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ftgram


Manual Reference Pages  - FTGRAM (1)

NAME

ftgram - Autocorrelogram auditory image.

CONTENTS

Syntax
Description
Examples
Copyright

SYNTAX

ftgram [arguments] [file]

DESCRIPTION

Short-time Fourier transform applied to each row of input frames. Output frames consist of row-wise magnitude spectra, computed using fft.

The program expects to read an AIM header, and interprets input as one large frame in column-wise format (eg output from genbmm, gennap, etc.), to be divided into input frames, each to be processed by row-wise fft. A new header is constructed, and each fft-gram frame is output in row-wise format (eg as if output from gensai).

The input is divided into frames according to the given options. The options "start" and "length" specify the input file. The special option value length=max specifies all the input file from the given start to its end. The options "width" and "frstep" specify the input frames. The width option is the framewidth of each input frame) and the frstep option is the frameshift between input frames in the input file. The special option value width=max specifies the input framewidth as equal to the given input file length, (and if this is also "max", then the input framewidth is the remainder of the input file).

Most options in the input header are copied to the output header. This enables options which are needed for the eventual display to pass straight through. Some options are set so that they can override the input header. For example, the display option is set on to enable display even when input has display=off. The animate option can be set on even when the input has animate=off. Some parts of the header are changed for the output format: (frames, frameshift, framewidth, frameheight, framebytes).

Each row of each input frame is padded with zeroes to the next power of 2 larger than the original input framewidth. 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:

( framewidth + 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 output framewidth (and hence the frequency resolution) depends upon the input framewidth and the padding.

EXAMPLES

1. ftgram of a NAP, animated, with framewidth 16ms

gennap len=128ms output=stdout display=off file | ftgram width=16ms animate=on > file.sai

gensai useprev=on headr=5 top=1000 file -(for landscape plot)

genspl useprev=on headr=5 top=1000 pensize=2 file -(for spiral plot)

2. ftgram of an SAI:
(gensai removes file.sai, so you must use some other name, eg foo.sai).

gensai len=64 pwidth=64 nwidth=0 output=stdout display=off file | saitonap frame=3 | ftgram width=32ms frame=1 > foo.sai

gensai useprev=on top=1000 headr=5 mag=2 foo

COPYRIGHT

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

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.

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 FTGRAM (1) 1 September 1993
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