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| 2 | mjames | 1 | /* ---------------------------------------------------------------------- |
| 2 | * Copyright (C) 2010-2014 ARM Limited. All rights reserved. |
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| 3 | * |
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| 4 | * $Date: 19. March 2015 |
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| 5 | * $Revision: V.1.4.5 |
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| 6 | * |
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| 7 | * Project: CMSIS DSP Library |
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| 8 | * Title: arm_dct4_init_q15.c |
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| 9 | * |
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| 10 | * Description: Initialization function of DCT-4 & IDCT4 Q15 |
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| 11 | * |
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| 12 | * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 |
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| 13 | * |
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| 14 | * Redistribution and use in source and binary forms, with or without |
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| 15 | * modification, are permitted provided that the following conditions |
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| 16 | * are met: |
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| 17 | * - Redistributions of source code must retain the above copyright |
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| 18 | * notice, this list of conditions and the following disclaimer. |
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| 19 | * - Redistributions in binary form must reproduce the above copyright |
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| 20 | * notice, this list of conditions and the following disclaimer in |
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| 21 | * the documentation and/or other materials provided with the |
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| 22 | * distribution. |
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| 23 | * - Neither the name of ARM LIMITED nor the names of its contributors |
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| 24 | * may be used to endorse or promote products derived from this |
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| 25 | * software without specific prior written permission. |
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| 26 | * |
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| 27 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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| 28 | * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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| 29 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
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| 30 | * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
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| 31 | * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
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| 32 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
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| 33 | * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
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| 34 | * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER |
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| 35 | * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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| 36 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN |
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| 37 | * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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| 38 | * POSSIBILITY OF SUCH DAMAGE. |
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| 39 | * -------------------------------------------------------------------- */ |
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| 40 | |||
| 41 | |||
| 42 | #include "arm_math.h" |
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| 43 | |||
| 44 | /** |
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| 45 | * @ingroup groupTransforms |
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| 46 | */ |
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| 47 | |||
| 48 | /** |
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| 49 | * @addtogroup DCT4_IDCT4 |
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| 50 | * @{ |
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| 51 | */ |
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| 52 | |||
| 53 | /* |
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| 54 | * @brief Weights Table |
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| 55 | */ |
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| 56 | |||
| 57 | /** |
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| 58 | * \par |
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| 59 | * Weights tables are generated using the formula : <pre>weights[n] = e^(-j*n*pi/(2*N))</pre> |
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| 60 | * \par |
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| 61 | * C command to generate the table |
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| 62 | * <pre> |
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| 63 | * for(i = 0; i< N; i++) |
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| 64 | * { |
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| 65 | * weights[2*i]= cos(i*c); |
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| 66 | * weights[(2*i)+1]= -sin(i * c); |
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| 67 | * } </pre> |
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| 68 | * \par |
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| 69 | * 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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| 70 | * \par |
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| 71 | * Converted the output to q15 format by multiplying with 2^31 and saturated if required. |
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| 72 | * \par |
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| 73 | * In the tables below the real and imaginary values are placed alternatively, hence the |
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| 74 | * array length is <code>2*N</code>. |
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| 75 | *//** |
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| 76 | |||
| 77 | * cosFactor tables are generated using the formula : <pre> cos_factors[n] = 2 * cos((2n+1)*pi/(4*N)) </pre> |
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| 78 | * \par |
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| 79 | * C command to generate the table |
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| 80 | * <pre> |
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| 81 | * for(i = 0; i< N; i++) |
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| 82 | * { |
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| 83 | * cos_factors[i]= 2 * cos((2*i+1)*c/2); |
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| 84 | * } </pre> |
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| 85 | * \par |
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| 86 | * 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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| 87 | * \par |
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| 88 | * Then converted to q15 format by multiplying with 2^31 and saturated if required. |
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| 89 | |
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| 90 | *//** |
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| 91 | * @brief Initialization function for the Q15 DCT4/IDCT4. |
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| 92 | * @param[in,out] *S points to an instance of Q15 DCT4/IDCT4 structure. |
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| 93 | * @param[in] *S_RFFT points to an instance of Q15 RFFT/RIFFT structure. |
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| 94 | * @param[in] *S_CFFT points to an instance of Q15 CFFT/CIFFT structure. |
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| 95 | * @param[in] N length of the DCT4. |
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| 96 | * @param[in] Nby2 half of the length of the DCT4. |
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| 97 | * @param[in] normalize normalizing factor. |
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| 98 | * @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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| 99 | * \par Normalizing factor: |
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| 100 | * The normalizing factor is <code>sqrt(2/N)</code>, which depends on the size of transform <code>N</code>. |
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| 101 | * Normalizing factors in 1.15 format are mentioned in the table below for different DCT sizes: |
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| 102 | * \image html dct4NormalizingQ15Table.gif |
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| 103 | */ |
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| 104 | |||
| 105 | arm_status arm_dct4_init_q15( |
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| 106 | arm_dct4_instance_q15 * S, |
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| 107 | arm_rfft_instance_q15 * S_RFFT, |
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| 108 | arm_cfft_radix4_instance_q15 * S_CFFT, |
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| 109 | uint16_t N, |
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| 110 | uint16_t Nby2, |
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| 111 | |||
| 112 | { |
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| 113 | /* Initialise the default arm status */ |
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| 114 | arm_status status = ARM_MATH_SUCCESS; |
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| 115 | |||
| 116 | /* Initializing the pointer array with the weight table base addresses of different lengths */ |
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| 117 | q15_t *twiddlePtr[4] = { (q15_t *) WeightsQ15_128, (q15_t *) WeightsQ15_512, |
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| 118 | (q15_t *) WeightsQ15_2048, (q15_t *) WeightsQ15_8192 |
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| 119 | }; |
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| 120 | |||
| 121 | /* Initializing the pointer array with the cos factor table base addresses of different lengths */ |
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| 122 | q15_t *pCosFactor[4] = |
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| 123 | { (q15_t *) cos_factorsQ15_128, (q15_t *) cos_factorsQ15_512, |
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| 124 | (q15_t *) cos_factorsQ15_2048, (q15_t *) cos_factorsQ15_8192 |
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| 125 | }; |
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| 126 | |||
| 127 | /* Initialize the DCT4 length */ |
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| 128 | S->N = N; |
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| 129 | |||
| 130 | /* Initialize the half of DCT4 length */ |
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| 131 | S->Nby2 = Nby2; |
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| 132 | |||
| 133 | /* Initialize the DCT4 Normalizing factor */ |
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| 134 | S->normalize = normalize; |
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| 135 | |||
| 136 | /* Initialize Real FFT Instance */ |
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| 137 | S->pRfft = S_RFFT; |
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| 138 | |||
| 139 | /* Initialize Complex FFT Instance */ |
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| 140 | S->pCfft = S_CFFT; |
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| 141 | |||
| 142 | switch (N) |
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| 143 | { |
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| 144 | /* Initialize the table modifier values */ |
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| 145 | case 8192u: |
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| 146 | S->pTwiddle = twiddlePtr[3]; |
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| 147 | S->pCosFactor = pCosFactor[3]; |
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| 148 | break; |
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| 149 | case 2048u: |
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| 150 | S->pTwiddle = twiddlePtr[2]; |
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| 151 | S->pCosFactor = pCosFactor[2]; |
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| 152 | break; |
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| 153 | case 512u: |
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| 154 | S->pTwiddle = twiddlePtr[1]; |
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| 155 | S->pCosFactor = pCosFactor[1]; |
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| 156 | break; |
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| 157 | case 128u: |
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| 158 | S->pTwiddle = twiddlePtr[0]; |
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| 159 | S->pCosFactor = pCosFactor[0]; |
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| 160 | break; |
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| 161 | default: |
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| 162 | status = ARM_MATH_ARGUMENT_ERROR; |
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| 163 | } |
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| 164 | |||
| 165 | /* Initialize the RFFT/RIFFT */ |
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| 166 | arm_rfft_init_q15(S->pRfft, S->N, 0u, 1u); |
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| 167 | |||
| 168 | /* return the status of DCT4 Init function */ |
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| 169 | return (status); |
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| 170 | } |
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| 171 | |||
| 172 | /** |
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| 173 | * @} end of DCT4_IDCT4 group |
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| 174 | */ |
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| 175 | |||
| 176 |