| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_q31_to_q15.c |
| * Description: Converts the elements of the Q31 vector to Q15 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 groupSupport |
| */ |
| |
| /** |
| @addtogroup q31_to_x |
| @{ |
| */ |
| |
| /** |
| @brief Converts the elements of the Q31 vector to Q15 vector. |
| @param[in] pSrc points to the Q31 input vector |
| @param[out] pDst points to the Q15 output vector |
| @param[in] blockSize number of samples in each vector |
| @return none |
| |
| @par Details |
| The equation used for the conversion process is: |
| <pre> |
| pDst[n] = (q15_t) pSrc[n] >> 16; 0 <= n < blockSize. |
| </pre> |
| */ |
| |
| void arm_q31_to_q15( |
| const q31_t * pSrc, |
| q15_t * pDst, |
| uint32_t blockSize) |
| { |
| uint32_t blkCnt; /* Loop counter */ |
| const q31_t *pIn = pSrc; /* Source pointer */ |
| |
| #if defined (ARM_MATH_LOOPUNROLL) && defined (ARM_MATH_DSP) |
| q31_t in1, in2, in3, in4; |
| q31_t out1, out2; |
| #endif |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 outputs at a time */ |
| blkCnt = blockSize >> 2U; |
| |
| while (blkCnt > 0U) |
| { |
| /* C = (q15_t) (A >> 16) */ |
| |
| /* Convert from q31 to q15 and store result in destination buffer */ |
| #if defined (ARM_MATH_DSP) |
| |
| in1 = *pIn++; |
| in2 = *pIn++; |
| in3 = *pIn++; |
| in4 = *pIn++; |
| |
| /* pack two higher 16-bit values from two 32-bit values */ |
| #ifndef ARM_MATH_BIG_ENDIAN |
| out1 = __PKHTB(in2, in1, 16); |
| out2 = __PKHTB(in4, in3, 16); |
| #else |
| out1 = __PKHTB(in1, in2, 16); |
| out2 = __PKHTB(in3, in4, 16); |
| #endif /* #ifdef ARM_MATH_BIG_ENDIAN */ |
| |
| write_q15x2_ia (&pDst, out1); |
| write_q15x2_ia (&pDst, out2); |
| |
| #else |
| |
| *pDst++ = (q15_t) (*pIn++ >> 16); |
| *pDst++ = (q15_t) (*pIn++ >> 16); |
| *pDst++ = (q15_t) (*pIn++ >> 16); |
| *pDst++ = (q15_t) (*pIn++ >> 16); |
| |
| #endif /* #if defined (ARM_MATH_DSP) */ |
| |
| /* 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 = (q15_t) (A >> 16) */ |
| |
| /* Convert from q31 to q15 and store result in destination buffer */ |
| *pDst++ = (q15_t) (*pIn++ >> 16); |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| } |
| |
| /** |
| @} end of q31_to_x group |
| */ |