Provided by: siggen_2.3.10-9_amd64 
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, frequency, 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 fragments 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