/libraries/dsp/cmsis_dsp/FilteringFunctions/arm_iir_lattice_q31.c
C | 350 lines | 133 code | 66 blank | 151 comment | 0 complexity | 087a1e601e1ea2cd95fce2d05bf0424d MD5 | raw file
- /* ----------------------------------------------------------------------
- * 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_q31.c
- *
- * Description: Q31 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
- * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
- * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
- * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
- * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
- * -------------------------------------------------------------------- */
- #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_FAMILY
- /* 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_FAMILY */
- }
- /**
- * @} end of IIR_Lattice group
- */