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.TH sweepgen 1 "20 Feb 1998" "Release 2" "Linux System Manual"
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.I sweepgen \- an Ncurses based sweep generator program
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.IP sweepgen\ [options]
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is a simple sweep signal generator program, with an Ncurses based user
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interface, that can digitally generate waveforms on the LINUX
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8 or 16 bit samples can be generated depending on the hardware.
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mode outputs the generated swept waveform. In
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mode the swept waveform is output on one channel, and the sweeping waveform
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is output on the second channel.
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The sweeping frequency is by default
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specified as an integer number of Hertz. Fractional Hertz frequencies,
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specifiable to 0.1Hz or 0.01Hz resolution, are
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supported by use of the
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command line option, or the
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parameter in the configuration file(s). However
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at 0.1Hz resolution the basic waveform sample buffers generated
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(and at 0.01Hz resolution 100 times) as big as the samplerate. It typically
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requires 5.5Mbytes of memory to run at 0.1Hz resolution, 16bit 32000
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samples/sec. and 55Mbytes of memory to run at 0.01Hz resolution. Because of the
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large buffer sizes, the initial waveform calculation time can also be lengthy.
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Remember also that the waveforms are re-calculated whenever the playing
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parameters, 8/16bit, mono/stereo, samplerate are changed.
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The swept waveform frequencies are specified either as a lower and upper
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frequency, or as a centre frequency with a frequency variation.
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would signify a range of 1000-500 Hz to 1000+500 Hz, i.e. 500 to 1500 Hz
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Of course, only frequencies less than half the samplerate
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(number of samples/sec) can be generated. Although this is not checked.
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The waveforms that can be used as either the sweeping or swept signals are:
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a standard square wave with a 50% mark space ratio
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a linear rise from 0 to peak, thru' 0 to negative peak, and back to 0
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a ramp waveform with 'infinitely' fast flyback (:-) An ideal oscilloscope
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This is weak. All it consists of is one second of pseudo-randomly generated
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samples, played repeatedly. I'd love to do proper white/pink noise,
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but I don't know enough, and I don't think the structure of the program
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is conducive to accurate noise generation.
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A square waveform where the mark/space ratio (as a percentage)
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is 10% (mark/space ratio of 1:9).
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A lot of thought has gone into the algorithms for generating the waveforms.
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I believe the sin/cos wave to be very pure (modulo your sound card :-), but
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I don't have access to a THD meter to measure it.
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generates one seconds worth of 1 Hz samples at the specified samplerate, for
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each waveform, and generates sweeping frequency F by circularly sampling
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every Fth sample. These samples are scaled to fit the swept frequency range
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and are used to sample the swept waveform to generate the swept signal.
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Each buffer fragment is generated for the parameter(s)
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set at that moment. By default, buffer fragment sizes are set so that aprox. 10
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fragments/sec are generated. Changing a generation parameter, e.g. waveform,
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frequency, will impact the next buffer fragment generated, and hence
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changes appear to be almost immediate.
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If your sounds periodically 'breaks' up with clicks or breaks,
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that siggen is not being scheduled sufficiently often. Either up the
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et al.), kill off other processes, get a faster processor, or increase the
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number of audio buffer fragments that siggen uses. This last will make
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siggen respond more sluggishly to changes in generation parameters.
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are two processes that I've found useful to kill off - YMMV.
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output to /dev/dsp, 22050 samples/sec, stereo if stereo card else mono,
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16 bit samples if possible, else 8 bit.
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.SH CONFIGURATION\ FILES
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Three possible configuration files can be used: a LOCAL config file (usually
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in current directory), a HOME config file in user's $HOME directory and a
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All the siggen suite of programs are compiled with the names of the config
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files built in. By default the configuration files are:
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is the LOCAL config file.
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.IP $HOME/.siggen.conf
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is the HOME config file.
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is the GLOBAL config file.
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will indicate which config files will be searched for.
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The config files do not have to exist. If they exist and are readable by the
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program they are used, otherwise they are simply ignored.
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The config files are always searched for configuration values in the order
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LOCAL, HOME, GLOBAL. This allows a scheme where the sysadmin sets up default
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config values in the GLOBAL config file, but allows a user to set some or
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all different values in their own HOME config file, and to set yet more
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specific values when run from a particular directory.
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If no configuration files exist, the program provides builtin
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default values, and most of these values can be set
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by appropriate command line switches and flags.
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See siggen.conf(5) for details of the configuration files.
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looks for configuration values BUFFERSPERSEC, CHANNELS, DACFILE, FRAGMENTS,
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RESOLUTION, SAMPLERATE, SAMPLESIZE, VERBOSE, VI_KEYS.
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The aprox. number of sound buffer fragments to play every second
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(Sound buffersize is always a power of 2).
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sets the number of channels, mono or stereo.
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allows the name of the DAC/DSP/PCM device to be changed from /dev/dsp
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The number of Audio Buffers to configure in the driver.
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The minimum change possible to the frequency setting. Only 3 values allowed:
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1Hz , 0.1Hz or 0.01Hz
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sets the number of samples/sec for the DAC device
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sets whether 8 or 16 bit samples to be generated
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sets whether or not to run in verbose mode.
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if set then the VI cursor moving keys "HJKL" are enabled
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display usage and help info
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generate with samplerate of samples/sec
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.IP -8|-16\ or\ -b\ 8|16
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force 8 bit or 16 bit mode.
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set resolution of frequency generation. Valid values are: 1Hz, 0.l1Hz or 0.01Hz
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swgen, sgen, siggen, tones
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.I Copyright\ 1995-2008\ Jim\ Jackson
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The software described by this manual is covered by the GNU General
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Public License, Version 2, June 1991, issued by :
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Free Software Foundation, Inc.,
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Cambridge, MA 02139, USA
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Permission is granted to make and distribute verbatim copies of
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this manual provided the copyright notice and this permission notice
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are preserved on all copies.
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Permission is granted to copy and distribute modified versions of this
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manual under the conditions for verbatim copying, provided that the
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entire resulting derived work is distributed under the terms of a
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permission notice identical to this one.
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Permission is granted to copy and distribute translations of this
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manual into another language, under the above conditions for modified
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versions, except that this permission notice may be included in
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translation instead of in the original English.
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.I Email: jj@franjam.org.uk
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