NAME

conv - Convolution.

CONTENTS

Syntax
Description
Options
Copyright

conv [options] signal_file impulse_response_file

The response of a linear filter to an arbitiary input signal is theconvolution of the signal with the filter’s impulse response.The ‘impulse_response_file’ contains the impulse response which characterises thefilter, and the result of the convolution operation is the response ofthat filter to the signal contained in the ‘signal_file’.

The ‘signal_file’ must consist of binary 16-bit numbers (ie. shorts).The ‘impulse_response_file’ must consist of binary floats.The output signal is the same length as the input signal and is written onthe stdout in binary 16-bit numbers.

If the ‘signal_file’ consists of an impulse train, then the output shouldbe a repeated impulse response, ie. should be a repeated version of the‘response_file’.

1. length

The amount of the signal file to convolve in time units (s or ms) or insamples (no units). Time units are converted to samples using the given‘samplerate’ option. The string "max" is recognised as the remainder ofinput.

2. domain

Select algorithm for convolution. In the time domain ("domain=time") thediscrete convolution formula is applied directly as a local averagingoperation on the input signal with weights obtained by time-reversing andshifting the impulse response. The impulse response is assumed to be zerofor all time outside the given file. In the frequency domain("domain=frequency") the FFT of the whole input signal is multiplied by afrequency response function (the FFT of the impulse response), andthe result inverse FFT’d.

3. scale

A scale factor for scaling the output.

options smooth fft acf

Copyright (c) Applied Psychology Unit, Medical Research Council, 1995

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