/* ---------------------------------------------------------------------- * Project: CMSIS DSP Library * Title: arm_q15_to_q7.c * Description: Converts the elements of the Q15 vector to Q7 vector * * $Date: 23 April 2021 * $Revision: V1.9.0 * * Target Processor: Cortex-M and Cortex-A cores * -------------------------------------------------------------------- */ /* * Copyright (C) 2010-2021 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 "dsp/support_functions.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:
      pDst[n] = (q7_t) pSrc[n] >> 8;   0 <= n < blockSize.
  
*/ #if defined(ARM_MATH_MVEI) && !defined(ARM_MATH_AUTOVECTORIZE) void arm_q15_to_q7( const q15_t * pSrc, q7_t * pDst, uint32_t blockSize) { uint32_t blkCnt; /* loop counters */ q15x8x2_t tmp; q15_t const *pSrcVec; q7x16_t vecDst; pSrcVec = (q15_t const *) pSrc; blkCnt = blockSize >> 4; while (blkCnt > 0U) { /* C = (q7_t) A >> 8 */ /* convert from q15 to q7 and then store the results in the destination buffer */ tmp = vld2q(pSrcVec); pSrcVec += 16; vecDst = vqshrnbq_n_s16(vecDst, tmp.val[0], 8); vecDst = vqshrntq_n_s16(vecDst, tmp.val[1], 8); vst1q(pDst, vecDst); pDst += 16; /* * Decrement the blockSize loop counter */ blkCnt--; } blkCnt = blockSize & 0xF; while (blkCnt > 0U) { /* C = (q7_t) A >> 8 */ /* Convert from q15 to q7 and store result in destination buffer */ *pDst++ = (q7_t) (*pSrcVec++ >> 8); /* Decrement loop counter */ blkCnt--; } } #else 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--; } } #endif /* defined(ARM_MATH_MVEI) */ /** @} end of q15_to_x group */