arm_fir_interpolate_f32.c
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r71 | /* ---------------------------------------------------------------------- | |||
* Copyright (C) 2010 ARM Limited. All rights reserved. | ||||
* | ||||
* $Date: 15. July 2011 | ||||
* $Revision: V1.0.10 | ||||
* | ||||
* 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 | ||||
* | ||||
* Version 1.0.10 2011/7/15 | ||||
* Big Endian support added and Merged M0 and M3/M4 Source code. | ||||
* | ||||
* Version 1.0.3 2010/11/29 | ||||
* Re-organized the CMSIS folders and updated documentation. | ||||
* | ||||
* Version 1.0.2 2010/11/11 | ||||
* Documentation updated. | ||||
* | ||||
* Version 1.0.1 2010/10/05 | ||||
* Production release and review comments incorporated. | ||||
* | ||||
* Version 1.0.0 2010/09/20 | ||||
* Production release and review comments incorporated | ||||
* | ||||
* Version 0.0.7 2010/06/10 | ||||
* Misra-C changes done | ||||
* -------------------------------------------------------------------- */ | ||||
#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. | ||||
* | ||||
* \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. | ||||
*/ | ||||
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 */ | ||||
#ifndef ARM_MATH_CM0 | ||||
/* Run the below code for Cortex-M4 and Cortex-M3 */ | ||||
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 */ | ||||
/* 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++; | ||||
/* 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 */ | ||||
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; | ||||
while(tapCnt > 0u) | ||||
{ | ||||
*pStateCurnt++ = *pState++; | ||||
/* Decrement the loop counter */ | ||||
tapCnt--; | ||||
} | ||||
#else | ||||
/* Run the below code for Cortex-M0 */ | ||||
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 */ | ||||
} | ||||
/** | ||||
* @} end of FIR_Interpolate group | ||||
*/ | ||||