/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_q15_to_q7.c
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* Description: Converts the elements of the Q15 vector to Q7 vector
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*
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* $Date: 27. January 2017
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* $Revision: V.1.5.1
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*
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* Target Processor: Cortex-M cores
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* -------------------------------------------------------------------- */
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/*
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* Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an AS IS BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "arm_math.h"
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/**
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* @ingroup groupSupport
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*/
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/**
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* @addtogroup q15_to_x
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* @{
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*/
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/**
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* @brief Converts the elements of the Q15 vector to Q7 vector.
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* @param[in] *pSrc points to the Q15 input vector
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* @param[out] *pDst points to the Q7 output vector
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* @param[in] blockSize length of the input vector
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* @return none.
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*
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* \par Description:
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*
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* The equation used for the conversion process is:
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*
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* <pre>
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* pDst[n] = (q7_t) pSrc[n] >> 8; 0 <= n < blockSize.
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* </pre>
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*
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*/
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void arm_q15_to_q7(
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q15_t * pSrc,
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q7_t * pDst,
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uint32_t blockSize)
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{
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q15_t *pIn = pSrc; /* Src pointer */
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uint32_t blkCnt; /* loop counter */
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#if defined (ARM_MATH_DSP)
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/* Run the below code for Cortex-M4 and Cortex-M3 */
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q31_t in1, in2;
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q31_t out1, out2;
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/*loop Unrolling */
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blkCnt = blockSize >> 2U;
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/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
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** a second loop below computes the remaining 1 to 3 samples. */
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while (blkCnt > 0U)
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{
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/* C = (q7_t) A >> 8 */
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/* convert from q15 to q7 and then store the results in the destination buffer */
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in1 = *__SIMD32(pIn)++;
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in2 = *__SIMD32(pIn)++;
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#ifndef ARM_MATH_BIG_ENDIAN
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out1 = __PKHTB(in2, in1, 16);
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out2 = __PKHBT(in2, in1, 16);
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#else
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out1 = __PKHTB(in1, in2, 16);
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out2 = __PKHBT(in1, in2, 16);
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#endif // #ifndef ARM_MATH_BIG_ENDIAN
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/* rotate packed value by 24 */
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out2 = ((uint32_t) out2 << 8) | ((uint32_t) out2 >> 24);
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/* anding with 0xff00ff00 to get two 8 bit values */
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out1 = out1 & 0xFF00FF00;
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/* anding with 0x00ff00ff to get two 8 bit values */
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out2 = out2 & 0x00FF00FF;
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/* oring two values(contains two 8 bit values) to get four packed 8 bit values */
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out1 = out1 | out2;
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/* store 4 samples at a time to destiantion buffer */
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*__SIMD32(pDst)++ = out1;
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
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** No loop unrolling is used. */
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blkCnt = blockSize % 0x4U;
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#else
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/* Run the below code for Cortex-M0 */
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/* Loop over blockSize number of values */
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blkCnt = blockSize;
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#endif /* #if defined (ARM_MATH_DSP) */
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while (blkCnt > 0U)
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{
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/* C = (q7_t) A >> 8 */
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/* convert from q15 to q7 and then store the results in the destination buffer */
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*pDst++ = (q7_t) (*pIn++ >> 8);
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/* Decrement the loop counter */
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blkCnt--;
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}
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}
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/**
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* @} end of q15_to_x group
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*/
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