Overview

Applies a time domain window and optionally aliases the result to a shorter length

Discussion

This module applies a time domain window to a signal and then optionally aliases the result. 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 and aliasing operation applied. The length of the window (WLEN) and the size of the output (OLEN) are specified at instantiation time. If OLEN == WLEN, then no aliasing occurs and the module simply applies a window. For aliasing, set WLEN equal to a multiple of OLEN. This causes the window to be applied and the result to be time aliased to OLEN samples. WLEN must be a multiple of OLEN so that an integer number of complete blocks are aliased.

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

Type Definition

typedef struct _ModuleWindowAlias
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    INT32 winLen;                                 // Length of the window
    INT32 stateIndex;                             // Index of the oldest state variable in the array of state variables
    INT32 numAliasSections;                       // Number of sections that are aliased to form the output. Equals WLEN/OLEN
    FLOAT32* window;                              // Window coefficients
    FLOAT32* state;                               // State variable array
} ModuleWindowAliasClass;

Variables

Properties

Pins

Input Pins

Name: in

Description: audio input

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Sample rate range: Unrestricted

Complex support: Real

Output Pins

Name: out

Description: audio output

Data type: float

MATLAB Usage

File Name: window_alias_module.m

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