/* postProcessing.c Copyright (C) 2011 Belledonne Communications, Grenoble, France Author : Johan Pascal 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 2 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, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ #include "typedef.h" #include "codecParameters.h" #include "basicOperationsMacros.h" #include "preProcessing.h" /*****************************************************************************/ /* */ /* Define filter coefficients */ /* Coefficient are given by the filter transfert function : */ /* */ /* 0.46363718 - 0.92724705z(-1) + 0.46363718z(-2) */ /* H(z) = −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− */ /* 1 - 1.9059465z(-1) + 0.9114024z(-2) */ /* */ /* giving: */ /* y[i] = B0*x[i] + B1*x[i-1] + B2*x[i-2] */ /* + A1*y[i-1] + A2*y[i-2] */ /* */ /*****************************************************************************/ /* coefficients are stored in Q1.13 */ #define A1 ((word16_t)(15836)) #define A2 ((word16_t)(-7667)) #define B0 ((word16_t)(7699)) #define B1 ((word16_t)(-15398)) #define B2 ((word16_t)(7699)) /* Initialization of context values */ void initPostProcessing(bcg729DecoderChannelContextStruct *decoderChannelContext) { decoderChannelContext->outputY2 = 0; decoderChannelContext->outputY1 = 0; decoderChannelContext->inputX0 = 0; decoderChannelContext->inputX1 = 0; } /*****************************************************************************/ /* postProcessing : high pass filtering and upscaling Spec 4.2.5 */ /* Algorithm: */ /* y[i] = BO*x[i] + B1*x[i-1] + B2*x[i-2] + A1*y[i-1] + A2*y[i-2] */ /* parameters: */ /* -(i/o) decoderChannelContext : the channel context data */ /* -(i/o) signal : 40 values in Q0, reconstructed speech, output */ /* replaces the input in buffer */ /* */ /*****************************************************************************/ void postProcessing(bcg729DecoderChannelContextStruct *decoderChannelContext, word16_t signal[]) { int i; word16_t inputX2; word32_t acc; /* in Q13 */ for(i=0; iinputX1; decoderChannelContext->inputX1 = decoderChannelContext->inputX0; decoderChannelContext->inputX0 = signal[i]; /* compute with acc and coefficients in Q13 */ acc = MULT16_32_Q13(A1, decoderChannelContext->outputY1); /* Y1 in Q14.13 * A1 in Q1.13 -> acc in Q17.13*/ acc = MAC16_32_Q13(acc, A2, decoderChannelContext->outputY2); /* Y2 in Q14.13 * A2 in Q0.13 -> Q15.13 + acc in Q17.13 -> acc in Q18.12 */ /* 3*(Xi in Q15.0 * Bi in Q0.13)->Q17.13 + acc in Q18.13 -> acc in 19.13(Overflow??) */ acc = MAC16_16(acc, decoderChannelContext->inputX0, B0); acc = MAC16_16(acc, decoderChannelContext->inputX1, B1); acc = SATURATE(MAC16_16(acc, inputX2, B2), MAXINT29); /* saturate the acc to keep in Q15.13 */ signal[i] = SATURATE(PSHR(acc,12), MAXINT16); /* acc in Q13 -> *2 and scale back to Q0 */ decoderChannelContext->outputY2 = decoderChannelContext->outputY1; decoderChannelContext->outputY1 = acc; } return; }