sweepgen.1

.TH sweepgen 1 "20 Feb 1998" "Release 2" "Linux System Manual"
.SH NAME
.I sweepgen \- an Ncurses based sweep generator program
.SH SYNOPSIS
.IP sweepgen\ [options]
.SH DESCRIPTION
.I sweepgen
is a simple sweep signal generator program, with an Ncurses based user 
interface, that can digitally generate waveforms on the LINUX 
.B /dev/dsp
device.
8 or 16 bit samples can be generated depending on the hardware.
.PP
.I sweepgen
in 
.B MONO
mode outputs the generated swept waveform. In 
.B STEREO
mode the swept waveform is output on one channel, and the sweeping waveform
is output on the second channel.
.PP
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 
.I -res
command line option, or the
.I resolution
parameter in the configuration file(s). However
.I 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.

.PP
The swept waveform frequencies are specified either as a lower and upper
frequency, or as a centre frequency with a frequency variation.
.IP 1000\ 500
would signify a range of 1000-500 Hz to 1000+500 Hz, i.e. 500 to 1500 Hz
.PP
Of course, only frequencies less than half the samplerate
(number of samples/sec) can be generated. Although this is not checked. 
.PP 
The waveforms that can be used as either the sweeping or swept signals are:
.IP sine
A standard sine wave
.IP square
a standard square wave with a 50% mark space ratio
.IP triangle
a linear rise from 0 to peak, thru' 0 to negative peak, and back to 0
.IP sawtooth
a ramp waveform with 'infinitely' fast flyback (:-) An ideal oscilloscope
timebase signal.
.IP 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.
.IP pulse
A square waveform where the mark/space ratio (as a percentage)
is 10% (mark/space ratio of 1:9).
.PP
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. 
.PP
At 1Hz resolution,
.I 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.
.PP
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 
.I 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.
.I syslogd
and
.I crond
are two processes that I've found useful to kill off - YMMV.
.IP Defaults
output to /dev/dsp, 22050 samples/sec, stereo if stereo card else mono,
16 bit samples if possible, else 8 bit. 
.SH CONFIGURATION\ FILES
.PP
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.
.PP
All the siggen suite of programs are compiled with the names of the config
files built in. By default the configuration files are:
.IP ./.siggen.conf
is the LOCAL config file.
.IP $HOME/.siggen.conf
is the HOME config file.
.IP /etc/siggen.conf
is the GLOBAL config file.
.IP siggen\ -h
will indicate which config files will be searched for.
.PP
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.
.PP
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.
.PP
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.
.PP
See siggen.conf(5) for details of the configuration files.
.PP
.I sweepgen
looks for configuration values BUFFERSPERSEC, CHANNELS, DACFILE, FRAGMENTS,
RESOLUTION, SAMPLERATE, SAMPLESIZE, VERBOSE, VI_KEYS.
.IP BUFFERSPERSEC
The aprox. number of sound buffer fragments to play every second
(Sound buffersize is always a power of 2).
.IP CHANNELS
sets the number of channels, mono or stereo.
.IP DACFILE
allows the name of the DAC/DSP/PCM device to be changed from /dev/dsp
.IP FRAGMENTS
The number of Audio Buffers to configure in the driver.
.IP RESOLUTION
The minimum change possible to the frequency setting. Only 3 values allowed:
1Hz , 0.1Hz or 0.01Hz
.IP SAMPLERATE
sets the number of samples/sec for the DAC device
.IP SAMPLESIZE
sets whether 8 or 16 bit samples to be generated
.IP VERBOSE
sets whether or not to run in verbose mode.
.IP VI_KEYS
if set then the VI cursor moving keys "HJKL" are enabled

.SH OPTIONS
.IP -h
display usage and help info
.IP -v
be verbose
.IP -s\ samples
generate with samplerate of samples/sec
.IP -8|-16\ or\ -b\ 8|16
force 8 bit or 16 bit mode.
.IP -1|-2
mono or stereo mode
.IP -res\ n
set resolution of frequency generation. Valid values are: 1Hz, 0.l1Hz or 0.01Hz
.SH EXAMPLES
.SH
.SH FILES
.SH
.SH SEE ALSO
swgen, sgen, siggen, tones
.SH BUGS
.SH
.SH COPYING
.I Copyright\ 1995-2008\ Jim\ Jackson
.PP
The software described by this manual is covered by the GNU General
Public License, Version 2, June 1991, issued by :
.IP
Free Software Foundation, Inc.,
.br
675 Mass Ave,
.br
Cambridge, MA 02139, USA
.PP
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.
.PP
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.
.PP
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.
.SH AUTHOR
.I Jim Jackson
.br
.sp
.I Email: jj@franjam.org.uk
.br