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git.gir.st - tmk_keyboard.git/blob - tmk_core/tool/mbed/mbed-sdk/libraries/dsp/cmsis_dsp/SupportFunctions/arm_q15_to_q7.c
1 /* ----------------------------------------------------------------------------
2 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
4 * $Date: 17. January 2013
7 * Project: CMSIS DSP Library
8 * Title: arm_q15_to_q7.c
10 * Description: Converts the elements of the Q15 vector to Q7 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 q15_to_x
54 * @brief Converts the elements of the Q15 vector to Q7 vector.
55 * @param[in] *pSrc points to the Q15 input vector
56 * @param[out] *pDst points to the Q7 output vector
57 * @param[in] blockSize length of the input vector
62 * The equation used for the conversion process is:
65 * pDst[n] = (q7_t) pSrc[n] >> 8; 0 <= n < blockSize.
76 q15_t
*pIn
= pSrc
; /* Src pointer */
77 uint32_t blkCnt
; /* loop counter */
79 #ifndef ARM_MATH_CM0_FAMILY
81 /* Run the below code for Cortex-M4 and Cortex-M3 */
86 blkCnt
= blockSize
>> 2u;
88 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
89 ** a second loop below computes the remaining 1 to 3 samples. */
92 /* C = (q7_t) A >> 8 */
93 /* convert from q15 to q7 and then store the results in the destination buffer */
94 in1
= *__SIMD32(pIn
)++;
95 in2
= *__SIMD32(pIn
)++;
97 #ifndef ARM_MATH_BIG_ENDIAN
99 out1
= __PKHTB(in2
, in1
, 16);
100 out2
= __PKHBT(in2
, in1
, 16);
104 out1
= __PKHTB(in1
, in2
, 16);
105 out2
= __PKHBT(in1
, in2
, 16);
107 #endif // #ifndef ARM_MATH_BIG_ENDIAN
109 /* rotate packed value by 24 */
110 out2
= ((uint32_t) out2
<< 8) | ((uint32_t) out2
>> 24);
112 /* anding with 0xff00ff00 to get two 8 bit values */
113 out1
= out1
& 0xFF00FF00;
114 /* anding with 0x00ff00ff to get two 8 bit values */
115 out2
= out2
& 0x00FF00FF;
117 /* oring two values(contains two 8 bit values) to get four packed 8 bit values */
120 /* store 4 samples at a time to destiantion buffer */
121 *__SIMD32(pDst
)++ = out1
;
123 /* Decrement the loop counter */
127 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
128 ** No loop unrolling is used. */
129 blkCnt
= blockSize
% 0x4u
;
133 /* Run the below code for Cortex-M0 */
135 /* Loop over blockSize number of values */
138 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
142 /* C = (q7_t) A >> 8 */
143 /* convert from q15 to q7 and then store the results in the destination buffer */
144 *pDst
++ = (q7_t
) (*pIn
++ >> 8);
146 /* Decrement the loop counter */
153 * @} end of q15_to_x group