siggen - an Ncurses based signal generator program

JimJacksonEmail:jj@franjam.org.uk

Release 2                                          20 Feb 1998                                         siggen(1)

Copyright1995-2008JimJackson

       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

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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.

siggen-anNcursesbasedsignalgeneratorprogram

       -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

       signalgen, swgen, tones, sweepgen

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