| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_rms_q31.c |
| * Description: Root Mean Square of the elements of a Q31 vector |
| * |
| * $Date: 18. March 2019 |
| * $Revision: V1.6.0 |
| * |
| * Target Processor: Cortex-M cores |
| * -------------------------------------------------------------------- */ |
| /* |
| * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved. |
| * |
| * SPDX-License-Identifier: Apache-2.0 |
| * |
| * Licensed under the Apache License, Version 2.0 (the License); you may |
| * not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an AS IS BASIS, WITHOUT |
| * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include "arm_math.h" |
| |
| /** |
| @ingroup groupStats |
| */ |
| |
| /** |
| @addtogroup RMS |
| @{ |
| */ |
| |
| /** |
| @brief Root Mean Square of the elements of a Q31 vector. |
| @param[in] pSrc points to the input vector |
| @param[in] blockSize number of samples in input vector |
| @param[out] pResult root mean square value returned here |
| @return none |
| |
| @par Scaling and Overflow Behavior |
| The function is implemented using an internal 64-bit accumulator. |
| The input is represented in 1.31 format, and intermediate multiplication |
| yields a 2.62 format. |
| The accumulator maintains full precision of the intermediate multiplication results, |
| but provides only a single guard bit. |
| There is no saturation on intermediate additions. |
| If the accumulator overflows, it wraps around and distorts the result. |
| In order to avoid overflows completely, the input signal must be scaled down by |
| log2(blockSize) bits, as a total of blockSize additions are performed internally. |
| Finally, the 2.62 accumulator is right shifted by 31 bits to yield a 1.31 format value. |
| */ |
| |
| void arm_rms_q31( |
| const q31_t * pSrc, |
| uint32_t blockSize, |
| q31_t * pResult) |
| { |
| uint32_t blkCnt; /* Loop counter */ |
| uint64_t sum = 0; /* Temporary result storage (can get never negative. changed type from q63 to uint64 */ |
| q31_t in; /* Temporary variable to store input value */ |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 outputs at a time */ |
| blkCnt = blockSize >> 2U; |
| |
| while (blkCnt > 0U) |
| { |
| /* C = A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1] */ |
| |
| in = *pSrc++; |
| /* Compute sum of squares and store result in a temporary variable, sum. */ |
| sum += ((q63_t) in * in); |
| |
| in = *pSrc++; |
| sum += ((q63_t) in * in); |
| |
| in = *pSrc++; |
| sum += ((q63_t) in * in); |
| |
| in = *pSrc++; |
| sum += ((q63_t) in * in); |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining outputs */ |
| blkCnt = blockSize % 0x4U; |
| |
| #else |
| |
| /* Initialize blkCnt with number of samples */ |
| blkCnt = blockSize; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (blkCnt > 0U) |
| { |
| /* C = A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1] */ |
| |
| in = *pSrc++; |
| /* Compute sum of squares and store result in a temporary variable. */ |
| sum += ((q63_t) in * in); |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Convert data in 2.62 to 1.31 by 31 right shifts and saturate */ |
| /* Compute Rms and store result in destination vector */ |
| arm_sqrt_q31(clip_q63_to_q31((sum / (q63_t) blockSize) >> 31), pResult); |
| } |
| |
| /** |
| @} end of RMS group |
| */ |