1];
498 double res_nrg;
499
500 const double HearThresOffset = -28.0;
501 const double H_T_H = pow(10.0, 0.05 * HearThresOffset);
502 /* divide by sqrt(12) = 3.46 */
503 const double S_N_R = pow(10.0, 0.05 * signal_noise_ratio) / 3.46;
504
505 aPolynom[0] = 1;
506 for(subFrameCntr = 0; subFrameCntr < numVecs; subFrameCntr++)
507 {
508 if(subFrameCntr == SUBFRAMES)
509 {
510 // we are in second half of a SWB frame. use new varscale
511 varscale++;
512 }
513 memcpy(&aPolynom[1], &filtCoeffVecs[(subFrameCntr * (UB_LPC_ORDER + 1)) +
514 1], sizeof(double) * UB_LPC_ORDER);
515
516 /* residual energy */
517 res_nrg = 0.0;
518 for(j = 0; j <= UB_LPC_ORDER; j++)
519 {
520 for(n = 0; n <= j; n++)
521 {
522 res_nrg += aPolynom[j] * corrMat[subFrameCntr][j-n] *
523 aPolynom[n];
524 }
525 for(n = j+1; n <= UB_LPC_ORDER; n++)
526 {
527 res_nrg += aPolynom[j] * corrMat[subFrameCntr][n-j] *
528 aPolynom[n];
529 }
530 }
531
532 /* add hearing threshold and compute the gain */
533 gain[subFrameCntr] = S_N_R / (sqrt(res_nrg) / *varscale + H_T_H);
534 }
535 }
536