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  external
       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
       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, 3 audio buffer fragments.

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