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94 lines
4.5 KiB
94 lines
4.5 KiB
/*
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* Copyright (c) 2011-2019 Belledonne Communications SARL.
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*
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* This file is part of bcg729.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "typedef.h"
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#include "codecParameters.h"
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#include "basicOperationsMacros.h"
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/* local function */
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void computePolynomialCoefficients(word16_t qLSP[], word32_t f[]);
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/*****************************************************************************/
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/* qLSP2LP : convert qLSP into LP parameters according to spec. 3.2.6 */
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/* parameters: */
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/* -(i) qLSP : 10 LSP to be converted in Q0.15 range [-1, +1[ */
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/* -(o) LP : 10 LP coefficients in Q12 */
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/* */
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/*****************************************************************************/
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void qLSP2LP(word16_t qLSP[], word16_t LP[])
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{
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int i;
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word32_t f1[6], f2[6]; /* define two buffer to store the polynomials coefficients (size is 6 for 5 coefficient because fx[0] is used during computation as a buffer) */
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/* pointers to access directly the elements 1 of f1 and f2 */
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word32_t *fp1=&(f1[1]);
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word32_t *fp2=&(f2[1]);
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computePolynomialCoefficients(qLSP, f1);
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computePolynomialCoefficients(&(qLSP[1]), f2);
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/* convert f coefficient in f' coefficient f'1[i] = f1[i]+f[i-1] and f'2[i] = f2[i] - f2[i-1] */
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for (i=5; i>0; i--) {
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f1[i] = ADD32(f1[i], f1[i-1]); /* f1 is still in Q24 */
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f2[i] = SUB32(f2[i], f2[i-1]); /* f1 is still in Q24 */
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}
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/* compute the LP coefficients */
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/* fx[0] is not needed anymore, acces the f1 and f2 buffers via the fp1 and fp2 pointers */
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for (i=0; i<5; i++) {
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/* i in [0,5[ : LP[i] = (f1[i] + f2[i])/2 */
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LP[i] = PSHR(ADD32(fp1[i], fp2[i]),13); /* f1 and f2 in Q24, LP in Q12 */
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/* i in [5,9[ : LP[i] = (f1[9-i] - f2[9-i])/2 */
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LP[9-i] = PSHR(SUB32(fp1[i], fp2[i]),13); /* f1 and f2 in Q24, LP in Q12 */
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}
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return;
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}
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/*****************************************************************************/
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/* computePolynomialCoefficients : according to spec. 3.2.6 */
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/* parameters: */
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/* -(i) qLSP : 10 LSP to be converted in Q0.15 range [-1, +1[ */
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/* -(o) f : 6 values in Q24 : polynomial coefficients on 32 bits */
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/* */
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/*****************************************************************************/
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void computePolynomialCoefficients(word16_t qLSP[], word32_t f[])
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{
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int i,j;
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/* init values */
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/* f[-1] which is not available is to be egal at 0, it is directly removed in the following when used as a factor */
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f[0] = 16777216; /* 1 in Q24, f[0] is used only for the other coefficient computation */
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/* correspont to i=1 in the algorithm description in spec. 3.2.6 */
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f[1] = MULT16_16(qLSP[0], -1024); /* f[1] = -2*qLSP[0], with qLSP in Q0.15 * -2*2^9(-1024) -> f[1] in Q1.24 */
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/* so we start with i=2 */
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/* Note : index of qLSP are -1 respect of what is in the spec because qLSP array is indexed from 0-9 and not 1-10 */
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for (i=2; i<6; i++) {
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/* spec: f[i] = 2(f[i-2] - qLSP[2i-1]*f[i-1]) */
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f[i] = SSHL(SUB32(f[i-2], MULT16_32_P15(qLSP[2*i-2], f[i-1])),1); /* with qLSP in Q0.15 and f in Q24 */
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for (j=i-1; j>1; j--) { /* case of j=1 is just doing f[1] -= 2*qLSP[2i-1], done after the loop in order to avoid reference to f[-1] */
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/* spec: f[j] = f[j] -2*qLSP[2i-i]*f[j-1] + f[j-2] (all right terms refer to the value at the previous iteration on i indexed loop) */
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f[j] = ADD32(f[j], SUB32(f[j-2], MULT16_32_P14(qLSP[2*i-2], f[j-1]))); /* qLPS in Q0.15 and f in Q24, using MULT16_32_P14 instead of P15 does the *2 on qLSP. Result in Q24 */
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}
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/* f[1] -= 2*qLSP[2i-1] */
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f[1] = SUB32(f[1], SSHL(qLSP[2*i-2],10)); /* qLSP in Q0.15, must be shift by 9 to get in Q24 and one more to be *2 */
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}
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return;
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}
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