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