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bcg729/src/postFilter.c

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/*
postFilter.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 <string.h>
#include "typedef.h"
#include "codecParameters.h"
#include "basicOperationsMacros.h"
#include "utils.h"
#include "g729FixedPointMath.h"
/* init function */
void initPostFilter(bcg729DecoderChannelContextStruct *decoderChannelContext)
{
/* set to zero the residual signal memory */
memset(decoderChannelContext->residualSignalBuffer, 0, MAXIMUM_INT_PITCH_DELAY*sizeof(word16_t));
memset(decoderChannelContext->scaledResidualSignalBuffer, 0, MAXIMUM_INT_PITCH_DELAY*sizeof(word16_t));
/* set to zero the one word of longTermFilteredResidualSignal needed as memory for tilt compensation filter */
decoderChannelContext->longTermFilteredResidualSignalBuffer[0] = 0;
decoderChannelContext->longTermFilteredResidualSignal = &(decoderChannelContext->longTermFilteredResidualSignalBuffer[1]); /* init the pointer to the begining of longTermFilteredResidualSignal current subframe */
/* intialise the shortTermFilteredResidualSignal filter memory and pointer*/
memset(decoderChannelContext->shortTermFilteredResidualSignalBuffer, 0, NB_LSP_COEFF*sizeof(word16_t));
decoderChannelContext->shortTermFilteredResidualSignal = &(decoderChannelContext->shortTermFilteredResidualSignalBuffer[NB_LSP_COEFF]);
/* initialise the previous Gain for adaptative gain control */
decoderChannelContext->previousAdaptativeGain = 4096; /* 1 in Q12 */
}
/*****************************************************************************/
/* postFilter: filter the reconstructed speech according to spec A.4.2 */
/* parameters: */
/* -(i/o) decoderChannelContext : the channel context data */
/* -(i) LPCoefficients: 10 LP coeff for current subframe in Q12 */
/* -(i) reconstructedSpeech: output of LP Synthesis, 50 values in Q0 */
/* 10 values of previous subframe, accessed in range [-10, 39] */
/* -(i) intPitchDelay: the integer part of Pitch Delay in Q0 */
/* -(i) subframeIndex: 0 or L_SUBFRAME for subframe 0 or 1 */
/* -(o) postFilteredSignal: 40 values in Q0 */
/* */
/*****************************************************************************/
void postFilter(bcg729DecoderChannelContextStruct *decoderChannelContext, word16_t *LPCoefficients, word16_t *reconstructedSpeech, int16_t intPitchDelay, int subframeIndex,
word16_t *postFilteredSignal)
{
int i,j;
word16_t LPGammaNCoefficients[NB_LSP_COEFF]; /* in Q12 */
word16_t *residualSignal;
word16_t *scaledResidualSignal;
word32_t correlationMax = (word32_t)MININT32;
int16_t bestIntPitchDelay = 0;
word16_t *delayedResidualSignal;
word32_t residualSignalEnergy = 0; /* in Q-4 */
word32_t delayedResidualSignalEnergy = 0; /* in Q-4 */
word32_t maximumThree;
int16_t leadingZeros = 0;
word16_t correlationMaxWord16 = 0;
word16_t residualSignalEnergyWord16 = 0;
word16_t delayedResidualSignalEnergyWord16 = 0;
word16_t LPGammaDCoefficients[NB_LSP_COEFF]; /* in Q12 */
word16_t hf[22]; /* the truncated impulse response to short term filter Hf in Q12 */
word32_t rh1;
word16_t tiltCompensatedSignal[L_SUBFRAME]; /* in Q0 */
word16_t gainScalingFactor; /* in Q12 */
uword32_t shortTermFilteredResidualSignalSquareSum = 0;
/********************************************************************/
/* Long Term Post Filter */
/********************************************************************/
/*** Compute LPGammaN and LPGammaD coefficients : LPGamma[0] = LP[0]*Gamma^(i+1) (i=0..9) ***/
/* GAMMA_XX constants are in Q15 */
LPGammaNCoefficients[0] = MULT16_16_P15(LPCoefficients[0], GAMMA_N1);
LPGammaNCoefficients[1] = MULT16_16_P15(LPCoefficients[1], GAMMA_N2);
LPGammaNCoefficients[2] = MULT16_16_P15(LPCoefficients[2], GAMMA_N3);
LPGammaNCoefficients[3] = MULT16_16_P15(LPCoefficients[3], GAMMA_N4);
LPGammaNCoefficients[4] = MULT16_16_P15(LPCoefficients[4], GAMMA_N5);
LPGammaNCoefficients[5] = MULT16_16_P15(LPCoefficients[5], GAMMA_N6);
LPGammaNCoefficients[6] = MULT16_16_P15(LPCoefficients[6], GAMMA_N7);
LPGammaNCoefficients[7] = MULT16_16_P15(LPCoefficients[7], GAMMA_N8);
LPGammaNCoefficients[8] = MULT16_16_P15(LPCoefficients[8], GAMMA_N9);
LPGammaNCoefficients[9] = MULT16_16_P15(LPCoefficients[9], GAMMA_N10);
/*** Compute the residual signal as described in spec 4.2.1 eq79 ***/
/* Compute also a scaled residual signal: shift right by 2 to avoid overflows on 32 bits when computing correlation and energy */
/* pointers to current subframe beginning */
residualSignal = &(decoderChannelContext->residualSignalBuffer[MAXIMUM_INT_PITCH_DELAY+subframeIndex]);
scaledResidualSignal = &(decoderChannelContext->scaledResidualSignalBuffer[MAXIMUM_INT_PITCH_DELAY+subframeIndex]);
for (i=0; i<L_SUBFRAME; i++) {
word32_t acc = SHL((word32_t)reconstructedSpeech[i], 12); /* reconstructedSpeech in Q0 shifted to set acc in Q12 */
for (j=0; j<NB_LSP_COEFF; j++) {
acc = MAC16_16(acc, LPGammaNCoefficients[j],reconstructedSpeech[i-j-1]); /* LPGammaNCoefficients in Q12, reconstructedSpeech in Q0 -> acc in Q12 */
}
residualSignal[i] = (word16_t)SATURATE(PSHR(acc, 12), MAXINT16); /* shift back acc to Q0 and saturate it to avoid overflow when going back to 16 bits */
scaledResidualSignal[i] = PSHR(residualSignal[i], 2); /* shift acc to Q-2 and saturate it to get the scaled version of the signal */
}
/*** Compute the maximum correlation on scaledResidualSignal delayed by intPitchDelay +/- 3 to get the best delay. Spec 4.2.1 eq80 ***/
/* using a scaled(Q-2) signals gives correlation in Q-4. */
if (intPitchDelay>MAXIMUM_INT_PITCH_DELAY-3) { /* intPitchDelay shall be < MAXIMUM_INT_PITCH_DELAY-3 (140) */
intPitchDelay = MAXIMUM_INT_PITCH_DELAY-3;
}
for (i=intPitchDelay-3; i<=intPitchDelay+3; i++) {
word32_t correlation = 0;
delayedResidualSignal = &(scaledResidualSignal[-i]); /* delayedResidualSignal points to scaledResidualSignal[-i] */
/* compute correlation: ∑r(n)*rk(n) */
for (j=0; j<L_SUBFRAME; j++) {
correlation = MAC16_16(correlation, delayedResidualSignal[j], scaledResidualSignal[j]);
}
/* if we have a maximum correlation */
if (correlation>correlationMax) {
correlationMax = correlation;
bestIntPitchDelay = i; /* get the intPitchDelay */
}
}
/* saturate correlation to a positive integer */
if (correlationMax<0) {
correlationMax = 0;
}
/*** Compute the signal energy ∑r(n)*r(n) and delayed signal energy ∑rk(n)*rk(n) which shall be used to compute gl spec 4.2.1 eq81, eq 82 and eq83 ***/
delayedResidualSignal = &(scaledResidualSignal[-bestIntPitchDelay]); /* in Q-2, points to the residual signal delayed to give the higher correlation: rk(n) */
for (i=0; i<L_SUBFRAME; i++) {
residualSignalEnergy = MAC16_16(residualSignalEnergy, scaledResidualSignal[i], scaledResidualSignal[i]);
delayedResidualSignalEnergy = MAC16_16(delayedResidualSignalEnergy, delayedResidualSignal[i], delayedResidualSignal[i]);
}
/*** Scale correlationMax, residualSignalEnergy and delayedResidualSignalEnergy to the best fit on 16 bits ***/
/* these variables must fit on 16bits for the following computation, to avoid loosing information, scale them */
/* at best fit: scale the higher of three to get the value over 2^14 and shift the other two from the same amount */
/* Note: all three value are >= 0 */
maximumThree = correlationMax;
if (maximumThree<residualSignalEnergy) {
maximumThree = residualSignalEnergy;
}
if (maximumThree<delayedResidualSignalEnergy) {
maximumThree = delayedResidualSignalEnergy;
}
if (maximumThree>0) { /* if all of them a null, just do nothing otherwise shift right to get the max number in range [0x4000,0x8000[ */
leadingZeros = countLeadingZeros(maximumThree);
if (leadingZeros<16) {
correlationMaxWord16 = (word16_t)SHR32(correlationMax, 16-leadingZeros);
residualSignalEnergyWord16 = (word16_t)SHR32(residualSignalEnergy, 16-leadingZeros);
delayedResidualSignalEnergyWord16 = (word16_t)SHR32(delayedResidualSignalEnergy, 16-leadingZeros);
} else { /* if the values already fit on 16 bits, no need to shift */
correlationMaxWord16 = (word16_t)correlationMax;
residualSignalEnergyWord16 = (word16_t)residualSignalEnergy;
delayedResidualSignalEnergyWord16 = (word16_t)delayedResidualSignalEnergy;
}
}
/* eq78: Hp(z)=(1 + γp*gl*z(−T))/(1 + γp*gl) -> (with g=γp*gl) Hp(z)=1/(1+g) + (g/(1+g))*z(-T) = g0 + g1*z(-T) */
/* g = gl/2 (as γp=0.5)= (eq83) correlationMax/(2*delayedResidualSignalEnergy) */
/* compute g0 = 1/(1+g)= delayedResidualSignalEnergy/(delayedResidualSignalEnergy+correlationMax/2) = 1-g1*/
/* compute g1 = g/(1+g) = correlationMax/(2*delayedResidualSignalEnergy+correlationMax) = 1-g0 */
/*** eq82 -> (correlationMax^2)/(residualSignalEnergy*delayedResidualSignalEnergy)<0.5 ***/
/* (correlationMax^2) < (residualSignalEnergy*delayedResidualSignalEnergy)*0.5 */
if ((MULT16_16(correlationMaxWord16, correlationMaxWord16) < SHR(MULT16_16(residualSignalEnergyWord16, delayedResidualSignalEnergyWord16), 1)) /* eq82 */
|| ((correlationMaxWord16==0) && (delayedResidualSignalEnergyWord16==0))) { /* correlationMax and delayedResidualSignalEnergy values are 0 -> unable to compute g0 and g1 -> disable filter */
/* long term post filter disabled */
for (i=0; i<L_SUBFRAME; i++) {
decoderChannelContext->longTermFilteredResidualSignal[i] = residualSignal[i];
}
} else { /* eq82 gives long term filter enabled, */
word16_t g0, g1;
/* eq83: gl = correlationMax/delayedResidualSignalEnergy bounded in ]0,1] */
/* check if gl > 1 -> gl=1 -> g=1/2 -> g0=2/3 and g1=1/3 */
if (correlationMax > delayedResidualSignalEnergy) {
g0 = 21845; /* 2/3 in Q15 */
g1 = 10923; /* 1/3 in Q15 */
} else {
/* g1 = correlationMax/(2*delayedResidualSignalEnergy+correlationMax) */
g1 = DIV32((word32_t)SHL32(correlationMaxWord16,15),(word32_t)ADD32(SHL32(delayedResidualSignalEnergyWord16,1), correlationMaxWord16)); /* g1 in Q15 */
g0 = SUB16(32767, g1); /* g0 = 1 - g1 in Q15 */
}
/* longTermFilteredResidualSignal[i] = g0*residualSignal[i] + g1*delayedResidualSignal[i]*/
delayedResidualSignal = &(residualSignal[-bestIntPitchDelay]);
for (i=0; i<L_SUBFRAME; i++) {
decoderChannelContext->longTermFilteredResidualSignal[i] = (word16_t)SATURATE(PSHR(ADD32(MULT16_16(g0, residualSignal[i]), MULT16_16(g1, delayedResidualSignal[i])), 15), MAXINT16);
}
}
/********************************************************************/
/* Tilt Compensation Filter */
/********************************************************************/
/* compute hf the truncated (to 22 coefficients) impulse response of the filter A(z/γn)/A(z/γd) described in spec 4.2.2 eq84 */
/* hf(i) = LPGammaNCoeff[i] - ∑[j:0..9]LPGammaDCoeff[j]*hf[i-j-1]) */
/* GAMMA_XX constants are in Q15 */
LPGammaDCoefficients[0] = MULT16_16_P15(LPCoefficients[0], GAMMA_D1);
LPGammaDCoefficients[1] = MULT16_16_P15(LPCoefficients[1], GAMMA_D2);
LPGammaDCoefficients[2] = MULT16_16_P15(LPCoefficients[2], GAMMA_D3);
LPGammaDCoefficients[3] = MULT16_16_P15(LPCoefficients[3], GAMMA_D4);
LPGammaDCoefficients[4] = MULT16_16_P15(LPCoefficients[4], GAMMA_D5);
LPGammaDCoefficients[5] = MULT16_16_P15(LPCoefficients[5], GAMMA_D6);
LPGammaDCoefficients[6] = MULT16_16_P15(LPCoefficients[6], GAMMA_D7);
LPGammaDCoefficients[7] = MULT16_16_P15(LPCoefficients[7], GAMMA_D8);
LPGammaDCoefficients[8] = MULT16_16_P15(LPCoefficients[8], GAMMA_D9);
LPGammaDCoefficients[9] = MULT16_16_P15(LPCoefficients[9], GAMMA_D10);
hf[0] = 4096; /* 1 in Q12 as LPGammaNCoefficients and LPGammaDCoefficient doesn't contain the first element which is 1 and past values of hf are 0 */
for (i=1; i<11; i++) {
word32_t acc = (word32_t)SHL(LPGammaNCoefficients[i-1],12); /* LPGammaNCoefficients in Q12 -> acc in Q24 */
for (j=0; j<NB_LSP_COEFF && j<i; j++) { /* j<i to avoid access to negative index of hf(past values are 0 anyway) */
acc = MSU16_16(acc, LPGammaDCoefficients[j], hf[i-j-1]); /* LPGammaDCoefficient in Q12, hf in Q12 -> Q24 TODO: Possible overflow?? */
}
hf[i] = (word16_t)SATURATE(PSHR(acc, 12), MAXINT16); /* get result back in Q12 and saturate on 16 bits */
}
for (i=11; i<22; i++) {
word32_t acc = 0;
for (j=0; j<NB_LSP_COEFF; j++) { /* j<i to avoid access to negative index of hf(past values are 0 anyway) */
acc = MSU16_16(acc, LPGammaDCoefficients[j], hf[i-j-1]); /* LPGammaDCoefficient in Q12, hf in Q12 -> Q24 TODO: Possible overflow?? */
}
hf[i] = (word16_t)SATURATE(PSHR(acc, 12), MAXINT16); /* get result back in Q12 and saturate on 16 bits */
}
/* hf is then used to compute k'1 spec 4.2.3 eq87: k'1 = -rh1/rh0 */
/* rh0 = ∑[i:0..21]hf[i]*hf[i] */
/* rh1 = ∑[i:0..20]hf[i]*hf[i+1] */
rh1 = MULT16_16(hf[0], hf[1]);
for (i=1; i<21; i++) {
rh1 = MAC16_16(rh1, hf[i], hf[i+1]); /* rh1 in Q24 */
}
/* tiltCompensationGain is set to 0 if k'1>0 -> rh1<0 (as rh0 is always>0) */
if (rh1<0) { /* tiltCompensationGain = 0 -> no gain filter is off, just copy the input */
memcpy(tiltCompensatedSignal, decoderChannelContext->longTermFilteredResidualSignal, L_SUBFRAME*sizeof(word16_t));
} else { /*compute tiltCompensationGain = k'1*γt */
word16_t tiltCompensationGain;
word32_t rh0 = MULT16_16(hf[0], hf[0]);
for (i=1; i<22; i++) {
rh0 = MAC16_16(rh0, hf[i], hf[i]); /* rh0 in Q24 */
}
rh1 = MULT16_32_Q15(GAMMA_T, rh1); /* GAMMA_T in Q15, rh1 in Q24*/
tiltCompensationGain = (word16_t)SATURATE((word32_t)(DIV32(rh1,PSHR(rh0,12))), MAXINT16); /* rh1 in Q24, PSHR(rh0,12) in Q12 -> tiltCompensationGain in Q12 */
/* compute filter Ht (spec A.4.2.3 eqA14) = 1 + gain*z(-1) */
for (i=0; i<L_SUBFRAME; i++) {
tiltCompensatedSignal[i] = MSU16_16_Q12(decoderChannelContext->longTermFilteredResidualSignal[i], tiltCompensationGain, decoderChannelContext->longTermFilteredResidualSignal[i-1]);
}
}
/* update memory word of longTermFilteredResidualSignal for next subframe */
decoderChannelContext->longTermFilteredResidualSignal[-1] = decoderChannelContext->longTermFilteredResidualSignal[L_SUBFRAME-1];
/********************************************************************/
/* synthesis filter 1/[Â(z /γd)] spec A.4.2.2 */
/* */
/* Note: Â(z/γn) was done before when computing residual signal */
/********************************************************************/
/* shortTermFilteredResidualSignal is accessed in range [-NB_LSP_COEFF,L_SUBFRAME[ */
synthesisFilter(tiltCompensatedSignal, LPGammaDCoefficients, decoderChannelContext->shortTermFilteredResidualSignal);
/* get the last NB_LSP_COEFF of shortTermFilteredResidualSignal and set them as memory for next subframe(they do not overlap so use memcpy) */
memcpy(decoderChannelContext->shortTermFilteredResidualSignalBuffer, &(decoderChannelContext->shortTermFilteredResidualSignalBuffer[L_SUBFRAME]), NB_LSP_COEFF*sizeof(word16_t));
/********************************************************************/
/* Adaptive Gain Control spec A.4.2.4 */
/* */
/********************************************************************/
/*** compute G(gain scaling factor) according to eqA15 : G = Sqrt((∑s(n)^2)/∑sf(n)^2 ) ***/
/* compute ∑sf(n)^2, scale the signal shifting right by 4 to avoid possible overflow on 32 bits sum */
for (i=0; i<L_SUBFRAME; i++) {
shortTermFilteredResidualSignalSquareSum = UMAC16_16_Q4(shortTermFilteredResidualSignalSquareSum, decoderChannelContext->shortTermFilteredResidualSignal[i], decoderChannelContext->shortTermFilteredResidualSignal[i]); /* inputs are both in Q0, output is in Q-4 */
}
/* if the sum is null we can't compute gain -> output of postfiltering is the output of shortTermFilter and previousAdaptativeGain is set to 0 */
/* the reset of previousAdaptativeGain is not mentionned in the spec but in ITU code only */
if (shortTermFilteredResidualSignalSquareSum == 0) {
decoderChannelContext->previousAdaptativeGain = 0;
for (i=0; i<L_SUBFRAME; i++) {
postFilteredSignal[i] = decoderChannelContext->shortTermFilteredResidualSignal[i];
}
} else { /* we can compute adaptativeGain and output signal */
word16_t currentAdaptativeGain;
/* compute ∑s(n)^2 scale the signal shifting right by 4 to avoid possible overflow on 32 bits sum, same shift was applied at denominator */
uword32_t reconstructedSpeechSquareSum = 0;
for (i=0; i<L_SUBFRAME; i++) {
reconstructedSpeechSquareSum = UMAC16_16_Q4(reconstructedSpeechSquareSum, reconstructedSpeech[i], reconstructedSpeech[i]); /* inputs are both in Q0, output is in Q-4 */
}
if (reconstructedSpeechSquareSum==0) { /* numerator is null -> current gain is null */
gainScalingFactor = 0;
} else {
uword32_t fractionResult; /* stores ∑s(n)^2)/∑sf(n)^2 in Q10 on a 32 bit unsigned */
word32_t scaledShortTermFilteredResidualSignalSquareSum;
/* Compute ∑s(n)^2)/∑sf(n)^2 result shall be in Q10 */
/* normalise the numerator on 32 bits */
word16_t numeratorShift = unsignedCountLeadingZeros(reconstructedSpeechSquareSum);
reconstructedSpeechSquareSum = USHL(reconstructedSpeechSquareSum, numeratorShift); /* reconstructedSpeechSquareSum*2^numeratorShift */
/* normalise denominator to get the result directly in Q10 if possible */
scaledShortTermFilteredResidualSignalSquareSum = VSHR32(shortTermFilteredResidualSignalSquareSum, 10-numeratorShift); /* shortTermFilteredResidualSignalSquareSum*2^(numeratorShift-10)*/
if (scaledShortTermFilteredResidualSignalSquareSum==0) {/* shift might have sent to zero the denominator */
fractionResult = UDIV32(reconstructedSpeechSquareSum, shortTermFilteredResidualSignalSquareSum); /* result in QnumeratorShift */
fractionResult = VSHR32(fractionResult, numeratorShift-10); /* result in Q10 */
} else { /* ok denominator is still > 0 */
fractionResult = UDIV32(reconstructedSpeechSquareSum, scaledShortTermFilteredResidualSignalSquareSum); /* result in Q10 */
}
/* now compute current Gain = Sqrt((∑s(n)^2)/∑sf(n)^2 ) */
/* g729Sqrt_Q0Q7(Q0)->Q7, by giving a Q10 as input, output is in Q12 */
gainScalingFactor = (word16_t)SATURATE(g729Sqrt_Q0Q7(fractionResult), MAXINT16);
/* multiply by 0.1 as described in spec A.4.2.4 */
gainScalingFactor = MULT16_16_P15(gainScalingFactor, 3277); /* in Q12, 3277 = 0.1 in Q15*/
}
/* Compute the signal according to eq89 (spec 4.2.4 and section A4.2.4) */
/* currentGain = 0.9*previousGain + 0.1*gainScalingFactor the 0.1 factor has already been integrated in the variable gainScalingFactor */
/* outputsignal = currentGain*shortTermFilteredResidualSignal */
currentAdaptativeGain = decoderChannelContext->previousAdaptativeGain;
for (i=0; i<L_SUBFRAME; i++) {
currentAdaptativeGain = ADD16(gainScalingFactor, MULT16_16_P15(currentAdaptativeGain, 29491)); /* 29492 = 0.9 in Q15, result in Q12 */
postFilteredSignal[i] = MULT16_16_Q12(currentAdaptativeGain, decoderChannelContext->shortTermFilteredResidualSignal[i]);
}
decoderChannelContext->previousAdaptativeGain = currentAdaptativeGain;
}
/* shift buffers if needed */
if (subframeIndex>0) { /* only after 2nd subframe treatment */
/* shift left by L_FRAME the residualSignal and scaledResidualSignal buffers */
memmove(decoderChannelContext->residualSignalBuffer, &(decoderChannelContext->residualSignalBuffer[L_FRAME]), MAXIMUM_INT_PITCH_DELAY*sizeof(word16_t));
memmove(decoderChannelContext->scaledResidualSignalBuffer, &(decoderChannelContext->scaledResidualSignalBuffer[L_FRAME]), MAXIMUM_INT_PITCH_DELAY*sizeof(word16_t));
}
return;
}