Rev 2 | Details | Compare with Previous | Last modification | View Log | RSS feed
| Rev | Author | Line No. | Line |
|---|---|---|---|
| 2 | mjames | 1 | /* ---------------------------------------------------------------------- |
| 2 | * Project: CMSIS DSP Library |
||
| 3 | * Title: arm_rms_q31.c |
||
| 4 | * Description: Root Mean Square of the elements of a Q31 vector |
||
| 5 | * |
||
| 6 | * $Date: 27. January 2017 |
||
| 7 | * $Revision: V.1.5.1 |
||
| 8 | * |
||
| 9 | * Target Processor: Cortex-M cores |
||
| 10 | * -------------------------------------------------------------------- */ |
||
| 11 | /* |
||
| 12 | * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved. |
||
| 13 | * |
||
| 14 | * SPDX-License-Identifier: Apache-2.0 |
||
| 15 | * |
||
| 16 | * Licensed under the Apache License, Version 2.0 (the License); you may |
||
| 17 | * not use this file except in compliance with the License. |
||
| 18 | * You may obtain a copy of the License at |
||
| 19 | * |
||
| 20 | * www.apache.org/licenses/LICENSE-2.0 |
||
| 21 | * |
||
| 22 | * Unless required by applicable law or agreed to in writing, software |
||
| 23 | * distributed under the License is distributed on an AS IS BASIS, WITHOUT |
||
| 24 | * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
||
| 25 | * See the License for the specific language governing permissions and |
||
| 26 | * limitations under the License. |
||
| 27 | */ |
||
| 28 | |||
| 29 | #include "arm_math.h" |
||
| 30 | |||
| 31 | /** |
||
| 32 | * @addtogroup RMS |
||
| 33 | * @{ |
||
| 34 | */ |
||
| 35 | |||
| 36 | |||
| 37 | /** |
||
| 38 | * @brief Root Mean Square of the elements of a Q31 vector. |
||
| 39 | * @param[in] *pSrc points to the input vector |
||
| 40 | * @param[in] blockSize length of the input vector |
||
| 41 | * @param[out] *pResult rms value returned here |
||
| 42 | * @return none. |
||
| 43 | * |
||
| 44 | * @details |
||
| 45 | * <b>Scaling and Overflow Behavior:</b> |
||
| 46 | * |
||
| 47 | *\par |
||
| 48 | * The function is implemented using an internal 64-bit accumulator. |
||
| 49 | * The input is represented in 1.31 format, and intermediate multiplication |
||
| 50 | * yields a 2.62 format. |
||
| 51 | * The accumulator maintains full precision of the intermediate multiplication results, |
||
| 52 | * but provides only a single guard bit. |
||
| 53 | * There is no saturation on intermediate additions. |
||
| 54 | * If the accumulator overflows, it wraps around and distorts the result. |
||
| 55 | * In order to avoid overflows completely, the input signal must be scaled down by |
||
| 56 | * log2(blockSize) bits, as a total of blockSize additions are performed internally. |
||
| 57 | * Finally, the 2.62 accumulator is right shifted by 31 bits to yield a 1.31 format value. |
||
| 58 | * |
||
| 59 | */ |
||
| 60 | |||
| 61 | void arm_rms_q31( |
||
| 62 | q31_t * pSrc, |
||
| 63 | uint32_t blockSize, |
||
| 64 | q31_t * pResult) |
||
| 65 | { |
||
| 66 | q63_t sum = 0; /* accumulator */ |
||
| 67 | q31_t in; /* Temporary variable to store the input */ |
||
| 68 | uint32_t blkCnt; /* loop counter */ |
||
| 69 | |||
| 70 | #if defined (ARM_MATH_DSP) |
||
| 71 | /* Run the below code for Cortex-M4 and Cortex-M3 */ |
||
| 72 | |||
| 73 | q31_t in1, in2, in3, in4; /* Temporary input variables */ |
||
| 74 | |||
| 75 | /*loop Unrolling */ |
||
| 76 | blkCnt = blockSize >> 2U; |
||
| 77 | |||
| 78 | /* First part of the processing with loop unrolling. Compute 8 outputs at a time. |
||
| 79 | ** a second loop below computes the remaining 1 to 7 samples. */ |
||
| 80 | while (blkCnt > 0U) |
||
| 81 | { |
||
| 82 | /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */ |
||
| 83 | /* Compute sum of the squares and then store the result in a temporary variable, sum */ |
||
| 84 | /* read two samples from source buffer */ |
||
| 85 | in1 = pSrc[0]; |
||
| 86 | in2 = pSrc[1]; |
||
| 87 | |||
| 88 | /* calculate power and accumulate to accumulator */ |
||
| 89 | sum += (q63_t) in1 *in1; |
||
| 90 | sum += (q63_t) in2 *in2; |
||
| 91 | |||
| 92 | /* read two samples from source buffer */ |
||
| 93 | in3 = pSrc[2]; |
||
| 94 | in4 = pSrc[3]; |
||
| 95 | |||
| 96 | /* calculate power and accumulate to accumulator */ |
||
| 97 | sum += (q63_t) in3 *in3; |
||
| 98 | sum += (q63_t) in4 *in4; |
||
| 99 | |||
| 100 | |||
| 101 | /* update source buffer to process next samples */ |
||
| 102 | pSrc += 4U; |
||
| 103 | |||
| 104 | /* Decrement the loop counter */ |
||
| 105 | blkCnt--; |
||
| 106 | } |
||
| 107 | |||
| 108 | /* If the blockSize is not a multiple of 8, compute any remaining output samples here. |
||
| 109 | ** No loop unrolling is used. */ |
||
| 110 | blkCnt = blockSize % 0x4U; |
||
| 111 | |||
| 112 | #else |
||
| 113 | /* Run the below code for Cortex-M0 */ |
||
| 114 | |||
| 115 | blkCnt = blockSize; |
||
| 116 | |||
| 117 | #endif /* #if defined (ARM_MATH_DSP) */ |
||
| 118 | |||
| 119 | while (blkCnt > 0U) |
||
| 120 | { |
||
| 121 | /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */ |
||
| 122 | /* Compute sum of the squares and then store the results in a temporary variable, sum */ |
||
| 123 | in = *pSrc++; |
||
| 124 | sum += (q63_t) in *in; |
||
| 125 | |||
| 126 | /* Decrement the loop counter */ |
||
| 127 | blkCnt--; |
||
| 128 | } |
||
| 129 | |||
| 130 | /* Convert data in 2.62 to 1.31 by 31 right shifts and saturate */ |
||
| 131 | /* Compute Rms and store the result in the destination vector */ |
||
| 132 | arm_sqrt_q31(clip_q63_to_q31((sum / (q63_t) blockSize) >> 31), pResult); |
||
| 133 | } |
||
| 134 | |||
| 135 | /** |
||
| 136 | * @} end of RMS group |
||
| 137 | */ |