Content-type: text/html Man page of mlib_SignalIFFTW_4

mlib_SignalIFFTW_4

Section: mediaLib Library Functions (3MLIB)
Updated: 2 Mar 2007
Index Return to Main Contents
 

NAME

mlib_SignalIFFTW_4, mlib_SignalIFFTW_4_S16_S16, mlib_SignalIFFTW_4_S16C_S16C, mlib_SignalIFFTW_4_S16_S16C, mlib_SignalIFFTW_4_S16, mlib_SignalIFFTW_4_S16C - signal Inverse Fast Fourier Transform with windowing (IFFTW)  

SYNOPSIS

cc [ flag... ] file... -lmlib [ library... ]
#include <mlib.h>

mlib_status mlib_SignalIFFTW_4_S16_S16(mlib_s16 *dstr, mlib_s16 *dsti,
    const mlib_s16 *srcr, const mlib_s16 *srci, const mlib_s16 *window,
    mlib_s32 order, mlib_s32 *scale);

mlib_status mlib_SignalIFFTW_4_S16C_S16C(mlib_s16 *dstc,
    const mlib_s16 *srcc,
    const mlib_s16 *window, mlib_s32 order, mlib_s32 *scale);

mlib_status mlib_SignalIFFTW_4_S16_S16C(mlib_s16 *dstr,
    const mlib_s16 *srcc,
    const mlib_s16 *window, mlib_s32 order, mlib_s32 *scale);

mlib_status mlib_SignalIFFTW_4_S16(mlib_s16 *srcdstr,
    mlib_s16 *srcdsti,
    const mlib_s16 *window, mlib_s32 order, mlib_s32 *scale);

mlib_status mlib_SignalIFFTW_4_S16C(mlib_s16 *srcdstc,
    const mlib_s16 *window,
    mlib_s32 order, mlib_s32 *scale);

 

DESCRIPTION

Each of the functions in this group performs Inverse Fast Fourier Transform with windowing (IFFTW).

The FFTW functions use the following equation:

          1   N-1
dst[k] = ---- SUM {src[n] * window[n] * exp(-j2*PI*n*k/N)}
         C1  n=0

and the IFFTW functions use the following equation:

          1   N-1
dst[n] = ---- SUM {src[k] * window[k] * exp(j2*PI*n*k/N)}
         C2  k=0

where

k = 0, 1, ..., (N - 1)
n = 0, 1, ..., (N - 1)
N = 2**order

The signal FFTW/IFFTW functions can be categorized into four groups according to the ScaleMode in the function names in the following form:

mlib_Signal[FFTW|IFFTW]_ScaleMode_OutType_InType_OpMode()
mlib_Signal[FFTW|IFFTW]_ScaleMode_DataType_OpMode()

The scaling factors C1 and C2 used in the equations are defined as follows:

o For ScaleMode = 1, C1 = 1 and C2 = 2**order.
o For ScaleMode = 2, C1 = 2**order and C2 = 1.
o For ScaleMode = 3, C1 = C2 = 2**(order/2) when order is even, or C1 = 2**((order+1)/2) and C2 = 2**((order-1)/2) when order is odd.
o For ScaleMode = 4, C1 = 2**P and C2 = 2**Q, where P and Q are adaptive scaling factors and are generated by the functions.

For functions with only real parts for the source signal, the imaginary parts are assumed to be all zero. For functions with only real parts for the destination signal, the imaginary parts are discarded. The functions with only one data type in their names perform the operation in place.  

PARAMETERS

Each function takes some of the following arguments:

dstr

Destination signal array that contains the real parts.

dsti

Destination signal array that contains the imaginary parts.

srcr

Source signal array that contains the real parts.

srci

Source signal array that contains the imaginary parts.

dstc

Complex destination signal array. dstc[2*i] contains the real parts, and dstc[2*i+1] contains the imaginary parts.

srcc

Complex source signal array. srcc[2*i] contains the real parts, and srcc[2*i+1] contains the imaginary parts.

srcdstr

Source and destination signal array that contains the real parts.

srcdsti

Source and destination signal array that contains the imaginary parts.

srcdstc

Complex source and destination signal array. srcdstc[2*i] contains the real parts, and srcdstc[2*i+1] contains the imaginary parts.

window

Window coefficient array with 2**order real elements. The window coefficients are in Q15 format for the S16 data type, or in float format for the F32 data type.

order

Order of the transformation. The base-2 logarithm of the number of data samples.

scale

Adaptive scaling factor.

 

RETURN VALUES

Each function returns MLIB_SUCCESS if successful. Otherwise it returns MLIB_FAILURE.  

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPEATTRIBUTE VALUE

Interface StabilityCommitted

MT-Level

 

SEE ALSO

mlib_SignalFFTW_1(3MLIB), mlib_SignalFFTW_2(3MLIB), mlib_SignalFFTW_3(3MLIB), mlib_SignalFFTW_4(3MLIB), mlib_SignalIFFTW_1(3MLIB), mlib_SignalIFFTW_2(3MLIB), mlib_SignalIFFTW_3(3MLIB), attributes(5)


 

Index

NAME
SYNOPSIS
DESCRIPTION
PARAMETERS
RETURN VALUES
ATTRIBUTES
SEE ALSO

This document was created by man2html, using the manual pages.
Time: 02:38:03 GMT, October 02, 2010