/* ----------------------------------------------------------------------
* Copyright (C) 2010-2013 ARM Limited. All rights reserved.
*
* $Date: 17. January 2013
* $Revision: V1.4.1
*
* 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:
* - 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"
/**
* @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
* blockSize samples through the filter. pSrc and
* pDst point to input and output arrays containing blockSize values.
* \par Algorithm:
* \image html IIRLattice.gif "Infinite Impulse Response Lattice filter"
*
* 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)
*
* \par
* pkCoeffs points to array of reflection coefficients of size numStages.
* Reflection coefficients are stored in time-reversed order.
* \par
*
* {kN, kN-1, ....k1}
*
* pvCoeffs points to the array of ladder coefficients of size (numStages+1).
* Ladder coefficients are stored in time-reversed order.
* \par
*
* {vN, vN-1, ...v0}
*
* pState points to a state array of size numStages + blockSize.
* The state variables shown in the figure above (the g values) are stored in the pState 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:
*
*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};
*
* \par
* where numStages is the number of stages in the filter; pState points to the state buffer array;
* pkCoeffs points to array of the reflection coefficients; pvCoeffs 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
*/