| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_fir_decimate_f32.c |
| * Description: FIR decimation for floating-point sequences |
| * |
| * $Date: 23 April 2021 |
| * $Revision: V1.9.0 |
| * |
| * Target Processor: Cortex-M and Cortex-A cores |
| * -------------------------------------------------------------------- */ |
| /* |
| * Copyright (C) 2010-2021 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 "dsp/filtering_functions.h" |
| |
| /** |
| @ingroup groupFilters |
| */ |
| |
| /** |
| @defgroup FIR_decimate Finite Impulse Response (FIR) Decimator |
| |
| These functions combine an FIR filter together with a decimator. |
| They are used in multirate systems for reducing the sample rate of a signal without introducing aliasing distortion. |
| Conceptually, the functions are equivalent to the block diagram below: |
| \image html FIRDecimator.gif "Components included in the FIR Decimator functions" |
| When decimating by a factor of <code>M</code>, the signal should be prefiltered by a lowpass filter with a normalized |
| cutoff frequency of <code>1/M</code> in order to prevent aliasing distortion. |
| The user of the function is responsible for providing the filter coefficients. |
| |
| The FIR decimator functions provided in the CMSIS DSP Library combine the FIR filter and the decimator in an efficient manner. |
| Instead of calculating all of the FIR filter outputs and discarding <code>M-1</code> out of every <code>M</code>, only the |
| samples output by the decimator are computed. |
| The functions operate on blocks of input and output data. |
| <code>pSrc</code> points to an array of <code>blockSize</code> input values and |
| <code>pDst</code> points to an array of <code>blockSize/M</code> output values. |
| In order to have an integer number of output samples <code>blockSize</code> |
| must always be a multiple of the decimation factor <code>M</code>. |
| |
| The library provides separate functions for Q15, Q31 and floating-point data types. |
| |
| @par Algorithm: |
| The FIR portion of the algorithm uses the standard form filter: |
| <pre> |
| y[n] = b[0] * x[n] + b[1] * x[n-1] + b[2] * x[n-2] + ...+ b[numTaps-1] * x[n-numTaps+1] |
| </pre> |
| where, <code>b[n]</code> are the filter coefficients. |
| @par |
| The <code>pCoeffs</code> points to a coefficient array of size <code>numTaps</code>. |
| Coefficients are stored in time reversed order. |
| @par |
| <pre> |
| {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]} |
| </pre> |
| @par |
| <code>pState</code> points to a state array of size <code>numTaps + blockSize - 1</code>. |
| Samples in the state buffer are stored in the order: |
| @par |
| <pre> |
| {x[n-numTaps+1], x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2]....x[0], x[1], ..., x[blockSize-1]} |
| </pre> |
| The state variables are updated after each block of data is processed, the coefficients are untouched. |
| |
| @par Instance Structure |
| The coefficients and state variables for a filter are stored together in an instance data structure. |
| A separate instance structure must be defined for each filter. |
| Coefficient arrays may be shared among several instances while state variable array should be allocated separately. |
| There are separate instance structure declarations for each of the 3 supported data types. |
| |
| @par Initialization Functions |
| There is also an associated initialization function for each data type. |
| The initialization function performs the following operations: |
| - Sets the values of the internal structure fields. |
| - Zeros out the values in the state buffer. |
| - Checks to make sure that the size of the input is a multiple of the decimation factor. |
| To do this manually without calling the init function, assign the follow subfields of the instance structure: |
| numTaps, pCoeffs, M (decimation factor), pState. Also set all of the values in pState to zero. |
| @par |
| Use of the initialization function is optional. |
| However, if the initialization function is used, then the instance structure cannot be placed into a const data section. |
| To place an instance structure into a const data section, the instance structure must be manually initialized. |
| The code below statically initializes each of the 3 different data type filter instance structures |
| <pre> |
| arm_fir_decimate_instance_f32 S = {M, numTaps, pCoeffs, pState}; |
| arm_fir_decimate_instance_q31 S = {M, numTaps, pCoeffs, pState}; |
| arm_fir_decimate_instance_q15 S = {M, numTaps, pCoeffs, pState}; |
| </pre> |
| where <code>M</code> is the decimation factor; <code>numTaps</code> is the number of filter coefficients in the filter; |
| <code>pCoeffs</code> is the address of the coefficient buffer; |
| <code>pState</code> is the address of the state buffer. |
| Be sure to set the values in the state buffer to zeros when doing static initialization. |
| |
| @par Fixed-Point Behavior |
| Care must be taken when using the fixed-point versions of the FIR decimate filter functions. |
| In particular, the overflow and saturation behavior of the accumulator used in each function must be considered. |
| Refer to the function specific documentation below for usage guidelines. |
| */ |
| |
| /** |
| @addtogroup FIR_decimate |
| @{ |
| */ |
| |
| /** |
| @brief Processing function for floating-point FIR decimator. |
| @param[in] S points to an instance of the floating-point FIR decimator 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 samples to process |
| @return none |
| */ |
| #if defined(ARM_MATH_MVEF) && !defined(ARM_MATH_AUTOVECTORIZE) |
| |
| #include "arm_helium_utils.h" |
| |
| void arm_fir_decimate_f32( |
| const arm_fir_decimate_instance_f32 * S, |
| const float32_t * pSrc, |
| float32_t * pDst, |
| uint32_t blockSize) |
| { |
| float32_t *pState = S->pState; /* State pointer */ |
| const float32_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| float32_t *pStateCurnt; /* Points to the current sample of the state */ |
| const float32_t *px, *pb; /* Temporary pointers for state and coefficient buffers */ |
| uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */ |
| uint32_t i, tapCnt, blkCnt, outBlockSize = blockSize / S->M; /* Loop counters */ |
| uint32_t blkCntN4; |
| const float32_t *px0, *px1, *px2, *px3; |
| f32x4_t accv = { 0 }, acc0v, acc1v, acc2v, acc3v; |
| f32x4_t x0v, x1v, x2v, x3v; |
| f32x4_t c0v; |
| |
| /* |
| * S->pState buffer contains previous frame (numTaps - 1) samples |
| * pStateCurnt points to the location where the new input data should be written |
| */ |
| pStateCurnt = S->pState + (numTaps - 1U); |
| /* |
| * Total number of output samples to be computed |
| */ |
| blkCnt = outBlockSize / 4; |
| blkCntN4 = outBlockSize - (4 * blkCnt); |
| |
| while (blkCnt > 0U) |
| { |
| /* |
| * Copy 4 * decimation factor number of new input samples into the state buffer |
| */ |
| i = (4 * S->M) >> 2; |
| do |
| { |
| vst1q(pStateCurnt, vld1q((const float32_t *)pSrc)); |
| pSrc += 4; |
| pStateCurnt += 4; |
| i--; |
| } |
| while (i > 0U); |
| |
| /* |
| * Set accumulators to zero |
| */ |
| acc0v = vdupq_n_f32(0.0f); |
| acc1v = vdupq_n_f32(0.0f); |
| acc2v = vdupq_n_f32(0.0f); |
| acc3v = vdupq_n_f32(0.0f); |
| |
| /* |
| * Initialize state pointer for all the samples |
| */ |
| px0 = pState; |
| px1 = pState + S->M; |
| px2 = pState + 2 * S->M; |
| px3 = pState + 3 * S->M; |
| /* |
| * Initialize coeff pointer |
| */ |
| pb = pCoeffs; |
| /* |
| * Loop unrolling. Process 4 taps at a time. |
| */ |
| tapCnt = numTaps >> 2; |
| /* |
| * Loop over the number of taps. Unroll by a factor of 4. |
| * Repeat until we've computed numTaps-4 coefficients. |
| */ |
| while (tapCnt > 0U) |
| { |
| /* |
| * Read the b[numTaps-1] coefficient |
| */ |
| c0v = vld1q((const float32_t *)pb); |
| pb += 4; |
| /* |
| * Read x[n-numTaps-1] sample for acc0 |
| */ |
| x0v = vld1q(px0); |
| x1v = vld1q(px1); |
| x2v = vld1q(px2); |
| x3v = vld1q(px3); |
| px0 += 4; |
| px1 += 4; |
| px2 += 4; |
| px3 += 4; |
| |
| acc0v = vfmaq(acc0v, x0v, c0v); |
| acc1v = vfmaq(acc1v, x1v, c0v); |
| acc2v = vfmaq(acc2v, x2v, c0v); |
| acc3v = vfmaq(acc3v, x3v, c0v); |
| /* |
| * Decrement the loop counter |
| */ |
| tapCnt--; |
| } |
| |
| /* |
| * If the filter length is not a multiple of 4, compute the remaining filter taps |
| * should be tail predicated |
| */ |
| tapCnt = numTaps % 0x4U; |
| if (tapCnt > 0U) |
| { |
| mve_pred16_t p0 = vctp32q(tapCnt); |
| /* |
| * Read the b[numTaps-1] coefficient |
| */ |
| c0v = vldrwq_z_f32(pb, p0); |
| pb += 4; |
| /* |
| * Read x[n-numTaps-1] sample for acc0 |
| */ |
| x0v = vld1q(px0); |
| x1v = vld1q(px1); |
| x2v = vld1q(px2); |
| x3v = vld1q(px3); |
| px0 += 4; |
| px1 += 4; |
| px2 += 4; |
| px3 += 4; |
| |
| acc0v = vfmaq_f32(acc0v, x0v, c0v); |
| acc1v = vfmaq_f32(acc1v, x1v, c0v); |
| acc2v = vfmaq_f32(acc2v, x2v, c0v); |
| acc3v = vfmaq_f32(acc3v, x3v, c0v); |
| } |
| |
| /* reduction */ |
| accv[0] = vecAddAcrossF32Mve(acc0v); |
| accv[1] = vecAddAcrossF32Mve(acc1v); |
| accv[2] = vecAddAcrossF32Mve(acc2v); |
| accv[3] = vecAddAcrossF32Mve(acc3v); |
| |
| /* |
| * Advance the state pointer by the decimation factor |
| * to process the next group of decimation factor number samples |
| */ |
| pState = pState + 4 * S->M; |
| /* |
| * The result is in the accumulator, store in the destination buffer. |
| */ |
| vst1q(pDst, accv); |
| pDst += 4; |
| |
| /* |
| * Decrement the loop counter |
| */ |
| blkCnt--; |
| } |
| |
| while (blkCntN4 > 0U) |
| { |
| /* |
| * Copy decimation factor number of new input samples into the state buffer |
| */ |
| i = S->M; |
| do |
| { |
| *pStateCurnt++ = *pSrc++; |
| } |
| while (--i); |
| /* |
| * Set accumulator to zero |
| */ |
| acc0v = vdupq_n_f32(0.0f); |
| /* |
| * Initialize state pointer |
| */ |
| px = pState; |
| /* |
| * Initialize coeff pointer |
| */ |
| pb = pCoeffs; |
| /* |
| * Loop unrolling. Process 4 taps at a time. |
| */ |
| tapCnt = numTaps >> 2; |
| /* |
| * Loop over the number of taps. Unroll by a factor of 4. |
| * Repeat until we've computed numTaps-4 coefficients. |
| */ |
| while (tapCnt > 0U) |
| { |
| c0v = vldrwq_f32(pb); |
| x0v = vldrwq_f32(px); |
| pb += 4; |
| px += 4; |
| acc0v = vfmaq_f32(acc0v, x0v, c0v); |
| /* |
| * Decrement the loop counter |
| */ |
| tapCnt--; |
| } |
| tapCnt = numTaps % 0x4U; |
| if (tapCnt > 0U) |
| { |
| mve_pred16_t p0 = vctp32q(tapCnt); |
| c0v = vldrwq_z_f32(pb, p0); |
| x0v = vldrwq_f32(px); |
| acc0v = vfmaq_f32(acc0v, x0v, c0v); |
| } |
| accv[0] = vecAddAcrossF32Mve(acc0v); |
| |
| /* |
| * Advance the state pointer by the decimation factor |
| * * to process the next group of decimation factor number samples |
| */ |
| pState = pState + S->M; |
| /* |
| * The result is in the accumulator, store in the destination buffer. |
| */ |
| *pDst++ = accv[0]; |
| /* |
| * Decrement the loop counter |
| */ |
| blkCntN4--; |
| } |
| |
| /* |
| * Processing is complete. |
| * Now copy the last numTaps - 1 samples to the start of the state buffer. |
| * This prepares the state buffer for the next function call. |
| */ |
| |
| pStateCurnt = S->pState; |
| blkCnt =(numTaps - 1) >> 2; |
| while (blkCnt > 0U) |
| { |
| vst1q(pStateCurnt, vldrwq_f32(pState)); |
| pState += 4; |
| pStateCurnt += 4; |
| blkCnt--; |
| } |
| blkCnt = (numTaps - 1) & 3; |
| if (blkCnt > 0U) |
| { |
| mve_pred16_t p0 = vctp32q(blkCnt); |
| vstrwq_p_f32(pStateCurnt, vldrwq_f32(pState), p0); |
| } |
| } |
| #else |
| #if defined(ARM_MATH_NEON) |
| void arm_fir_decimate_f32( |
| const arm_fir_decimate_instance_f32 * S, |
| const float32_t * pSrc, |
| float32_t * pDst, |
| uint32_t blockSize) |
| { |
| float32_t *pState = S->pState; /* State pointer */ |
| const float32_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| float32_t *pStateCurnt; /* Points to the current sample of the state */ |
| float32_t *px; /* Temporary pointer for state buffer */ |
| const float32_t *pb; /* Temporary pointer for coefficient buffer */ |
| float32_t sum0; /* Accumulator */ |
| float32_t x0, c0; /* Temporary variables to hold state and coefficient values */ |
| uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */ |
| uint32_t i, tapCnt, blkCnt, outBlockSize = blockSize / S->M; /* Loop counters */ |
| |
| uint32_t blkCntN4; |
| float32_t *px0, *px1, *px2, *px3; |
| float32_t x1, x2, x3; |
| |
| float32x4_t accv,acc0v,acc1v,acc2v,acc3v; |
| float32x4_t x0v, x1v, x2v, x3v; |
| float32x4_t c0v; |
| float32x2_t temp; |
| float32x4_t sum0v; |
| |
| /* S->pState buffer contains previous frame (numTaps - 1) samples */ |
| /* pStateCurnt points to the location where the new input data should be written */ |
| pStateCurnt = S->pState + (numTaps - 1U); |
| |
| /* Total number of output samples to be computed */ |
| blkCnt = outBlockSize / 4; |
| blkCntN4 = outBlockSize - (4 * blkCnt); |
| |
| while (blkCnt > 0U) |
| { |
| /* Copy 4 * decimation factor number of new input samples into the state buffer */ |
| i = 4 * S->M; |
| |
| do |
| { |
| *pStateCurnt++ = *pSrc++; |
| |
| } while (--i); |
| |
| /* Set accumulators to zero */ |
| acc0v = vdupq_n_f32(0.0); |
| acc1v = vdupq_n_f32(0.0); |
| acc2v = vdupq_n_f32(0.0); |
| acc3v = vdupq_n_f32(0.0); |
| |
| /* Initialize state pointer for all the samples */ |
| px0 = pState; |
| px1 = pState + S->M; |
| px2 = pState + 2 * S->M; |
| px3 = pState + 3 * S->M; |
| |
| /* Initialize coeff pointer */ |
| pb = pCoeffs; |
| |
| /* Process 4 taps at a time. */ |
| tapCnt = numTaps >> 2; |
| |
| /* Loop over the number of taps. |
| ** Repeat until we've computed numTaps-4 coefficients. */ |
| |
| while (tapCnt > 0U) |
| { |
| /* Read the b[numTaps-1] coefficient */ |
| c0v = vld1q_f32(pb); |
| pb += 4; |
| |
| /* Read x[n-numTaps-1] sample for acc0 */ |
| x0v = vld1q_f32(px0); |
| x1v = vld1q_f32(px1); |
| x2v = vld1q_f32(px2); |
| x3v = vld1q_f32(px3); |
| |
| px0 += 4; |
| px1 += 4; |
| px2 += 4; |
| px3 += 4; |
| |
| acc0v = vmlaq_f32(acc0v, x0v, c0v); |
| acc1v = vmlaq_f32(acc1v, x1v, c0v); |
| acc2v = vmlaq_f32(acc2v, x2v, c0v); |
| acc3v = vmlaq_f32(acc3v, x3v, c0v); |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| temp = vpadd_f32(vget_low_f32(acc0v),vget_high_f32(acc0v)); |
| accv = vsetq_lane_f32(vget_lane_f32(temp, 0) + vget_lane_f32(temp, 1),accv,0); |
| |
| temp = vpadd_f32(vget_low_f32(acc1v),vget_high_f32(acc1v)); |
| accv = vsetq_lane_f32(vget_lane_f32(temp, 0) + vget_lane_f32(temp, 1),accv,1); |
| |
| temp = vpadd_f32(vget_low_f32(acc2v),vget_high_f32(acc2v)); |
| accv = vsetq_lane_f32(vget_lane_f32(temp, 0) + vget_lane_f32(temp, 1),accv,2); |
| |
| temp = vpadd_f32(vget_low_f32(acc3v),vget_high_f32(acc3v)); |
| accv = vsetq_lane_f32(vget_lane_f32(temp, 0) + vget_lane_f32(temp, 1),accv,3); |
| |
| /* If the filter length is not a multiple of 4, compute the remaining filter taps */ |
| tapCnt = numTaps % 0x4U; |
| |
| while (tapCnt > 0U) |
| { |
| /* Read coefficients */ |
| c0 = *(pb++); |
| |
| /* Fetch state variables for acc0, acc1, acc2, acc3 */ |
| x0 = *(px0++); |
| x1 = *(px1++); |
| x2 = *(px2++); |
| x3 = *(px3++); |
| |
| /* Perform the multiply-accumulate */ |
| accv = vsetq_lane_f32(vgetq_lane_f32(accv, 0) + x0 * c0,accv,0); |
| accv = vsetq_lane_f32(vgetq_lane_f32(accv, 1) + x1 * c0,accv,1); |
| accv = vsetq_lane_f32(vgetq_lane_f32(accv, 2) + x2 * c0,accv,2); |
| accv = vsetq_lane_f32(vgetq_lane_f32(accv, 3) + x3 * c0,accv,3); |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| /* Advance the state pointer by the decimation factor |
| * to process the next group of decimation factor number samples */ |
| pState = pState + 4 * S->M; |
| |
| /* The result is in the accumulator, store in the destination buffer. */ |
| vst1q_f32(pDst,accv); |
| pDst += 4; |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| |
| while (blkCntN4 > 0U) |
| { |
| /* Copy decimation factor number of new input samples into the state buffer */ |
| i = S->M; |
| |
| do |
| { |
| *pStateCurnt++ = *pSrc++; |
| |
| } while (--i); |
| |
| /* Set accumulator to zero */ |
| sum0v = vdupq_n_f32(0.0); |
| |
| /* Initialize state pointer */ |
| px = pState; |
| |
| /* Initialize coeff pointer */ |
| pb = pCoeffs; |
| |
| /* Process 4 taps at a time. */ |
| tapCnt = numTaps >> 2; |
| |
| /* Loop over the number of taps. |
| ** Repeat until we've computed numTaps-4 coefficients. */ |
| while (tapCnt > 0U) |
| { |
| c0v = vld1q_f32(pb); |
| pb += 4; |
| |
| x0v = vld1q_f32(px); |
| px += 4; |
| |
| sum0v = vmlaq_f32(sum0v, x0v, c0v); |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| temp = vpadd_f32(vget_low_f32(sum0v),vget_high_f32(sum0v)); |
| sum0 = vget_lane_f32(temp, 0) + vget_lane_f32(temp, 1); |
| |
| /* If the filter length is not a multiple of 4, compute the remaining filter taps */ |
| tapCnt = numTaps % 0x4U; |
| |
| while (tapCnt > 0U) |
| { |
| /* Read coefficients */ |
| c0 = *(pb++); |
| |
| /* Fetch 1 state variable */ |
| x0 = *(px++); |
| |
| /* Perform the multiply-accumulate */ |
| sum0 += x0 * c0; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| /* Advance the state pointer by the decimation factor |
| * to process the next group of decimation factor number samples */ |
| pState = pState + S->M; |
| |
| /* The result is in the accumulator, store in the destination buffer. */ |
| *pDst++ = sum0; |
| |
| /* Decrement the loop counter */ |
| blkCntN4--; |
| } |
| |
| /* Processing is complete. |
| ** Now copy the last numTaps - 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; |
| |
| i = (numTaps - 1U) >> 2; |
| |
| /* Copy data */ |
| while (i > 0U) |
| { |
| sum0v = vld1q_f32(pState); |
| vst1q_f32(pStateCurnt,sum0v); |
| pState += 4; |
| pStateCurnt += 4; |
| |
| /* Decrement the loop counter */ |
| i--; |
| } |
| |
| i = (numTaps - 1U) % 0x04U; |
| |
| /* Copy data */ |
| while (i > 0U) |
| { |
| *pStateCurnt++ = *pState++; |
| |
| /* Decrement the loop counter */ |
| i--; |
| } |
| } |
| #else |
| void arm_fir_decimate_f32( |
| const arm_fir_decimate_instance_f32 * S, |
| const float32_t * pSrc, |
| float32_t * pDst, |
| uint32_t blockSize) |
| { |
| float32_t *pState = S->pState; /* State pointer */ |
| const float32_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| float32_t *pStateCur; /* Points to the current sample of the state */ |
| float32_t *px0; /* Temporary pointer for state buffer */ |
| const float32_t *pb; /* Temporary pointer for coefficient buffer */ |
| float32_t x0, c0; /* Temporary variables to hold state and coefficient values */ |
| float32_t acc0; /* Accumulator */ |
| uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */ |
| uint32_t i, tapCnt, blkCnt, outBlockSize = blockSize / S->M; /* Loop counters */ |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| float32_t *px1, *px2, *px3; |
| float32_t x1, x2, x3; |
| float32_t acc1, acc2, acc3; |
| #endif |
| |
| /* S->pState buffer contains previous frame (numTaps - 1) samples */ |
| /* pStateCur points to the location where the new input data should be written */ |
| pStateCur = S->pState + (numTaps - 1U); |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 samples at a time */ |
| blkCnt = outBlockSize >> 2U; |
| |
| /* Samples loop unrolled by 4 */ |
| while (blkCnt > 0U) |
| { |
| /* Copy 4 * decimation factor number of new input samples into the state buffer */ |
| i = S->M * 4; |
| |
| do |
| { |
| *pStateCur++ = *pSrc++; |
| |
| } while (--i); |
| |
| /* Set accumulators to zero */ |
| acc0 = 0.0f; |
| acc1 = 0.0f; |
| acc2 = 0.0f; |
| acc3 = 0.0f; |
| |
| /* Initialize state pointer for all the samples */ |
| px0 = pState; |
| px1 = pState + S->M; |
| px2 = pState + 2 * S->M; |
| px3 = pState + 3 * S->M; |
| |
| /* Initialize coeff pointer */ |
| pb = pCoeffs; |
| |
| /* Loop unrolling: Compute 4 taps at a time */ |
| tapCnt = numTaps >> 2U; |
| |
| while (tapCnt > 0U) |
| { |
| /* Read the b[numTaps-1] coefficient */ |
| c0 = *(pb++); |
| |
| /* Read x[n-numTaps-1] sample for acc0 */ |
| x0 = *(px0++); |
| /* Read x[n-numTaps-1] sample for acc1 */ |
| x1 = *(px1++); |
| /* Read x[n-numTaps-1] sample for acc2 */ |
| x2 = *(px2++); |
| /* Read x[n-numTaps-1] sample for acc3 */ |
| x3 = *(px3++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x0 * c0; |
| acc1 += x1 * c0; |
| acc2 += x2 * c0; |
| acc3 += x3 * c0; |
| |
| /* Read the b[numTaps-2] coefficient */ |
| c0 = *(pb++); |
| |
| /* Read x[n-numTaps-2] sample for acc0, acc1, acc2, acc3 */ |
| x0 = *(px0++); |
| x1 = *(px1++); |
| x2 = *(px2++); |
| x3 = *(px3++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x0 * c0; |
| acc1 += x1 * c0; |
| acc2 += x2 * c0; |
| acc3 += x3 * c0; |
| |
| /* Read the b[numTaps-3] coefficient */ |
| c0 = *(pb++); |
| |
| /* Read x[n-numTaps-3] sample acc0, acc1, acc2, acc3 */ |
| x0 = *(px0++); |
| x1 = *(px1++); |
| x2 = *(px2++); |
| x3 = *(px3++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x0 * c0; |
| acc1 += x1 * c0; |
| acc2 += x2 * c0; |
| acc3 += x3 * c0; |
| |
| /* Read the b[numTaps-4] coefficient */ |
| c0 = *(pb++); |
| |
| /* Read x[n-numTaps-4] sample acc0, acc1, acc2, acc3 */ |
| x0 = *(px0++); |
| x1 = *(px1++); |
| x2 = *(px2++); |
| x3 = *(px3++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x0 * c0; |
| acc1 += x1 * c0; |
| acc2 += x2 * c0; |
| acc3 += x3 * c0; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining taps */ |
| tapCnt = numTaps % 0x4U; |
| |
| while (tapCnt > 0U) |
| { |
| /* Read coefficients */ |
| c0 = *(pb++); |
| |
| /* Fetch state variables for acc0, acc1, acc2, acc3 */ |
| x0 = *(px0++); |
| x1 = *(px1++); |
| x2 = *(px2++); |
| x3 = *(px3++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x0 * c0; |
| acc1 += x1 * c0; |
| acc2 += x2 * c0; |
| acc3 += x3 * c0; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Advance the state pointer by the decimation factor |
| * to process the next group of decimation factor number samples */ |
| pState = pState + S->M * 4; |
| |
| /* The result is in the accumulator, store in the destination buffer. */ |
| *pDst++ = acc0; |
| *pDst++ = acc1; |
| *pDst++ = acc2; |
| *pDst++ = acc3; |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining samples */ |
| blkCnt = outBlockSize % 0x4U; |
| |
| #else |
| |
| /* Initialize blkCnt with number of samples */ |
| blkCnt = outBlockSize; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (blkCnt > 0U) |
| { |
| /* Copy decimation factor number of new input samples into the state buffer */ |
| i = S->M; |
| |
| do |
| { |
| *pStateCur++ = *pSrc++; |
| |
| } while (--i); |
| |
| /* Set accumulator to zero */ |
| acc0 = 0.0f; |
| |
| /* Initialize state pointer */ |
| px0 = pState; |
| |
| /* Initialize coeff pointer */ |
| pb = pCoeffs; |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 taps at a time */ |
| tapCnt = numTaps >> 2U; |
| |
| while (tapCnt > 0U) |
| { |
| /* Read the b[numTaps-1] coefficient */ |
| c0 = *pb++; |
| |
| /* Read x[n-numTaps-1] sample */ |
| x0 = *px0++; |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x0 * c0; |
| |
| /* Read the b[numTaps-2] coefficient */ |
| c0 = *pb++; |
| |
| /* Read x[n-numTaps-2] sample */ |
| x0 = *px0++; |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x0 * c0; |
| |
| /* Read the b[numTaps-3] coefficient */ |
| c0 = *pb++; |
| |
| /* Read x[n-numTaps-3] sample */ |
| x0 = *px0++; |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x0 * c0; |
| |
| /* Read the b[numTaps-4] coefficient */ |
| c0 = *pb++; |
| |
| /* Read x[n-numTaps-4] sample */ |
| x0 = *px0++; |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x0 * c0; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining taps */ |
| tapCnt = numTaps % 0x4U; |
| |
| #else |
| |
| /* Initialize tapCnt with number of taps */ |
| tapCnt = numTaps; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (tapCnt > 0U) |
| { |
| /* Read coefficients */ |
| c0 = *pb++; |
| |
| /* Fetch 1 state variable */ |
| x0 = *px0++; |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x0 * c0; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Advance the state pointer by the decimation factor |
| * to process the next group of decimation factor number samples */ |
| pState = pState + S->M; |
| |
| /* The result is in the accumulator, store in the destination buffer. */ |
| *pDst++ = acc0; |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Processing is complete. |
| Now copy the last numTaps - 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 */ |
| pStateCur = S->pState; |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 taps at a time */ |
| tapCnt = (numTaps - 1U) >> 2U; |
| |
| /* Copy data */ |
| while (tapCnt > 0U) |
| { |
| *pStateCur++ = *pState++; |
| *pStateCur++ = *pState++; |
| *pStateCur++ = *pState++; |
| *pStateCur++ = *pState++; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining taps */ |
| tapCnt = (numTaps - 1U) % 0x04U; |
| |
| #else |
| |
| /* Initialize tapCnt with number of taps */ |
| tapCnt = (numTaps - 1U); |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| /* Copy data */ |
| while (tapCnt > 0U) |
| { |
| *pStateCur++ = *pState++; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| } |
| #endif /* #if defined(ARM_MATH_NEON) */ |
| |
| #endif /*defined(ARM_MATH_MVEF) && !defined(ARM_MATH_AUTOVECTORIZE) */ |
| /** |
| @} end of FIR_decimate group |
| */ |
