| /* |
| * Copyright (c) 2011 The WebRTC project authors. All Rights Reserved. |
| * |
| * Use of this source code is governed by a BSD-style license |
| * that can be found in the LICENSE file in the root of the source |
| * tree. An additional intellectual property rights grant can be found |
| * in the file PATENTS. All contributing project authors may |
| * be found in the AUTHORS file in the root of the source tree. |
| */ |
| |
| #include "lpc_analysis.h" |
| #include "settings.h" |
| #include "codec.h" |
| #include "entropy_coding.h" |
| |
| #include <math.h> |
| #include <string.h> |
| |
| #define LEVINSON_EPS 1.0e-10 |
| |
| |
| /* window */ |
| /* Matlab generation code: |
| * t = (1:256)/257; r = 1-(1-t).^.45; w = sin(r*pi).^3; w = w/sum(w); plot((1:256)/8, w); grid; |
| * for k=1:16, fprintf(1, '%.8f, ', w(k*16 + (-15:0))); fprintf(1, '\n'); end |
| */ |
| static const double kLpcCorrWindow[WINLEN] = { |
| 0.00000000, 0.00000001, 0.00000004, 0.00000010, 0.00000020, |
| 0.00000035, 0.00000055, 0.00000083, 0.00000118, 0.00000163, |
| 0.00000218, 0.00000283, 0.00000361, 0.00000453, 0.00000558, 0.00000679, |
| 0.00000817, 0.00000973, 0.00001147, 0.00001342, 0.00001558, |
| 0.00001796, 0.00002058, 0.00002344, 0.00002657, 0.00002997, |
| 0.00003365, 0.00003762, 0.00004190, 0.00004651, 0.00005144, 0.00005673, |
| 0.00006236, 0.00006837, 0.00007476, 0.00008155, 0.00008875, |
| 0.00009636, 0.00010441, 0.00011290, 0.00012186, 0.00013128, |
| 0.00014119, 0.00015160, 0.00016252, 0.00017396, 0.00018594, 0.00019846, |
| 0.00021155, 0.00022521, 0.00023946, 0.00025432, 0.00026978, |
| 0.00028587, 0.00030260, 0.00031998, 0.00033802, 0.00035674, |
| 0.00037615, 0.00039626, 0.00041708, 0.00043863, 0.00046092, 0.00048396, |
| 0.00050775, 0.00053233, 0.00055768, 0.00058384, 0.00061080, |
| 0.00063858, 0.00066720, 0.00069665, 0.00072696, 0.00075813, |
| 0.00079017, 0.00082310, 0.00085692, 0.00089164, 0.00092728, 0.00096384, |
| 0.00100133, 0.00103976, 0.00107914, 0.00111947, 0.00116077, |
| 0.00120304, 0.00124630, 0.00129053, 0.00133577, 0.00138200, |
| 0.00142924, 0.00147749, 0.00152676, 0.00157705, 0.00162836, 0.00168070, |
| 0.00173408, 0.00178850, 0.00184395, 0.00190045, 0.00195799, |
| 0.00201658, 0.00207621, 0.00213688, 0.00219860, 0.00226137, |
| 0.00232518, 0.00239003, 0.00245591, 0.00252284, 0.00259079, 0.00265977, |
| 0.00272977, 0.00280078, 0.00287280, 0.00294582, 0.00301984, |
| 0.00309484, 0.00317081, 0.00324774, 0.00332563, 0.00340446, |
| 0.00348421, 0.00356488, 0.00364644, 0.00372889, 0.00381220, 0.00389636, |
| 0.00398135, 0.00406715, 0.00415374, 0.00424109, 0.00432920, |
| 0.00441802, 0.00450754, 0.00459773, 0.00468857, 0.00478001, |
| 0.00487205, 0.00496464, 0.00505775, 0.00515136, 0.00524542, 0.00533990, |
| 0.00543476, 0.00552997, 0.00562548, 0.00572125, 0.00581725, |
| 0.00591342, 0.00600973, 0.00610612, 0.00620254, 0.00629895, |
| 0.00639530, 0.00649153, 0.00658758, 0.00668341, 0.00677894, 0.00687413, |
| 0.00696891, 0.00706322, 0.00715699, 0.00725016, 0.00734266, |
| 0.00743441, 0.00752535, 0.00761540, 0.00770449, 0.00779254, |
| 0.00787947, 0.00796519, 0.00804963, 0.00813270, 0.00821431, 0.00829437, |
| 0.00837280, 0.00844949, 0.00852436, 0.00859730, 0.00866822, |
| 0.00873701, 0.00880358, 0.00886781, 0.00892960, 0.00898884, |
| 0.00904542, 0.00909923, 0.00915014, 0.00919805, 0.00924283, 0.00928436, |
| 0.00932252, 0.00935718, 0.00938821, 0.00941550, 0.00943890, |
| 0.00945828, 0.00947351, 0.00948446, 0.00949098, 0.00949294, |
| 0.00949020, 0.00948262, 0.00947005, 0.00945235, 0.00942938, 0.00940099, |
| 0.00936704, 0.00932738, 0.00928186, 0.00923034, 0.00917268, |
| 0.00910872, 0.00903832, 0.00896134, 0.00887763, 0.00878706, |
| 0.00868949, 0.00858478, 0.00847280, 0.00835343, 0.00822653, 0.00809199, |
| 0.00794970, 0.00779956, 0.00764145, 0.00747530, 0.00730103, |
| 0.00711857, 0.00692787, 0.00672888, 0.00652158, 0.00630597, |
| 0.00608208, 0.00584994, 0.00560962, 0.00536124, 0.00510493, 0.00484089, |
| 0.00456935, 0.00429062, 0.00400505, 0.00371310, 0.00341532, |
| 0.00311238, 0.00280511, 0.00249452, 0.00218184, 0.00186864, |
| 0.00155690, 0.00124918, 0.00094895, 0.00066112, 0.00039320, 0.00015881 |
| }; |
| |
| double WebRtcIsac_LevDurb(double *a, double *k, double *r, int order) |
| { |
| |
| double sum, alpha; |
| int m, m_h, i; |
| alpha = 0; //warning -DH |
| a[0] = 1.0; |
| if (r[0] < LEVINSON_EPS) { /* if r[0] <= 0, set LPC coeff. to zero */ |
| for (i = 0; i < order; i++) { |
| k[i] = 0; |
| a[i+1] = 0; |
| } |
| } else { |
| a[1] = k[0] = -r[1]/r[0]; |
| alpha = r[0] + r[1] * k[0]; |
| for (m = 1; m < order; m++){ |
| sum = r[m + 1]; |
| for (i = 0; i < m; i++){ |
| sum += a[i+1] * r[m - i]; |
| } |
| k[m] = -sum / alpha; |
| alpha += k[m] * sum; |
| m_h = (m + 1) >> 1; |
| for (i = 0; i < m_h; i++){ |
| sum = a[i+1] + k[m] * a[m - i]; |
| a[m - i] += k[m] * a[i+1]; |
| a[i+1] = sum; |
| } |
| a[m+1] = k[m]; |
| } |
| } |
| return alpha; |
| } |
| |
| |
| //was static before, but didn't work with MEX file |
| void WebRtcIsac_GetVars(const double *input, const WebRtc_Word16 *pitchGains_Q12, |
| double *oldEnergy, double *varscale) |
| { |
| double nrg[4], chng, pg; |
| int k; |
| |
| double pitchGains[4]={0,0,0,0};; |
| |
| /* Calculate energies of first and second frame halfs */ |
| nrg[0] = 0.0001; |
| for (k = QLOOKAHEAD/2; k < (FRAMESAMPLES_QUARTER + QLOOKAHEAD) / 2; k++) { |
| nrg[0] += input[k]*input[k]; |
| } |
| nrg[1] = 0.0001; |
| for ( ; k < (FRAMESAMPLES_HALF + QLOOKAHEAD) / 2; k++) { |
| nrg[1] += input[k]*input[k]; |
| } |
| nrg[2] = 0.0001; |
| for ( ; k < (FRAMESAMPLES*3/4 + QLOOKAHEAD) / 2; k++) { |
| nrg[2] += input[k]*input[k]; |
| } |
| nrg[3] = 0.0001; |
| for ( ; k < (FRAMESAMPLES + QLOOKAHEAD) / 2; k++) { |
| nrg[3] += input[k]*input[k]; |
| } |
| |
| /* Calculate average level change */ |
| chng = 0.25 * (fabs(10.0 * log10(nrg[3] / nrg[2])) + |
| fabs(10.0 * log10(nrg[2] / nrg[1])) + |
| fabs(10.0 * log10(nrg[1] / nrg[0])) + |
| fabs(10.0 * log10(nrg[0] / *oldEnergy))); |
| |
| |
| /* Find average pitch gain */ |
| pg = 0.0; |
| for (k=0; k<4; k++) |
| { |
| pitchGains[k] = ((float)pitchGains_Q12[k])/4096; |
| pg += pitchGains[k]; |
| } |
| pg *= 0.25; |
| |
| /* If pitch gain is low and energy constant - increase noise level*/ |
| /* Matlab code: |
| pg = 0:.01:.45; plot(pg, 0.0 + 1.0 * exp( -1.0 * exp(-200.0 * pg.*pg.*pg) / (1.0 + 0.4 * 0) )) |
| */ |
| *varscale = 0.0 + 1.0 * exp( -1.4 * exp(-200.0 * pg*pg*pg) / (1.0 + 0.4 * chng) ); |
| |
| *oldEnergy = nrg[3]; |
| } |
| |
| void |
| WebRtcIsac_GetVarsUB( |
| const double* input, |
| double* oldEnergy, |
| double* varscale) |
| { |
| double nrg[4], chng; |
| int k; |
| |
| /* Calculate energies of first and second frame halfs */ |
| nrg[0] = 0.0001; |
| for (k = 0; k < (FRAMESAMPLES_QUARTER) / 2; k++) { |
| nrg[0] += input[k]*input[k]; |
| } |
| nrg[1] = 0.0001; |
| for ( ; k < (FRAMESAMPLES_HALF) / 2; k++) { |
| nrg[1] += input[k]*input[k]; |
| } |
| nrg[2] = 0.0001; |
| for ( ; k < (FRAMESAMPLES*3/4) / 2; k++) { |
| nrg[2] += input[k]*input[k]; |
| } |
| nrg[3] = 0.0001; |
| for ( ; k < (FRAMESAMPLES) / 2; k++) { |
| nrg[3] += input[k]*input[k]; |
| } |
| |
| /* Calculate average level change */ |
| chng = 0.25 * (fabs(10.0 * log10(nrg[3] / nrg[2])) + |
| fabs(10.0 * log10(nrg[2] / nrg[1])) + |
| fabs(10.0 * log10(nrg[1] / nrg[0])) + |
| fabs(10.0 * log10(nrg[0] / *oldEnergy))); |
| |
| |
| /* If pitch gain is low and energy constant - increase noise level*/ |
| /* Matlab code: |
| pg = 0:.01:.45; plot(pg, 0.0 + 1.0 * exp( -1.0 * exp(-200.0 * pg.*pg.*pg) / (1.0 + 0.4 * 0) )) |
| */ |
| *varscale = exp( -1.4 / (1.0 + 0.4 * chng) ); |
| |
| *oldEnergy = nrg[3]; |
| } |
| |
| void WebRtcIsac_GetLpcCoefLb(double *inLo, double *inHi, MaskFiltstr *maskdata, |
| double signal_noise_ratio, const WebRtc_Word16 *pitchGains_Q12, |
| double *lo_coeff, double *hi_coeff) |
| { |
| int k, n, j, pos1, pos2; |
| double varscale; |
| |
| double DataLo[WINLEN], DataHi[WINLEN]; |
| double corrlo[ORDERLO+2], corrlo2[ORDERLO+1]; |
| double corrhi[ORDERHI+1]; |
| double k_veclo[ORDERLO], k_vechi[ORDERHI]; |
| |
| double a_LO[ORDERLO+1], a_HI[ORDERHI+1]; |
| double tmp, res_nrg; |
| |
| double FwdA, FwdB; |
| |
| /* hearing threshold level in dB; higher value gives more noise */ |
| const double HearThresOffset = -28.0; |
| |
| /* bandwdith expansion factors for low- and high band */ |
| const double gammaLo = 0.9; |
| const double gammaHi = 0.8; |
| |
| /* less-noise-at-low-frequencies factor */ |
| double aa; |
| |
| |
| /* convert from dB to signal level */ |
| const double H_T_H = pow(10.0, 0.05 * HearThresOffset); |
| double S_N_R = pow(10.0, 0.05 * signal_noise_ratio) / 3.46; /* divide by sqrt(12) */ |
| |
| /* change quallevel depending on pitch gains and level fluctuations */ |
| WebRtcIsac_GetVars(inLo, pitchGains_Q12, &(maskdata->OldEnergy), &varscale); |
| |
| /* less-noise-at-low-frequencies factor */ |
| aa = 0.35 * (0.5 + 0.5 * varscale); |
| |
| /* replace data in buffer by new look-ahead data */ |
| for (pos1 = 0; pos1 < QLOOKAHEAD; pos1++) |
| maskdata->DataBufferLo[pos1 + WINLEN - QLOOKAHEAD] = inLo[pos1]; |
| |
| for (k = 0; k < SUBFRAMES; k++) { |
| |
| /* Update input buffer and multiply signal with window */ |
| for (pos1 = 0; pos1 < WINLEN - UPDATE/2; pos1++) { |
| maskdata->DataBufferLo[pos1] = maskdata->DataBufferLo[pos1 + UPDATE/2]; |
| maskdata->DataBufferHi[pos1] = maskdata->DataBufferHi[pos1 + UPDATE/2]; |
| DataLo[pos1] = maskdata->DataBufferLo[pos1] * kLpcCorrWindow[pos1]; |
| DataHi[pos1] = maskdata->DataBufferHi[pos1] * kLpcCorrWindow[pos1]; |
| } |
| pos2 = k * UPDATE/2; |
| for (n = 0; n < UPDATE/2; n++, pos1++) { |
| maskdata->DataBufferLo[pos1] = inLo[QLOOKAHEAD + pos2]; |
| maskdata->DataBufferHi[pos1] = inHi[pos2++]; |
| DataLo[pos1] = maskdata->DataBufferLo[pos1] * kLpcCorrWindow[pos1]; |
| DataHi[pos1] = maskdata->DataBufferHi[pos1] * kLpcCorrWindow[pos1]; |
| } |
| |
| /* Get correlation coefficients */ |
| WebRtcIsac_AutoCorr(corrlo, DataLo, WINLEN, ORDERLO+1); /* computing autocorrelation */ |
| WebRtcIsac_AutoCorr(corrhi, DataHi, WINLEN, ORDERHI); |
| |
| |
| /* less noise for lower frequencies, by filtering/scaling autocorrelation sequences */ |
| corrlo2[0] = (1.0+aa*aa) * corrlo[0] - 2.0*aa * corrlo[1]; |
| tmp = (1.0 + aa*aa); |
| for (n = 1; n <= ORDERLO; n++) { |
| corrlo2[n] = tmp * corrlo[n] - aa * (corrlo[n-1] + corrlo[n+1]); |
| } |
| tmp = (1.0+aa) * (1.0+aa); |
| for (n = 0; n <= ORDERHI; n++) { |
| corrhi[n] = tmp * corrhi[n]; |
| } |
| |
| /* add white noise floor */ |
| corrlo2[0] += 1e-6; |
| corrhi[0] += 1e-6; |
| |
| |
| FwdA = 0.01; |
| FwdB = 0.01; |
| |
| /* recursive filtering of correlation over subframes */ |
| for (n = 0; n <= ORDERLO; n++) { |
| maskdata->CorrBufLo[n] = FwdA * maskdata->CorrBufLo[n] + corrlo2[n]; |
| corrlo2[n] = ((1.0-FwdA)*FwdB) * maskdata->CorrBufLo[n] + (1.0-FwdB) * corrlo2[n]; |
| } |
| for (n = 0; n <= ORDERHI; n++) { |
| maskdata->CorrBufHi[n] = FwdA * maskdata->CorrBufHi[n] + corrhi[n]; |
| corrhi[n] = ((1.0-FwdA)*FwdB) * maskdata->CorrBufHi[n] + (1.0-FwdB) * corrhi[n]; |
| } |
| |
| /* compute prediction coefficients */ |
| WebRtcIsac_LevDurb(a_LO, k_veclo, corrlo2, ORDERLO); |
| WebRtcIsac_LevDurb(a_HI, k_vechi, corrhi, ORDERHI); |
| |
| /* bandwidth expansion */ |
| tmp = gammaLo; |
| for (n = 1; n <= ORDERLO; n++) { |
| a_LO[n] *= tmp; |
| tmp *= gammaLo; |
| } |
| |
| /* residual energy */ |
| res_nrg = 0.0; |
| for (j = 0; j <= ORDERLO; j++) { |
| for (n = 0; n <= j; n++) { |
| res_nrg += a_LO[j] * corrlo2[j-n] * a_LO[n]; |
| } |
| for (n = j+1; n <= ORDERLO; n++) { |
| res_nrg += a_LO[j] * corrlo2[n-j] * a_LO[n]; |
| } |
| } |
| |
| /* add hearing threshold and compute the gain */ |
| *lo_coeff++ = S_N_R / (sqrt(res_nrg) / varscale + H_T_H); |
| |
| /* copy coefficients to output array */ |
| for (n = 1; n <= ORDERLO; n++) { |
| *lo_coeff++ = a_LO[n]; |
| } |
| |
| |
| /* bandwidth expansion */ |
| tmp = gammaHi; |
| for (n = 1; n <= ORDERHI; n++) { |
| a_HI[n] *= tmp; |
| tmp *= gammaHi; |
| } |
| |
| /* residual energy */ |
| res_nrg = 0.0; |
| for (j = 0; j <= ORDERHI; j++) { |
| for (n = 0; n <= j; n++) { |
| res_nrg += a_HI[j] * corrhi[j-n] * a_HI[n]; |
| } |
| for (n = j+1; n <= ORDERHI; n++) { |
| res_nrg += a_HI[j] * corrhi[n-j] * a_HI[n]; |
| } |
| } |
| |
| /* add hearing threshold and compute of the gain */ |
| *hi_coeff++ = S_N_R / (sqrt(res_nrg) / varscale + H_T_H); |
| |
| /* copy coefficients to output array */ |
| for (n = 1; n <= ORDERHI; n++) { |
| *hi_coeff++ = a_HI[n]; |
| } |
| } |
| } |
| |
| |
| |
| /****************************************************************************** |
| * WebRtcIsac_GetLpcCoefUb() |
| * |
| * Compute LP coefficients and correlation coefficients. At 12 kHz LP |
| * coefficients of the first and the last sub-frame is computed. At 16 kHz |
| * LP coefficients of 4th, 8th and 12th sub-frames are computed. We always |
| * compute correlation coefficients of all sub-frames. |
| * |
| * Inputs: |
| * -inSignal : Input signal |
| * -maskdata : a structure keeping signal from previous frame. |
| * -bandwidth : specifies if the codec is in 0-16 kHz mode or |
| * 0-12 kHz mode. |
| * |
| * Outputs: |
| * -lpCoeff : pointer to a buffer where A-polynomials are |
| * written to (first coeff is 1 and it is not |
| * written) |
| * -corrMat : a matrix where correlation coefficients of each |
| * sub-frame are written to one row. |
| * -varscale : a scale used to compute LPC gains. |
| */ |
| void |
| WebRtcIsac_GetLpcCoefUb( |
| double* inSignal, |
| MaskFiltstr* maskdata, |
| double* lpCoeff, |
| double corrMat[][UB_LPC_ORDER + 1], |
| double* varscale, |
| WebRtc_Word16 bandwidth) |
| { |
| int frameCntr, activeFrameCntr, n, pos1, pos2; |
| WebRtc_Word16 criterion1; |
| WebRtc_Word16 criterion2; |
| WebRtc_Word16 numSubFrames = SUBFRAMES * (1 + (bandwidth == isac16kHz)); |
| double data[WINLEN]; |
| double corrSubFrame[UB_LPC_ORDER+2]; |
| double reflecCoeff[UB_LPC_ORDER]; |
| |
| double aPolynom[UB_LPC_ORDER+1]; |
| double tmp; |
| |
| /* bandwdith expansion factors */ |
| const double gamma = 0.9; |
| |
| /* change quallevel depending on pitch gains and level fluctuations */ |
| WebRtcIsac_GetVarsUB(inSignal, &(maskdata->OldEnergy), varscale); |
| |
| /* replace data in buffer by new look-ahead data */ |
| for(frameCntr = 0, activeFrameCntr = 0; frameCntr < numSubFrames; |
| frameCntr++) |
| { |
| if(frameCntr == SUBFRAMES) |
| { |
| // we are in 16 kHz |
| varscale++; |
| WebRtcIsac_GetVarsUB(&inSignal[FRAMESAMPLES_HALF], |
| &(maskdata->OldEnergy), varscale); |
| } |
| /* Update input buffer and multiply signal with window */ |
| for(pos1 = 0; pos1 < WINLEN - UPDATE/2; pos1++) |
| { |
| maskdata->DataBufferLo[pos1] = maskdata->DataBufferLo[pos1 + |
| UPDATE/2]; |
| data[pos1] = maskdata->DataBufferLo[pos1] * kLpcCorrWindow[pos1]; |
| } |
| pos2 = frameCntr * UPDATE/2; |
| for(n = 0; n < UPDATE/2; n++, pos1++, pos2++) |
| { |
| maskdata->DataBufferLo[pos1] = inSignal[pos2]; |
| data[pos1] = maskdata->DataBufferLo[pos1] * kLpcCorrWindow[pos1]; |
| } |
| |
| /* Get correlation coefficients */ |
| /* computing autocorrelation */ |
| WebRtcIsac_AutoCorr(corrSubFrame, data, WINLEN, UB_LPC_ORDER+1); |
| memcpy(corrMat[frameCntr], corrSubFrame, |
| (UB_LPC_ORDER+1)*sizeof(double)); |
| |
| criterion1 = ((frameCntr == 0) || (frameCntr == (SUBFRAMES - 1))) && |
| (bandwidth == isac12kHz); |
| criterion2 = (((frameCntr+1) % 4) == 0) && |
| (bandwidth == isac16kHz); |
| if(criterion1 || criterion2) |
| { |
| /* add noise */ |
| corrSubFrame[0] += 1e-6; |
| /* compute prediction coefficients */ |
| WebRtcIsac_LevDurb(aPolynom, reflecCoeff, corrSubFrame, |
| UB_LPC_ORDER); |
| |
| /* bandwidth expansion */ |
| tmp = gamma; |
| for (n = 1; n <= UB_LPC_ORDER; n++) |
| { |
| *lpCoeff++ = aPolynom[n] * tmp; |
| tmp *= gamma; |
| } |
| activeFrameCntr++; |
| } |
| } |
| } |
| |
| |
| |
| /****************************************************************************** |
| * WebRtcIsac_GetLpcGain() |
| * |
| * Compute the LPC gains for each sub-frame, given the LPC of each sub-frame |
| * and the corresponding correlation coefficients. |
| * |
| * Inputs: |
| * -signal_noise_ratio : the desired SNR in dB. |
| * -numVecs : number of sub-frames |
| * -corrMat : a matrix of correlation coefficients where |
| * each row is a set of correlation coefficients of |
| * one sub-frame. |
| * -varscale : a scale computed when WebRtcIsac_GetLpcCoefUb() |
| * is called. |
| * |
| * Outputs: |
| * -gain : pointer to a buffer where LP gains are written. |
| * |
| */ |
| void |
| WebRtcIsac_GetLpcGain( |
| double signal_noise_ratio, |
| const double* filtCoeffVecs, |
| int numVecs, |
| double* gain, |
| double corrMat[][UB_LPC_ORDER + 1], |
| const double* varscale) |
| { |
| WebRtc_Word16 j, n; |
| WebRtc_Word16 subFrameCntr; |
| double aPolynom[ORDERLO + 1]; |
| double res_nrg; |
| |
| const double HearThresOffset = -28.0; |
| const double H_T_H = pow(10.0, 0.05 * HearThresOffset); |
| /* divide by sqrt(12) = 3.46 */ |
| const double S_N_R = pow(10.0, 0.05 * signal_noise_ratio) / 3.46; |
| |
| aPolynom[0] = 1; |
| for(subFrameCntr = 0; subFrameCntr < numVecs; subFrameCntr++) |
| { |
| if(subFrameCntr == SUBFRAMES) |
| { |
| // we are in second half of a SWB frame. use new varscale |
| varscale++; |
| } |
| memcpy(&aPolynom[1], &filtCoeffVecs[(subFrameCntr * (UB_LPC_ORDER + 1)) + |
| 1], sizeof(double) * UB_LPC_ORDER); |
| |
| /* residual energy */ |
| res_nrg = 0.0; |
| for(j = 0; j <= UB_LPC_ORDER; j++) |
| { |
| for(n = 0; n <= j; n++) |
| { |
| res_nrg += aPolynom[j] * corrMat[subFrameCntr][j-n] * |
| aPolynom[n]; |
| } |
| for(n = j+1; n <= UB_LPC_ORDER; n++) |
| { |
| res_nrg += aPolynom[j] * corrMat[subFrameCntr][n-j] * |
| aPolynom[n]; |
| } |
| } |
| |
| /* add hearing threshold and compute the gain */ |
| gain[subFrameCntr] = S_N_R / (sqrt(res_nrg) / *varscale + H_T_H); |
| } |
| } |
