arm_iir_lattice_q31.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_iir_lattice_q31.c | ||||
* | ||||
* Description: Q31 IIR lattice filter processing function. | ||||
* | ||||
* 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" | ||||
/** | ||||
* @ingroup groupFilters | ||||
*/ | ||||
/** | ||||
* @addtogroup IIR_Lattice | ||||
* @{ | ||||
*/ | ||||
/** | ||||
* @brief Processing function for the Q31 IIR lattice filter. | ||||
* @param[in] *S points to an instance of the Q31 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. | ||||
* | ||||
* @details | ||||
* <b>Scaling and Overflow Behavior:</b> | ||||
* \par | ||||
* The function is implemented using an internal 64-bit accumulator. | ||||
* The accumulator has a 2.62 format and maintains full precision of the intermediate multiplication results but provides only a single guard bit. | ||||
* Thus, if the accumulator result overflows it wraps around rather than clip. | ||||
* In order to avoid overflows completely the input signal must be scaled down by 2*log2(numStages) bits. | ||||
* After all multiply-accumulates are performed, the 2.62 accumulator is saturated to 1.32 format and then truncated to 1.31 format. | ||||
*/ | ||||
void arm_iir_lattice_q31( | ||||
const arm_iir_lattice_instance_q31 * S, | ||||
q31_t * pSrc, | ||||
q31_t * pDst, | ||||
uint32_t blockSize) | ||||
{ | ||||
q31_t fcurr, fnext = 0, gcurr = 0, gnext; /* Temporary variables for lattice stages */ | ||||
q63_t acc; /* Accumlator */ | ||||
uint32_t blkCnt, tapCnt; /* Temporary variables for counts */ | ||||
q31_t *px1, *px2, *pk, *pv; /* Temporary pointers for state and coef */ | ||||
uint32_t numStages = S->numStages; /* number of stages */ | ||||
q31_t *pState; /* State pointer */ | ||||
q31_t *pStateCurnt; /* State current pointer */ | ||||
blkCnt = blockSize; | ||||
pState = &S->pState[0]; | ||||
#ifndef ARM_MATH_CM0 | ||||
/* Run the below code for Cortex-M4 and Cortex-M3 */ | ||||
/* 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; | ||||
/* 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 = __QSUB(fcurr, (q31_t) (((q63_t) gcurr * (*pk)) >> 31)); | ||||
/* gN(n) = kN * fN-1(n) + gN-1(n-1) */ | ||||
gnext = __QADD(gcurr, (q31_t) (((q63_t) fnext * (*pk++)) >> 31)); | ||||
/* write gN-1(n-1) into state for next sample processing */ | ||||
*px2++ = gnext; | ||||
/* y(n) += gN(n) * vN */ | ||||
acc += ((q63_t) 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++; | ||||
/* fN-2(n) = fN-1(n) - kN-1 * gN-2(n-1) */ | ||||
fnext = __QSUB(fcurr, (q31_t) (((q63_t) gcurr * (*pk)) >> 31)); | ||||
/* gN-1(n) = kN-1 * fN-2(n) + gN-2(n-1) */ | ||||
gnext = __QADD(gcurr, (q31_t) (((q63_t) fnext * (*pk++)) >> 31)); | ||||
/* y(n) += gN-1(n) * vN-1 */ | ||||
/* process for gN-5(n) * vN-5, gN-9(n) * vN-9 ... */ | ||||
acc += ((q63_t) 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 = __QSUB(fnext, (q31_t) (((q63_t) gcurr * (*pk)) >> 31)); | ||||
/* gN-2(n) = kN-2 * fN-3(n) + gN-3(n-1) */ | ||||
gnext = __QADD(gcurr, (q31_t) (((q63_t) fcurr * (*pk++)) >> 31)); | ||||
/* y(n) += gN-2(n) * vN-2 */ | ||||
/* process for gN-6(n) * vN-6, gN-10(n) * vN-10 ... */ | ||||
acc += ((q63_t) 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 = __QSUB(fcurr, (q31_t) (((q63_t) gcurr * (*pk)) >> 31)); | ||||
/* gN-3(n) = kN-3 * fN-4(n) + gN-4(n-1) */ | ||||
gnext = __QADD(gcurr, (q31_t) (((q63_t) fnext * (*pk++)) >> 31)); | ||||
/* y(n) += gN-3(n) * vN-3 */ | ||||
/* process for gN-7(n) * vN-7, gN-11(n) * vN-11 ... */ | ||||
acc += ((q63_t) 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 = __QSUB(fnext, (q31_t) (((q63_t) gcurr * (*pk)) >> 31)); | ||||
/* gN-4(n) = kN-4 * fN-5(n) + gN-5(n-1) */ | ||||
gnext = __QADD(gcurr, (q31_t) (((q63_t) fcurr * (*pk++)) >> 31)); | ||||
/* y(n) += gN-4(n) * vN-4 */ | ||||
/* process for gN-8(n) * vN-8, gN-12(n) * vN-12 ... */ | ||||
acc += ((q63_t) 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 = __QSUB(fcurr, (q31_t) (((q63_t) gcurr * (*pk)) >> 31)); | ||||
gnext = __QADD(gcurr, (q31_t) (((q63_t) fnext * (*pk++)) >> 31)); | ||||
/* Output samples for last taps */ | ||||
acc += ((q63_t) gnext * *pv++); | ||||
*px2++ = gnext; | ||||
fcurr = fnext; | ||||
tapCnt--; | ||||
} | ||||
/* y(n) += g0(n) * v0 */ | ||||
acc += (q63_t) fnext *( | ||||
*pv++); | ||||
*px2++ = fnext; | ||||
/* write out into pDst */ | ||||
*pDst++ = (q31_t) (acc >> 31u); | ||||
/* 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 | ||||
/* Run the below code for Cortex-M0 */ | ||||
/* 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; | ||||
/* Initialize Ladder coeff pointer */ | ||||
pv = &S->pvCoeffs[0]; | ||||
/* Initialize Reflection coeff pointer */ | ||||
pk = &S->pkCoeffs[0]; | ||||
tapCnt = numStages; | ||||
while(tapCnt > 0u) | ||||
{ | ||||
gcurr = *px1++; | ||||
/* Process sample */ | ||||
/* fN-1(n) = fN(n) - kN * gN-1(n-1) */ | ||||
fnext = | ||||
clip_q63_to_q31(((q63_t) fcurr - | ||||
((q31_t) (((q63_t) gcurr * (*pk)) >> 31)))); | ||||
/* gN(n) = kN * fN-1(n) + gN-1(n-1) */ | ||||
gnext = | ||||
clip_q63_to_q31(((q63_t) gcurr + | ||||
((q31_t) (((q63_t) fnext * (*pk++)) >> 31)))); | ||||
/* Output samples */ | ||||
/* y(n) += gN(n) * vN */ | ||||
acc += ((q63_t) gnext * *pv++); | ||||
/* write gN-1(n-1) into state for next sample processing */ | ||||
*px2++ = gnext; | ||||
/* Update f values for next coefficient processing */ | ||||
fcurr = fnext; | ||||
tapCnt--; | ||||
} | ||||
/* y(n) += g0(n) * v0 */ | ||||
acc += (q63_t) fnext *( | ||||
*pv++); | ||||
*px2++ = fnext; | ||||
/* write out into pDst */ | ||||
*pDst++ = (q31_t) (acc >> 31u); | ||||
/* 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 remaining q31_t data */ | ||||
while(tapCnt > 0u) | ||||
{ | ||||
*pStateCurnt++ = *pState++; | ||||
/* Decrement the loop counter */ | ||||
tapCnt--; | ||||
} | ||||
#endif /* #ifndef ARM_MATH_CM0 */ | ||||
} | ||||
/** | ||||
* @} end of IIR_Lattice group | ||||
*/ | ||||