/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_fir_interpolate_q31.c
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* Description: Q31 FIR interpolation
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*
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* $Date: 27. January 2017
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* $Revision: V.1.5.1
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*
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* Target Processor: Cortex-M cores
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* -------------------------------------------------------------------- */
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/*
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* Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an AS IS BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "arm_math.h"
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/**
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* @ingroup groupFilters
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*/
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/**
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* @addtogroup FIR_Interpolate
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* @{
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*/
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/**
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* @brief Processing function for the Q31 FIR interpolator.
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* @param[in] *S points to an instance of the Q31 FIR interpolator structure.
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* @param[in] *pSrc points to the block of input data.
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* @param[out] *pDst points to the block of output data.
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* @param[in] blockSize number of input samples to process per call.
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* @return none.
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*
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* <b>Scaling and Overflow Behavior:</b>
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* \par
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* The function is implemented using an internal 64-bit accumulator.
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* The accumulator has a 2.62 format and maintains full precision of the intermediate multiplication results but provides only a single guard bit.
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* Thus, if the accumulator result overflows it wraps around rather than clip.
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* In order to avoid overflows completely the input signal must be scaled down by <code>1/(numTaps/L)</code>.
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* since <code>numTaps/L</code> additions occur per output sample.
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* After all multiply-accumulates are performed, the 2.62 accumulator is truncated to 1.32 format and then saturated to 1.31 format.
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*/
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#if defined (ARM_MATH_DSP)
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/* Run the below code for Cortex-M4 and Cortex-M3 */
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void arm_fir_interpolate_q31(
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const arm_fir_interpolate_instance_q31 * S,
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q31_t * pSrc,
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q31_t * pDst,
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uint32_t blockSize)
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{
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q31_t *pState = S->pState; /* State pointer */
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q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
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q31_t *pStateCurnt; /* Points to the current sample of the state */
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q31_t *ptr1, *ptr2; /* Temporary pointers for state and coefficient buffers */
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q63_t sum0; /* Accumulators */
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q31_t x0, c0; /* Temporary variables to hold state and coefficient values */
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uint32_t i, blkCnt, j; /* Loop counters */
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uint16_t phaseLen = S->phaseLength, tapCnt; /* Length of each polyphase filter component */
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uint32_t blkCntN2;
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q63_t acc0, acc1;
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q31_t x1;
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/* S->pState buffer contains previous frame (phaseLen - 1) samples */
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/* pStateCurnt points to the location where the new input data should be written */
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pStateCurnt = S->pState + ((q31_t) phaseLen - 1);
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/* Initialise blkCnt */
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blkCnt = blockSize / 2;
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blkCntN2 = blockSize - (2 * blkCnt);
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/* Samples loop unrolled by 2 */
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while (blkCnt > 0U)
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{
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/* Copy new input sample into the state buffer */
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*pStateCurnt++ = *pSrc++;
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*pStateCurnt++ = *pSrc++;
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/* Address modifier index of coefficient buffer */
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j = 1U;
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/* Loop over the Interpolation factor. */
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i = (S->L);
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while (i > 0U)
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{
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/* Set accumulator to zero */
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acc0 = 0;
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acc1 = 0;
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/* Initialize state pointer */
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ptr1 = pState;
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/* Initialize coefficient pointer */
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ptr2 = pCoeffs + (S->L - j);
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/* Loop over the polyPhase length. Unroll by a factor of 4.
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** Repeat until we've computed numTaps-(4*S->L) coefficients. */
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tapCnt = phaseLen >> 2U;
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x0 = *(ptr1++);
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while (tapCnt > 0U)
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{
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/* Read the input sample */
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x1 = *(ptr1++);
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/* Read the coefficient */
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c0 = *(ptr2);
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/* Perform the multiply-accumulate */
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acc0 += (q63_t) x0 *c0;
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acc1 += (q63_t) x1 *c0;
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/* Read the coefficient */
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c0 = *(ptr2 + S->L);
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/* Read the input sample */
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x0 = *(ptr1++);
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/* Perform the multiply-accumulate */
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acc0 += (q63_t) x1 *c0;
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acc1 += (q63_t) x0 *c0;
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/* Read the coefficient */
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c0 = *(ptr2 + S->L * 2);
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/* Read the input sample */
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x1 = *(ptr1++);
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/* Perform the multiply-accumulate */
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acc0 += (q63_t) x0 *c0;
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acc1 += (q63_t) x1 *c0;
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/* Read the coefficient */
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c0 = *(ptr2 + S->L * 3);
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/* Read the input sample */
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x0 = *(ptr1++);
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/* Perform the multiply-accumulate */
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acc0 += (q63_t) x1 *c0;
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acc1 += (q63_t) x0 *c0;
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/* Upsampling is done by stuffing L-1 zeros between each sample.
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* So instead of multiplying zeros with coefficients,
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* Increment the coefficient pointer by interpolation factor times. */
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ptr2 += 4 * S->L;
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */
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tapCnt = phaseLen % 0x4U;
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while (tapCnt > 0U)
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{
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/* Read the input sample */
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x1 = *(ptr1++);
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/* Read the coefficient */
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c0 = *(ptr2);
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/* Perform the multiply-accumulate */
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acc0 += (q63_t) x0 *c0;
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acc1 += (q63_t) x1 *c0;
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/* Increment the coefficient pointer by interpolation factor times. */
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ptr2 += S->L;
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/* update states for next sample processing */
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x0 = x1;
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* The result is in the accumulator, store in the destination buffer. */
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*pDst = (q31_t) (acc0 >> 31);
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*(pDst + S->L) = (q31_t) (acc1 >> 31);
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pDst++;
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/* Increment the address modifier index of coefficient buffer */
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j++;
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/* Decrement the loop counter */
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i--;
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}
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/* Advance the state pointer by 1
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* to process the next group of interpolation factor number samples */
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pState = pState + 2;
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pDst += S->L;
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* If the blockSize is not a multiple of 2, compute any remaining output samples here.
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** No loop unrolling is used. */
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blkCnt = blkCntN2;
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/* Loop over the blockSize. */
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while (blkCnt > 0U)
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{
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/* Copy new input sample into the state buffer */
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*pStateCurnt++ = *pSrc++;
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/* Address modifier index of coefficient buffer */
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j = 1U;
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/* Loop over the Interpolation factor. */
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i = S->L;
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while (i > 0U)
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{
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/* Set accumulator to zero */
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sum0 = 0;
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/* Initialize state pointer */
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ptr1 = pState;
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/* Initialize coefficient pointer */
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ptr2 = pCoeffs + (S->L - j);
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/* Loop over the polyPhase length. Unroll by a factor of 4.
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** Repeat until we've computed numTaps-(4*S->L) coefficients. */
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tapCnt = phaseLen >> 2;
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while (tapCnt > 0U)
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{
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/* Read the coefficient */
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c0 = *(ptr2);
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/* Upsampling is done by stuffing L-1 zeros between each sample.
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* So instead of multiplying zeros with coefficients,
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* Increment the coefficient pointer by interpolation factor times. */
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ptr2 += S->L;
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/* Read the input sample */
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x0 = *(ptr1++);
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/* Perform the multiply-accumulate */
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sum0 += (q63_t) x0 *c0;
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/* Read the coefficient */
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c0 = *(ptr2);
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/* Increment the coefficient pointer by interpolation factor times. */
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ptr2 += S->L;
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/* Read the input sample */
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x0 = *(ptr1++);
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/* Perform the multiply-accumulate */
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sum0 += (q63_t) x0 *c0;
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/* Read the coefficient */
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c0 = *(ptr2);
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/* Increment the coefficient pointer by interpolation factor times. */
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ptr2 += S->L;
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/* Read the input sample */
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x0 = *(ptr1++);
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/* Perform the multiply-accumulate */
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sum0 += (q63_t) x0 *c0;
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/* Read the coefficient */
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c0 = *(ptr2);
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/* Increment the coefficient pointer by interpolation factor times. */
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ptr2 += S->L;
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/* Read the input sample */
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x0 = *(ptr1++);
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/* Perform the multiply-accumulate */
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sum0 += (q63_t) x0 *c0;
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */
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tapCnt = phaseLen & 0x3U;
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while (tapCnt > 0U)
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{
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/* Read the coefficient */
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c0 = *(ptr2);
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/* Increment the coefficient pointer by interpolation factor times. */
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ptr2 += S->L;
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/* Read the input sample */
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x0 = *(ptr1++);
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/* Perform the multiply-accumulate */
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sum0 += (q63_t) x0 *c0;
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* The result is in the accumulator, store in the destination buffer. */
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*pDst++ = (q31_t) (sum0 >> 31);
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/* Increment the address modifier index of coefficient buffer */
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j++;
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/* Decrement the loop counter */
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i--;
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}
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/* Advance the state pointer by 1
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* to process the next group of interpolation factor number samples */
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pState = pState + 1;
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* Processing is complete.
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** Now copy the last phaseLen - 1 samples to the satrt of the state buffer.
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** This prepares the state buffer for the next function call. */
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/* Points to the start of the state buffer */
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pStateCurnt = S->pState;
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tapCnt = (phaseLen - 1U) >> 2U;
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/* copy data */
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while (tapCnt > 0U)
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{
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*pStateCurnt++ = *pState++;
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*pStateCurnt++ = *pState++;
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*pStateCurnt++ = *pState++;
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*pStateCurnt++ = *pState++;
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/* Decrement the loop counter */
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tapCnt--;
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}
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tapCnt = (phaseLen - 1U) % 0x04U;
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/* copy data */
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while (tapCnt > 0U)
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{
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*pStateCurnt++ = *pState++;
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/* Decrement the loop counter */
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tapCnt--;
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}
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}
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#else
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void arm_fir_interpolate_q31(
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const arm_fir_interpolate_instance_q31 * S,
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q31_t * pSrc,
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q31_t * pDst,
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uint32_t blockSize)
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{
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q31_t *pState = S->pState; /* State pointer */
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q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
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q31_t *pStateCurnt; /* Points to the current sample of the state */
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q31_t *ptr1, *ptr2; /* Temporary pointers for state and coefficient buffers */
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/* Run the below code for Cortex-M0 */
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q63_t sum; /* Accumulator */
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q31_t x0, c0; /* Temporary variables to hold state and coefficient values */
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uint32_t i, blkCnt; /* Loop counters */
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uint16_t phaseLen = S->phaseLength, tapCnt; /* Length of each polyphase filter component */
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/* S->pState buffer contains previous frame (phaseLen - 1) samples */
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/* pStateCurnt points to the location where the new input data should be written */
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pStateCurnt = S->pState + ((q31_t) phaseLen - 1);
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/* Total number of intput samples */
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blkCnt = blockSize;
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/* Loop over the blockSize. */
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while (blkCnt > 0U)
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{
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/* Copy new input sample into the state buffer */
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*pStateCurnt++ = *pSrc++;
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/* Loop over the Interpolation factor. */
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i = S->L;
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while (i > 0U)
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{
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/* Set accumulator to zero */
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sum = 0;
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/* Initialize state pointer */
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ptr1 = pState;
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/* Initialize coefficient pointer */
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ptr2 = pCoeffs + (i - 1U);
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tapCnt = phaseLen;
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while (tapCnt > 0U)
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{
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/* Read the coefficient */
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c0 = *(ptr2);
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/* Increment the coefficient pointer by interpolation factor times. */
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ptr2 += S->L;
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/* Read the input sample */
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x0 = *ptr1++;
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/* Perform the multiply-accumulate */
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sum += (q63_t) x0 *c0;
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* The result is in the accumulator, store in the destination buffer. */
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*pDst++ = (q31_t) (sum >> 31);
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/* Decrement the loop counter */
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i--;
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}
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/* Advance the state pointer by 1
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* to process the next group of interpolation factor number samples */
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pState = pState + 1;
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* Processing is complete.
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** Now copy the last phaseLen - 1 samples to the satrt of the state buffer.
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** This prepares the state buffer for the next function call. */
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/* Points to the start of the state buffer */
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pStateCurnt = S->pState;
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tapCnt = phaseLen - 1U;
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/* copy data */
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while (tapCnt > 0U)
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{
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*pStateCurnt++ = *pState++;
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/* Decrement the loop counter */
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tapCnt--;
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}
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}
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#endif /* #if defined (ARM_MATH_DSP) */
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/**
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* @} end of FIR_Interpolate group
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*/
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