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Diffstat (limited to 'media/libav/libavcodec/rdft.c')
| -rw-r--r-- | media/libav/libavcodec/rdft.c | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/media/libav/libavcodec/rdft.c b/media/libav/libavcodec/rdft.c new file mode 100644 index 000000000..54cf14aa2 --- /dev/null +++ b/media/libav/libavcodec/rdft.c @@ -0,0 +1,133 @@ +/* + * (I)RDFT transforms + * Copyright (c) 2009 Alex Converse <alex dot converse at gmail dot com> + * + * This file is part of Libav. + * + * Libav 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. + * + * Libav 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 Libav; 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/mathematics.h" +#include "rdft.h" + +/** + * @file + * (Inverse) Real Discrete Fourier Transforms. + */ + +/* sin(2*pi*x/n) for 0<=x<n/4, followed by n/2<=x<3n/4 */ +#if !CONFIG_HARDCODED_TABLES +SINTABLE(16); +SINTABLE(32); +SINTABLE(64); +SINTABLE(128); +SINTABLE(256); +SINTABLE(512); +SINTABLE(1024); +SINTABLE(2048); +SINTABLE(4096); +SINTABLE(8192); +SINTABLE(16384); +SINTABLE(32768); +SINTABLE(65536); +#endif +static SINTABLE_CONST FFTSample * const ff_sin_tabs[] = { + NULL, NULL, NULL, NULL, + ff_sin_16, ff_sin_32, ff_sin_64, ff_sin_128, ff_sin_256, ff_sin_512, ff_sin_1024, + ff_sin_2048, ff_sin_4096, ff_sin_8192, ff_sin_16384, ff_sin_32768, ff_sin_65536, +}; + +/** 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; + 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]; + 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[i1 ]-data[i2 ]); + 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 */ + data[i1 ] = ev.re + od.re*tcos[i] - od.im*tsin[i]; + data[i1+1] = ev.im + od.im*tcos[i] + od.re*tsin[i]; + data[i2 ] = ev.re - od.re*tcos[i] + od.im*tsin[i]; + data[i2+1] = -ev.im + od.im*tcos[i] + od.re*tsin[i]; + } + 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 i; + const double theta = (trans == DFT_R2C || trans == DFT_C2R ? -1 : 1)*2*M_PI/n; + + s->nbits = nbits; + s->inverse = trans == IDFT_C2R || trans == DFT_C2R; + s->sign_convention = trans == IDFT_R2C || trans == DFT_C2R ? 1 : -1; + + if (nbits < 4 || nbits > 16) + return -1; + + if (ff_fft_init(&s->fft, nbits-1, trans == IDFT_C2R || trans == IDFT_R2C) < 0) + return -1; + + ff_init_ff_cos_tabs(nbits); + s->tcos = ff_cos_tabs[nbits]; + s->tsin = ff_sin_tabs[nbits]+(trans == DFT_R2C || trans == DFT_C2R)*(n>>2); +#if !CONFIG_HARDCODED_TABLES + for (i = 0; i < (n>>2); i++) { + s->tsin[i] = sin(i*theta); + } +#endif + s->rdft_calc = rdft_calc_c; + + if (ARCH_ARM) ff_rdft_init_arm(s); + + return 0; +} + +av_cold void ff_rdft_end(RDFTContext *s) +{ + ff_fft_end(&s->fft); +} |