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94 lines
4.7 KiB
94 lines
4.7 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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#include "preProcessing.h"
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/*****************************************************************************/
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/* */
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/* Define filter coefficients */
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/* Coefficient are given by the filter transfert function : */
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/* */
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/* 0.46363718 - 0.92724705z(-1) + 0.46363718z(-2) */
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/* H(z) = −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− */
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/* 1 - 1.9059465z(-1) + 0.9114024z(-2) */
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/* */
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/* giving: */
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/* y[i] = B0*x[i] + B1*x[i-1] + B2*x[i-2] */
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/* + A1*y[i-1] + A2*y[i-2] */
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/* */
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/*****************************************************************************/
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/* coefficients a stored in Q1.12 for A1 (the only one having a float value > 1) and Q0.12 for all the others */
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#define A1 ((word16_t)(7807))
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#define A2 ((word16_t)(-3733))
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#define B0 ((word16_t)(1899))
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#define B1 ((word16_t)(-3798))
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#define B2 ((word16_t)(1899))
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/* Initialization of context values */
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void initPreProcessing(bcg729EncoderChannelContextStruct *encoderChannelContext) {
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encoderChannelContext->outputY2 = 0;
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encoderChannelContext->outputY1 = 0;
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encoderChannelContext->inputX0 = 0;
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encoderChannelContext->inputX1 = 0;
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}
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/*****************************************************************************/
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/* preProcessing : 2nd order highpass filter with cut off frequency at 140Hz */
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/* Algorithm: */
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/* y[i] = BO*x[i] + B1*x[i-1] + B2*x[i-2] + A1*y[i-1] + A2*y[i-2] */
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/* parameters : */
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/* -(i/o) encoderChannelContext : the channel context data */
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/* -(i) signal : 80 values in Q0 */
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/* -(o) preProcessedSignal : 80 values in Q0 */
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/* */
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/*****************************************************************************/
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void preProcessing(bcg729EncoderChannelContextStruct *encoderChannelContext, const word16_t signal[], word16_t preProcessedSignal[]) {
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int i;
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word16_t inputX2;
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word32_t acc; /* in Q12 */
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for(i=0; i<L_FRAME; i++) {
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inputX2 = encoderChannelContext->inputX1;
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encoderChannelContext->inputX1 = encoderChannelContext->inputX0;
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encoderChannelContext->inputX0 = signal[i];
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/* compute with acc and coefficients in Q12 */
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acc = MULT16_32_Q12(A1, encoderChannelContext->outputY1); /* Y1 in Q15.12 * A1 in Q1.12 -> acc in Q17.12*/
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acc = MAC16_32_Q12(acc, A2, encoderChannelContext->outputY2); /* Y2 in Q15.12 * A2 in Q0.12 -> Q15.12 + acc in Q17.12 -> acc in Q18.12 */
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/* 3*(Xi in Q15.0 * Bi in Q0.12)->Q17.12 + acc in Q18.12 -> acc in 19.12 */
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acc = MAC16_16(acc, encoderChannelContext->inputX0, B0);
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acc = MAC16_16(acc, encoderChannelContext->inputX1, B1);
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acc = MAC16_16(acc, inputX2, B2);
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/* acc in Q19.12 : We must check it won't overflow
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- the Q15.12 of Y
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- the Q15.0 extracted from it by shifting 12 right
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-> saturate to 28 bits -> acc in Q15.12 */
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acc = SATURATE(acc, MAXINT28);
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preProcessedSignal[i] = PSHR(acc,12); /* extract integer value of the Q15.12 representation */
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encoderChannelContext->outputY2 = encoderChannelContext->outputY1;
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encoderChannelContext->outputY1 = acc;
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}
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return;
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}
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