man1/afft.1

#

    afft(1)								      afft(1)

    Name
      afft - A Realtime FFT	display	client

    SYNOPSIS
      afft [-color]	[-d device] [-file file] [-gain	gainvalue] [-length
      fftlength] [-log] [-min minvalue] [-max maxvalue] [-nodc] [-noscope]
      [-nowindow] [-realtime] [-sine] [-spec] [-stride stridelength]

    Description

      afft accepts mu-law audio data from one of several sources, executes a run-
      ning Fourier transform on the	data, and displays the transform result.  The
      display is updated continuously in either "waterfall"	or "spectrogram" for-
      mat.

      afft is initially configured through command line switches.  Many of the
      parameters can be changed while the progogram	is running via the graphical
      user interface, as described below.

      The source of	the audio that is displayed depends on the configuration as
      folows: If the -file switch is given,	then the audio source is a file	of
      mu-law samples.  Otherwise, if the -sine switch is given, the	audio source
      is a "canned"	sine wave that sweeps up and down the frequency	spectrum.  If
      neither -file	or -sine are given, then afft takes its	audio data from	the
      audio	server local input.

    Options

      -color

           Specifies that the display is to	be in color.  The default is grays-
           cale.  The color	scheme can be changed while afft is running by means
           of a pull-down menu labeled "Colors".

      -d device

           Specifies the name of the audio device.	If not given, afft defaults
           to the local audio device.

      -file	file

           Input will be taken from	file, which should contain raw mu-law samples
           of audio	data.  afft will continuously loop through the file from
           beginning to end, rewind	the file, and repeat.  If file is given	as
           "-", input is taken from	stdin.	Since it is not	possible to rewind
           stdin, afft will	terminate on end-of-file in this case.

           If afft can connect to the audio	server,	then the file is played
           through the audio output	device in synchronization with the fft
           display.

      -gain	gainvalue

           Sets the	gain in	DB to be applied to the	audio samples.	Should be in
           the range of -100 to -5,	and represents a level down from a theoreti-
           cal peak	value of 0DB.  Applies only when log mode is selected, see
           -log switch.  Default value is -20.  The	gain value may be controlled
           while afft is running by	a slider labeled "Gain".

      -length fftlength

           Sets the	number of samples over which each FFT transform	is computed.
           Legal values are	512, 256, 128, and 64.	Default	value is 512.  The
           length can be changed while afft	is running by means of a pull-down
           menu labeled "FFT Length"

      -log

           Selects the initial display mode	to be logarithmic.  If not specified,
           the initial display mode	is linear.  The	selection between log and
           linear mode may be changed while	afft is	running	by a pair of radio
           buttons labeled "Log" and "Linear".

      -min minvalue

           Sets the	lowest audio level that	will be	displayed.  Value is in	DB
           for log mode, or	in percent of peak value in linear mode.  Default is
           -100 in log mode, and 0 in linear.  The minimum value may be con-
           trolled while afft is running by	a slider labeled "Minimum".

      -max maxvalue

           Sets the	hightest audio level that will be displayed.  Value is in DB
           for log mode, or	in percent of peak value in linear mode.  Default is
           0 in log	mode, and  100 in linear.  The maximum value may be con-
           trolled while afft is running by	a slider labeled "Maximum".

      -nodc

           Supresses display of the	DC component.  Default is to include the DC
           component in the	fft display.  Inclusion	or supression of the DC	com-
           ponent may be changed while afft	is running by a	pair of	radio buttons
           labeled "NoDC" and "DC".

      -noscope

           Suppresses display of the audio stream in an oscilloscope-like form.
           The default is to show this display.  Oscilloscope display can also be
           turned on and off while afft is running by a pair of radio buttons
           labeled "Scope On" and "Scope Off".

      -nowindow

           Supresses the window function.  By default, a Hamming window is used.
           Other window functions can be selected through a	pulldown menu labeled
           "Windows".  Additional window functions include Hanning,	and Triangu-
           lar.

      -realtime
           If this switch is given,	afft attempts to stay synchronized with	the
           audio server in real time.  If afft cannot get enough CPU cycles	to
           keep up with the	incoming audio stream, it may fall behind enough that
           it no longer captures valid audio data.	In non-realtime	mode (the
           default), afft will discard audio samples in order to keep up with
           real time.

      -sine

           Causes afft to begin operation in demo mode, which displays a sine
           curve sweep from	the minimum frequency up to the	Nyquist	cut-off	fre-
           quency.	afft can operate in this mode even if the audio	server is not
           running or no audio hardware is available.  afft	can be switched
           between demonstration mode and live mode	(input from the	audio server)
           by a pair of radio buttons labeled "Live" and "Demo.

      -spec

           Selects spectrogram display.  Otherwise,	a waterfall style of display
           is used.	 You can switch	at will	between	spectrogram and	waterfall by
           a pair of radio buttons labeled "Waterfall" and "Spec".

      -stride stridelength

           Sets the	number of samples that afft advances between FFT frames.
           Legal values are	512, 256, 128, and 64.	Default	value is 512.  How-
           ever, the stride	will never be greater than the FFT length (see
           above).	The stride can be changed while	afft is	running	by means of a
           pull-down menu labeled "Stride"

    Owner

           Original	by L. Stewart

           User Interface by J. Morse

    Copyright
      Copyright 1992-1994 Digital Equipment	Corporation