| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_fir_sparse_f32.c |
| * Description: Floating-point sparse FIR filter processing function |
| * |
| * $Date: 18. March 2019 |
| * $Revision: V1.6.0 |
| * |
| * Target Processor: Cortex-M cores |
| * -------------------------------------------------------------------- */ |
| /* |
| * Copyright (C) 2010-2019 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 |
| */ |
| |
| /** |
| @defgroup FIR_Sparse Finite Impulse Response (FIR) Sparse Filters |
| |
| This group of functions implements sparse FIR filters. |
| Sparse FIR filters are equivalent to standard FIR filters except that most of the coefficients are equal to zero. |
| Sparse filters are used for simulating reflections in communications and audio applications. |
| |
| There are separate functions for Q7, Q15, Q31, and floating-point data types. |
| The functions operate on blocks of input and output data and each call to the function processes |
| <code>blockSize</code> samples through the filter. <code>pSrc</code> and |
| <code>pDst</code> points to input and output arrays respectively containing <code>blockSize</code> values. |
| |
| @par Algorithm |
| The sparse filter instant structure contains an array of tap indices <code>pTapDelay</code> which specifies the locations of the non-zero coefficients. |
| This is in addition to the coefficient array <code>b</code>. |
| The implementation essentially skips the multiplications by zero and leads to an efficient realization. |
| <pre> |
| y[n] = b[0] * x[n-pTapDelay[0]] + b[1] * x[n-pTapDelay[1]] + b[2] * x[n-pTapDelay[2]] + ...+ b[numTaps-1] * x[n-pTapDelay[numTaps-1]] |
| </pre> |
| @par |
| \image html FIRSparse.gif "Sparse FIR filter. b[n] represents the filter coefficients" |
| @par |
| <code>pCoeffs</code> points to a coefficient array of size <code>numTaps</code>; |
| <code>pTapDelay</code> points to an array of nonzero indices and is also of size <code>numTaps</code>; |
| <code>pState</code> points to a state array of size <code>maxDelay + blockSize</code>, where |
| <code>maxDelay</code> is the largest offset value that is ever used in the <code>pTapDelay</code> array. |
| Some of the processing functions also require temporary working buffers. |
| |
| @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 and offset arrays may be shared among several instances while state variable arrays cannot be shared. |
| There are separate instance structure declarations for each of the 4 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. |
| To do this manually without calling the init function, assign the follow subfields of the instance structure: |
| numTaps, pCoeffs, pTapDelay, maxDelay, stateIndex, 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. |
| Set the values in the state buffer to zeros before static initialization. |
| The code below statically initializes each of the 4 different data type filter instance structures |
| <pre> |
| arm_fir_sparse_instance_f32 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay}; |
| arm_fir_sparse_instance_q31 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay}; |
| arm_fir_sparse_instance_q15 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay}; |
| arm_fir_sparse_instance_q7 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay}; |
| </pre> |
| |
| @par Fixed-Point Behavior |
| Care must be taken when using the fixed-point versions of the sparse FIR 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_Sparse |
| @{ |
| */ |
| |
| /** |
| @brief Processing function for the floating-point sparse FIR filter. |
| @param[in] S points to an instance of the floating-point sparse FIR structure |
| @param[in] pSrc points to the block of input data |
| @param[out] pDst points to the block of output data |
| @param[in] pScratchIn points to a temporary buffer of size blockSize |
| @param[in] blockSize number of input samples to process |
| @return none |
| */ |
| |
| void arm_fir_sparse_f32( |
| arm_fir_sparse_instance_f32 * S, |
| const float32_t * pSrc, |
| float32_t * pDst, |
| float32_t * pScratchIn, |
| uint32_t blockSize) |
| { |
| float32_t *pState = S->pState; /* State pointer */ |
| const float32_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| float32_t *px; /* Scratch buffer pointer */ |
| float32_t *py = pState; /* Temporary pointers for state buffer */ |
| float32_t *pb = pScratchIn; /* Temporary pointers for scratch buffer */ |
| float32_t *pOut; /* Destination pointer */ |
| int32_t *pTapDelay = S->pTapDelay; /* Pointer to the array containing offset of the non-zero tap values. */ |
| uint32_t delaySize = S->maxDelay + blockSize; /* state length */ |
| uint16_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */ |
| int32_t readIndex; /* Read index of the state buffer */ |
| uint32_t tapCnt, blkCnt; /* loop counters */ |
| float32_t coeff = *pCoeffs++; /* Read the first coefficient value */ |
| |
| |
| /* BlockSize of Input samples are copied into the state buffer */ |
| /* StateIndex points to the starting position to write in the state buffer */ |
| arm_circularWrite_f32((int32_t *) py, delaySize, &S->stateIndex, 1, (int32_t *) pSrc, 1, blockSize); |
| |
| /* Read Index, from where the state buffer should be read, is calculated. */ |
| readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++; |
| |
| /* Wraparound of readIndex */ |
| if (readIndex < 0) |
| { |
| readIndex += (int32_t) delaySize; |
| } |
| |
| /* Working pointer for state buffer is updated */ |
| py = pState; |
| |
| /* blockSize samples are read from the state buffer */ |
| arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1, |
| (int32_t *) pb, (int32_t *) pb, blockSize, 1, blockSize); |
| |
| /* Working pointer for the scratch buffer of state values */ |
| px = pb; |
| |
| /* Working pointer for scratch buffer of output values */ |
| pOut = pDst; |
| |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 outputs at a time. */ |
| blkCnt = blockSize >> 2U; |
| |
| while (blkCnt > 0U) |
| { |
| /* Perform Multiplications and store in destination buffer */ |
| *pOut++ = *px++ * coeff; |
| |
| *pOut++ = *px++ * coeff; |
| |
| *pOut++ = *px++ * coeff; |
| |
| *pOut++ = *px++ * coeff; |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining outputs */ |
| blkCnt = blockSize % 0x4U; |
| |
| #else |
| |
| /* Initialize blkCnt with number of samples */ |
| blkCnt = blockSize; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (blkCnt > 0U) |
| { |
| /* Perform Multiplication and store in destination buffer */ |
| *pOut++ = *px++ * coeff; |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Load the coefficient value and |
| * increment the coefficient buffer for the next set of state values */ |
| coeff = *pCoeffs++; |
| |
| /* Read Index, from where the state buffer should be read, is calculated. */ |
| readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++; |
| |
| /* Wraparound of readIndex */ |
| if (readIndex < 0) |
| { |
| readIndex += (int32_t) delaySize; |
| } |
| |
| /* Loop over the number of taps. */ |
| tapCnt = (uint32_t) numTaps - 2U; |
| |
| while (tapCnt > 0U) |
| { |
| /* Working pointer for state buffer is updated */ |
| py = pState; |
| |
| /* blockSize samples are read from the state buffer */ |
| arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1, |
| (int32_t *) pb, (int32_t *) pb, blockSize, 1, blockSize); |
| |
| /* Working pointer for the scratch buffer of state values */ |
| px = pb; |
| |
| /* Working pointer for scratch buffer of output values */ |
| pOut = pDst; |
| |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 outputs at a time. */ |
| blkCnt = blockSize >> 2U; |
| |
| while (blkCnt > 0U) |
| { |
| /* Perform Multiply-Accumulate */ |
| *pOut++ += *px++ * coeff; |
| |
| *pOut++ += *px++ * coeff; |
| |
| *pOut++ += *px++ * coeff; |
| |
| *pOut++ += *px++ * coeff; |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining outputs */ |
| blkCnt = blockSize % 0x4U; |
| |
| #else |
| |
| /* Initialize blkCnt with number of samples */ |
| blkCnt = blockSize; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (blkCnt > 0U) |
| { |
| /* Perform Multiply-Accumulate */ |
| *pOut++ += *px++ * coeff; |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Load the coefficient value and |
| * increment the coefficient buffer for the next set of state values */ |
| coeff = *pCoeffs++; |
| |
| /* Read Index, from where the state buffer should be read, is calculated. */ |
| readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++; |
| |
| /* Wraparound of readIndex */ |
| if (readIndex < 0) |
| { |
| readIndex += (int32_t) delaySize; |
| } |
| |
| /* Decrement tap loop counter */ |
| tapCnt--; |
| } |
| |
| /* Compute last tap without the final read of pTapDelay */ |
| |
| /* Working pointer for state buffer is updated */ |
| py = pState; |
| |
| /* blockSize samples are read from the state buffer */ |
| arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1, |
| (int32_t *) pb, (int32_t *) pb, blockSize, 1, blockSize); |
| |
| /* Working pointer for the scratch buffer of state values */ |
| px = pb; |
| |
| /* Working pointer for scratch buffer of output values */ |
| pOut = pDst; |
| |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 outputs at a time. */ |
| blkCnt = blockSize >> 2U; |
| |
| while (blkCnt > 0U) |
| { |
| /* Perform Multiply-Accumulate */ |
| *pOut++ += *px++ * coeff; |
| *pOut++ += *px++ * coeff; |
| *pOut++ += *px++ * coeff; |
| *pOut++ += *px++ * coeff; |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining outputs */ |
| blkCnt = blockSize % 0x4U; |
| |
| #else |
| |
| /* Initialize blkCnt with number of samples */ |
| blkCnt = blockSize; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (blkCnt > 0U) |
| { |
| /* Perform Multiply-Accumulate */ |
| *pOut++ += *px++ * coeff; |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| } |
| |
| /** |
| @} end of FIR_Sparse group |
| */ |