sweepgen(1)							Linux System Manual						       sweepgen(1)

NAME

       sweepgen - an Ncurses based sweep generator program

SYNOPSIS

       sweepgen [options]

DESCRIPTION

       sweepgen  is  a	simple	sweep signal generator program, with an Ncurses based user interface, that can digitally generate waveforms on the
       LINUX /dev/dsp device.  8 or 16 bit samples can be generated depending on the hardware.

       sweepgen in MONO mode outputs the generated swept waveform. In STEREO mode the swept waveform is output on one channel,	and  the  sweeping
       waveform is output on the second channel.

       The  sweeping frequency is by default specified as an integer number of Hertz. Fractional Hertz frequencies, specifiable to 0.1Hz or 0.01Hz
       resolution, are supported by use of the -res command line option, or  the  resolution  parameter  in  the  configuration  file(s).  However
       be warned  at 0.1Hz resolution the basic waveform sample buffers generated are each 10 times (and at 0.01Hz resolution 100 times) as big as
       the samplerate. It typically requires 5.5Mbytes of memory to run at 0.1Hz resolution, 16bit 32000 samples/sec. and 55Mbytes  of	memory	to
       run at 0.01Hz resolution. Because of the large buffer sizes, the initial waveform calculation time can also be lengthy.	Remember also that
       the waveforms are re-calculated whenever the playing parameters, 8/16bit, mono/stereo, samplerate are changed.

       The swept waveform frequencies are specified either as a lower and upper frequency, or as a centre frequency with a frequency variation.

       1000 500
	      would signify a range of 1000-500 Hz to 1000+500 Hz, i.e. 500 to 1500 Hz

       Of course, only frequencies less than half the samplerate (number of samples/sec) can be generated. Although this is not checked.

       The waveforms that can be used as either the sweeping or swept signals are:

       sine   A standard sine wave

       square a standard square wave with a 50% mark space ratio

       triangle
	      a linear rise from 0 to peak, thru' 0 to negative peak, and back to 0

       sawtooth
	      a ramp waveform with 'infinitely' fast flyback (:-) An ideal oscilloscope timebase signal.

       noise  This is weak. All it consists of is one second of pseudo-randomly generated samples,  played  repeatedly.  I'd  love  to	do  proper
	      white/pink noise, but I don't know enough, and I don't think the structure of the program is conducive to accurate noise generation.

       pulse  A square waveform where the mark/space ratio (as a percentage) is 10% (mark/space ratio of 1:9).

       A  lot of thought has gone into the algorithms for generating the waveforms.  I believe the sin/cos wave to be very pure (modulo your sound
       card :-), but I don't have access to a THD meter to measure it.

       At 1Hz resolution, sweepgen generates one seconds worth of 1 Hz samples at the specified  samplerate,  for  each  waveform,  and  generates
       sweeping  frequency  F  by  circularly sampling every Fth sample. These samples are scaled to fit the swept frequency range and are used to
       sample the swept waveform to generate the swept signal.	Each buffer fragment is generated for the parameter(s)	set  at  that  moment.	By
       default,  buffer fragment sizes are set so that aprox. 10 fragments/sec are generated. Changing a generation parameter, e.g. waveform, fre-
       quency, will impact the next buffer fragment generated, and hence changes appear to be almost immediate.

       If your sounds periodically 'breaks' up with clicks or breaks, it is usually a sign that siggen is not being scheduled sufficiently  often.
       Either  up  the	priority (see nice et al.), kill off other processes, get a faster processor, or increase the number of audio buffer frag-
       ments that siggen uses. This last will make siggen respond more sluggishly to changes in generation parameters.	syslogd and crond are  two
       processes that I've found useful to kill off - YMMV.

       Defaults
	      output to /dev/dsp, 22050 samples/sec, stereo if stereo card else mono, 16 bit samples if possible, else 8 bit.

CONFIGURATION FILES

       Three  possible	configuration  files  can  be used: a LOCAL config file (usually in current directory), a HOME config file in user's $HOME
       directory and a GLOBAL config file.

       All the siggen suite of programs are compiled with the names of the config files built in. By default the configuration files are:

       ./.siggen.conf
	      is the LOCAL config file.

       $HOME/.siggen.conf
	      is the HOME config file.

       /etc/siggen.conf
	      is the GLOBAL config file.

       siggen -h
	      will indicate which config files will be searched for.

       The config files do not have to exist. If they exist and are readable by the program they are used, otherwise they are simply ignored.

       The config files are always searched for configuration values in the order LOCAL, HOME, GLOBAL. This allows a  scheme  where  the  sysadmin
       sets  up  default  config  values in the GLOBAL config file, but allows a user to set some or all different values in their own HOME config
       file, and to set yet more specific values when run from a particular directory.

       If no configuration files exist, the program provides builtin default values, and most of these values can be set  by  appropriate  command
       line switches and flags.

       See siggen.conf(5) for details of the configuration files.

       sweepgen looks for configuration values BUFFERSPERSEC, CHANNELS, DACFILE, FRAGMENTS, RESOLUTION, SAMPLERATE, SAMPLESIZE, VERBOSE, VI_KEYS.

       BUFFERSPERSEC
	      The aprox. number of sound buffer fragments to play every second (Sound buffersize is always a power of 2).

       CHANNELS
	      sets the number of channels, mono or stereo.

       DACFILE
	      allows the name of the DAC/DSP/PCM device to be changed from /dev/dsp

       FRAGMENTS
	      The number of Audio Buffers to configure in the driver.

       RESOLUTION
	      The minimum change possible to the frequency setting. Only 3 values allowed: 1Hz , 0.1Hz or 0.01Hz

       SAMPLERATE
	      sets the number of samples/sec for the DAC device

       SAMPLESIZE
	      sets whether 8 or 16 bit samples to be generated

       VERBOSE
	      sets whether or not to run in verbose mode.

       VI_KEYS
	      if set then the VI cursor moving keys "HJKL" are enabled

OPTIONS

       -h     display usage and help info

       -v     be verbose

       -s samples
	      generate with samplerate of samples/sec

       -8|-16 or -b 8|16
	      force 8 bit or 16 bit mode.

       -1|-2  mono or stereo mode

       -res n set resolution of frequency generation. Valid values are: 1Hz, 0.l1Hz or 0.01Hz

EXAMPLES


FILES


SEE ALSO

       swgen, signalgen, siggen, tones

BUGS


COPYING

       Copyright 1995-2008 Jim Jackson

       The software described by this manual is covered by the GNU General Public License, Version 2, June 1991, issued by :

	      Free Software Foundation, Inc.,
	      675 Mass Ave,
	      Cambridge, MA 02139, USA

       Permission  is  granted	to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are
       preserved on all copies.

       Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that  the
       entire resulting derived work is distributed under the terms of a permission notice identical to this one.

       Permission  is  granted	to  copy and distribute translations of this manual into another language, under the above conditions for modified
       versions, except that this permission notice may be included in translation instead of in the original English.

AUTHOR

       Jim Jackson

       Email: jj@franjam.org.uk

Release 2							    20 Feb 1998 						       sweepgen(1)