xref: /third_party/ffmpeg/libavcodec/avfft.h (revision cabdff1a) 
1/*
2 * This file is part of FFmpeg.
3 *
4 * FFmpeg is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation; either
7 * version 2.1 of the License, or (at your option) any later version.
8 *
9 * FFmpeg is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12 * Lesser General Public License for more details.
13 *
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with FFmpeg; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17 */
18
19#ifndef AVCODEC_AVFFT_H
20#define AVCODEC_AVFFT_H
21
22/**
23 * @file
24 * @ingroup lavc_fft
25 * FFT functions
26 */
27
28/**
29 * @defgroup lavc_fft FFT functions
30 * @ingroup lavc_misc
31 *
32 * @{
33 */
34
35typedef float FFTSample;
36
37typedef struct FFTComplex {
38    FFTSample re, im;
39} FFTComplex;
40
41typedef struct FFTContext FFTContext;
42
43/**
44 * Set up a complex FFT.
45 * @param nbits           log2 of the length of the input array
46 * @param inverse         if 0 perform the forward transform, if 1 perform the inverse
47 */
48FFTContext *av_fft_init(int nbits, int inverse);
49
50/**
51 * Do the permutation needed BEFORE calling ff_fft_calc().
52 */
53void av_fft_permute(FFTContext *s, FFTComplex *z);
54
55/**
56 * Do a complex FFT with the parameters defined in av_fft_init(). The
57 * input data must be permuted before. No 1.0/sqrt(n) normalization is done.
58 */
59void av_fft_calc(FFTContext *s, FFTComplex *z);
60
61void av_fft_end(FFTContext *s);
62
63FFTContext *av_mdct_init(int nbits, int inverse, double scale);
64void av_imdct_calc(FFTContext *s, FFTSample *output, const FFTSample *input);
65void av_imdct_half(FFTContext *s, FFTSample *output, const FFTSample *input);
66void av_mdct_calc(FFTContext *s, FFTSample *output, const FFTSample *input);
67void av_mdct_end(FFTContext *s);
68
69/* Real Discrete Fourier Transform */
70
71enum RDFTransformType {
72    DFT_R2C,
73    IDFT_C2R,
74    IDFT_R2C,
75    DFT_C2R,
76};
77
78typedef struct RDFTContext RDFTContext;
79
80/**
81 * Set up a real FFT.
82 * @param nbits           log2 of the length of the input array
83 * @param trans           the type of transform
84 */
85RDFTContext *av_rdft_init(int nbits, enum RDFTransformType trans);
86void av_rdft_calc(RDFTContext *s, FFTSample *data);
87void av_rdft_end(RDFTContext *s);
88
89/* Discrete Cosine Transform */
90
91typedef struct DCTContext DCTContext;
92
93enum DCTTransformType {
94    DCT_II = 0,
95    DCT_III,
96    DCT_I,
97    DST_I,
98};
99
100/**
101 * Set up DCT.
102 *
103 * @param nbits           size of the input array:
104 *                        (1 << nbits)     for DCT-II, DCT-III and DST-I
105 *                        (1 << nbits) + 1 for DCT-I
106 * @param type            the type of transform
107 *
108 * @note the first element of the input of DST-I is ignored
109 */
110DCTContext *av_dct_init(int nbits, enum DCTTransformType type);
111void av_dct_calc(DCTContext *s, FFTSample *data);
112void av_dct_end (DCTContext *s);
113
114/**
115 * @}
116 */
117
118#endif /* AVCODEC_AVFFT_H */
119