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/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_q15_to_q7.c
* Description: Converts the elements of the Q15 vector to Q7 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 q15_to_x
@{
*/
/**
@brief Converts the elements of the Q15 vector to Q7 vector.
@param[in] pSrc points to the Q15 input vector
@param[out] pDst points to the Q7 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] = (q7_t) pSrc[n] >> 8; 0 <= n < blockSize.
</pre>
*/
void arm_q15_to_q7(
const q15_t * pSrc,
q7_t * pDst,
uint32_t blockSize)
{
uint32_t blkCnt; /* Loop counter */
const q15_t *pIn = pSrc; /* Source pointer */
#if defined (ARM_MATH_LOOPUNROLL) && defined (ARM_MATH_DSP)
q31_t in1, in2;
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 = (q7_t) A >> 8 */
/* Convert from q15 to q7 and store result in destination buffer */
#if defined (ARM_MATH_DSP)
in1 = read_q15x2_ia ((q15_t **) &pIn);
in2 = read_q15x2_ia ((q15_t **) &pIn);
#ifndef ARM_MATH_BIG_ENDIAN
out1 = __PKHTB(in2, in1, 16);
out2 = __PKHBT(in2, in1, 16);
#else
out1 = __PKHTB(in1, in2, 16);
out2 = __PKHBT(in1, in2, 16);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* rotate packed value by 24 */
out2 = ((uint32_t) out2 << 8) | ((uint32_t) out2 >> 24);
/* anding with 0xff00ff00 to get two 8 bit values */
out1 = out1 & 0xFF00FF00;
/* anding with 0x00ff00ff to get two 8 bit values */
out2 = out2 & 0x00FF00FF;
/* oring two values(contains two 8 bit values) to get four packed 8 bit values */
out1 = out1 | out2;
/* store 4 samples at a time to destiantion buffer */
write_q7x4_ia (&pDst, out1);
#else
*pDst++ = (q7_t) (*pIn++ >> 8);
*pDst++ = (q7_t) (*pIn++ >> 8);
*pDst++ = (q7_t) (*pIn++ >> 8);
*pDst++ = (q7_t) (*pIn++ >> 8);
#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 = (q7_t) A >> 8 */
/* Convert from q15 to q7 and store result in destination buffer */
*pDst++ = (q7_t) (*pIn++ >> 8);
/* Decrement loop counter */
blkCnt--;
}
}
/**
@} end of q15_to_x group
*/
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