Overview

Applies a time domain window

Discussion

This module applies a time domain window to a signal. This operation is useful prior to taking the FFT of a signal and commonly occurs in STFT-based filterbanks. The module operates on multiple channels with all channels having the same window. The length of the window (WLEN) is specified at instantiation time. The module outputs a block of size [WLEN numChannels], where numChannels equals the number of channels in the input signal. This block is output everytime that the module's processing function is called.

The window coefficients are set to a Hamming window (raised cosine) at instantiation time. The window coefficients may subsequently be changed.

Type Definition

typedef struct _ModuleWindowFract32
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    INT32 winLen;                                 // Length of the window
    INT32 postShift;                              // Number of bits to shift
    FLOAT32* window;                              // Window coefficients
    fract32* windowFract32;                       // Window coefficients in fractional representation
} ModuleWindowFract32Class;

Variables

Properties

Name	Type	Usage	isHidden	Default value	Range	Units
winLen	int	const	0	256	1:1:8192	samples
postShift	int	derived	1	0	Unrestricted
window	float*	parameter	0	[256 x 1]	Unrestricted
windowFract32	fract32*	derived	1	[256 x 1]	Unrestricted

Pins

Input Pins

Name: in

Description: audio input

Data type: fract32

Channel range: Unrestricted

Block size range: 256

Sample rate range: Unrestricted

Complex support: Real

Output Pins

Name: out

Description: audio output

Data type: fract32

MATLAB Usage

File Name: window_fract32_module.m

 M=windowFract32_module(NAME, ILEN, WLEN)
 Creates a module which applies a window.
  Arguments:
    NAME - name of the module.
    ILEN - lenght of the input
    WLEN - length of the window to apply.
 This module is often used as part of a short term Fourier transform
 filterbank.  The module operates on an arbitrary number of channels
 with the same window and length parameters applied.