1 /* ----------------------------------------------------------------------------
2 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
4 * $Date: 17. January 2013
7 * Project: CMSIS DSP Library
8 * Title: arm_q31_to_q15.c
10 * Description: Converts the elements of the Q31 vector to Q15 vector.
12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions
17 * - Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 * - Redistributions in binary form must reproduce the above copyright
20 * notice, this list of conditions and the following disclaimer in
21 * the documentation and/or other materials provided with the
23 * - Neither the name of ARM LIMITED nor the names of its contributors
24 * may be used to endorse or promote products derived from this
25 * software without specific prior written permission.
27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
30 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
31 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
33 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
34 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
37 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
38 * POSSIBILITY OF SUCH DAMAGE.
39 * ---------------------------------------------------------------------------- */
44 * @ingroup groupSupport
48 * @addtogroup q31_to_x
53 * @brief Converts the elements of the Q31 vector to Q15 vector.
54 * @param[in] *pSrc points to the Q31 input vector
55 * @param[out] *pDst points to the Q15 output vector
56 * @param[in] blockSize length of the input vector
61 * The equation used for the conversion process is:
64 * pDst[n] = (q15_t) pSrc[n] >> 16; 0 <= n < blockSize.
75 q31_t *pIn = pSrc; /* Src pointer */
76 uint32_t blkCnt; /* loop counter */
78 #ifndef ARM_MATH_CM0_FAMILY
80 /* Run the below code for Cortex-M4 and Cortex-M3 */
81 q31_t in1, in2, in3, in4;
85 blkCnt = blockSize >> 2u;
87 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
88 ** a second loop below computes the remaining 1 to 3 samples. */
91 /* C = (q15_t) A >> 16 */
92 /* convert from q31 to q15 and then store the results in the destination buffer */
98 /* pack two higher 16-bit values from two 32-bit values */
99 #ifndef ARM_MATH_BIG_ENDIAN
101 out1 = __PKHTB(in2, in1, 16);
102 out2 = __PKHTB(in4, in3, 16);
106 out1 = __PKHTB(in1, in2, 16);
107 out2 = __PKHTB(in3, in4, 16);
109 #endif // #ifdef ARM_MATH_BIG_ENDIAN
111 *__SIMD32(pDst)++ = out1;
112 *__SIMD32(pDst)++ = out2;
114 /* Decrement the loop counter */
118 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
119 ** No loop unrolling is used. */
120 blkCnt = blockSize % 0x4u;
124 /* Run the below code for Cortex-M0 */
126 /* Loop over blockSize number of values */
129 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
133 /* C = (q15_t) A >> 16 */
134 /* convert from q31 to q15 and then store the results in the destination buffer */
135 *pDst++ = (q15_t) (*pIn++ >> 16);
137 /* Decrement the loop counter */
144 * @} end of q31_to_x group