| /* ---------------------------------------------------------------------- |
| * Copyright (C) 2010-2014 ARM Limited. All rights reserved. |
| * |
| * $Date: 19. March 2015 |
| * $Revision: V.1.4.5 |
| * |
| * Project: CMSIS DSP Library |
| * Title: arm_fir_interpolate_f32.c |
| * |
| * Description: FIR interpolation for floating-point sequences. |
| * |
| * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * - Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * - Neither the name of ARM LIMITED nor the names of its contributors |
| * may be used to endorse or promote products derived from this |
| * software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
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| * -------------------------------------------------------------------- */ |
| |
| #include "arm_math.h" |
| |
| /** |
| * @defgroup FIR_Interpolate Finite Impulse Response (FIR) Interpolator |
| * |
| * These functions combine an upsampler (zero stuffer) and an FIR filter. |
| * They are used in multirate systems for increasing the sample rate of a signal without introducing high frequency images. |
| * Conceptually, the functions are equivalent to the block diagram below: |
| * \image html FIRInterpolator.gif "Components included in the FIR Interpolator functions" |
| * After upsampling by a factor of <code>L</code>, the signal should be filtered by a lowpass filter with a normalized |
| * cutoff frequency of <code>1/L</code> in order to eliminate high frequency copies of the spectrum. |
| * The user of the function is responsible for providing the filter coefficients. |
| * |
| * The FIR interpolator functions provided in the CMSIS DSP Library combine the upsampler and FIR filter in an efficient manner. |
| * The upsampler inserts <code>L-1</code> zeros between each sample. |
| * Instead of multiplying by these zero values, the FIR filter is designed to skip them. |
| * This leads to an efficient implementation without any wasted effort. |
| * 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*L</code> output values. |
| * |
| * The library provides separate functions for Q15, Q31, and floating-point data types. |
| * |
| * \par Algorithm: |
| * The functions use a polyphase filter structure: |
| * <pre> |
| * y[n] = b[0] * x[n] + b[L] * x[n-1] + ... + b[L*(phaseLength-1)] * x[n-phaseLength+1] |
| * y[n+1] = b[1] * x[n] + b[L+1] * x[n-1] + ... + b[L*(phaseLength-1)+1] * x[n-phaseLength+1] |
| * ... |
| * y[n+(L-1)] = b[L-1] * x[n] + b[2*L-1] * x[n-1] + ....+ b[L*(phaseLength-1)+(L-1)] * x[n-phaseLength+1] |
| * </pre> |
| * This approach is more efficient than straightforward upsample-then-filter algorithms. |
| * With this method the computation is reduced by a factor of <code>1/L</code> when compared to using a standard FIR filter. |
| * \par |
| * <code>pCoeffs</code> points to a coefficient array of size <code>numTaps</code>. |
| * <code>numTaps</code> must be a multiple of the interpolation factor <code>L</code> and this is checked by the |
| * initialization functions. |
| * Internally, the function divides the FIR filter's impulse response into shorter filters of length |
| * <code>phaseLength=numTaps/L</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>blockSize + phaseLength - 1</code>. |
| * Samples in the state buffer are stored in the order: |
| * \par |
| * <pre> |
| * {x[n-phaseLength+1], x[n-phaseLength], x[n-phaseLength-1], x[n-phaseLength-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 length of the filter is a multiple of the interpolation factor. |
| * To do this manually without calling the init function, assign the follow subfields of the instance structure: |
| * L (interpolation factor), pCoeffs, phaseLength (numTaps / L), 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_interpolate_instance_f32 S = {L, phaseLength, pCoeffs, pState}; |
| * arm_fir_interpolate_instance_q31 S = {L, phaseLength, pCoeffs, pState}; |
| * arm_fir_interpolate_instance_q15 S = {L, phaseLength, pCoeffs, pState}; |
| * </pre> |
| * where <code>L</code> is the interpolation factor; <code>phaseLength=numTaps/L</code> is the |
| * length of each of the shorter FIR filters used internally, |
| * <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 interpolate 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_Interpolate |
| * @{ |
| */ |
| |
| /** |
| * @brief Processing function for the floating-point FIR interpolator. |
| * @param[in] *S points to an instance of the floating-point 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. |
| */ |
| #ifndef ARM_MATH_CM0_FAMILY |
| |
| /* Run the below code for Cortex-M4 and Cortex-M3 */ |
| |
| void arm_fir_interpolate_f32( |
| const arm_fir_interpolate_instance_f32 * S, |
| float32_t * pSrc, |
| float32_t * pDst, |
| uint32_t blockSize) |
| { |
| float32_t *pState = S->pState; /* State pointer */ |
| float32_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| float32_t *pStateCurnt; /* Points to the current sample of the state */ |
| float32_t *ptr1, *ptr2; /* Temporary pointers for state and coefficient buffers */ |
| float32_t sum0; /* Accumulators */ |
| float32_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 */ |
| float32_t acc0, acc1, acc2, acc3; |
| float32_t x1, x2, x3; |
| uint32_t blkCntN4; |
| float32_t c1, c2, c3; |
| |
| /* 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 + (phaseLen - 1u); |
| |
| /* Initialise blkCnt */ |
| blkCnt = blockSize / 4; |
| blkCntN4 = blockSize - (4 * blkCnt); |
| |
| /* Samples loop unrolled by 4 */ |
| while(blkCnt > 0u) |
| { |
| /* Copy new input sample into the state buffer */ |
| *pStateCurnt++ = *pSrc++; |
| *pStateCurnt++ = *pSrc++; |
| *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 = 0.0f; |
| acc1 = 0.0f; |
| acc2 = 0.0f; |
| acc3 = 0.0f; |
| |
| /* 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 += x0 * c0; |
| acc1 += x1 * c0; |
| acc2 += x2 * c0; |
| acc3 += x3 * c0; |
| |
| /* Read the coefficient */ |
| c1 = *(ptr2 + S->L); |
| |
| /* Read the input sample */ |
| x0 = *(ptr1++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x1 * c1; |
| acc1 += x2 * c1; |
| acc2 += x3 * c1; |
| acc3 += x0 * c1; |
| |
| /* Read the coefficient */ |
| c2 = *(ptr2 + S->L * 2); |
| |
| /* Read the input sample */ |
| x1 = *(ptr1++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x2 * c2; |
| acc1 += x3 * c2; |
| acc2 += x0 * c2; |
| acc3 += x1 * c2; |
| |
| /* Read the coefficient */ |
| c3 = *(ptr2 + S->L * 3); |
| |
| /* Read the input sample */ |
| x2 = *(ptr1++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x3 * c3; |
| acc1 += x0 * c3; |
| acc2 += x1 * c3; |
| acc3 += 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 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 */ |
| x3 = *(ptr1++); |
| |
| /* Read the coefficient */ |
| c0 = *(ptr2); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x0 * c0; |
| acc1 += x1 * c0; |
| acc2 += x2 * c0; |
| acc3 += 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 the loop counter */ |
| tapCnt--; |
| } |
| |
| /* The result is in the accumulator, store in the destination buffer. */ |
| *pDst = acc0; |
| *(pDst + S->L) = acc1; |
| *(pDst + 2 * S->L) = acc2; |
| *(pDst + 3 * S->L) = acc3; |
| |
| 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 + 4; |
| |
| pDst += S->L * 3; |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| |
| /* If the blockSize is not a multiple of 4, compute any remaining output samples here. |
| ** No loop unrolling is used. */ |
| |
| while(blkCntN4 > 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 = 0.0f; |
| |
| /* 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; |
| 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 += 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 += 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 += 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 += x0 * c0; |
| |
| /* 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) |
| { |
| /* Perform the multiply-accumulate */ |
| sum0 += *(ptr1++) * (*ptr2); |
| |
| /* Increment the coefficient pointer by interpolation factor times. */ |
| ptr2 += S->L; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| /* The result is in the accumulator, store in the destination buffer. */ |
| *pDst++ = sum0; |
| |
| /* 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 */ |
| blkCntN4--; |
| } |
| |
| /* 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 |
| |
| /* Run the below code for Cortex-M0 */ |
| |
| void arm_fir_interpolate_f32( |
| const arm_fir_interpolate_instance_f32 * S, |
| float32_t * pSrc, |
| float32_t * pDst, |
| uint32_t blockSize) |
| { |
| float32_t *pState = S->pState; /* State pointer */ |
| float32_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| float32_t *pStateCurnt; /* Points to the current sample of the state */ |
| float32_t *ptr1, *ptr2; /* Temporary pointers for state and coefficient buffers */ |
| |
| |
| float32_t sum; /* Accumulator */ |
| 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 + (phaseLen - 1u); |
| |
| /* 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 = 0.0f; |
| |
| /* 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 */ |
| sum += *ptr1++ * *ptr2; |
| |
| /* Increment the coefficient pointer by interpolation factor times. */ |
| ptr2 += S->L; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| /* The result is in the accumulator, store in the destination buffer. */ |
| *pDst++ = sum; |
| |
| /* 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 start 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; |
| |
| while(tapCnt > 0u) |
| { |
| *pStateCurnt++ = *pState++; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| } |
| |
| #endif /* #ifndef ARM_MATH_CM0_FAMILY */ |
| |
| |
| |
| /** |
| * @} end of FIR_Interpolate group |
| */ |
