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Rev	Author	Line No.	Line
2	mjames	1	/* ----------------------------------------------------------------------
		2	* Project: CMSIS DSP Library
		3	* Title: arm_dct4_init_q15.c
		4	* Description: Initialization function of DCT-4 & IDCT4 Q15
		5	*
		6	* $Date: 27. January 2017
		7	* $Revision: V.1.5.1
		8	*
		9	* Target Processor: Cortex-M cores
		10	* -------------------------------------------------------------------- */
		11	/*
		12	* Copyright (C) 2010-2017 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 "arm_math.h"
		30
		31	/**
		32	* @ingroup DCT4_IDCT4
		33	*/
		34
		35	/**
		36	* @addtogroup DCT4_IDCT4_Table DCT Type IV Tables
		37	* @{
		38	*/
		39
		40	/*
		41	* @brief Weights Table
		42	*/
		43
		44	/**
		45	* \par
		46	* Weights tables are generated using the formula : <pre>weights[n] = e^(-jnpi/(2*N))</pre>
		47	* \par
		48	* C command to generate the table
		49	* <pre>
		50	* for(i = 0; i< N; i++)
		51	* {
		52	* weights[2i]= cos(ic);
		53	* weights[(2i)+1]= -sin(i c);
		54	* } </pre>
		55	* \par
		56	* where <code>N</code> is the Number of weights to be calculated and <code>c</code> is <code>pi/(2*N)</code>
		57	* \par
		58	* Converted the output to q15 format by multiplying with 2^31 and saturated if required.
		59	* \par
		60	* In the tables below the real and imaginary values are placed alternatively, hence the
		61	* array length is <code>2*N</code>.
		62	//*
		63
		64	* cosFactor tables are generated using the formula : <pre> cos_factors[n] = 2 * cos((2n+1)pi/(4N)) </pre>
		65	* \par
		66	* C command to generate the table
		67	* <pre>
		68	* for(i = 0; i< N; i++)
		69	* {
		70	* cos_factors[i]= 2 * cos((2i+1)c/2);
		71	* } </pre>
		72	* \par
		73	* where <code>N</code> is the number of factors to generate and <code>c</code> is <code>pi/(2*N)</code>
		74	* \par
		75	* Then converted to q15 format by multiplying with 2^31 and saturated if required.
		76
		77	//*
		78	* @} end of DCT4_IDCT4_Table group
		79	*/
		80
		81	/**
		82	* @addtogroup DCT4_IDCT4
		83	* @{
		84	*/
		85
		86	/**
		87	* @brief Initialization function for the Q15 DCT4/IDCT4.
		88	* @param[in,out] *S points to an instance of Q15 DCT4/IDCT4 structure.
		89	* @param[in] *S_RFFT points to an instance of Q15 RFFT/RIFFT structure.
		90	* @param[in] *S_CFFT points to an instance of Q15 CFFT/CIFFT structure.
		91	* @param[in] N length of the DCT4.
		92	* @param[in] Nby2 half of the length of the DCT4.
		93	* @param[in] normalize normalizing factor.
		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.
		95	* \par Normalizing factor:
		96	* The normalizing factor is <code>sqrt(2/N)</code>, which depends on the size of transform <code>N</code>.
		97	* Normalizing factors in 1.15 format are mentioned in the table below for different DCT sizes:
		98
		99	*/
		100
		101	arm_status arm_dct4_init_q15(
		102	arm_dct4_instance_q15 * S,
		103	arm_rfft_instance_q15 * S_RFFT,
		104	arm_cfft_radix4_instance_q15 * S_CFFT,
		105	uint16_t N,
		106	uint16_t Nby2,
		107	q15_t normalize)
		108	{
		109	/* Initialise the default arm status */
		110	arm_status status = ARM_MATH_SUCCESS;
		111
		112	/* Initializing the pointer array with the weight table base addresses of different lengths */
		113	q15_t twiddlePtr[4] = { (q15_t ) WeightsQ15_128, (q15_t *) WeightsQ15_512,
		114	(q15_t ) WeightsQ15_2048, (q15_t ) WeightsQ15_8192
		115	};
		116
		117	/* Initializing the pointer array with the cos factor table base addresses of different lengths */
		118	q15_t *pCosFactor[4] =
		119	{ (q15_t ) cos_factorsQ15_128, (q15_t ) cos_factorsQ15_512,
		120	(q15_t ) cos_factorsQ15_2048, (q15_t ) cos_factorsQ15_8192
		121	};
		122
		123	/* Initialize the DCT4 length */
		124	S->N = N;
		125
		126	/* Initialize the half of DCT4 length */
		127	S->Nby2 = Nby2;
		128
		129	/* Initialize the DCT4 Normalizing factor */
		130	S->normalize = normalize;
		131
		132	/* Initialize Real FFT Instance */
		133	S->pRfft = S_RFFT;
		134
		135	/* Initialize Complex FFT Instance */
		136	S->pCfft = S_CFFT;
		137
		138	switch (N)
		139	{
		140	/* Initialize the table modifier values */
		141	case 8192U:
		142	S->pTwiddle = twiddlePtr[3];
		143	S->pCosFactor = pCosFactor[3];
		144	break;
		145	case 2048U:
		146	S->pTwiddle = twiddlePtr[2];
		147	S->pCosFactor = pCosFactor[2];
		148	break;
		149	case 512U:
		150	S->pTwiddle = twiddlePtr[1];
		151	S->pCosFactor = pCosFactor[1];
		152	break;
		153	case 128U:
		154	S->pTwiddle = twiddlePtr[0];
		155	S->pCosFactor = pCosFactor[0];
		156	break;
		157	default:
		158	status = ARM_MATH_ARGUMENT_ERROR;
		159	}
		160
		161	/* Initialize the RFFT/RIFFT */
		162	arm_rfft_init_q15(S->pRfft, S->N, 0U, 1U);
		163
		164	/* return the status of DCT4 Init function */
		165	return (status);
		166	}
		167
		168	/**
		169	* @} end of DCT4_IDCT4 group
		170	*/
		171
		172

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