Laxmi Kant Tiwari / mbed-dsp

Important changes to repositories hosted on mbed.com

Mbed hosted mercurial repositories are deprecated and are due to be permanently deleted in July 2026.

To keep a copy of this software download the repository Zip archive or clone locally using Mercurial.

It is also possible to export all your personal repositories from the account settings page.

Fork of mbed-dsp by mbed official

cmsis_dsp/StatisticsFunctions/arm_rms_q31.c@1:fdd22bb7aa52, 2012-11-28 (annotated)

Committer:
emilmont
Date:
Wed Nov 28 12:30:09 2012 +0000
Revision:
1:fdd22bb7aa52
Child:
2:da51fb522205
DSP library code

Who changed what in which revision?

UserRevisionLine numberNew contents of line
emilmont 1:fdd22bb7aa52 1 /* ----------------------------------------------------------------------
emilmont 1:fdd22bb7aa52 2 * Copyright (C) 2010 ARM Limited. All rights reserved.
emilmont 1:fdd22bb7aa52 3 *
emilmont 1:fdd22bb7aa52 4 * $Date: 15. February 2012
emilmont 1:fdd22bb7aa52 5 * $Revision: V1.1.0
emilmont 1:fdd22bb7aa52 6 *
emilmont 1:fdd22bb7aa52 7 * Project: CMSIS DSP Library
emilmont 1:fdd22bb7aa52 8 * Title: arm_rms_q31.c
emilmont 1:fdd22bb7aa52 9 *
emilmont 1:fdd22bb7aa52 10 * Description: Root Mean Square of the elements of a Q31 vector.
emilmont 1:fdd22bb7aa52 11 *
emilmont 1:fdd22bb7aa52 12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
emilmont 1:fdd22bb7aa52 13 *
emilmont 1:fdd22bb7aa52 14 * Version 1.1.0 2012/02/15
emilmont 1:fdd22bb7aa52 15 * Updated with more optimizations, bug fixes and minor API changes.
emilmont 1:fdd22bb7aa52 16 *
emilmont 1:fdd22bb7aa52 17 * Version 1.0.10 2011/7/15
emilmont 1:fdd22bb7aa52 18 * Big Endian support added and Merged M0 and M3/M4 Source code.
emilmont 1:fdd22bb7aa52 19 *
emilmont 1:fdd22bb7aa52 20 * Version 1.0.3 2010/11/29
emilmont 1:fdd22bb7aa52 21 * Re-organized the CMSIS folders and updated documentation.
emilmont 1:fdd22bb7aa52 22 *
emilmont 1:fdd22bb7aa52 23 * Version 1.0.2 2010/11/11
emilmont 1:fdd22bb7aa52 24 * Documentation updated.
emilmont 1:fdd22bb7aa52 25 *
emilmont 1:fdd22bb7aa52 26 * Version 1.0.1 2010/10/05
emilmont 1:fdd22bb7aa52 27 * Production release and review comments incorporated.
emilmont 1:fdd22bb7aa52 28 *
emilmont 1:fdd22bb7aa52 29 * Version 1.0.0 2010/09/20
emilmont 1:fdd22bb7aa52 30 * Production release and review comments incorporated.
emilmont 1:fdd22bb7aa52 31 * ---------------------------------------------------------------------------- */
emilmont 1:fdd22bb7aa52 32
emilmont 1:fdd22bb7aa52 33 #include "arm_math.h"
emilmont 1:fdd22bb7aa52 34
emilmont 1:fdd22bb7aa52 35 /**
emilmont 1:fdd22bb7aa52 36 * @addtogroup RMS
emilmont 1:fdd22bb7aa52 37 * @{
emilmont 1:fdd22bb7aa52 38 */
emilmont 1:fdd22bb7aa52 39
emilmont 1:fdd22bb7aa52 40
emilmont 1:fdd22bb7aa52 41 /**
emilmont 1:fdd22bb7aa52 42 * @brief Root Mean Square of the elements of a Q31 vector.
emilmont 1:fdd22bb7aa52 43 * @param[in] *pSrc points to the input vector
emilmont 1:fdd22bb7aa52 44 * @param[in] blockSize length of the input vector
emilmont 1:fdd22bb7aa52 45 * @param[out] *pResult rms value returned here
emilmont 1:fdd22bb7aa52 46 * @return none.
emilmont 1:fdd22bb7aa52 47 *
emilmont 1:fdd22bb7aa52 48 * @details
emilmont 1:fdd22bb7aa52 49 * <b>Scaling and Overflow Behavior:</b>
emilmont 1:fdd22bb7aa52 50 *
emilmont 1:fdd22bb7aa52 51 *\par
emilmont 1:fdd22bb7aa52 52 * The function is implemented using an internal 64-bit accumulator.
emilmont 1:fdd22bb7aa52 53 * The input is represented in 1.31 format, and intermediate multiplication
emilmont 1:fdd22bb7aa52 54 * yields a 2.62 format.
emilmont 1:fdd22bb7aa52 55 * The accumulator maintains full precision of the intermediate multiplication results,
emilmont 1:fdd22bb7aa52 56 * but provides only a single guard bit.
emilmont 1:fdd22bb7aa52 57 * There is no saturation on intermediate additions.
emilmont 1:fdd22bb7aa52 58 * If the accumulator overflows, it wraps around and distorts the result.
emilmont 1:fdd22bb7aa52 59 * In order to avoid overflows completely, the input signal must be scaled down by
emilmont 1:fdd22bb7aa52 60 * log2(blockSize) bits, as a total of blockSize additions are performed internally.
emilmont 1:fdd22bb7aa52 61 * Finally, the 2.62 accumulator is right shifted by 31 bits to yield a 1.31 format value.
emilmont 1:fdd22bb7aa52 62 *
emilmont 1:fdd22bb7aa52 63 */
emilmont 1:fdd22bb7aa52 64
emilmont 1:fdd22bb7aa52 65 void arm_rms_q31(
emilmont 1:fdd22bb7aa52 66 q31_t * pSrc,
emilmont 1:fdd22bb7aa52 67 uint32_t blockSize,
emilmont 1:fdd22bb7aa52 68 q31_t * pResult)
emilmont 1:fdd22bb7aa52 69 {
emilmont 1:fdd22bb7aa52 70 q63_t sum = 0; /* accumulator */
emilmont 1:fdd22bb7aa52 71 q31_t in; /* Temporary variable to store the input */
emilmont 1:fdd22bb7aa52 72 uint32_t blkCnt; /* loop counter */
emilmont 1:fdd22bb7aa52 73
emilmont 1:fdd22bb7aa52 74 #ifndef ARM_MATH_CM0
emilmont 1:fdd22bb7aa52 75
emilmont 1:fdd22bb7aa52 76 /* Run the below code for Cortex-M4 and Cortex-M3 */
emilmont 1:fdd22bb7aa52 77
emilmont 1:fdd22bb7aa52 78 q31_t in1, in2, in3, in4; /* Temporary input variables */
emilmont 1:fdd22bb7aa52 79
emilmont 1:fdd22bb7aa52 80 /*loop Unrolling */
emilmont 1:fdd22bb7aa52 81 blkCnt = blockSize >> 2u;
emilmont 1:fdd22bb7aa52 82
emilmont 1:fdd22bb7aa52 83 /* First part of the processing with loop unrolling. Compute 8 outputs at a time.
emilmont 1:fdd22bb7aa52 84 ** a second loop below computes the remaining 1 to 7 samples. */
emilmont 1:fdd22bb7aa52 85 while(blkCnt > 0u)
emilmont 1:fdd22bb7aa52 86 {
emilmont 1:fdd22bb7aa52 87 /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
emilmont 1:fdd22bb7aa52 88 /* Compute sum of the squares and then store the result in a temporary variable, sum */
emilmont 1:fdd22bb7aa52 89 /* read two samples from source buffer */
emilmont 1:fdd22bb7aa52 90 in1 = pSrc[0];
emilmont 1:fdd22bb7aa52 91 in2 = pSrc[1];
emilmont 1:fdd22bb7aa52 92
emilmont 1:fdd22bb7aa52 93 /* calculate power and accumulate to accumulator */
emilmont 1:fdd22bb7aa52 94 sum += (q63_t) in1 *in1;
emilmont 1:fdd22bb7aa52 95 sum += (q63_t) in2 *in2;
emilmont 1:fdd22bb7aa52 96
emilmont 1:fdd22bb7aa52 97 /* read two samples from source buffer */
emilmont 1:fdd22bb7aa52 98 in3 = pSrc[2];
emilmont 1:fdd22bb7aa52 99 in4 = pSrc[3];
emilmont 1:fdd22bb7aa52 100
emilmont 1:fdd22bb7aa52 101 /* calculate power and accumulate to accumulator */
emilmont 1:fdd22bb7aa52 102 sum += (q63_t) in3 *in3;
emilmont 1:fdd22bb7aa52 103 sum += (q63_t) in4 *in4;
emilmont 1:fdd22bb7aa52 104
emilmont 1:fdd22bb7aa52 105
emilmont 1:fdd22bb7aa52 106 /* update source buffer to process next samples */
emilmont 1:fdd22bb7aa52 107 pSrc += 4u;
emilmont 1:fdd22bb7aa52 108
emilmont 1:fdd22bb7aa52 109 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 110 blkCnt--;
emilmont 1:fdd22bb7aa52 111 }
emilmont 1:fdd22bb7aa52 112
emilmont 1:fdd22bb7aa52 113 /* If the blockSize is not a multiple of 8, compute any remaining output samples here.
emilmont 1:fdd22bb7aa52 114 ** No loop unrolling is used. */
emilmont 1:fdd22bb7aa52 115 blkCnt = blockSize % 0x4u;
emilmont 1:fdd22bb7aa52 116
emilmont 1:fdd22bb7aa52 117 #else
emilmont 1:fdd22bb7aa52 118
emilmont 1:fdd22bb7aa52 119 /* Run the below code for Cortex-M0 */
emilmont 1:fdd22bb7aa52 120 blkCnt = blockSize;
emilmont 1:fdd22bb7aa52 121
emilmont 1:fdd22bb7aa52 122 #endif /* #ifndef ARM_MATH_CM0 */
emilmont 1:fdd22bb7aa52 123
emilmont 1:fdd22bb7aa52 124 while(blkCnt > 0u)
emilmont 1:fdd22bb7aa52 125 {
emilmont 1:fdd22bb7aa52 126 /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
emilmont 1:fdd22bb7aa52 127 /* Compute sum of the squares and then store the results in a temporary variable, sum */
emilmont 1:fdd22bb7aa52 128 in = *pSrc++;
emilmont 1:fdd22bb7aa52 129 sum += (q63_t) in *in;
emilmont 1:fdd22bb7aa52 130
emilmont 1:fdd22bb7aa52 131 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 132 blkCnt--;
emilmont 1:fdd22bb7aa52 133 }
emilmont 1:fdd22bb7aa52 134
emilmont 1:fdd22bb7aa52 135 /* Convert data in 2.62 to 1.31 by 31 right shifts and saturate */
emilmont 1:fdd22bb7aa52 136
emilmont 1:fdd22bb7aa52 137 sum = __SSAT(sum >> 31, 31);
emilmont 1:fdd22bb7aa52 138
emilmont 1:fdd22bb7aa52 139
emilmont 1:fdd22bb7aa52 140 /* Compute Rms and store the result in the destination vector */
emilmont 1:fdd22bb7aa52 141 arm_sqrt_q31((q31_t) ((q31_t) sum / (int32_t) blockSize), pResult);
emilmont 1:fdd22bb7aa52 142 }
emilmont 1:fdd22bb7aa52 143
emilmont 1:fdd22bb7aa52 144 /**
emilmont 1:fdd22bb7aa52 145 * @} end of RMS group
emilmont 1:fdd22bb7aa52 146 */