arm_iir_lattice_f32.c
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r16 | /* ---------------------------------------------------------------------- | ||
* Copyright (C) 2010 ARM Limited. All rights reserved. | ||||
* | ||||
* $Date: 29. November 2010 | ||||
* $Revision: V1.0.3 | ||||
* | ||||
* Project: CMSIS DSP Library | ||||
* Title: arm_iir_lattice_f32.c | ||||
* | ||||
* Description: Floating-point IIR Lattice filter processing function. | ||||
* | ||||
* Target Processor: Cortex-M4/Cortex-M3 | ||||
* | ||||
* 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" | ||||
/** | ||||
* @ingroup groupFilters | ||||
*/ | ||||
/** | ||||
* @defgroup IIR_Lattice Infinite Impulse Response (IIR) Lattice Filters | ||||
* | ||||
* This set of functions implements lattice filters | ||||
* for Q15, Q31 and floating-point data types. Lattice filters are used in a | ||||
* variety of adaptive filter applications. The filter structure has feedforward and | ||||
* feedback components and the net impulse response is infinite length. | ||||
* 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> point to input and output arrays containing <code>blockSize</code> values. | ||||
* \par Algorithm: | ||||
* \image html IIRLattice.gif "Infinite Impulse Response Lattice filter" | ||||
* <pre> | ||||
* fN(n) = x(n) | ||||
* fm-1(n) = fm(n) - km * gm-1(n-1) for m = N, N-1, ...1 | ||||
* gm(n) = km * fm-1(n) + gm-1(n-1) for m = N, N-1, ...1 | ||||
* y(n) = vN * gN(n) + vN-1 * gN-1(n) + ...+ v0 * g0(n) | ||||
* </pre> | ||||
* \par | ||||
* <code>pkCoeffs</code> points to array of reflection coefficients of size <code>numStages</code>. | ||||
* Reflection coefficients are stored in time-reversed order. | ||||
* \par | ||||
* <pre> | ||||
* {kN, kN-1, ....k1} | ||||
* </pre> | ||||
* <code>pvCoeffs</code> points to the array of ladder coefficients of size <code>(numStages+1)</code>. | ||||
* Ladder coefficients are stored in time-reversed order. | ||||
* \par | ||||
* <pre> | ||||
* {vN, vN-1, ...v0} | ||||
* </pre> | ||||
* <code>pState</code> points to a state array of size <code>numStages + blockSize</code>. | ||||
* The state variables shown in the figure above (the g values) are stored in the <code>pState</code> array. | ||||
* 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 arrays cannot be shared. | ||||
* 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. | ||||
* | ||||
* \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 and then manually initialize the instance structure as follows: | ||||
* <pre> | ||||
*arm_iir_lattice_instance_f32 S = {numStages, pState, pkCoeffs, pvCoeffs}; | ||||
*arm_iir_lattice_instance_q31 S = {numStages, pState, pkCoeffs, pvCoeffs}; | ||||
*arm_iir_lattice_instance_q15 S = {numStages, pState, pkCoeffs, pvCoeffs}; | ||||
* </pre> | ||||
* \par | ||||
* where <code>numStages</code> is the number of stages in the filter; <code>pState</code> points to the state buffer array; | ||||
* <code>pkCoeffs</code> points to array of the reflection coefficients; <code>pvCoeffs</code> points to the array of ladder coefficients. | ||||
* \par Fixed-Point Behavior | ||||
* Care must be taken when using the fixed-point versions of the IIR lattice 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 IIR_Lattice | ||||
* @{ | ||||
*/ | ||||
/** | ||||
* @brief Processing function for the floating-point IIR lattice filter. | ||||
* @param[in] *S points to an instance of the floating-point IIR lattice 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. | ||||
*/ | ||||
void arm_iir_lattice_f32( | ||||
const arm_iir_lattice_instance_f32 * S, | ||||
float32_t * pSrc, | ||||
float32_t * pDst, | ||||
uint32_t blockSize) | ||||
{ | ||||
float32_t fcurr, fnext, gcurr, gnext; /* Temporary variables for lattice stages */ | ||||
float32_t acc; /* Accumlator */ | ||||
uint32_t blkCnt, tapCnt; /* temporary variables for counts */ | ||||
float32_t *px1, *px2, *pk, *pv; /* temporary pointers for state and coef */ | ||||
uint32_t numStages = S->numStages; /* number of stages */ | ||||
float32_t *pState; /* State pointer */ | ||||
float32_t *pStateCurnt; /* State current pointer */ | ||||
gcurr = 0.0f; | ||||
blkCnt = blockSize; | ||||
pState = &S->pState[0]; | ||||
/* Sample processing */ | ||||
while(blkCnt > 0u) | ||||
{ | ||||
/* Read Sample from input buffer */ | ||||
/* fN(n) = x(n) */ | ||||
fcurr = *pSrc++; | ||||
/* Initialize state read pointer */ | ||||
px1 = pState; | ||||
/* Initialize state write pointer */ | ||||
px2 = pState; | ||||
/* Set accumulator to zero */ | ||||
acc = 0.0f; | ||||
/* Initialize Ladder coeff pointer */ | ||||
pv = &S->pvCoeffs[0]; | ||||
/* Initialize Reflection coeff pointer */ | ||||
pk = &S->pkCoeffs[0]; | ||||
/* Process sample for first tap */ | ||||
gcurr = *px1++; | ||||
/* fN-1(n) = fN(n) - kN * gN-1(n-1) */ | ||||
fnext = fcurr - ((*pk) * gcurr); | ||||
/* gN(n) = kN * fN-1(n) + gN-1(n-1) */ | ||||
gnext = (fnext * (*pk++)) + gcurr; | ||||
/* write gN(n) into state for next sample processing */ | ||||
*px2++ = gnext; | ||||
/* y(n) += gN(n) * vN */ | ||||
acc += (gnext * (*pv++)); | ||||
/* Update f values for next coefficient processing */ | ||||
fcurr = fnext; | ||||
/* Loop unrolling. Process 4 taps at a time. */ | ||||
tapCnt = (numStages - 1u) >> 2; | ||||
while(tapCnt > 0u) | ||||
{ | ||||
/* Process sample for 2nd, 6th ...taps */ | ||||
/* Read gN-2(n-1) from state buffer */ | ||||
gcurr = *px1++; | ||||
/* Process sample for 2nd, 6th .. taps */ | ||||
/* fN-2(n) = fN-1(n) - kN-1 * gN-2(n-1) */ | ||||
fnext = fcurr - ((*pk) * gcurr); | ||||
/* gN-1(n) = kN-1 * fN-2(n) + gN-2(n-1) */ | ||||
gnext = (fnext * (*pk++)) + gcurr; | ||||
/* y(n) += gN-1(n) * vN-1 */ | ||||
/* process for gN-5(n) * vN-5, gN-9(n) * vN-9 ... */ | ||||
acc += (gnext * (*pv++)); | ||||
/* write gN-1(n) into state for next sample processing */ | ||||
*px2++ = gnext; | ||||
/* Process sample for 3nd, 7th ...taps */ | ||||
/* Read gN-3(n-1) from state buffer */ | ||||
gcurr = *px1++; | ||||
/* Process sample for 3rd, 7th .. taps */ | ||||
/* fN-3(n) = fN-2(n) - kN-2 * gN-3(n-1) */ | ||||
fcurr = fnext - ((*pk) * gcurr); | ||||
/* gN-2(n) = kN-2 * fN-3(n) + gN-3(n-1) */ | ||||
gnext = (fcurr * (*pk++)) + gcurr; | ||||
/* y(n) += gN-2(n) * vN-2 */ | ||||
/* process for gN-6(n) * vN-6, gN-10(n) * vN-10 ... */ | ||||
acc += (gnext * (*pv++)); | ||||
/* write gN-2(n) into state for next sample processing */ | ||||
*px2++ = gnext; | ||||
/* Process sample for 4th, 8th ...taps */ | ||||
/* Read gN-4(n-1) from state buffer */ | ||||
gcurr = *px1++; | ||||
/* Process sample for 4th, 8th .. taps */ | ||||
/* fN-4(n) = fN-3(n) - kN-3 * gN-4(n-1) */ | ||||
fnext = fcurr - ((*pk) * gcurr); | ||||
/* gN-3(n) = kN-3 * fN-4(n) + gN-4(n-1) */ | ||||
gnext = (fnext * (*pk++)) + gcurr; | ||||
/* y(n) += gN-3(n) * vN-3 */ | ||||
/* process for gN-7(n) * vN-7, gN-11(n) * vN-11 ... */ | ||||
acc += (gnext * (*pv++)); | ||||
/* write gN-3(n) into state for next sample processing */ | ||||
*px2++ = gnext; | ||||
/* Process sample for 5th, 9th ...taps */ | ||||
/* Read gN-5(n-1) from state buffer */ | ||||
gcurr = *px1++; | ||||
/* Process sample for 5th, 9th .. taps */ | ||||
/* fN-5(n) = fN-4(n) - kN-4 * gN-1(n-1) */ | ||||
fcurr = fnext - ((*pk) * gcurr); | ||||
/* gN-4(n) = kN-4 * fN-5(n) + gN-5(n-1) */ | ||||
gnext = (fcurr * (*pk++)) + gcurr; | ||||
/* y(n) += gN-4(n) * vN-4 */ | ||||
/* process for gN-8(n) * vN-8, gN-12(n) * vN-12 ... */ | ||||
acc += (gnext * (*pv++)); | ||||
/* write gN-4(n) into state for next sample processing */ | ||||
*px2++ = gnext; | ||||
tapCnt--; | ||||
} | ||||
fnext = fcurr; | ||||
/* If the filter length is not a multiple of 4, compute the remaining filter taps */ | ||||
tapCnt = (numStages - 1u) % 0x4u; | ||||
while(tapCnt > 0u) | ||||
{ | ||||
gcurr = *px1++; | ||||
/* Process sample for last taps */ | ||||
fnext = fcurr - ((*pk) * gcurr); | ||||
gnext = (fnext * (*pk++)) + gcurr; | ||||
/* Output samples for last taps */ | ||||
acc += (gnext * (*pv++)); | ||||
*px2++ = gnext; | ||||
fcurr = fnext; | ||||
tapCnt--; | ||||
} | ||||
/* y(n) += g0(n) * v0 */ | ||||
acc += (fnext * (*pv)); | ||||
*px2++ = fnext; | ||||
/* write out into pDst */ | ||||
*pDst++ = acc; | ||||
/* Advance the state pointer by 4 to process the next group of 4 samples */ | ||||
pState = pState + 1u; | ||||
blkCnt--; | ||||
} | ||||
/* Processing is complete. Now copy last S->numStages samples to start of the buffer | ||||
for the preperation of next frame process */ | ||||
/* Points to the start of the state buffer */ | ||||
pStateCurnt = &S->pState[0]; | ||||
pState = &S->pState[blockSize]; | ||||
tapCnt = numStages >> 2u; | ||||
/* copy data */ | ||||
while(tapCnt > 0u) | ||||
{ | ||||
*pStateCurnt++ = *pState++; | ||||
*pStateCurnt++ = *pState++; | ||||
*pStateCurnt++ = *pState++; | ||||
*pStateCurnt++ = *pState++; | ||||
/* Decrement the loop counter */ | ||||
tapCnt--; | ||||
} | ||||
/* Calculate remaining number of copies */ | ||||
tapCnt = (numStages) % 0x4u; | ||||
/* Copy the remaining q31_t data */ | ||||
while(tapCnt > 0u) | ||||
{ | ||||
*pStateCurnt++ = *pState++; | ||||
/* Decrement the loop counter */ | ||||
tapCnt--; | ||||
} | ||||
} | ||||
/** | ||||
* @} end of IIR_Lattice group | ||||
*/ | ||||