CMSIS DSP Software Library: arm_fir_interpolate_q31.c Source File
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arm_fir_interpolate_q31.c
Go to the documentation of this file.00001 /*-----------------------------------------------------------------------------
00002 * Copyright (C) 2010 ARM Limited. All rights reserved.
00003 *
00004 * $Date: 29. November 2010
00005 * $Revision: V1.0.3
00006 *
00007 * Project: CMSIS DSP Library
00008 * Title: arm_fir_interpolate_q31.c
00009 *
00010 * Description: Q31 FIR interpolation.
00011 *
00012 * Target Processor: Cortex-M4/Cortex-M3
00013 *
00014 * Version 1.0.3 2010/11/29
00015 * Re-organized the CMSIS folders and updated documentation.
00016 *
00017 * Version 1.0.2 2010/11/11
00018 * Documentation updated.
00019 *
00020 * Version 1.0.1 2010/10/05
00021 * Production release and review comments incorporated.
00022 *
00023 * Version 1.0.0 2010/09/20
00024 * Production release and review comments incorporated
00025 *
00026 * Version 0.0.7 2010/06/10
00027 * Misra-C changes done
00028 * ---------------------------------------------------------------------------*/
00029
00030 #include "arm_math.h"
00031
00060 void arm_fir_interpolate_q31(
00061 const arm_fir_interpolate_instance_q31 * S,
00062 q31_t * pSrc,
00063 q31_t * pDst,
00064 uint32_t blockSize)
00065 {
00066 q31_t *pState = S->pState; /* State pointer */
00067 q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
00068 q31_t *pStateCurnt; /* Points to the current sample of the state */
00069 q31_t *ptr1, *ptr2; /* Temporary pointers for state and coefficient buffers */
00070 q63_t sum0; /* Accumulators */
00071 q31_t x0, c0; /* Temporary variables to hold state and coefficient values */
00072 uint32_t i, blkCnt, j; /* Loop counters */
00073 uint16_t phaseLen = S->phaseLength, tapCnt; /* Length of each polyphase filter component */
00074
00075
00076 /* S->pState buffer contains previous frame (phaseLen - 1) samples */
00077 /* pStateCurnt points to the location where the new input data should be written */
00078 pStateCurnt = S->pState + ((q31_t) phaseLen - 1);
00079
00080 /* Total number of intput samples */
00081 blkCnt = blockSize;
00082
00083 /* Loop over the blockSize. */
00084 while(blkCnt > 0u)
00085 {
00086 /* Copy new input sample into the state buffer */
00087 *pStateCurnt++ = *pSrc++;
00088
00089 /* Address modifier index of coefficient buffer */
00090 j = 1u;
00091
00092 /* Loop over the Interpolation factor. */
00093 i = S->L;
00094 while(i > 0u)
00095 {
00096 /* Set accumulator to zero */
00097 sum0 = 0;
00098
00099 /* Initialize state pointer */
00100 ptr1 = pState;
00101
00102 /* Initialize coefficient pointer */
00103 ptr2 = pCoeffs + (S->L - j);
00104
00105 /* Loop over the polyPhase length. Unroll by a factor of 4.
00106 ** Repeat until we've computed numTaps-(4*S->L) coefficients. */
00107 tapCnt = phaseLen >> 2;
00108 while(tapCnt > 0u)
00109 {
00110
00111 /* Read the coefficient */
00112 c0 = *(ptr2);
00113
00114 /* Upsampling is done by stuffing L-1 zeros between each sample.
00115 * So instead of multiplying zeros with coefficients,
00116 * Increment the coefficient pointer by interpolation factor times. */
00117 ptr2 += S->L;
00118
00119 /* Read the input sample */
00120 x0 = *(ptr1++);
00121
00122 /* Perform the multiply-accumulate */
00123 sum0 += (q63_t) x0 *c0;
00124
00125 /* Read the coefficient */
00126 c0 = *(ptr2);
00127
00128 /* Increment the coefficient pointer by interpolation factor times. */
00129 ptr2 += S->L;
00130
00131 /* Read the input sample */
00132 x0 = *(ptr1++);
00133
00134 /* Perform the multiply-accumulate */
00135 sum0 += (q63_t) x0 *c0;
00136
00137 /* Read the coefficient */
00138 c0 = *(ptr2);
00139
00140 /* Increment the coefficient pointer by interpolation factor times. */
00141 ptr2 += S->L;
00142
00143 /* Read the input sample */
00144 x0 = *(ptr1++);
00145
00146 /* Perform the multiply-accumulate */
00147 sum0 += (q63_t) x0 *c0;
00148
00149 /* Read the coefficient */
00150 c0 = *(ptr2);
00151
00152 /* Increment the coefficient pointer by interpolation factor times. */
00153 ptr2 += S->L;
00154
00155 /* Read the input sample */
00156 x0 = *(ptr1++);
00157
00158 /* Perform the multiply-accumulate */
00159 sum0 += (q63_t) x0 *c0;
00160
00161 /* Decrement the loop counter */
00162 tapCnt--;
00163 }
00164
00165 /* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */
00166 tapCnt = phaseLen & 0x3u;
00167
00168 while(tapCnt > 0u)
00169 {
00170 /* Read the coefficient */
00171 c0 = *(ptr2);
00172
00173 /* Increment the coefficient pointer by interpolation factor times. */
00174 ptr2 += S->L;
00175
00176 /* Read the input sample */
00177 x0 = *(ptr1++);
00178
00179 /* Perform the multiply-accumulate */
00180 sum0 += (q63_t) x0 *c0;
00181
00182 /* Decrement the loop counter */
00183 tapCnt--;
00184 }
00185
00186 /* The result is in the accumulator, store in the destination buffer. */
00187 *pDst++ = (q31_t) (sum0 >> 31);
00188
00189 /* Increment the address modifier index of coefficient buffer */
00190 j++;
00191
00192 /* Decrement the loop counter */
00193 i--;
00194 }
00195
00196 /* Advance the state pointer by 1
00197 * to process the next group of interpolation factor number samples */
00198 pState = pState + 1;
00199
00200 /* Decrement the loop counter */
00201 blkCnt--;
00202 }
00203
00204 /* Processing is complete.
00205 ** Now copy the last phaseLen - 1 samples to the satrt of the state buffer.
00206 ** This prepares the state buffer for the next function call. */
00207
00208 /* Points to the start of the state buffer */
00209 pStateCurnt = S->pState;
00210
00211 tapCnt = (phaseLen - 1u) >> 2u;
00212
00213 /* copy data */
00214 while(tapCnt > 0u)
00215 {
00216 *pStateCurnt++ = *pState++;
00217 *pStateCurnt++ = *pState++;
00218 *pStateCurnt++ = *pState++;
00219 *pStateCurnt++ = *pState++;
00220
00221 /* Decrement the loop counter */
00222 tapCnt--;
00223 }
00224
00225 tapCnt = (phaseLen - 1u) % 0x04u;
00226
00227 /* copy data */
00228 while(tapCnt > 0u)
00229 {
00230 *pStateCurnt++ = *pState++;
00231
00232 /* Decrement the loop counter */
00233 tapCnt--;
00234 }
00235 }
00236
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