tmk_core/tool/mbed/mbed-sdk/libraries/dsp/cmsis_dsp/FilteringFunctions/arm_iir_lattice_q31.c

   1 /* ----------------------------------------------------------------------
   2 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
   3 *
   4 * $Date:        17. January 2013
   5 * $Revision:    V1.4.1
   6 *
   7 * Project:          CMSIS DSP Library
   8 * Title:            arm_iir_lattice_q31.c
   9 *
  10 * Description:  Q31 IIR lattice filter processing function.
  11 *
  12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
  13 *
  14 * Redistribution and use in source and binary forms, with or without
  15 * modification, are permitted provided that the following conditions
  16 * are met:
  17 *   - Redistributions of source code must retain the above copyright
  18 *     notice, this list of conditions and the following disclaimer.
  19 *   - Redistributions in binary form must reproduce the above copyright
  20 *     notice, this list of conditions and the following disclaimer in
  21 *     the documentation and/or other materials provided with the
  22 *     distribution.
  23 *   - Neither the name of ARM LIMITED nor the names of its contributors
  24 *     may be used to endorse or promote products derived from this
  25 *     software without specific prior written permission.
  26 *
  27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  30 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  31 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  33 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  34 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  37 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  38 * POSSIBILITY OF SUCH DAMAGE.
  39 * -------------------------------------------------------------------- */
  40
  41 #include "arm_math.h"
  42
  43 /**
  44  * @ingroup groupFilters
  45  */
  46
  47 /**
  48  * @addtogroup IIR_Lattice
  49  * @{
  50  */
  51
  52 /**
  53  * @brief Processing function for the Q31 IIR lattice filter.
  54  * @param[in] *S points to an instance of the Q31 IIR lattice structure.
  55  * @param[in] *pSrc points to the block of input data.
  56  * @param[out] *pDst points to the block of output data.
  57  * @param[in] blockSize number of samples to process.
  58  * @return none.
  59  *
  60  * @details
  61  * <b>Scaling and Overflow Behavior:</b>
  62  * \par
  63  * The function is implemented using an internal 64-bit accumulator.
  64  * The accumulator has a 2.62 format and maintains full precision of the intermediate multiplication results but provides only a single guard bit.
  65  * Thus, if the accumulator result overflows it wraps around rather than clip.
  66  * In order to avoid overflows completely the input signal must be scaled down by 2*log2(numStages) bits.
  67  * After all multiply-accumulates are performed, the 2.62 accumulator is saturated to 1.32 format and then truncated to 1.31 format.
  68  */
  69
  70 void arm_iir_lattice_q31(
  71   const arm_iir_lattice_instance_q31 * S,
  72   q31_t * pSrc,
  73   q31_t * pDst,
  74   uint32_t blockSize)
  75 {
  76   q31_t fcurr, fnext = 0, gcurr = 0, gnext;      /* Temporary variables for lattice stages */
  77   q63_t acc;                                     /* Accumlator */
  78   uint32_t blkCnt, tapCnt;                       /* Temporary variables for counts */
  79   q31_t *px1, *px2, *pk, *pv;                    /* Temporary pointers for state and coef */
  80   uint32_t numStages = S->numStages;             /* number of stages */
  81   q31_t *pState;                                 /* State pointer */
  82   q31_t *pStateCurnt;                            /* State current pointer */
  83
  84   blkCnt = blockSize;
  85
  86   pState = &S->pState[0];
  87
  88
  89 #ifndef ARM_MATH_CM0_FAMILY
  90
  91   /* Run the below code for Cortex-M4 and Cortex-M3 */
  92
  93   /* Sample processing */
  94   while(blkCnt > 0u)
  95   {
  96     /* Read Sample from input buffer */
  97     /* fN(n) = x(n) */
  98     fcurr = *pSrc++;
  99
 100     /* Initialize state read pointer */
 101     px1 = pState;
 102     /* Initialize state write pointer */
 103     px2 = pState;
 104     /* Set accumulator to zero */
 105     acc = 0;
 106     /* Initialize Ladder coeff pointer */
 107     pv = &S->pvCoeffs[0];
 108     /* Initialize Reflection coeff pointer */
 109     pk = &S->pkCoeffs[0];
 110
 111
 112     /* Process sample for first tap */
 113     gcurr = *px1++;
 114     /* fN-1(n) = fN(n) - kN * gN-1(n-1) */
 115     fnext = __QSUB(fcurr, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
 116     /* gN(n) = kN * fN-1(n) + gN-1(n-1) */
 117     gnext = __QADD(gcurr, (q31_t) (((q63_t) fnext * (*pk++)) >> 31));
 118     /* write gN-1(n-1) into state for next sample processing */
 119     *px2++ = gnext;
 120     /* y(n) += gN(n) * vN  */
 121     acc += ((q63_t) gnext * *pv++);
 122
 123     /* Update f values for next coefficient processing */
 124     fcurr = fnext;
 125
 126     /* Loop unrolling.  Process 4 taps at a time. */
 127     tapCnt = (numStages - 1u) >> 2;
 128
 129     while(tapCnt > 0u)
 130     {
 131
 132       /* Process sample for 2nd, 6th .. taps */
 133       /* Read gN-2(n-1) from state buffer */
 134       gcurr = *px1++;
 135       /* fN-2(n) = fN-1(n) - kN-1 * gN-2(n-1) */
 136       fnext = __QSUB(fcurr, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
 137       /* gN-1(n) = kN-1 * fN-2(n) + gN-2(n-1) */
 138       gnext = __QADD(gcurr, (q31_t) (((q63_t) fnext * (*pk++)) >> 31));
 139       /* y(n) += gN-1(n) * vN-1  */
 140       /* process for gN-5(n) * vN-5, gN-9(n) * vN-9 ... */
 141       acc += ((q63_t) gnext * *pv++);
 142       /* write gN-1(n) into state for next sample processing */
 143       *px2++ = gnext;
 144
 145       /* Process sample for 3nd, 7th ...taps */
 146       /* Read gN-3(n-1) from state buffer */
 147       gcurr = *px1++;
 148       /* Process sample for 3rd, 7th .. taps */
 149       /* fN-3(n) = fN-2(n) - kN-2 * gN-3(n-1) */
 150       fcurr = __QSUB(fnext, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
 151       /* gN-2(n) = kN-2 * fN-3(n) + gN-3(n-1) */
 152       gnext = __QADD(gcurr, (q31_t) (((q63_t) fcurr * (*pk++)) >> 31));
 153       /* y(n) += gN-2(n) * vN-2  */
 154       /* process for gN-6(n) * vN-6, gN-10(n) * vN-10 ... */
 155       acc += ((q63_t) gnext * *pv++);
 156       /* write gN-2(n) into state for next sample processing */
 157       *px2++ = gnext;
 158
 159
 160       /* Process sample for 4th, 8th ...taps */
 161       /* Read gN-4(n-1) from state buffer */
 162       gcurr = *px1++;
 163       /* Process sample for 4th, 8th .. taps */
 164       /* fN-4(n) = fN-3(n) - kN-3 * gN-4(n-1) */
 165       fnext = __QSUB(fcurr, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
 166       /* gN-3(n) = kN-3 * fN-4(n) + gN-4(n-1) */
 167       gnext = __QADD(gcurr, (q31_t) (((q63_t) fnext * (*pk++)) >> 31));
 168       /* y(n) += gN-3(n) * vN-3  */
 169       /* process for gN-7(n) * vN-7, gN-11(n) * vN-11 ... */
 170       acc += ((q63_t) gnext * *pv++);
 171       /* write gN-3(n) into state for next sample processing */
 172       *px2++ = gnext;
 173
 174
 175       /* Process sample for 5th, 9th ...taps */
 176       /* Read gN-5(n-1) from state buffer */
 177       gcurr = *px1++;
 178       /* Process sample for 5th, 9th .. taps */
 179       /* fN-5(n) = fN-4(n) - kN-4 * gN-1(n-1) */
 180       fcurr = __QSUB(fnext, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
 181       /* gN-4(n) = kN-4 * fN-5(n) + gN-5(n-1) */
 182       gnext = __QADD(gcurr, (q31_t) (((q63_t) fcurr * (*pk++)) >> 31));
 183       /* y(n) += gN-4(n) * vN-4  */
 184       /* process for gN-8(n) * vN-8, gN-12(n) * vN-12 ... */
 185       acc += ((q63_t) gnext * *pv++);
 186       /* write gN-4(n) into state for next sample processing */
 187       *px2++ = gnext;
 188
 189       tapCnt--;
 190
 191     }
 192
 193     fnext = fcurr;
 194
 195     /* If the filter length is not a multiple of 4, compute the remaining filter taps */
 196     tapCnt = (numStages - 1u) % 0x4u;
 197
 198     while(tapCnt > 0u)
 199     {
 200       gcurr = *px1++;
 201       /* Process sample for last taps */
 202       fnext = __QSUB(fcurr, (q31_t) (((q63_t) gcurr * (*pk)) >> 31));
 203       gnext = __QADD(gcurr, (q31_t) (((q63_t) fnext * (*pk++)) >> 31));
 204       /* Output samples for last taps */
 205       acc += ((q63_t) gnext * *pv++);
 206       *px2++ = gnext;
 207       fcurr = fnext;
 208
 209       tapCnt--;
 210
 211     }
 212
 213     /* y(n) += g0(n) * v0 */
 214     acc += (q63_t) fnext *(
 215   *pv++);
 216
 217     *px2++ = fnext;
 218
 219     /* write out into pDst */
 220     *pDst++ = (q31_t) (acc >> 31u);
 221
 222     /* Advance the state pointer by 4 to process the next group of 4 samples */
 223     pState = pState + 1u;
 224     blkCnt--;
 225
 226   }
 227
 228   /* Processing is complete. Now copy last S->numStages samples to start of the buffer
 229      for the preperation of next frame process */
 230
 231   /* Points to the start of the state buffer */
 232   pStateCurnt = &S->pState[0];
 233   pState = &S->pState[blockSize];
 234
 235   tapCnt = numStages >> 2u;
 236
 237   /* copy data */
 238   while(tapCnt > 0u)
 239   {
 240     *pStateCurnt++ = *pState++;
 241     *pStateCurnt++ = *pState++;
 242     *pStateCurnt++ = *pState++;
 243     *pStateCurnt++ = *pState++;
 244
 245     /* Decrement the loop counter */
 246     tapCnt--;
 247
 248   }
 249
 250   /* Calculate remaining number of copies */
 251   tapCnt = (numStages) % 0x4u;
 252
 253   /* Copy the remaining q31_t data */
 254   while(tapCnt > 0u)
 255   {
 256     *pStateCurnt++ = *pState++;
 257
 258     /* Decrement the loop counter */
 259     tapCnt--;
 260   };
 261
 262 #else
 263
 264   /* Run the below code for Cortex-M0 */
 265   /* Sample processing */
 266   while(blkCnt > 0u)
 267   {
 268     /* Read Sample from input buffer */
 269     /* fN(n) = x(n) */
 270     fcurr = *pSrc++;
 271
 272     /* Initialize state read pointer */
 273     px1 = pState;
 274     /* Initialize state write pointer */
 275     px2 = pState;
 276     /* Set accumulator to zero */
 277     acc = 0;
 278     /* Initialize Ladder coeff pointer */
 279     pv = &S->pvCoeffs[0];
 280     /* Initialize Reflection coeff pointer */
 281     pk = &S->pkCoeffs[0];
 282
 283     tapCnt = numStages;
 284
 285     while(tapCnt > 0u)
 286     {
 287       gcurr = *px1++;
 288       /* Process sample */
 289       /* fN-1(n) = fN(n) - kN * gN-1(n-1) */
 290       fnext =
 291         clip_q63_to_q31(((q63_t) fcurr -
 292                          ((q31_t) (((q63_t) gcurr * (*pk)) >> 31))));
 293       /* gN(n) = kN * fN-1(n) + gN-1(n-1) */
 294       gnext =
 295         clip_q63_to_q31(((q63_t) gcurr +
 296                          ((q31_t) (((q63_t) fnext * (*pk++)) >> 31))));
 297       /* Output samples */
 298       /* y(n) += gN(n) * vN  */
 299       acc += ((q63_t) gnext * *pv++);
 300       /* write gN-1(n-1) into state for next sample processing */
 301       *px2++ = gnext;
 302       /* Update f values for next coefficient processing */
 303       fcurr = fnext;
 304
 305       tapCnt--;
 306     }
 307
 308     /* y(n) += g0(n) * v0 */
 309     acc += (q63_t) fnext *(
 310   *pv++);
 311
 312     *px2++ = fnext;
 313
 314     /* write out into pDst */
 315     *pDst++ = (q31_t) (acc >> 31u);
 316
 317     /* Advance the state pointer by 1 to process the next group of samples */
 318     pState = pState + 1u;
 319     blkCnt--;
 320
 321   }
 322
 323   /* Processing is complete. Now copy last S->numStages samples to start of the buffer
 324      for the preperation of next frame process */
 325
 326   /* Points to the start of the state buffer */
 327   pStateCurnt = &S->pState[0];
 328   pState = &S->pState[blockSize];
 329
 330   tapCnt = numStages;
 331
 332   /* Copy the remaining q31_t data */
 333   while(tapCnt > 0u)
 334   {
 335     *pStateCurnt++ = *pState++;
 336
 337     /* Decrement the loop counter */
 338     tapCnt--;
 339   }
 340
 341 #endif /*   #ifndef ARM_MATH_CM0_FAMILY */
 342
 343 }
 344
 345
 346
 347
 348 /**
 349  * @} end of IIR_Lattice group
 350  */