You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
163 lines
8.1 KiB
163 lines
8.1 KiB
/*
|
|
* Copyright (c) 2011-2019 Belledonne Communications SARL.
|
|
*
|
|
* This file is part of bcg729.
|
|
*
|
|
* This program is free software: you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation, either version 3 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program. If not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
#include "typedef.h"
|
|
#include "codecParameters.h"
|
|
#include "basicOperationsMacros.h"
|
|
#include "utils.h"
|
|
|
|
#include "LP2LSPConversion.h"
|
|
|
|
/* local functions and codebook */
|
|
word32_t ChebyshevPolynomial(word16_t x, word32_t f[]); /* return value in Q24 */
|
|
static const word16_t cosW0pi[NB_COMPUTED_VALUES_CHEBYSHEV_POLYNOMIAL]; /* cos(w) from 0 to Pi in 50 steps */
|
|
|
|
/*****************************************************************************/
|
|
/* LP2LSPConversion : Compute polynomials, find their roots as in spec A3.2.3*/
|
|
/* parameters: */
|
|
/* -(i) LPCoefficients[] : 10 coefficients in Q12 */
|
|
/* -(o) LSPCoefficients[] : 10 coefficients in Q15 */
|
|
/* */
|
|
/* return value : */
|
|
/* - boolean: 1 if all roots found, 0 if unable to compute 10 roots */
|
|
/* */
|
|
/*****************************************************************************/
|
|
int LP2LSPConversion(word16_t LPCoefficients[], word16_t LSPCoefficients[])
|
|
{
|
|
uint8_t i;
|
|
word32_t f1[6];
|
|
word32_t f2[6]; /* coefficients for polynomials F1 anf F2 in Q12 for computation, then converted in Q15 for the Chebyshev Polynomial function */
|
|
uint8_t numberOfRootFound = 0; /* used to check the final number of roots found and exit the loop on each polynomial computation when we have 10 roots */
|
|
word32_t *polynomialCoefficients;
|
|
word32_t previousCx;
|
|
word32_t Cx; /* value of Chebyshev Polynomial at current point in Q15 */
|
|
|
|
/*** Compute the polynomials coefficients according to spec 3.2.3 eq15 ***/
|
|
f1[0] = ONE_IN_Q12; /* values 0 are not part of the output, they are just used for computation purpose */
|
|
f2[0] = ONE_IN_Q12;
|
|
/* for (i = 0; i< 5; i++) { */
|
|
/* f1[i+1] = a[i+1] + a[10-i] - f1[i]; */
|
|
/* f2[i+1] = a[i+1] - a[10-i] + f2[i]; */
|
|
/* } */
|
|
for (i=0; i<5; i++) {
|
|
f1[i+1] = ADD32(LPCoefficients[i], SUB32(LPCoefficients[9-i], f1[i])); /* note: index on LPCoefficients are -1 respect to spec because the unused value 0 is not stored */
|
|
f2[i+1] = ADD32(f2[i], SUB32(LPCoefficients[i], LPCoefficients[9-i])); /* note: index on LPCoefficients are -1 respect to spec because the unused value 0 is not stored */
|
|
}
|
|
/* convert the coefficients from Q12 to Q15 to be used by the Chebyshev Polynomial function (f1/2[0] aren't used so they are not converted) */
|
|
for (i=1; i<6; i++) {
|
|
f1[i] = SHL(f1[i], 3);
|
|
f2[i] = SHL(f2[i], 3);
|
|
}
|
|
|
|
/*** Compute at each step(50 steps for the AnnexA version) the Chebyshev polynomial to find the 10 roots ***/
|
|
/* start using f1 polynomials coefficients and altern with f2 after founding each root (spec 3.2.3 eq13 and eq14) */
|
|
polynomialCoefficients = f1; /* start with f1 coefficients */
|
|
previousCx = ChebyshevPolynomial(cosW0pi[0], polynomialCoefficients); /* compute the first point and store it as the previous value for polynomial */
|
|
|
|
for (i=1; i<NB_COMPUTED_VALUES_CHEBYSHEV_POLYNOMIAL; i++) {
|
|
Cx = ChebyshevPolynomial(cosW0pi[i], polynomialCoefficients);
|
|
if ((previousCx^Cx)&0x10000000) { /* check signe change by XOR on the value of first bit */
|
|
/* divide 2 times the interval to find a more accurate root */
|
|
uint8_t j;
|
|
word16_t xLow = cosW0pi[i-1];
|
|
word16_t xHigh = cosW0pi[i];
|
|
word16_t xMean;
|
|
for (j=0; j<2; j++) {
|
|
word32_t middleCx;
|
|
xMean = (word16_t)SHR(ADD32(xLow, xHigh), 1);
|
|
middleCx = ChebyshevPolynomial(xMean, polynomialCoefficients); /* compute the polynome for the value in the middle of current interval */
|
|
|
|
if ((previousCx^middleCx)&0x10000000) { /* check signe change by XOR on the value of first bit */
|
|
xHigh = xMean;
|
|
Cx = middleCx; /* used for linear interpolation on root */
|
|
} else {
|
|
xLow = xMean;
|
|
previousCx = middleCx;
|
|
}
|
|
}
|
|
|
|
/* toggle the polynomial coefficients in use between f1 and f2 */
|
|
if (polynomialCoefficients==f1) {
|
|
polynomialCoefficients = f2;
|
|
} else {
|
|
polynomialCoefficients = f1;
|
|
}
|
|
|
|
/* linear interpolation for better root accuracy */
|
|
/* xMean = xLow - (xHigh-xLow)* previousCx/(Cx-previousCx); */
|
|
xMean = (word16_t)SUB32(xLow, MULT16_32_Q15(SUB32(xHigh, xLow), DIV32(SHL(previousCx, 14), SHR(SUB32(Cx, previousCx), 1)))); /* Cx are in Q2.15 so we can shift them left 14 bits, the denominator is shifted righ by 1 so the division result is in Q15 */
|
|
|
|
/* recompute previousCx with the new coefficients */
|
|
previousCx = ChebyshevPolynomial(xMean, polynomialCoefficients);
|
|
|
|
LSPCoefficients[numberOfRootFound] = xMean;
|
|
|
|
numberOfRootFound++;
|
|
if (numberOfRootFound == NB_LSP_COEFF) break; /* exit the for loop as soon as we habe all the LSP*/
|
|
}
|
|
|
|
}
|
|
if (numberOfRootFound != NB_LSP_COEFF) return 0; /* we were not able to find the 10 roots */
|
|
|
|
|
|
return 1;
|
|
}
|
|
|
|
/*****************************************************************************/
|
|
/* ChebyshevPolynomial : Compute the Chebyshev polynomial, spec 3.2.3 eq17 */
|
|
/* parameters: */
|
|
/* -(i) x : input value of polynomial function in Q15 */
|
|
/* -(i) f : the polynome coefficients, 6 values in Q15 on 32 bits */
|
|
/* f[0] is not used */
|
|
/* return value : */
|
|
/* - result of polynomial function in Q15 */
|
|
/* */
|
|
/*****************************************************************************/
|
|
word32_t ChebyshevPolynomial(word16_t x, word32_t f[])
|
|
{
|
|
/* bk in Q15*/
|
|
word32_t bk;
|
|
word32_t bk1 = ADD32(SHL(x,1), f[1]); /* init: b4=2x+f1 */
|
|
word32_t bk2 = ONE_IN_Q15; /* init: b5=1 */
|
|
uint8_t k;
|
|
for (k=3; k>0; k--) { /* at the end of loop execution we have b1 in bk1 and b2 in bk2 */
|
|
bk = SUB32(ADD32(SHL(MULT16_32_Q15(x,bk1), 1), f[5-k]), bk2); /* bk = 2*x*bk1 − bk2 + f(5-k) all in Q15*/
|
|
bk2 = bk1;
|
|
bk1 = bk;
|
|
}
|
|
|
|
return SUB32(ADD32(MULT16_32_Q15(x,bk1), SHR(f[5],1)), bk2); /* C(x) = x*b1 - b2 + f(5)/2 */
|
|
}
|
|
|
|
/*****************************************************************************/
|
|
/* */
|
|
/* Codebook: */
|
|
/* */
|
|
/* x = cos(w) with w in [0,Pi] in 50 steps */
|
|
/* */
|
|
/*****************************************************************************/
|
|
static const word16_t cosW0pi[NB_COMPUTED_VALUES_CHEBYSHEV_POLYNOMIAL] = { /* in Q15 */
|
|
32760, 32703, 32509, 32187, 31738, 31164,
|
|
30466, 29649, 28714, 27666, 26509, 25248,
|
|
23886, 22431, 20887, 19260, 17557, 15786,
|
|
13951, 12062, 10125, 8149, 6140, 4106,
|
|
2057, 0, -2057, -4106, -6140, -8149,
|
|
-10125, -12062, -13951, -15786, -17557, -19260,
|
|
-20887, -22431, -23886, -25248, -26509, -27666,
|
|
-28714, -29649, -30466, -31164, -31738, -32187,
|
|
-32509, -32703, -32760};
|