DSP/Source/FilteringFunctions/arm_lms_norm_q31.c

/* ----------------------------------------------------------------------
 * Project:      CMSIS DSP Library
 * Title:        arm_lms_norm_q31.c
 * Description:  Processing function for the Q31 NLMS filter
 *
 * $Date:        27. January 2017
 * $Revision:    V.1.5.1
 *
 * Target Processor: Cortex-M cores
 * -------------------------------------------------------------------- */
/*
 * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 (the License); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup LMS_NORM
 * @{
 */

/**
* @brief Processing function for Q31 normalized LMS filter.
* @param[in] *S points to an instance of the Q31 normalized LMS filter structure.
* @param[in] *pSrc points to the block of input data.
* @param[in] *pRef points to the block of reference data.
* @param[out] *pOut points to the block of output data.
* @param[out] *pErr points to the block of error data.
* @param[in] blockSize number of samples to process.
* @return none.
*
* <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
* log2(numTaps) bits. The reference signal should not be scaled down.
* After all multiply-accumulates are performed, the 2.62 accumulator is shifted
* and saturated to 1.31 format to yield the final result.
* The output signal and error signal are in 1.31 format.
*
* \par
* 	In this filter, filter coefficients are updated for each sample and the
* updation of filter cofficients are saturted.
*
*/

void arm_lms_norm_q31(
  arm_lms_norm_instance_q31 * S,
  q31_t * pSrc,
  q31_t * pRef,
  q31_t * pOut,
  q31_t * pErr,
  uint32_t blockSize)
{
  q31_t *pState = S->pState;                     /* State pointer */
  q31_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
  q31_t *pStateCurnt;                            /* Points to the current sample of the state */
  q31_t *px, *pb;                                /* Temporary pointers for state and coefficient buffers */
  q31_t mu = S->mu;                              /* Adaptive factor */
  uint32_t numTaps = S->numTaps;                 /* Number of filter coefficients in the filter */
  uint32_t tapCnt, blkCnt;                       /* Loop counters */
  q63_t energy;                                  /* Energy of the input */
  q63_t acc;                                     /* Accumulator */
  q31_t e = 0, d = 0;                            /* error, reference data sample */
  q31_t w = 0, in;                               /* weight factor and state */
  q31_t x0;                                      /* temporary variable to hold input sample */
//  uint32_t shift = 32U - ((uint32_t) S->postShift + 1U);        /* Shift to be applied to the output */
  q31_t errorXmu, oneByEnergy;                   /* Temporary variables to store error and mu product and reciprocal of energy */
  q31_t postShift;                               /* Post shift to be applied to weight after reciprocal calculation */
  q31_t coef;                                    /* Temporary variable for coef */
  q31_t acc_l, acc_h;                            /*  temporary input */
  uint32_t uShift = ((uint32_t) S->postShift + 1U);
  uint32_t lShift = 32U - uShift;                /*  Shift to be applied to the output */

  energy = S->energy;
  x0 = S->x0;

  /* S->pState points to buffer which contains previous frame (numTaps - 1) samples */
  /* pStateCurnt points to the location where the new input data should be written */
  pStateCurnt = &(S->pState[(numTaps - 1U)]);

  /* Loop over blockSize number of values */
  blkCnt = blockSize;


#if defined (ARM_MATH_DSP)

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

  while (blkCnt > 0U)
  {

    /* Copy the new input sample into the state buffer */
    *pStateCurnt++ = *pSrc;

    /* Initialize pState pointer */
    px = pState;

    /* Initialize coeff pointer */
    pb = (pCoeffs);

    /* Read the sample from input buffer */
    in = *pSrc++;

    /* Update the energy calculation */
    energy = (q31_t) ((((q63_t) energy << 32) -
                       (((q63_t) x0 * x0) << 1)) >> 32);
    energy = (q31_t) (((((q63_t) in * in) << 1) + (energy << 32)) >> 32);

    /* Set the accumulator to zero */
    acc = 0;

    /* Loop unrolling.  Process 4 taps at a time. */
    tapCnt = numTaps >> 2;

    while (tapCnt > 0U)
    {
      /* Perform the multiply-accumulate */
      acc += ((q63_t) (*px++)) * (*pb++);
      acc += ((q63_t) (*px++)) * (*pb++);
      acc += ((q63_t) (*px++)) * (*pb++);
      acc += ((q63_t) (*px++)) * (*pb++);

      /* Decrement the loop counter */
      tapCnt--;
    }

    /* If the filter length is not a multiple of 4, compute the remaining filter taps */
    tapCnt = numTaps % 0x4U;

    while (tapCnt > 0U)
    {
      /* Perform the multiply-accumulate */
      acc += ((q63_t) (*px++)) * (*pb++);

      /* Decrement the loop counter */
      tapCnt--;
    }

    /* Converting the result to 1.31 format */
    /* Calc lower part of acc */
    acc_l = acc & 0xffffffff;

    /* Calc upper part of acc */
    acc_h = (acc >> 32) & 0xffffffff;

    acc = (uint32_t) acc_l >> lShift | acc_h << uShift;

    /* Store the result from accumulator into the destination buffer. */
    *pOut++ = (q31_t) acc;

    /* Compute and store error */
    d = *pRef++;
    e = d - (q31_t) acc;
    *pErr++ = e;

    /* Calculates the reciprocal of energy */
    postShift = arm_recip_q31(energy + DELTA_Q31,
                              &oneByEnergy, &S->recipTable[0]);

    /* Calculation of product of (e * mu) */
    errorXmu = (q31_t) (((q63_t) e * mu) >> 31);

    /* Weighting factor for the normalized version */
    w = clip_q63_to_q31(((q63_t) errorXmu * oneByEnergy) >> (31 - postShift));

    /* Initialize pState pointer */
    px = pState;

    /* Initialize coeff pointer */
    pb = (pCoeffs);

    /* Loop unrolling.  Process 4 taps at a time. */
    tapCnt = numTaps >> 2;

    /* Update filter coefficients */
    while (tapCnt > 0U)
    {
      /* Perform the multiply-accumulate */

      /* coef is in 2.30 format */
      coef = (q31_t) (((q63_t) w * (*px++)) >> (32));
      /* get coef in 1.31 format by left shifting */
      *pb = clip_q63_to_q31((q63_t) * pb + (coef << 1U));
      /* update coefficient buffer to next coefficient */
      pb++;

      coef = (q31_t) (((q63_t) w * (*px++)) >> (32));
      *pb = clip_q63_to_q31((q63_t) * pb + (coef << 1U));
      pb++;

      coef = (q31_t) (((q63_t) w * (*px++)) >> (32));
      *pb = clip_q63_to_q31((q63_t) * pb + (coef << 1U));
      pb++;

      coef = (q31_t) (((q63_t) w * (*px++)) >> (32));
      *pb = clip_q63_to_q31((q63_t) * pb + (coef << 1U));
      pb++;

      /* Decrement the loop counter */
      tapCnt--;
    }

    /* If the filter length is not a multiple of 4, compute the remaining filter taps */
    tapCnt = numTaps % 0x4U;

    while (tapCnt > 0U)
    {
      /* Perform the multiply-accumulate */
      coef = (q31_t) (((q63_t) w * (*px++)) >> (32));
      *pb = clip_q63_to_q31((q63_t) * pb + (coef << 1U));
      pb++;

      /* Decrement the loop counter */
      tapCnt--;
    }

    /* Read the sample from state buffer */
    x0 = *pState;

    /* Advance state pointer by 1 for the next sample */
    pState = pState + 1;

    /* Decrement the loop counter */
    blkCnt--;
  }

  /* Save energy and x0 values for the next frame */
  S->energy = (q31_t) energy;
  S->x0 = x0;

  /* Processing is complete. Now copy the last numTaps - 1 samples to the
     satrt of the state buffer. This prepares the state buffer for the
     next function call. */

  /* Points to the start of the pState buffer */
  pStateCurnt = S->pState;

  /* Loop unrolling for (numTaps - 1U) samples copy */
  tapCnt = (numTaps - 1U) >> 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 = (numTaps - 1U) % 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 */

  while (blkCnt > 0U)
  {

    /* Copy the new input sample into the state buffer */
    *pStateCurnt++ = *pSrc;

    /* Initialize pState pointer */
    px = pState;

    /* Initialize pCoeffs pointer */
    pb = pCoeffs;

    /* Read the sample from input buffer */
    in = *pSrc++;

    /* Update the energy calculation */
    energy =
      (q31_t) ((((q63_t) energy << 32) - (((q63_t) x0 * x0) << 1)) >> 32);
    energy = (q31_t) (((((q63_t) in * in) << 1) + (energy << 32)) >> 32);

    /* Set the accumulator to zero */
    acc = 0;

    /* Loop over numTaps number of values */
    tapCnt = numTaps;

    while (tapCnt > 0U)
    {
      /* Perform the multiply-accumulate */
      acc += ((q63_t) (*px++)) * (*pb++);

      /* Decrement the loop counter */
      tapCnt--;
    }

    /* Converting the result to 1.31 format */
    /* Converting the result to 1.31 format */
    /* Calc lower part of acc */
    acc_l = acc & 0xffffffff;

    /* Calc upper part of acc */
    acc_h = (acc >> 32) & 0xffffffff;

    acc = (uint32_t) acc_l >> lShift | acc_h << uShift;


    //acc = (q31_t) (acc >> shift);

    /* Store the result from accumulator into the destination buffer. */
    *pOut++ = (q31_t) acc;

    /* Compute and store error */
    d = *pRef++;
    e = d - (q31_t) acc;
    *pErr++ = e;

    /* Calculates the reciprocal of energy */
    postShift =
      arm_recip_q31(energy + DELTA_Q31, &oneByEnergy, &S->recipTable[0]);

    /* Calculation of product of (e * mu) */
    errorXmu = (q31_t) (((q63_t) e * mu) >> 31);

    /* Weighting factor for the normalized version */
    w = clip_q63_to_q31(((q63_t) errorXmu * oneByEnergy) >> (31 - postShift));

    /* Initialize pState pointer */
    px = pState;

    /* Initialize coeff pointer */
    pb = (pCoeffs);

    /* Loop over numTaps number of values */
    tapCnt = numTaps;

    while (tapCnt > 0U)
    {
      /* Perform the multiply-accumulate */
      /* coef is in 2.30 format */
      coef = (q31_t) (((q63_t) w * (*px++)) >> (32));
      /* get coef in 1.31 format by left shifting */
      *pb = clip_q63_to_q31((q63_t) * pb + (coef << 1U));
      /* update coefficient buffer to next coefficient */
      pb++;

      /* Decrement the loop counter */
      tapCnt--;
    }

    /* Read the sample from state buffer */
    x0 = *pState;

    /* Advance state pointer by 1 for the next sample */
    pState = pState + 1;

    /* Decrement the loop counter */
    blkCnt--;
  }

  /* Save energy and x0 values for the next frame */
  S->energy = (q31_t) energy;
  S->x0 = x0;

  /* Processing is complete. Now copy the last numTaps - 1 samples to the
     start of the state buffer. This prepares the state buffer for the
     next function call. */

  /* Points to the start of the pState buffer */
  pStateCurnt = S->pState;

  /* Loop for (numTaps - 1U) samples copy */
  tapCnt = (numTaps - 1U);

  /* Copy the remaining q31_t data */
  while (tapCnt > 0U)
  {
    *pStateCurnt++ = *pState++;

    /* Decrement the loop counter */
    tapCnt--;
  }

#endif /*   #if defined (ARM_MATH_DSP) */

}

/**
 * @} end of LMS_NORM group
 */