0,0 → 1,133 |
/* |
* (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/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); |
} |