pigweed / third_party / github / STMicroelectronics / cmsis_core / 7dd288b23bf605a3a2fafa81a29d2c96a2fd83ce / . / DSP_Lib / Source / FilteringFunctions / arm_iir_lattice_f32.c

/* ---------------------------------------------------------------------- | |

* Copyright (C) 2010-2014 ARM Limited. All rights reserved. | |

* | |

* $Date: 19. March 2015 | |

* $Revision: V.1.4.5 | |

* | |

* Project: CMSIS DSP Library | |

* Title: arm_iir_lattice_f32.c | |

* | |

* Description: Floating-point IIR Lattice filter processing function. | |

* | |

* 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: | |

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* - Redistributions in binary form must reproduce the above copyright | |

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* 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 | |

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* -------------------------------------------------------------------- */ | |

#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. | |

* To do this manually without calling the init function, assign the follow subfields of the instance structure: | |

* numStages, pkCoeffs, pvCoeffs, 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 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. | |

*/ | |

#ifndef ARM_MATH_CM0_FAMILY | |

/* Run the below code for Cortex-M4 and Cortex-M3 */ | |

void arm_iir_lattice_f32( | |

const arm_iir_lattice_instance_f32 * S, | |

float32_t * pSrc, | |

float32_t * pDst, | |

uint32_t blockSize) | |

{ | |

float32_t fnext1, gcurr1, 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 */ | |

float32_t k1, k2; | |

float32_t v1, v2, v3, v4; | |

float32_t gcurr2; | |

float32_t fnext2; | |

/* initialise loop count */ | |

blkCnt = blockSize; | |

/* initialise state pointer */ | |

pState = &S->pState[0]; | |

/* Sample processing */ | |

while(blkCnt > 0u) | |

{ | |

/* Read Sample from input buffer */ | |

/* fN(n) = x(n) */ | |

fnext2 = *pSrc++; | |

/* Initialize Ladder coeff pointer */ | |

pv = &S->pvCoeffs[0]; | |

/* Initialize Reflection coeff pointer */ | |

pk = &S->pkCoeffs[0]; | |

/* Initialize state read pointer */ | |

px1 = pState; | |

/* Initialize state write pointer */ | |

px2 = pState; | |

/* Set accumulator to zero */ | |

acc = 0.0; | |

/* Loop unrolling. Process 4 taps at a time. */ | |

tapCnt = (numStages) >> 2; | |

while(tapCnt > 0u) | |

{ | |

/* Read gN-1(n-1) from state buffer */ | |

gcurr1 = *px1; | |

/* read reflection coefficient kN */ | |

k1 = *pk; | |

/* fN-1(n) = fN(n) - kN * gN-1(n-1) */ | |

fnext1 = fnext2 - (k1 * gcurr1); | |

/* read ladder coefficient vN */ | |

v1 = *pv; | |

/* read next reflection coefficient kN-1 */ | |

k2 = *(pk + 1u); | |

/* Read gN-2(n-1) from state buffer */ | |

gcurr2 = *(px1 + 1u); | |

/* read next ladder coefficient vN-1 */ | |

v2 = *(pv + 1u); | |

/* fN-2(n) = fN-1(n) - kN-1 * gN-2(n-1) */ | |

fnext2 = fnext1 - (k2 * gcurr2); | |

/* gN(n) = kN * fN-1(n) + gN-1(n-1) */ | |

gnext = gcurr1 + (k1 * fnext1); | |

/* read reflection coefficient kN-2 */ | |

k1 = *(pk + 2u); | |

/* write gN(n) into state for next sample processing */ | |

*px2++ = gnext; | |

/* Read gN-3(n-1) from state buffer */ | |

gcurr1 = *(px1 + 2u); | |

/* y(n) += gN(n) * vN */ | |

acc += (gnext * v1); | |

/* fN-3(n) = fN-2(n) - kN-2 * gN-3(n-1) */ | |

fnext1 = fnext2 - (k1 * gcurr1); | |

/* gN-1(n) = kN-1 * fN-2(n) + gN-2(n-1) */ | |

gnext = gcurr2 + (k2 * fnext2); | |

/* Read gN-4(n-1) from state buffer */ | |

gcurr2 = *(px1 + 3u); | |

/* y(n) += gN-1(n) * vN-1 */ | |

acc += (gnext * v2); | |

/* read reflection coefficient kN-3 */ | |

k2 = *(pk + 3u); | |

/* write gN-1(n) into state for next sample processing */ | |

*px2++ = gnext; | |

/* fN-4(n) = fN-3(n) - kN-3 * gN-4(n-1) */ | |

fnext2 = fnext1 - (k2 * gcurr2); | |

/* gN-2(n) = kN-2 * fN-3(n) + gN-3(n-1) */ | |

gnext = gcurr1 + (k1 * fnext1); | |

/* read ladder coefficient vN-2 */ | |

v3 = *(pv + 2u); | |

/* y(n) += gN-2(n) * vN-2 */ | |

acc += (gnext * v3); | |

/* write gN-2(n) into state for next sample processing */ | |

*px2++ = gnext; | |

/* update pointer */ | |

pk += 4u; | |

/* gN-3(n) = kN-3 * fN-4(n) + gN-4(n-1) */ | |

gnext = (fnext2 * k2) + gcurr2; | |

/* read next ladder coefficient vN-3 */ | |

v4 = *(pv + 3u); | |

/* y(n) += gN-4(n) * vN-4 */ | |

acc += (gnext * v4); | |

/* write gN-3(n) into state for next sample processing */ | |

*px2++ = gnext; | |

/* update pointers */ | |

px1 += 4u; | |

pv += 4u; | |

tapCnt--; | |

} | |

/* If the filter length is not a multiple of 4, compute the remaining filter taps */ | |

tapCnt = (numStages) % 0x4u; | |

while(tapCnt > 0u) | |

{ | |

gcurr1 = *px1++; | |

/* Process sample for last taps */ | |

fnext1 = fnext2 - ((*pk) * gcurr1); | |

gnext = (fnext1 * (*pk++)) + gcurr1; | |

/* Output samples for last taps */ | |

acc += (gnext * (*pv++)); | |

*px2++ = gnext; | |

fnext2 = fnext1; | |

tapCnt--; | |

} | |

/* y(n) += g0(n) * v0 */ | |

acc += (fnext2 * (*pv)); | |

*px2++ = fnext2; | |

/* 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--; | |

} | |

} | |

#else | |

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 = 0, 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 */ | |

/* Run the below code for Cortex-M0 */ | |

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 numStages */ | |

tapCnt = numStages; | |

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; | |

/* Decrementing loop counter */ | |

tapCnt--; | |

} | |

/* y(n) += g0(n) * v0 */ | |

acc += (fnext * (*pv)); | |

*px2++ = fnext; | |

/* write out into pDst */ | |

*pDst++ = acc; | |

/* Advance the state pointer by 1 to process the next group of 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; | |

/* Copy the data */ | |

while(tapCnt > 0u) | |

{ | |

*pStateCurnt++ = *pState++; | |

/* Decrement the loop counter */ | |

tapCnt--; | |

} | |

} | |

#endif /* #ifndef ARM_MATH_CM0_FAMILY */ | |

/** | |

* @} end of IIR_Lattice group | |

*/ |