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| 56 | mjames | 1 | /* ---------------------------------------------------------------------- |
| 2 | * Project: CMSIS DSP Library |
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| 3 | * Title: arm_dct4_init_q15.c |
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| 4 | * Description: Initialization function of DCT-4 & IDCT4 Q15 |
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| 5 | * |
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| 6 | * $Date: 27. January 2017 |
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| 7 | * $Revision: V.1.5.1 |
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| 8 | * |
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| 9 | * Target Processor: Cortex-M cores |
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| 10 | * -------------------------------------------------------------------- */ |
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| 11 | /* |
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| 12 | * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved. |
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| 13 | * |
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| 14 | * SPDX-License-Identifier: Apache-2.0 |
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| 15 | * |
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| 16 | * Licensed under the Apache License, Version 2.0 (the License); you may |
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| 17 | * not use this file except in compliance with the License. |
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| 18 | * You may obtain a copy of the License at |
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| 19 | * |
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| 20 | * www.apache.org/licenses/LICENSE-2.0 |
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| 21 | * |
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| 22 | * Unless required by applicable law or agreed to in writing, software |
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| 23 | * distributed under the License is distributed on an AS IS BASIS, WITHOUT |
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| 24 | * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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| 25 | * See the License for the specific language governing permissions and |
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| 26 | * limitations under the License. |
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| 27 | */ |
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| 28 | |||
| 29 | #include "arm_math.h" |
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| 30 | |||
| 31 | /** |
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| 32 | * @ingroup DCT4_IDCT4 |
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| 33 | */ |
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| 34 | |||
| 35 | /** |
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| 36 | * @addtogroup DCT4_IDCT4_Table DCT Type IV Tables |
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| 37 | * @{ |
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| 38 | */ |
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| 39 | |||
| 40 | /* |
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| 41 | * @brief Weights Table |
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| 42 | */ |
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| 43 | |||
| 44 | /** |
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| 45 | * \par |
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| 46 | * Weights tables are generated using the formula : <pre>weights[n] = e^(-j*n*pi/(2*N))</pre> |
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| 47 | * \par |
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| 48 | * C command to generate the table |
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| 49 | * <pre> |
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| 50 | * for(i = 0; i< N; i++) |
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| 51 | * { |
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| 52 | * weights[2*i]= cos(i*c); |
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| 53 | * weights[(2*i)+1]= -sin(i * c); |
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| 54 | * } </pre> |
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| 55 | * \par |
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| 56 | * where <code>N</code> is the Number of weights to be calculated and <code>c</code> is <code>pi/(2*N)</code> |
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| 57 | * \par |
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| 58 | * Converted the output to q15 format by multiplying with 2^31 and saturated if required. |
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| 59 | * \par |
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| 60 | * In the tables below the real and imaginary values are placed alternatively, hence the |
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| 61 | * array length is <code>2*N</code>. |
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| 62 | *//** |
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| 63 | |||
| 64 | * cosFactor tables are generated using the formula : <pre> cos_factors[n] = 2 * cos((2n+1)*pi/(4*N)) </pre> |
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| 65 | * \par |
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| 66 | * C command to generate the table |
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| 67 | * <pre> |
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| 68 | * for(i = 0; i< N; i++) |
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| 69 | * { |
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| 70 | * cos_factors[i]= 2 * cos((2*i+1)*c/2); |
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| 71 | * } </pre> |
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| 72 | * \par |
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| 73 | * where <code>N</code> is the number of factors to generate and <code>c</code> is <code>pi/(2*N)</code> |
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| 74 | * \par |
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| 75 | * Then converted to q15 format by multiplying with 2^31 and saturated if required. |
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| 76 | |||
| 77 | *//** |
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| 78 | * @} end of DCT4_IDCT4_Table group |
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| 79 | */ |
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| 80 | |||
| 81 | /** |
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| 82 | * @addtogroup DCT4_IDCT4 |
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| 83 | * @{ |
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| 84 | */ |
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| 85 | |||
| 86 | /** |
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| 87 | * @brief Initialization function for the Q15 DCT4/IDCT4. |
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| 88 | * @param[in,out] *S points to an instance of Q15 DCT4/IDCT4 structure. |
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| 89 | * @param[in] *S_RFFT points to an instance of Q15 RFFT/RIFFT structure. |
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| 90 | * @param[in] *S_CFFT points to an instance of Q15 CFFT/CIFFT structure. |
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| 91 | * @param[in] N length of the DCT4. |
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| 92 | * @param[in] Nby2 half of the length of the DCT4. |
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| 93 | * @param[in] normalize normalizing factor. |
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| 94 | * @return arm_status function returns ARM_MATH_SUCCESS if initialization is successful or ARM_MATH_ARGUMENT_ERROR if <code>N</code> is not a supported transform length. |
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| 95 | * \par Normalizing factor: |
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| 96 | * The normalizing factor is <code>sqrt(2/N)</code>, which depends on the size of transform <code>N</code>. |
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| 97 | * Normalizing factors in 1.15 format are mentioned in the table below for different DCT sizes: |
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| 98 | |||
| 99 | */ |
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| 100 | |||
| 101 | arm_status arm_dct4_init_q15( |
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| 102 | arm_dct4_instance_q15 * S, |
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| 103 | arm_rfft_instance_q15 * S_RFFT, |
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| 104 | arm_cfft_radix4_instance_q15 * S_CFFT, |
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| 105 | uint16_t N, |
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| 106 | uint16_t Nby2, |
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| 107 | q15_t normalize) |
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| 108 | { |
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| 109 | /* Initialise the default arm status */ |
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| 110 | arm_status status = ARM_MATH_SUCCESS; |
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| 111 | |||
| 112 | /* Initializing the pointer array with the weight table base addresses of different lengths */ |
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| 113 | q15_t *twiddlePtr[4] = { (q15_t *) WeightsQ15_128, (q15_t *) WeightsQ15_512, |
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| 114 | (q15_t *) WeightsQ15_2048, (q15_t *) WeightsQ15_8192 |
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| 115 | }; |
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| 116 | |||
| 117 | /* Initializing the pointer array with the cos factor table base addresses of different lengths */ |
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| 118 | q15_t *pCosFactor[4] = |
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| 119 | { (q15_t *) cos_factorsQ15_128, (q15_t *) cos_factorsQ15_512, |
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| 120 | (q15_t *) cos_factorsQ15_2048, (q15_t *) cos_factorsQ15_8192 |
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| 121 | }; |
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| 122 | |||
| 123 | /* Initialize the DCT4 length */ |
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| 124 | S->N = N; |
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| 125 | |||
| 126 | /* Initialize the half of DCT4 length */ |
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| 127 | S->Nby2 = Nby2; |
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| 128 | |||
| 129 | /* Initialize the DCT4 Normalizing factor */ |
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| 130 | S->normalize = normalize; |
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| 131 | |||
| 132 | /* Initialize Real FFT Instance */ |
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| 133 | S->pRfft = S_RFFT; |
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| 134 | |||
| 135 | /* Initialize Complex FFT Instance */ |
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| 136 | S->pCfft = S_CFFT; |
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| 137 | |||
| 138 | switch (N) |
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| 139 | { |
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| 140 | /* Initialize the table modifier values */ |
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| 141 | case 8192U: |
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| 142 | S->pTwiddle = twiddlePtr[3]; |
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| 143 | S->pCosFactor = pCosFactor[3]; |
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| 144 | break; |
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| 145 | case 2048U: |
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| 146 | S->pTwiddle = twiddlePtr[2]; |
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| 147 | S->pCosFactor = pCosFactor[2]; |
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| 148 | break; |
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| 149 | case 512U: |
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| 150 | S->pTwiddle = twiddlePtr[1]; |
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| 151 | S->pCosFactor = pCosFactor[1]; |
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| 152 | break; |
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| 153 | case 128U: |
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| 154 | S->pTwiddle = twiddlePtr[0]; |
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| 155 | S->pCosFactor = pCosFactor[0]; |
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| 156 | break; |
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| 157 | default: |
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| 158 | status = ARM_MATH_ARGUMENT_ERROR; |
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| 159 | } |
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| 160 | |||
| 161 | /* Initialize the RFFT/RIFFT */ |
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| 162 | arm_rfft_init_q15(S->pRfft, S->N, 0U, 1U); |
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| 163 | |||
| 164 | /* return the status of DCT4 Init function */ |
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| 165 | return (status); |
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| 166 | } |
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| 167 | |||
| 168 | /** |
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| 169 | * @} end of DCT4_IDCT4 group |
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| 170 | */ |
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| 171 | |||
| 172 |