siggen(1)							Linux System Manual							 siggen(1)

NAME

       siggen - an Ncurses based signal generator program

SYNOPSIS

       siggen [-s samplerate] [-8|-16|-b 8|-b 16] [-1|-2]

DESCRIPTION

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

       siggen allows two independent waveforms to be generated.  In stereo the two signals appear on different channels. In mono the  two  signals
       are digitally mixed onto the one mono channel.

       The  frequency is specified as an integer number of Hertz. Fractional Hertz frequencies are not supported. Of course, only frequencies less
       than half the samplerate (number of samples/sec) are accurately meaningful. Higher frequencies can be specified, but don't expect  to  hear
       them!

       The waveforms that can be generated are:

       sine   A standard sine wave

       cosine a sine wave with a 90 degree phase shift

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

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

       sawtooth
	      shaped like equally spaced teeth on a saw (:-)

       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) can be specified. The default value 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. For best signal accuracy leave the gain setting at 100(%). The generator
       will then make the wave's peak value fit the maximum digital values allowed. Use a mixer program to control the output volume, or an exter-
       nal attenuator.

       The  gain  factor option can be useful for simulating a signal that has been subject to clipping, by specifying a gain of > 100%. In fact a
       trapezoid signal can be made by generating a clipped sawtooth wave. The greater the gain, the closer the signal approaches  a  square  wave
       (the rise and fall times decrease).

       siggen  generates one seconds worth of 1 Hz samples at the specified samplerate, for each waveform, and generates frequency F by circularly
       sampling every Fth sample. Each buffer fragment is generated for the parameter(s) set at that moment. Buffer fragment sizes are set so that
       aprox.  10  fragments/sec are generated. Changing a generation parameter, e.g. waveform, frequency, gain, will impact the next buffer frag-
       ment 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, 3 audio buffer frag-
	      ments.

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

EXAMPLES


FILES


SEE ALSO

       signalgen, swgen, tones, sweepgen

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 							 siggen(1)