rdft.c File Reference

(Inverse) Real Discrete Fourier Transforms. More...

#include <stdlib.h>
#include <math.h>
#include "libavutil/mathematics.h"
#include "rdft.h"

Macros
#define	RDFT_UNMANGLE(sign0, sign1)

Functions
av_cold int	ff_rdft_init (RDFTContext *s, int nbits, enum RDFTransformType trans)
	Set up a real FFT. More...
av_cold void	ff_rdft_end (RDFTContext *s)

Detailed Description

(Inverse) Real Discrete Fourier Transforms.

Macro Definition Documentation

RDFT_UNMANGLE

#define RDFT_UNMANGLE	(		sign0,
			sign1
	)

Value:

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;                                     \
    }

Function Documentation

ff_rdft_init()

av_cold int ff_rdft_init	(	RDFTContext *	s,
		int	nbits,
		enum RDFTransformType	trans
	)

Set up a real FFT.

Parameters

nbits	log2 of the length of the input array
trans	the type of transform