1 /* ----------------------------------------------------------------------
2 * Project: CMSIS DSP Library
3 * Title: arm_q15_to_q7.c
4 * Description: Converts the elements of the Q15 vector to Q7 vector
5 *
6 * $Date: 23 April 2021
7 * $Revision: V1.9.0
8 *
9 * Target Processor: Cortex-M and Cortex-A cores
10 * -------------------------------------------------------------------- */
11 /*
12 * Copyright (C) 2010-2021 ARM Limited or its affiliates. All rights reserved.
13 *
14 * SPDX-License-Identifier: Apache-2.0
15 *
16 * Licensed under the Apache License, Version 2.0 (the License); you may
17 * not use this file except in compliance with the License.
18 * You may obtain a copy of the License at
19 *
20 * www.apache.org/licenses/LICENSE-2.0
21 *
22 * Unless required by applicable law or agreed to in writing, software
23 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
24 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
25 * See the License for the specific language governing permissions and
26 * limitations under the License.
27 */
28
29 #include "dsp/support_functions.h"
30
31 /**
32 @ingroup groupSupport
33 */
34
35 /**
36 @addtogroup q15_to_x
37 @{
38 */
39
40 /**
41 @brief Converts the elements of the Q15 vector to Q7 vector.
42 @param[in] pSrc points to the Q15 input vector
43 @param[out] pDst points to the Q7 output vector
44 @param[in] blockSize number of samples in each vector
45 @return none
46
47 @par Details
48 The equation used for the conversion process is:
49 <pre>
50 pDst[n] = (q7_t) pSrc[n] >> 8; 0 <= n < blockSize.
51 </pre>
52 */
53 #if defined(ARM_MATH_MVEI) && !defined(ARM_MATH_AUTOVECTORIZE)
arm_q15_to_q7(const q15_t * pSrc,q7_t * pDst,uint32_t blockSize)54 void arm_q15_to_q7(
55 const q15_t * pSrc,
56 q7_t * pDst,
57 uint32_t blockSize)
58 {
59
60 uint32_t blkCnt; /* loop counters */
61 q15x8x2_t tmp;
62 q15_t const *pSrcVec;
63 q7x16_t vecDst = { 0 };
64
65
66 pSrcVec = (q15_t const *) pSrc;
67 blkCnt = blockSize >> 4;
68 while (blkCnt > 0U)
69 {
70 /* C = (q7_t) A >> 8 */
71 /* convert from q15 to q7 and then store the results in the destination buffer */
72 tmp = vld2q(pSrcVec);
73 pSrcVec += 16;
74 vecDst = vqshrnbq_n_s16(vecDst, tmp.val[0], 8);
75 vecDst = vqshrntq_n_s16(vecDst, tmp.val[1], 8);
76 vst1q(pDst, vecDst);
77 pDst += 16;
78 /*
79 * Decrement the blockSize loop counter
80 */
81 blkCnt--;
82 }
83
84 blkCnt = blockSize & 0xF;
85 while (blkCnt > 0U)
86 {
87 /* C = (q7_t) A >> 8 */
88
89 /* Convert from q15 to q7 and store result in destination buffer */
90 *pDst++ = (q7_t) (*pSrcVec++ >> 8);
91
92 /* Decrement loop counter */
93 blkCnt--;
94 }
95 }
96 #else
arm_q15_to_q7(const q15_t * pSrc,q7_t * pDst,uint32_t blockSize)97 void arm_q15_to_q7(
98 const q15_t * pSrc,
99 q7_t * pDst,
100 uint32_t blockSize)
101 {
102 uint32_t blkCnt; /* Loop counter */
103 const q15_t *pIn = pSrc; /* Source pointer */
104
105 #if defined (ARM_MATH_LOOPUNROLL) && defined (ARM_MATH_DSP)
106 q31_t in1, in2;
107 q31_t out1, out2;
108 #endif
109
110 #if defined (ARM_MATH_LOOPUNROLL)
111
112 /* Loop unrolling: Compute 4 outputs at a time */
113 blkCnt = blockSize >> 2U;
114
115 while (blkCnt > 0U)
116 {
117 /* C = (q7_t) A >> 8 */
118
119 /* Convert from q15 to q7 and store result in destination buffer */
120 #if defined (ARM_MATH_DSP)
121
122 in1 = read_q15x2_ia ((q15_t **) &pIn);
123 in2 = read_q15x2_ia ((q15_t **) &pIn);
124
125 #ifndef ARM_MATH_BIG_ENDIAN
126
127 out1 = __PKHTB(in2, in1, 16);
128 out2 = __PKHBT(in2, in1, 16);
129
130 #else
131
132 out1 = __PKHTB(in1, in2, 16);
133 out2 = __PKHBT(in1, in2, 16);
134
135 #endif /* #ifndef ARM_MATH_BIG_ENDIAN */
136
137 /* rotate packed value by 24 */
138 out2 = ((uint32_t) out2 << 8) | ((uint32_t) out2 >> 24);
139
140 /* anding with 0xff00ff00 to get two 8 bit values */
141 out1 = out1 & 0xFF00FF00;
142 /* anding with 0x00ff00ff to get two 8 bit values */
143 out2 = out2 & 0x00FF00FF;
144
145 /* oring two values(contains two 8 bit values) to get four packed 8 bit values */
146 out1 = out1 | out2;
147
148 /* store 4 samples at a time to destiantion buffer */
149 write_q7x4_ia (&pDst, out1);
150
151 #else
152
153 *pDst++ = (q7_t) (*pIn++ >> 8);
154 *pDst++ = (q7_t) (*pIn++ >> 8);
155 *pDst++ = (q7_t) (*pIn++ >> 8);
156 *pDst++ = (q7_t) (*pIn++ >> 8);
157
158 #endif /* #if defined (ARM_MATH_DSP) */
159
160 /* Decrement loop counter */
161 blkCnt--;
162 }
163
164 /* Loop unrolling: Compute remaining outputs */
165 blkCnt = blockSize % 0x4U;
166
167 #else
168
169 /* Initialize blkCnt with number of samples */
170 blkCnt = blockSize;
171
172 #endif /* #if defined (ARM_MATH_LOOPUNROLL) */
173
174 while (blkCnt > 0U)
175 {
176 /* C = (q7_t) A >> 8 */
177
178 /* Convert from q15 to q7 and store result in destination buffer */
179 *pDst++ = (q7_t) (*pIn++ >> 8);
180
181 /* Decrement loop counter */
182 blkCnt--;
183 }
184
185 }
186 #endif /* defined(ARM_MATH_MVEI) */
187
188 /**
189 @} end of q15_to_x group
190 */
191
