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acf


Manual Reference Pages  - ACF (1)

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

SYNTAX

acf [arguments] [file]

DESCRIPTION

The autocorrelation function (acf) is computed using the fft. The output framewidth is the given maximum acf lag, which must not be greater than the input framewidth. Each input frame is padded with zeroes to the next power of 2 larger than either the input framewidth, or twice the required max acf lag, (whichever is the larger). If necessary, extra padding can be enforced using the (silent) padding option to 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 is added 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.

EXAMPLES

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

Copyright (c) Applied Psychology Unit, Medical Research Council, 1995 .LP Permission to use, copy, modify, and distribute this software without fee is hereby granted for research purposes, provided that this copyright notice appears in all copies and in all supporting documentation, and that the software is not redistributed for any fee (except for a nominal shipping charge). Anyone wanting to incorporate all or part of this software in a commercial product must obtain a license from the Medical Research Council. .LP The MRC makes no representations about the suitability of this software for any purpose. It is provided "as is" without express or implied warranty.

THE MRC DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL THE A.P.U. BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.


SunOS 5.6 ACF (1) 15 September 1993
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