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