rdft.c File Reference

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

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

Go to the source code of this file.

Macros
#define	RDFT_UNMANGLE(sign0, sign1)

Functions
static void	rdft_calc_c (RDFTContext *s, FFTSample *data)
	Map one real FFT into two parallel real even and odd FFTs. More...
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.

Definition in file rdft.c.

Macro Definition Documentation

#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;                                     \
    }

Referenced by rdft_calc_c().

Function Documentation

static void rdft_calc_c ( RDFTContext *  s, FFTSample *  data  )

static

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

Definition at line 35 of file rdft.c.

Referenced by 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

Definition at line 88 of file rdft.c.

Referenced by decode_init(), ff_dct_init(), qdm2_decode_init(), and wmavoice_decode_init().

av_cold void ff_rdft_end

(

RDFTContext *

s

)

Definition at line 114 of file rdft.c.

Referenced by decode_end(), ff_dct_end(), qdm2_decode_close(), and wmavoice_decode_end().