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Diffstat (limited to 'media/ffvpx/libavcodec/rdft.c')
| -rw-r--r-- | media/ffvpx/libavcodec/rdft.c | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/media/ffvpx/libavcodec/rdft.c b/media/ffvpx/libavcodec/rdft.c new file mode 100644 index 0000000000..ac6f5d6781 --- /dev/null +++ b/media/ffvpx/libavcodec/rdft.c @@ -0,0 +1,120 @@ +/* + * (I)RDFT transforms + * Copyright (c) 2009 Alex Converse <alex dot converse at gmail dot com> + * + * This file is part of FFmpeg. + * + * FFmpeg is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * FFmpeg is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ +#include <stdlib.h> +#include <math.h> +#include "libavutil/error.h" +#include "libavutil/mathematics.h" +#include "rdft.h" + +/** + * @file + * (Inverse) Real Discrete Fourier Transforms. + */ + +/** Map one real FFT into two parallel real even and odd FFTs. Then interleave + * the two real FFTs into one complex FFT. Unmangle the results. + * ref: http://www.engineeringproductivitytools.com/stuff/T0001/PT10.HTM + */ +static void rdft_calc_c(RDFTContext *s, FFTSample *data) +{ + int i, i1, i2; + FFTComplex ev, od, odsum; + const int n = 1 << s->nbits; + const float k1 = 0.5; + const float k2 = 0.5 - s->inverse; + const FFTSample *tcos = s->tcos; + const FFTSample *tsin = s->tsin; + + if (!s->inverse) { + s->fft.fft_permute(&s->fft, (FFTComplex*)data); + s->fft.fft_calc(&s->fft, (FFTComplex*)data); + } + /* i=0 is a special case because of packing, the DC term is real, so we + are going to throw the N/2 term (also real) in with it. */ + ev.re = data[0]; + data[0] = ev.re+data[1]; + data[1] = ev.re-data[1]; + +#define RDFT_UNMANGLE(sign0, sign1) \ + for (i = 1; i < (n>>2); i++) { \ + i1 = 2*i; \ + i2 = n-i1; \ + /* Separate even and odd FFTs */ \ + ev.re = k1*(data[i1 ]+data[i2 ]); \ + od.im = k2*(data[i2 ]-data[i1 ]); \ + ev.im = k1*(data[i1+1]-data[i2+1]); \ + od.re = k2*(data[i1+1]+data[i2+1]); \ + /* Apply twiddle factors to the odd FFT and add to the even FFT */ \ + odsum.re = od.re*tcos[i] sign0 od.im*tsin[i]; \ + odsum.im = od.im*tcos[i] sign1 od.re*tsin[i]; \ + data[i1 ] = ev.re + odsum.re; \ + data[i1+1] = ev.im + odsum.im; \ + data[i2 ] = ev.re - odsum.re; \ + data[i2+1] = odsum.im - ev.im; \ + } + + if (s->negative_sin) { + RDFT_UNMANGLE(+,-) + } else { + RDFT_UNMANGLE(-,+) + } + + data[2*i+1]=s->sign_convention*data[2*i+1]; + if (s->inverse) { + data[0] *= k1; + data[1] *= k1; + s->fft.fft_permute(&s->fft, (FFTComplex*)data); + s->fft.fft_calc(&s->fft, (FFTComplex*)data); + } +} + +av_cold int ff_rdft_init(RDFTContext *s, int nbits, enum RDFTransformType trans) +{ + int n = 1 << nbits; + int ret; + + s->nbits = nbits; + s->inverse = trans == IDFT_C2R || trans == DFT_C2R; + s->sign_convention = trans == IDFT_R2C || trans == DFT_C2R ? 1 : -1; + s->negative_sin = trans == DFT_C2R || trans == DFT_R2C; + + if (nbits < 4 || nbits > 16) + return AVERROR(EINVAL); + + if ((ret = ff_fft_init(&s->fft, nbits-1, trans == IDFT_C2R || trans == IDFT_R2C)) < 0) + return ret; + + ff_init_ff_cos_tabs(nbits); + s->tcos = ff_cos_tabs[nbits]; + s->tsin = ff_cos_tabs[nbits] + (n >> 2); + s->rdft_calc = rdft_calc_c; + +#if ARCH_ARM + ff_rdft_init_arm(s); +#endif + + return 0; +} + +av_cold void ff_rdft_end(RDFTContext *s) +{ + ff_fft_end(&s->fft); +} |