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src/Cortex-M4-M3/FilteringFunctions/arm_iir_lattice_q31.c@0:1014af42efd9, 2011-03-10 (annotated)

Committer:: simon
Date:: Thu Mar 10 15:07:50 2011 +0000
Revision:: 0:1014af42efd9

Who changed what in which revision?

User	Revision	Line number	New contents of line
simon	0:1014af42efd9	1	/* ----------------------------------------------------------------------
simon	0:1014af42efd9	2	* Copyright (C) 2010 ARM Limited. All rights reserved.
simon	0:1014af42efd9	3	*
simon	0:1014af42efd9	4	* $Date: 29. November 2010
simon	0:1014af42efd9	5	* $Revision: V1.0.3
simon	0:1014af42efd9	6	*
simon	0:1014af42efd9	7	* Project: CMSIS DSP Library
simon	0:1014af42efd9	8	* Title: arm_iir_lattice_q31.c
simon	0:1014af42efd9	9	*
simon	0:1014af42efd9	10	* Description: Q31 IIR lattice filter processing function.
simon	0:1014af42efd9	11	*
simon	0:1014af42efd9	12	* Target Processor: Cortex-M4/Cortex-M3
simon	0:1014af42efd9	13	*
simon	0:1014af42efd9	14	* Version 1.0.3 2010/11/29
simon	0:1014af42efd9	15	* Re-organized the CMSIS folders and updated documentation.
simon	0:1014af42efd9	16	*
simon	0:1014af42efd9	17	* Version 1.0.2 2010/11/11
simon	0:1014af42efd9	18	* Documentation updated.
simon	0:1014af42efd9	19	*
simon	0:1014af42efd9	20	* Version 1.0.1 2010/10/05
simon	0:1014af42efd9	21	* Production release and review comments incorporated.
simon	0:1014af42efd9	22	*
simon	0:1014af42efd9	23	* Version 1.0.0 2010/09/20
simon	0:1014af42efd9	24	* Production release and review comments incorporated
simon	0:1014af42efd9	25	*
simon	0:1014af42efd9	26	* Version 0.0.7 2010/06/10
simon	0:1014af42efd9	27	* Misra-C changes done
simon	0:1014af42efd9	28	* -------------------------------------------------------------------- */
simon	0:1014af42efd9	29
simon	0:1014af42efd9	30	#include "arm_math.h"
simon	0:1014af42efd9	31
simon	0:1014af42efd9	32	/**
simon	0:1014af42efd9	33	* @ingroup groupFilters
simon	0:1014af42efd9	34	*/
simon	0:1014af42efd9	35
simon	0:1014af42efd9	36	/**
simon	0:1014af42efd9	37	* @addtogroup IIR_Lattice
simon	0:1014af42efd9	38	* @{
simon	0:1014af42efd9	39	*/
simon	0:1014af42efd9	40
simon	0:1014af42efd9	41	/**
simon	0:1014af42efd9	42	* @brief Processing function for the Q31 IIR lattice filter.
simon	0:1014af42efd9	43	* @param[in] *S points to an instance of the Q31 IIR lattice structure.
simon	0:1014af42efd9	44	* @param[in] *pSrc points to the block of input data.
simon	0:1014af42efd9	45	* @param[out] *pDst points to the block of output data.
simon	0:1014af42efd9	46	* @param[in] blockSize number of samples to process.
simon	0:1014af42efd9	47	* @return none.
simon	0:1014af42efd9	48	*
simon	0:1014af42efd9	49	* @details
simon	0:1014af42efd9	50	* <b>Scaling and Overflow Behavior:</b>
simon	0:1014af42efd9	51	* \par
simon	0:1014af42efd9	52	* The function is implemented using an internal 64-bit accumulator.
simon	0:1014af42efd9	53	* The accumulator has a 2.62 format and maintains full precision of the intermediate multiplication results but provides only a single guard bit.
simon	0:1014af42efd9	54	* Thus, if the accumulator result overflows it wraps around rather than clip.
simon	0:1014af42efd9	55	* In order to avoid overflows completely the input signal must be scaled down by 2*log2(numStages) bits.
simon	0:1014af42efd9	56	* After all multiply-accumulates are performed, the 2.62 accumulator is saturated to 1.32 format and then truncated to 1.31 format.
simon	0:1014af42efd9	57	*/
simon	0:1014af42efd9	58
simon	0:1014af42efd9	59	void arm_iir_lattice_q31(
simon	0:1014af42efd9	60	const arm_iir_lattice_instance_q31 * S,
simon	0:1014af42efd9	61	q31_t * pSrc,
simon	0:1014af42efd9	62	q31_t * pDst,
simon	0:1014af42efd9	63	uint32_t blockSize)
simon	0:1014af42efd9	64	{
simon	0:1014af42efd9	65	q31_t fcurr, fnext, gcurr = 0, gnext; /* Temporary variables for lattice stages */
simon	0:1014af42efd9	66	q63_t acc; /* Accumlator */
simon	0:1014af42efd9	67	uint32_t blkCnt, tapCnt; /* Temporary variables for counts */
simon	0:1014af42efd9	68	q31_t px1, px2, pk, pv; /* Temporary pointers for state and coef */
simon	0:1014af42efd9	69	uint32_t numStages = S->numStages; /* number of stages */
simon	0:1014af42efd9	70	q31_t pState; / State pointer */
simon	0:1014af42efd9	71	q31_t pStateCurnt; / State current pointer */
simon	0:1014af42efd9	72
simon	0:1014af42efd9	73	blkCnt = blockSize;
simon	0:1014af42efd9	74
simon	0:1014af42efd9	75	pState = &S->pState[0];
simon	0:1014af42efd9	76
simon	0:1014af42efd9	77	/* Sample processing */
simon	0:1014af42efd9	78	while(blkCnt > 0u)
simon	0:1014af42efd9	79	{
simon	0:1014af42efd9	80	/* Read Sample from input buffer */
simon	0:1014af42efd9	81	/* fN(n) = x(n) */
simon	0:1014af42efd9	82	fcurr = *pSrc++;
simon	0:1014af42efd9	83
simon	0:1014af42efd9	84	/* Initialize state read pointer */
simon	0:1014af42efd9	85	px1 = pState;
simon	0:1014af42efd9	86	/* Initialize state write pointer */
simon	0:1014af42efd9	87	px2 = pState;
simon	0:1014af42efd9	88	/* Set accumulator to zero */
simon	0:1014af42efd9	89	acc = 0;
simon	0:1014af42efd9	90	/* Initialize Ladder coeff pointer */
simon	0:1014af42efd9	91	pv = &S->pvCoeffs[0];
simon	0:1014af42efd9	92	/* Initialize Reflection coeff pointer */
simon	0:1014af42efd9	93	pk = &S->pkCoeffs[0];
simon	0:1014af42efd9	94
simon	0:1014af42efd9	95
simon	0:1014af42efd9	96	/* Process sample for first tap */
simon	0:1014af42efd9	97	gcurr = *px1++;
simon	0:1014af42efd9	98	/* fN-1(n) = fN(n) - kN * gN-1(n-1) */
simon	0:1014af42efd9	99	fnext = __QSUB(fcurr, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
simon	0:1014af42efd9	100	/* gN(n) = kN * fN-1(n) + gN-1(n-1) */
simon	0:1014af42efd9	101	gnext = __QADD(gcurr, (q31_t) (((q63_t) fnext * (*pk++)) >> 31));
simon	0:1014af42efd9	102	/* write gN-1(n-1) into state for next sample processing */
simon	0:1014af42efd9	103	*px2++ = gnext;
simon	0:1014af42efd9	104	/* y(n) += gN(n) * vN */
simon	0:1014af42efd9	105	acc += ((q63_t) gnext * *pv++);
simon	0:1014af42efd9	106
simon	0:1014af42efd9	107	/* Update f values for next coefficient processing */
simon	0:1014af42efd9	108	fcurr = fnext;
simon	0:1014af42efd9	109
simon	0:1014af42efd9	110	/* Loop unrolling. Process 4 taps at a time. */
simon	0:1014af42efd9	111	tapCnt = (numStages - 1u) >> 2;
simon	0:1014af42efd9	112
simon	0:1014af42efd9	113	while(tapCnt > 0u)
simon	0:1014af42efd9	114	{
simon	0:1014af42efd9	115
simon	0:1014af42efd9	116	/* Process sample for 2nd, 6th .. taps */
simon	0:1014af42efd9	117	/* Read gN-2(n-1) from state buffer */
simon	0:1014af42efd9	118	gcurr = *px1++;
simon	0:1014af42efd9	119	/* fN-2(n) = fN-1(n) - kN-1 * gN-2(n-1) */
simon	0:1014af42efd9	120	fnext = __QSUB(fcurr, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
simon	0:1014af42efd9	121	/* gN-1(n) = kN-1 * fN-2(n) + gN-2(n-1) */
simon	0:1014af42efd9	122	gnext = __QADD(gcurr, (q31_t) (((q63_t) fnext * (*pk++)) >> 31));
simon	0:1014af42efd9	123	/* y(n) += gN-1(n) * vN-1 */
simon	0:1014af42efd9	124	/* process for gN-5(n) * vN-5, gN-9(n) * vN-9 ... */
simon	0:1014af42efd9	125	acc += ((q63_t) gnext * *pv++);
simon	0:1014af42efd9	126	/* write gN-1(n) into state for next sample processing */
simon	0:1014af42efd9	127	*px2++ = gnext;
simon	0:1014af42efd9	128
simon	0:1014af42efd9	129	/* Process sample for 3nd, 7th ...taps */
simon	0:1014af42efd9	130	/* Read gN-3(n-1) from state buffer */
simon	0:1014af42efd9	131	gcurr = *px1++;
simon	0:1014af42efd9	132	/* Process sample for 3rd, 7th .. taps */
simon	0:1014af42efd9	133	/* fN-3(n) = fN-2(n) - kN-2 * gN-3(n-1) */
simon	0:1014af42efd9	134	fcurr = __QSUB(fnext, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
simon	0:1014af42efd9	135	/* gN-2(n) = kN-2 * fN-3(n) + gN-3(n-1) */
simon	0:1014af42efd9	136	gnext = __QADD(gcurr, (q31_t) (((q63_t) fcurr * (*pk++)) >> 31));
simon	0:1014af42efd9	137	/* y(n) += gN-2(n) * vN-2 */
simon	0:1014af42efd9	138	/* process for gN-6(n) * vN-6, gN-10(n) * vN-10 ... */
simon	0:1014af42efd9	139	acc += ((q63_t) gnext * *pv++);
simon	0:1014af42efd9	140	/* write gN-2(n) into state for next sample processing */
simon	0:1014af42efd9	141	*px2++ = gnext;
simon	0:1014af42efd9	142
simon	0:1014af42efd9	143
simon	0:1014af42efd9	144	/* Process sample for 4th, 8th ...taps */
simon	0:1014af42efd9	145	/* Read gN-4(n-1) from state buffer */
simon	0:1014af42efd9	146	gcurr = *px1++;
simon	0:1014af42efd9	147	/* Process sample for 4th, 8th .. taps */
simon	0:1014af42efd9	148	/* fN-4(n) = fN-3(n) - kN-3 * gN-4(n-1) */
simon	0:1014af42efd9	149	fnext = __QSUB(fcurr, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
simon	0:1014af42efd9	150	/* gN-3(n) = kN-3 * fN-4(n) + gN-4(n-1) */
simon	0:1014af42efd9	151	gnext = __QADD(gcurr, (q31_t) (((q63_t) fnext * (*pk++)) >> 31));
simon	0:1014af42efd9	152	/* y(n) += gN-3(n) * vN-3 */
simon	0:1014af42efd9	153	/* process for gN-7(n) * vN-7, gN-11(n) * vN-11 ... */
simon	0:1014af42efd9	154	acc += ((q63_t) gnext * *pv++);
simon	0:1014af42efd9	155	/* write gN-3(n) into state for next sample processing */
simon	0:1014af42efd9	156	*px2++ = gnext;
simon	0:1014af42efd9	157
simon	0:1014af42efd9	158
simon	0:1014af42efd9	159	/* Process sample for 5th, 9th ...taps */
simon	0:1014af42efd9	160	/* Read gN-5(n-1) from state buffer */
simon	0:1014af42efd9	161	gcurr = *px1++;
simon	0:1014af42efd9	162	/* Process sample for 5th, 9th .. taps */
simon	0:1014af42efd9	163	/* fN-5(n) = fN-4(n) - kN-4 * gN-1(n-1) */
simon	0:1014af42efd9	164	fcurr = __QSUB(fnext, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
simon	0:1014af42efd9	165	/* gN-4(n) = kN-4 * fN-5(n) + gN-5(n-1) */
simon	0:1014af42efd9	166	gnext = __QADD(gcurr, (q31_t) (((q63_t) fcurr * (*pk++)) >> 31));
simon	0:1014af42efd9	167	/* y(n) += gN-4(n) * vN-4 */
simon	0:1014af42efd9	168	/* process for gN-8(n) * vN-8, gN-12(n) * vN-12 ... */
simon	0:1014af42efd9	169	acc += ((q63_t) gnext * *pv++);
simon	0:1014af42efd9	170	/* write gN-4(n) into state for next sample processing */
simon	0:1014af42efd9	171	*px2++ = gnext;
simon	0:1014af42efd9	172
simon	0:1014af42efd9	173	tapCnt--;
simon	0:1014af42efd9	174
simon	0:1014af42efd9	175	}
simon	0:1014af42efd9	176
simon	0:1014af42efd9	177	fnext = fcurr;
simon	0:1014af42efd9	178
simon	0:1014af42efd9	179	/* If the filter length is not a multiple of 4, compute the remaining filter taps */
simon	0:1014af42efd9	180	tapCnt = (numStages - 1u) % 0x4u;
simon	0:1014af42efd9	181
simon	0:1014af42efd9	182	while(tapCnt > 0u)
simon	0:1014af42efd9	183	{
simon	0:1014af42efd9	184	gcurr = *px1++;
simon	0:1014af42efd9	185	/* Process sample for last taps */
simon	0:1014af42efd9	186	fnext = __QSUB(fcurr, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
simon	0:1014af42efd9	187	gnext = __QADD(gcurr, (q31_t) (((q63_t) fnext * (*pk++)) >> 31));
simon	0:1014af42efd9	188	/* Output samples for last taps */
simon	0:1014af42efd9	189	acc += ((q63_t) gnext * *pv++);
simon	0:1014af42efd9	190	*px2++ = gnext;
simon	0:1014af42efd9	191	fcurr = fnext;
simon	0:1014af42efd9	192
simon	0:1014af42efd9	193	tapCnt--;
simon	0:1014af42efd9	194
simon	0:1014af42efd9	195	}
simon	0:1014af42efd9	196
simon	0:1014af42efd9	197	/* y(n) += g0(n) * v0 */
simon	0:1014af42efd9	198	acc += (q63_t) fnext *(
simon	0:1014af42efd9	199	*pv++);
simon	0:1014af42efd9	200
simon	0:1014af42efd9	201	*px2++ = fnext;
simon	0:1014af42efd9	202
simon	0:1014af42efd9	203	/* write out into pDst */
simon	0:1014af42efd9	204	*pDst++ = (q31_t) (acc >> 31u);
simon	0:1014af42efd9	205
simon	0:1014af42efd9	206	/* Advance the state pointer by 4 to process the next group of 4 samples */
simon	0:1014af42efd9	207	pState = pState + 1u;
simon	0:1014af42efd9	208	blkCnt--;
simon	0:1014af42efd9	209
simon	0:1014af42efd9	210	}
simon	0:1014af42efd9	211
simon	0:1014af42efd9	212	/* Processing is complete. Now copy last S->numStages samples to start of the buffer
simon	0:1014af42efd9	213	for the preperation of next frame process */
simon	0:1014af42efd9	214
simon	0:1014af42efd9	215	/* Points to the start of the state buffer */
simon	0:1014af42efd9	216	pStateCurnt = &S->pState[0];
simon	0:1014af42efd9	217	pState = &S->pState[blockSize];
simon	0:1014af42efd9	218
simon	0:1014af42efd9	219	tapCnt = numStages >> 2u;
simon	0:1014af42efd9	220
simon	0:1014af42efd9	221	/* copy data */
simon	0:1014af42efd9	222	while(tapCnt > 0u)
simon	0:1014af42efd9	223	{
simon	0:1014af42efd9	224	pStateCurnt++ = pState++;
simon	0:1014af42efd9	225	pStateCurnt++ = pState++;
simon	0:1014af42efd9	226	pStateCurnt++ = pState++;
simon	0:1014af42efd9	227	pStateCurnt++ = pState++;
simon	0:1014af42efd9	228
simon	0:1014af42efd9	229	/* Decrement the loop counter */
simon	0:1014af42efd9	230	tapCnt--;
simon	0:1014af42efd9	231
simon	0:1014af42efd9	232	}
simon	0:1014af42efd9	233
simon	0:1014af42efd9	234	/* Calculate remaining number of copies */
simon	0:1014af42efd9	235	tapCnt = (numStages) % 0x4u;
simon	0:1014af42efd9	236
simon	0:1014af42efd9	237	/* Copy the remaining q31_t data */
simon	0:1014af42efd9	238	while(tapCnt > 0u)
simon	0:1014af42efd9	239	{
simon	0:1014af42efd9	240	pStateCurnt++ = pState++;
simon	0:1014af42efd9	241
simon	0:1014af42efd9	242	/* Decrement the loop counter */
simon	0:1014af42efd9	243	tapCnt--;
simon	0:1014af42efd9	244	};
simon	0:1014af42efd9	245
simon	0:1014af42efd9	246	}
simon	0:1014af42efd9	247
simon	0:1014af42efd9	248
simon	0:1014af42efd9	249
simon	0:1014af42efd9	250
simon	0:1014af42efd9	251	/**
simon	0:1014af42efd9	252	* @} end of IIR_Lattice group
simon	0:1014af42efd9	253	*/

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Type:	Library
Created:	10 Mar 2011
Imports:	907
Forks:	1
Commits:	3
Dependents:	5
Dependencies:	0
Followers:	35

src/Cortex-M4-M3/FilteringFunctions/arm_iir_lattice_q31.c@0:1014af42efd9, 2011-03-10 (annotated)

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