139 lines
3.7 KiB
C
139 lines
3.7 KiB
C
/****************************************************************************
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* include/nuttx/math/fft.h
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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#ifndef __INCLUDE_NUTTX_MATH_FFT_H
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#define __INCLUDE_NUTTX_MATH_FFT_H
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/****************************************************************************
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* Public Types
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****************************************************************************/
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/* fft/dct request type definition
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* FFT, fft for fast fourier transform
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* DCT, dct for discrete cosine transform
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* DCT-II, the normally so called DCT
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* DCT-III, inverse of DCT-II, so called IDCT
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* DCT-IV, inverse of DCT-IV is itself
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* see all the formula and more mathematics trueth in wikipedia:
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* https://en.wikipedia.org/wiki/Discrete_cosine_transform
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*/
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typedef enum
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{
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MATH_FFT = 0, /* FFT */
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MATH_DCT_TYPE_2 = 1, /* DCT-II */
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MATH_DCT_TYPE_3 = 2, /* DCT-III */
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MATH_DCT_TYPE_4 = 3, /* DCT-IV */
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} fft_type;
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/* fft calculate request */
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struct fft_calc_s
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{
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fft_type type;
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/* fft/dct bit width
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* power of 2, range from 8 to 32
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*/
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size_t bitwidth;
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/* input data, address must be 4 bytes aligned */
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FAR const void *input_data;
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/* output data, address must be 4 bytes aligned */
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FAR void *output_data;
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/* FFT Length, power of 2
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* fft support 16 to 4096
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* dct support 8 to 256
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*/
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size_t fft_length;
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/* Real flag. true: real fft/dct, false: complex fft/dct. */
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bool real;
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/* Inverse flag. true: ifft/idct, false: fft/dct */
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bool inverse;
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};
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/* This structure provides the "lower-half" driver operations available to
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* the "upper-half" driver.
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*/
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struct fft_lowerhalf_s;
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struct fft_ops_s
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{
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/* FFT calculate request */
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CODE int (*calc)(FAR struct fft_lowerhalf_s *lower,
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FAR struct fft_calc_s *calc);
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};
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/* This structure provides the publicly visible representation of the
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* "lower-half" driver state structure. "lower half" drivers will have an
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* internal structure definition that will be cast-compatible with this
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* structure definitions.
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*/
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struct fft_lowerhalf_s
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{
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/* Publicly visible portion of the "lower-half" driver state structure. */
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FAR const struct fft_ops_s *ops; /* Lower half operations */
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};
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/****************************************************************************
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* Public Function Prototypes
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****************************************************************************/
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#undef EXTERN
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#if defined(__cplusplus)
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#define EXTERN extern "C"
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extern "C"
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{
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#else
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#define EXTERN extern
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#endif
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/****************************************************************************
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* Name: fft_register
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*
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* Description:
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* Register a FFT driver.
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*
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****************************************************************************/
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int fft_register(FAR const char *path,
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FAR struct fft_lowerhalf_s *lower);
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#undef EXTERN
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#if defined(__cplusplus)
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}
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#endif
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#endif /* __INCLUDE_NUTTX_MATH_FFT_H */
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