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/**
* Copyright (C) 2022 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*------------------------------------------------------------------------------
*
* Subband processing consists of:
* inverse quantisation (defined in a separate file),
* predictor coefficient update (Pole and Zero Coeff update),
* predictor filtering.
*
*----------------------------------------------------------------------------*/
#ifndef SUBBANDFUNCTIONS_H
#define SUBBANDFUNCTIONS_H
#ifdef _GCC
#pragma GCC visibility push(hidden)
#endif
#include "AptxParameters.h"
XBT_INLINE_ void updatePredictorPoleCoefficients(
const int32_t invQ, const int32_t prevZfiltOutput,
PoleCoeff_data* PoleCoeffDataPt) {
int32_t adaptSum;
int32_t sgnP[3];
int32_t newCoeffs[2];
int32_t Bacc;
int32_t acc;
int32_t acc2;
int32_t tmp3_round0;
int16_t tmp2_round0;
int16_t tmp_round0;
/* Various constants in various Q formats */
const int32_t oneQ22 = 4194304L;
const int32_t minusOneQ22 = -4194304L;
const int32_t pointFiveQ21 = 1048576L;
const int32_t minusPointFiveQ21 = -1048576L;
const int32_t pointSevenFiveQ22 = 3145728L;
const int32_t minusPointSevenFiveQ22 = -3145728L;
const int32_t oneMinusTwoPowerMinusFourQ22 = 3932160L;
/* Symbolic indices for the pole coefficient arrays. Here we are using a1
* to represent the first pole filter coefficient and a2 the second. This
* seems to be common ADPCM terminology. */
enum { a1 = 0, a2 = 1 };
/* Symbolic indices for the sgn array (k, k-1 and k-2 respectively) */
enum { k = 0, k_1 = 1, k_2 = 2 };
/* Form the sum of the inverse quantiser and previous zero filter values */
adaptSum = invQ + prevZfiltOutput;
adaptSum = ssat24(adaptSum);
/* Form the sgn of the sum just formed (note +1 and -1 are Q22) */
if (adaptSum < 0L) {
sgnP[k] = minusOneQ22;
sgnP[k_1] = -(((int32_t)PoleCoeffDataPt->m_poleAdaptDelayLine.s16.l) << 22);
sgnP[k_2] = -(((int32_t)PoleCoeffDataPt->m_poleAdaptDelayLine.s16.h) << 22);
PoleCoeffDataPt->m_poleAdaptDelayLine.s16.h =
PoleCoeffDataPt->m_poleAdaptDelayLine.s16.l;
PoleCoeffDataPt->m_poleAdaptDelayLine.s16.l = -1;
} else if (adaptSum == 0L) {
sgnP[k] = 0L;
sgnP[k_1] = 0L;
sgnP[k_2] = 0L;
PoleCoeffDataPt->m_poleAdaptDelayLine.s16.h =
PoleCoeffDataPt->m_poleAdaptDelayLine.s16.l;
PoleCoeffDataPt->m_poleAdaptDelayLine.s16.l = 1;
} else { // adaptSum > 0L
sgnP[k] = oneQ22;
sgnP[k_1] = ((int32_t)PoleCoeffDataPt->m_poleAdaptDelayLine.s16.l) << 22;
sgnP[k_2] = ((int32_t)PoleCoeffDataPt->m_poleAdaptDelayLine.s16.h) << 22;
PoleCoeffDataPt->m_poleAdaptDelayLine.s16.h =
PoleCoeffDataPt->m_poleAdaptDelayLine.s16.l;
PoleCoeffDataPt->m_poleAdaptDelayLine.s16.l = 1;
}
/* Clear the accumulator and form -a1(k) * sgn(p(k))sgn(p(k-1)) in Q21. Clip
* it to +/- 0.5 (Q21) so that we can take f(a1) = 4 * a1. This is a partial
* result for the new a2 */
acc = 0;
acc -= PoleCoeffDataPt->m_poleCoeff[a1] * (sgnP[k_1] >> 22);
tmp3_round0 = acc & 0x3L;
acc += 0x001;
acc >>= 1;
if (tmp3_round0 == 0x001L) {
acc--;
}
newCoeffs[a2] = acc;
if (newCoeffs[a2] < minusPointFiveQ21) {
newCoeffs[a2] = minusPointFiveQ21;
}
if (newCoeffs[a2] > pointFiveQ21) {
newCoeffs[a2] = pointFiveQ21;
}
/* Load the accumulator with sgn(p(k))sgn(p(k-2)) right-shifted by 3. The
* 3-position shift is to multiply it by 0.25 and convert from Q22 to Q21.
*/
Bacc = (sgnP[k_2] >> 3);
/* Add the current a2 update value to the accumulator (Q21) */
Bacc += newCoeffs[a2];
/* Shift the accumulator right by 4 positions.
* Right 7 places to multiply by 2^(-7)
* Left 2 places to scale by 4 (0.25A + B -> A + 4B)
* Left 1 place to convert from Q21 to Q22
*/
Bacc >>= 4;
/* Add a2(k-1) * (1 - 2^(-7)) to the accumulator. Note that the constant is
* expressed as Q23, hence the product is Q22. Get the accumulator value
* back out. */
acc2 = PoleCoeffDataPt->m_poleCoeff[a2] << 8;
acc2 -= PoleCoeffDataPt->m_poleCoeff[a2] << 1;
Bacc = (int32_t)((uint32_t)Bacc << 8);
Bacc += acc2;
tmp2_round0 = (int16_t)Bacc & 0x01FFL;
Bacc += 0x0080L;
Bacc >>= 8;
if (tmp2_round0 == 0x0080L) {
Bacc--;
}
newCoeffs[a2] = Bacc;
/* Clip the new a2(k) value to +/- 0.75 (Q22) */
if (newCoeffs[a2] < minusPointSevenFiveQ22) {
newCoeffs[a2] = minusPointSevenFiveQ22;
}
if (newCoeffs[a2] > pointSevenFiveQ22) {
newCoeffs[a2] = pointSevenFiveQ22;
}
PoleCoeffDataPt->m_poleCoeff[a2] = newCoeffs[a2];
/* Form sgn(p(k))sgn(p(k-1)) * (3 * 2^(-8)). The constant is Q23, hence the
* product is Q22. */
/* Add a1(k-1) * (1 - 2^(-8)) to the accumulator. The constant is Q23, hence
* the product is Q22. Get the value from the accumulator. */
acc2 = PoleCoeffDataPt->m_poleCoeff[a1] << 8;
acc2 -= PoleCoeffDataPt->m_poleCoeff[a1];
acc2 += (sgnP[k_1] << 2);
acc2 -= (sgnP[k_1]);
tmp_round0 = (int16_t)acc2 & 0x01FF;
acc2 += 0x0080;
acc = (acc2 >> 8);
if (tmp_round0 == 0x0080) {
acc--;
}
newCoeffs[a1] = acc;
/* Clip the new value of a1(k) to +/- (1 - 2^4 - a2(k)). The constant 1 -
* 2^4 is expressed in Q22 format (as is a1 and a2) */
if (newCoeffs[a1] < (newCoeffs[a2] - oneMinusTwoPowerMinusFourQ22)) {
newCoeffs[a1] = newCoeffs[a2] - oneMinusTwoPowerMinusFourQ22;
}
if (newCoeffs[a1] > (oneMinusTwoPowerMinusFourQ22 - newCoeffs[a2])) {
newCoeffs[a1] = oneMinusTwoPowerMinusFourQ22 - newCoeffs[a2];
}
PoleCoeffDataPt->m_poleCoeff[a1] = newCoeffs[a1];
}
#ifdef _GCC
#pragma GCC visibility pop
#endif
#endif // SUBBANDFUNCTIONS_H
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