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Operating Systems OS X (Apple) A Bash Audio Sweep Generator... Post 302912357 by wisecracker on Thursday 7th of August 2014 02:00:26 PM
Old 08-07-2014
Hi Corona688...

Absolutely correct, even to the start click, in this particular case using "/dev/dsp", but, it is just as easy to create a header for stereo, signed, unsigned, various bit depths and sampling speeds manually this way too. Hence the proof of concept.

However, I used only the limits of " " and "~" which are 32 and 126 decimal respectively.

The idea was to make RAW waveform generation independent of any binary at all and it works a treat.

A sinewave VFO RAW sweeper using ASCII characters only is in the pipeline. It will take some time to work out all the values but I need this facility along with a constant amplitude amplifier to do flat bandwidth tests on the AudioScope.sh...

SriniShoo...

This is a starter:-
https://ccrma.stanford.edu/courses/4...ts/WaveFormat/

EDIT:
I forgot to add that it is not a pulse but an increasing pseudo-square wave. Due to the interpolation at the default "/dev/dsp" characteristics the square wave can have a lot of sinusoidal ringing on it. It entirely depends on the system. This is from measuring and looking at the earphone output(s) with professional test gear...

Last edited by wisecracker; 08-07-2014 at 04:08 PM.. Reason: See above...
 

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GLSWEEP(1)						      General Commands Manual							GLSWEEP(1)

NAME
glsweep - a program generating log sweep and inverse filter. SYNOPSIS
glsweep [parameters] sweepfile inversefile Usage: glsweep rate amplitude hzstart hzend duration silence leadin leadout sweepfile inversefile Example: glsweep 44100 0.5 10 21000 45 2 0.05 0.005 sweep.pcm inverse.pcm DESCRIPTION
This manual page documents briefly the glsweep program. This manual page was written for the Debian distribution because the original pro- gram does not have a manual page. glsweep is program to perform accurate time aligned impulse response measurements. glsweep is based on the log sweep method for impulse response measurement, which is one of the most accurate, especially for acoustic mea- surements. This method is based on a special signal, which is a logarithmic sinusoidal sweep, that need to be reproduced through the system under test, and an inverse filter, which, when convolved with the measured log sweep, gives back the impulse response of the system. The output format is the usual raw file with 32 bit IEEE floating point samples. If you need to convert the sweep generated using the exam- ple above to a 16 bit mono WAV file you can use SoX with a command line like this one: sox -t f32 -r 44100 -c 1 sweep.pcm -t wav -c 1 sweep.wav PARAMETERS
rate: reference sample rate amplitude: sweep amplitude hzstart: sweep start frequency hzend: sweep end frequency duration: sweep duration in seconds silence: leading and trailing silence duration in seconds leadin: leading window length as a fraction of duration leadout: trailing window length as a fraction of duration sweepfile: sweep file name inversefile: inverse sweep file name Refer to html documentation for more details. SEE ALSO
sox(1). AUTHOR
This manual page was written by Jaromir Mike <mira.mikes@seznam.cz>, for the Debian project (but may be used by others). August 30, 2011 GLSWEEP(1)
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