DSP/Source/FilteringFunctions/arm_iir_lattice_q31.c - third_party/github/STMicroelectronics/cmsis_core - Git at Google

 /* ----------------------------------------------------------------------
  * Project:      CMSIS DSP Library
  * Title:        arm_iir_lattice_q31.c
  * Description:  Q31 IIR lattice filter processing function
  *
  * $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 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];


 #if defined (ARM_MATH_DSP)

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

 }


 /**
  * @} end of IIR_Lattice group
  */
	/* ----------------------------------------------------------------------
	* Project: CMSIS DSP Library
	* Title: arm_iir_lattice_q31.c
	* Description: Q31 IIR lattice filter processing function
	*
	* $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 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];


	#if defined (ARM_MATH_DSP)

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

	}




	/**
	* @} end of IIR_Lattice group
	*/