NAME

acf - autocorrelation function of contiguous frames.

i/p and o/p data in binary shorts, (o/p data n/2 points per frame).

CONTENTS

Syntax
Description
Examples
Copyright

acf [arguments] [file]

The autocorrelation function (acf) is computed using the fft.The output framewidth is the given maximum acf lag, which must not begreater than the input framewidth.Each input frame is padded with zeroes to the next power of 2 larger thaneither the input framewidth, or twice the required max acf lag, (whicheveris the larger).If necessary, extra padding can be enforced using the (silent) padding optionto add extra zeroes, padding to a larger power of 2.The amount of extra padding is "exponential", expanding the basic size to:

( framesize + padding ) * 2**n

where the padding option is n.

(n=0 by default, so that no extra padding is added. When n=1 then padding isadded to double the size, and when n=2 the size is quadrupled, etc.).The input and output frame sizes in sample points may be printed using the"size" option.

1. To print the input and output frame sizes in sample points,   eg for a subsequent plotting program, use the size option:
acf ... size=on
2. An acf of a waveform sampled at 10kHz, computed to a max lag   of 12.8ms within a frame of 12.8ms, plotting the 2nd frame in   a sequence of frames with frameshift 12.8ms.
acf samp=10kHz width=12.8ms frstep=12.8ms frame=2 lag=12.8ms file    | x11plot
3. An animated plot of successive acf’s of a waveform sampled at   10kHz, each computed within a frame of 12.8ms, and shifted by   2 sample points.
acf samp=10kHz width=12.8ms frstep=2p lag=12.8ms file    | x11play -n128

Copyright (c) Applied Psychology Unit, MedicalResearch Council, 1995 .LP Permission to use, copy, modify, anddistribute this software without fee is hereby granted for researchpurposes, provided that this copyright notice appears in all copiesand in all supporting documentation, and that the software is notredistributed for any fee (except for a nominal shippingcharge). Anyone wanting to incorporate all or part of this software ina commercial product must obtain a license from the Medical ResearchCouncil. .LP The MRC makes no representations about the suitabilityof this software for any purpose. It is provided "as is" withoutexpress or implied warranty.

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