| /* ---------------------------------------------------------------------- | |
| * Project: CMSIS DSP Library | |
| * Title: arm_dct4_init_q31.c | |
| * Description: Initialization function of DCT-4 & IDCT4 Q31 | |
| * | |
| * $Date: 23 April 2021 | |
| * $Revision: V1.9.0 | |
| * | |
| * Target Processor: Cortex-M and Cortex-A cores | |
| * -------------------------------------------------------------------- */ | |
| /* | |
| * Copyright (C) 2010-2021 ARM Limited or its affiliates. All rights reserved. | |
| * | |
| * SPDX-License-Identifier: Apache-2.0 | |
| * | |
| * Licensed under the Apache License, Version 2.0 (the License); you may | |
| * not use this file except in compliance with the License. | |
| * You may obtain a copy of the License at | |
| * | |
| * www.apache.org/licenses/LICENSE-2.0 | |
| * | |
| * Unless required by applicable law or agreed to in writing, software | |
| * distributed under the License is distributed on an AS IS BASIS, WITHOUT | |
| * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
| * See the License for the specific language governing permissions and | |
| * limitations under the License. | |
| */ | |
| /** | |
| @ingroup groupTransforms | |
| */ | |
| /** | |
| @addtogroup DCT4_IDCT4 | |
| @{ | |
| */ | |
| /** | |
| @brief Initialization function for the Q31 DCT4/IDCT4. | |
| @param[in,out] S points to an instance of Q31 DCT4/IDCT4 structure. | |
| @param[in] S_RFFT points to an instance of Q31 RFFT/RIFFT structure | |
| @param[in] S_CFFT points to an instance of Q31 CFFT/CIFFT structure | |
| @param[in] N length of the DCT4. | |
| @param[in] Nby2 half of the length of the DCT4. | |
| @param[in] normalize normalizing factor. | |
| @return execution status | |
| - \ref ARM_MATH_SUCCESS : Operation successful | |
| - \ref ARM_MATH_ARGUMENT_ERROR : <code>N</code> is not a supported transform length | |
| @par Normalizing factor: | |
| The normalizing factor is <code>sqrt(2/N)</code>, which depends on the size of transform <code>N</code>. | |
| Normalizing factors in 1.31 format are mentioned in the table below for different DCT sizes: | |
| | DCT Size | Normalizing factor value (hexadecimal) | | |
| | --------: | ---------------------------------------:| | |
| | 2048 | 0x4000000 | | |
| | 512 | 0x8000000 | | |
| | 128 | 0x10000000 | | |
| */ | |
| arm_status arm_dct4_init_q31( | |
| arm_dct4_instance_q31 * S, | |
| arm_rfft_instance_q31 * S_RFFT, | |
| arm_cfft_radix4_instance_q31 * S_CFFT, | |
| uint16_t N, | |
| uint16_t Nby2, | |
| q31_t normalize) | |
| { | |
| /* Initialize the default arm status */ | |
| arm_status status = ARM_MATH_SUCCESS; | |
| /* Initialize the DCT4 length */ | |
| S->N = N; | |
| /* Initialize the half of DCT4 length */ | |
| S->Nby2 = Nby2; | |
| /* Initialize the DCT4 Normalizing factor */ | |
| S->normalize = normalize; | |
| /* Initialize Real FFT Instance */ | |
| S->pRfft = S_RFFT; | |
| /* Initialize Complex FFT Instance */ | |
| S->pCfft = S_CFFT; | |
| switch (N) | |
| { | |
| /* Initialize the table modifier values */ | |
| case 8192U: | |
| S->pTwiddle = WeightsQ31_8192; | |
| S->pCosFactor = cos_factorsQ31_8192; | |
| break; | |
| case 2048U: | |
| S->pTwiddle = WeightsQ31_2048; | |
| S->pCosFactor = cos_factorsQ31_2048; | |
| break; | |
| case 512U: | |
| S->pTwiddle = WeightsQ31_512; | |
| S->pCosFactor = cos_factorsQ31_512; | |
| break; | |
| case 128U: | |
| S->pTwiddle = WeightsQ31_128; | |
| S->pCosFactor = cos_factorsQ31_128; | |
| break; | |
| default: | |
| status = ARM_MATH_ARGUMENT_ERROR; | |
| } | |
| /* Initialize the RFFT/RIFFT Function */ | |
| arm_rfft_init_q31(S->pRfft, S->N, 0U, 1U); | |
| /* return the status of DCT4 Init function */ | |
| return (status); | |
| } | |
| /** | |
| @} end of DCT4_IDCT4 group | |
| */ | |