| Line | Branch | Exec | Source |
|---|---|---|---|
| 1 | /* | ||
| 2 | * (I)RDFT transforms | ||
| 3 | * Copyright (c) 2009 Alex Converse <alex dot converse at gmail dot com> | ||
| 4 | * | ||
| 5 | * This file is part of FFmpeg. | ||
| 6 | * | ||
| 7 | * FFmpeg is free software; you can redistribute it and/or | ||
| 8 | * modify it under the terms of the GNU Lesser General Public | ||
| 9 | * License as published by the Free Software Foundation; either | ||
| 10 | * version 2.1 of the License, or (at your option) any later version. | ||
| 11 | * | ||
| 12 | * FFmpeg is distributed in the hope that it will be useful, | ||
| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
| 15 | * Lesser General Public License for more details. | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU Lesser General Public | ||
| 18 | * License along with FFmpeg; if not, write to the Free Software | ||
| 19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | ||
| 20 | */ | ||
| 21 | #include <stdlib.h> | ||
| 22 | #include <math.h> | ||
| 23 | #include "libavutil/error.h" | ||
| 24 | #include "libavutil/mathematics.h" | ||
| 25 | #include "rdft.h" | ||
| 26 | |||
| 27 | /** | ||
| 28 | * @file | ||
| 29 | * (Inverse) Real Discrete Fourier Transforms. | ||
| 30 | */ | ||
| 31 | |||
| 32 | /** Map one real FFT into two parallel real even and odd FFTs. Then interleave | ||
| 33 | * the two real FFTs into one complex FFT. Unmangle the results. | ||
| 34 | * ref: http://www.engineeringproductivitytools.com/stuff/T0001/PT10.HTM | ||
| 35 | */ | ||
| 36 | ✗ | static void rdft_calc_c(RDFTContext *s, FFTSample *data) | |
| 37 | { | ||
| 38 | int i, i1, i2; | ||
| 39 | FFTComplex ev, od, odsum; | ||
| 40 | ✗ | const int n = 1 << s->nbits; | |
| 41 | ✗ | const float k1 = 0.5; | |
| 42 | ✗ | const float k2 = 0.5 - s->inverse; | |
| 43 | ✗ | const FFTSample *tcos = s->tcos; | |
| 44 | ✗ | const FFTSample *tsin = s->tsin; | |
| 45 | |||
| 46 | ✗ | if (!s->inverse) { | |
| 47 | ✗ | s->fft.fft_permute(&s->fft, (FFTComplex*)data); | |
| 48 | ✗ | s->fft.fft_calc(&s->fft, (FFTComplex*)data); | |
| 49 | } | ||
| 50 | /* i=0 is a special case because of packing, the DC term is real, so we | ||
| 51 | are going to throw the N/2 term (also real) in with it. */ | ||
| 52 | ✗ | ev.re = data[0]; | |
| 53 | ✗ | data[0] = ev.re+data[1]; | |
| 54 | ✗ | data[1] = ev.re-data[1]; | |
| 55 | |||
| 56 | #define RDFT_UNMANGLE(sign0, sign1) \ | ||
| 57 | for (i = 1; i < (n>>2); i++) { \ | ||
| 58 | i1 = 2*i; \ | ||
| 59 | i2 = n-i1; \ | ||
| 60 | /* Separate even and odd FFTs */ \ | ||
| 61 | ev.re = k1*(data[i1 ]+data[i2 ]); \ | ||
| 62 | od.im = k2*(data[i2 ]-data[i1 ]); \ | ||
| 63 | ev.im = k1*(data[i1+1]-data[i2+1]); \ | ||
| 64 | od.re = k2*(data[i1+1]+data[i2+1]); \ | ||
| 65 | /* Apply twiddle factors to the odd FFT and add to the even FFT */ \ | ||
| 66 | odsum.re = od.re*tcos[i] sign0 od.im*tsin[i]; \ | ||
| 67 | odsum.im = od.im*tcos[i] sign1 od.re*tsin[i]; \ | ||
| 68 | data[i1 ] = ev.re + odsum.re; \ | ||
| 69 | data[i1+1] = ev.im + odsum.im; \ | ||
| 70 | data[i2 ] = ev.re - odsum.re; \ | ||
| 71 | data[i2+1] = odsum.im - ev.im; \ | ||
| 72 | } | ||
| 73 | |||
| 74 | ✗ | if (s->negative_sin) { | |
| 75 | ✗ | RDFT_UNMANGLE(+,-) | |
| 76 | } else { | ||
| 77 | ✗ | RDFT_UNMANGLE(-,+) | |
| 78 | } | ||
| 79 | |||
| 80 | ✗ | data[2*i+1]=s->sign_convention*data[2*i+1]; | |
| 81 | ✗ | if (s->inverse) { | |
| 82 | ✗ | data[0] *= k1; | |
| 83 | ✗ | data[1] *= k1; | |
| 84 | ✗ | s->fft.fft_permute(&s->fft, (FFTComplex*)data); | |
| 85 | ✗ | s->fft.fft_calc(&s->fft, (FFTComplex*)data); | |
| 86 | } | ||
| 87 | ✗ | } | |
| 88 | |||
| 89 | ✗ | av_cold int ff_rdft_init(RDFTContext *s, int nbits, enum RDFTransformType trans) | |
| 90 | { | ||
| 91 | ✗ | int n = 1 << nbits; | |
| 92 | int ret; | ||
| 93 | |||
| 94 | ✗ | s->nbits = nbits; | |
| 95 | ✗ | s->inverse = trans == IDFT_C2R || trans == DFT_C2R; | |
| 96 | ✗ | s->sign_convention = trans == IDFT_R2C || trans == DFT_C2R ? 1 : -1; | |
| 97 | ✗ | s->negative_sin = trans == DFT_C2R || trans == DFT_R2C; | |
| 98 | |||
| 99 | ✗ | if (nbits < 4 || nbits > 16) | |
| 100 | ✗ | return AVERROR(EINVAL); | |
| 101 | |||
| 102 | ✗ | if ((ret = ff_fft_init(&s->fft, nbits-1, trans == IDFT_C2R || trans == IDFT_R2C)) < 0) | |
| 103 | ✗ | return ret; | |
| 104 | |||
| 105 | ✗ | ff_init_ff_cos_tabs(nbits); | |
| 106 | ✗ | s->tcos = ff_cos_tabs[nbits]; | |
| 107 | ✗ | s->tsin = ff_cos_tabs[nbits] + (n >> 2); | |
| 108 | ✗ | s->rdft_calc = rdft_calc_c; | |
| 109 | |||
| 110 | #if ARCH_ARM | ||
| 111 | ff_rdft_init_arm(s); | ||
| 112 | #endif | ||
| 113 | |||
| 114 | ✗ | return 0; | |
| 115 | } | ||
| 116 | |||
| 117 | ✗ | av_cold void ff_rdft_end(RDFTContext *s) | |
| 118 | { | ||
| 119 | ✗ | ff_fft_end(&s->fft); | |
| 120 | ✗ | } | |
| 121 |