| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_fir_interpolate_q15.c |
| * Description: Q15 FIR interpolation |
| * |
| * $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 |
| */ |
| |
| /** |
| @addtogroup FIR_Interpolate |
| @{ |
| */ |
| |
| /** |
| @brief Processing function for the Q15 FIR interpolator. |
| @param[in] S points to an instance of the Q15 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 samples to process |
| @return none |
| |
| @par Scaling and Overflow Behavior |
| The function is implemented using a 64-bit internal accumulator. |
| Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result. |
| The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format. |
| There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved. |
| After all additions have been performed, the accumulator is truncated to 34.15 format by discarding low 15 bits. |
| Lastly, the accumulator is saturated to yield a result in 1.15 format. |
| */ |
| |
| void arm_fir_interpolate_q15( |
| const arm_fir_interpolate_instance_q15 * S, |
| const q15_t * pSrc, |
| q15_t * pDst, |
| uint32_t blockSize) |
| { |
| #if (1) |
| //#if !defined(ARM_MATH_CM0_FAMILY) |
| |
| q15_t *pState = S->pState; /* State pointer */ |
| const q15_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| q15_t *pStateCur; /* Points to the current sample of the state */ |
| q15_t *ptr1; /* Temporary pointer for state buffer */ |
| const q15_t *ptr2; /* Temporary pointer for coefficient buffer */ |
| q63_t sum0; /* Accumulators */ |
| uint32_t i, blkCnt, tapCnt; /* Loop counters */ |
| uint32_t phaseLen = S->phaseLength; /* Length of each polyphase filter component */ |
| uint32_t j; |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| q63_t acc0, acc1, acc2, acc3; |
| q15_t x0, x1, x2, x3; |
| q15_t c0, c1, c2, c3; |
| #endif |
| |
| /* S->pState buffer contains previous frame (phaseLen - 1) samples */ |
| /* pStateCur points to the location where the new input data should be written */ |
| pStateCur = S->pState + (phaseLen - 1U); |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 outputs at a time */ |
| blkCnt = blockSize >> 2U; |
| |
| while (blkCnt > 0U) |
| { |
| /* Copy new input sample into the state buffer */ |
| *pStateCur++ = *pSrc++; |
| *pStateCur++ = *pSrc++; |
| *pStateCur++ = *pSrc++; |
| *pStateCur++ = *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; |
| acc2 = 0; |
| acc3 = 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++); |
| x1 = *(ptr1++); |
| x2 = *(ptr1++); |
| |
| while (tapCnt > 0U) |
| { |
| /* Read the input sample */ |
| x3 = *(ptr1++); |
| |
| /* Read the coefficient */ |
| c0 = *(ptr2); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += (q63_t) x0 * c0; |
| acc1 += (q63_t) x1 * c0; |
| acc2 += (q63_t) x2 * c0; |
| acc3 += (q63_t) x3 * c0; |
| |
| /* Read the coefficient */ |
| c1 = *(ptr2 + S->L); |
| |
| /* Read the input sample */ |
| x0 = *(ptr1++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += (q63_t) x1 * c1; |
| acc1 += (q63_t) x2 * c1; |
| acc2 += (q63_t) x3 * c1; |
| acc3 += (q63_t) x0 * c1; |
| |
| /* Read the coefficient */ |
| c2 = *(ptr2 + S->L * 2); |
| |
| /* Read the input sample */ |
| x1 = *(ptr1++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += (q63_t) x2 * c2; |
| acc1 += (q63_t) x3 * c2; |
| acc2 += (q63_t) x0 * c2; |
| acc3 += (q63_t) x1 * c2; |
| |
| /* Read the coefficient */ |
| c3 = *(ptr2 + S->L * 3); |
| |
| /* Read the input sample */ |
| x2 = *(ptr1++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += (q63_t) x3 * c3; |
| acc1 += (q63_t) x0 * c3; |
| acc2 += (q63_t) x1 * c3; |
| acc3 += (q63_t) x2 * c3; |
| |
| |
| /* 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 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 */ |
| x3 = *(ptr1++); |
| |
| /* Read the coefficient */ |
| c0 = *(ptr2); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += (q63_t) x0 * c0; |
| acc1 += (q63_t) x1 * c0; |
| acc2 += (q63_t) x2 * c0; |
| acc3 += (q63_t) x3 * c0; |
| |
| /* Increment the coefficient pointer by interpolation factor times. */ |
| ptr2 += S->L; |
| |
| /* update states for next sample processing */ |
| x0 = x1; |
| x1 = x2; |
| x2 = x3; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* The result is in the accumulator, store in the destination buffer. */ |
| *(pDst ) = (q15_t) (__SSAT((acc0 >> 15), 16)); |
| *(pDst + S->L) = (q15_t) (__SSAT((acc1 >> 15), 16)); |
| *(pDst + 2 * S->L) = (q15_t) (__SSAT((acc2 >> 15), 16)); |
| *(pDst + 3 * S->L) = (q15_t) (__SSAT((acc3 >> 15), 16)); |
| |
| pDst++; |
| |
| /* Increment the address modifier index of coefficient buffer */ |
| j++; |
| |
| /* Decrement loop counter */ |
| i--; |
| } |
| |
| /* Advance the state pointer by 1 |
| * to process the next group of interpolation factor number samples */ |
| pState = pState + 4; |
| |
| pDst += S->L * 3; |
| |
| /* 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) |
| { |
| /* Copy new input sample into the state buffer */ |
| *pStateCur++ = *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. |
| Repeat until we've computed numTaps-(4*S->L) coefficients. */ |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 outputs at a time */ |
| tapCnt = phaseLen >> 2U; |
| |
| while (tapCnt > 0U) |
| { |
| /* Perform the multiply-accumulate */ |
| sum0 += (q63_t) *ptr1++ * *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; |
| |
| sum0 += (q63_t) *ptr1++ * *ptr2; |
| ptr2 += S->L; |
| |
| sum0 += (q63_t) *ptr1++ * *ptr2; |
| ptr2 += S->L; |
| |
| sum0 += (q63_t) *ptr1++ * *ptr2; |
| ptr2 += S->L; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining outputs */ |
| tapCnt = phaseLen % 0x4U; |
| |
| #else |
| |
| /* Initialize tapCnt with number of samples */ |
| tapCnt = phaseLen; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (tapCnt > 0U) |
| { |
| /* Perform the multiply-accumulate */ |
| sum0 += (q63_t) *ptr1++ * *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; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* The result is in the accumulator, store in the destination buffer. */ |
| *pDst++ = (q15_t) (__SSAT((sum0 >> 15), 16)); |
| |
| /* 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 */ |
| pStateCur = S->pState; |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 outputs at a time */ |
| tapCnt = (phaseLen - 1U) >> 2U; |
| |
| /* copy data */ |
| while (tapCnt > 0U) |
| { |
| write_q15x2_ia (&pStateCur, read_q15x2_ia (&pState)); |
| write_q15x2_ia (&pStateCur, read_q15x2_ia (&pState)); |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining outputs */ |
| tapCnt = (phaseLen - 1U) % 0x04U; |
| |
| #else |
| |
| /* Initialize tapCnt with number of samples */ |
| tapCnt = (phaseLen - 1U); |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| /* Copy data */ |
| while (tapCnt > 0U) |
| { |
| *pStateCur++ = *pState++; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| #else |
| /* alternate version for CM0_FAMILY */ |
| |
| q15_t *pState = S->pState; /* State pointer */ |
| const q15_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| q15_t *pStateCur; /* Points to the current sample of the state */ |
| q15_t *ptr1; /* Temporary pointer for state buffer */ |
| const q15_t *ptr2; /* Temporary pointer for coefficient buffer */ |
| q63_t sum0; /* Accumulators */ |
| uint32_t i, blkCnt, tapCnt; /* Loop counters */ |
| uint32_t phaseLen = S->phaseLength; /* Length of each polyphase filter component */ |
| |
| /* S->pState buffer contains previous frame (phaseLen - 1) samples */ |
| /* pStateCur points to the location where the new input data should be written */ |
| pStateCur = S->pState + (phaseLen - 1U); |
| |
| /* Total number of intput samples */ |
| blkCnt = blockSize; |
| |
| /* Loop over the blockSize. */ |
| while (blkCnt > 0U) |
| { |
| /* Copy new input sample into the state buffer */ |
| *pStateCur++ = *pSrc++; |
| |
| /* 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 + (i - 1U); |
| |
| /* Loop over the polyPhase length */ |
| tapCnt = phaseLen; |
| |
| while (tapCnt > 0U) |
| { |
| /* Perform the multiply-accumulate */ |
| sum0 += ((q63_t) *ptr1++ * *ptr2); |
| |
| /* Increment the coefficient pointer by interpolation factor times. */ |
| ptr2 += S->L; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| /* Store the result after converting to 1.15 format in the destination buffer. */ |
| *pDst++ = (q15_t) (__SSAT((sum0 >> 15), 16)); |
| |
| /* Decrement loop counter */ |
| i--; |
| } |
| |
| /* Advance the state pointer by 1 |
| * to process the next group of interpolation factor number samples */ |
| pState = pState + 1; |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Processing is complete. |
| ** Now copy the last phaseLen - 1 samples to the start 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; |
| |
| tapCnt = phaseLen - 1U; |
| |
| /* Copy data */ |
| while (tapCnt > 0U) |
| { |
| *pStateCur++ = *pState++; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| #endif /* #if !defined(ARM_MATH_CM0_FAMILY) */ |
| |
| } |
| |
| /** |
| @} end of FIR_Interpolate group |
| */ |