Convolve

Overview

Vector convolution

Discussion

This module convolves the signals on its input pins a block at a time. It differs from the FIR module because it doesn't maintain any history between blocks. The output is computed by \(s[n] = \sum_{k=0}^{M-1} x[n-k] y[k]\), where \(x[n]\) is on pin 1 with length \(M\) and \(y[n]\) is on pin 2, also of length \(M\). This operation could be generalized to allow different block sizes if needed.

The parameters shape, skip and length allows control of the range of \(n\) that gets calculated. Shape is for quick setting of common ranges. shape = 0: sets skip=0, olen=2*M-1 to compute the full convolution shape = 1: sets skip=M/2, olen=M to compute the center part that has the same length as the inputs. shape = 2: leaves skip and olen to be user-defined. skip: starts storing output at \(n = \mathit{skip}\) olen: writes only this many output samples, so \(\mathit{skip} <= n < \mathit{skip} + \mathit{olen}\).

Module Pack

Advanced

ClassID

classID = 1243

Type Definition

typedef struct _ModuleConvolve
{
ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
INT32 shape;                                  // Shape of subsection
INT32 skip;                                   // Number of samples of full convolution to skip at output
INT32 olen;                                   // Length of output
} ModuleConvolveClass;

Variables

Properties

Name	Type	Usage	Default Value	Range	Units
shape	int	parameter	0	0:2
skip	int	parameter	0	0:63	samples
olen	int	parameter	63	0:63	samples

Pins

Input Pins


Name	in0
Description	Input signal 0
Data type	float
Channel range	Unrestricted
Block size range	Unrestricted
Sample rate range	Unrestricted
Complex support	Real


Name	in1
Description	Input signal 1
Data type	float
Channel range	Unrestricted
Block size range	Unrestricted
Sample rate range	Unrestricted
Complex support	Real

Output Pins


Name	out
Description	Convolution output
Data Type	float

Matlab Usage

File Name: convolve_module.m 
 M = convolve_module(NAME, SHAPE) 
 This module implements a partial convolution of the two signals on its 
 input pins. How much of the convolution to write can be controlled by 
 the parameters. Also see correlate_module, which is very similar. 

 Arguments: 
   NAME - name of the module 
   SHAPE - enum of standard subset to calculate