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amesh(6D)							     amesh(6D)

NAME    [Toc]    [Back]

     amesh - audio spectrum analyzer

SYNOPSIS    [Toc]    [Back]


DESCRIPTION    [Toc]    [Back]

     amesh computes an estimation of the spectrum of an	audio input every
     frame and displays	a 3D graph of the last 25 frames in a window.  The
     frequencies range from 0 Hz on the	left to	half the input sampling	rate
     on	the right.

     The audio source should be	selected using the audio control panel,	and
     the input gain should be adjusted to get a	reasonable input level.	 amesh
     does not copy the audio input to the output.

     Holding down the middle mouse button acts as a track-ball interface to
     change the	viewing	angle.	Holding	down the left mouse button and moving
     the mouse zooms in	and out	on the graphics.  The right mouse button pops
     up	a menu with the	following items.

     Draw Modes    [Toc]    [Back]
	  Each of three	options	on a sub-menu can independently	toggled.
	  amesh	will draw lines	along the time axis, the frequency axis, the
	  amplitude axis, or any combination of	the three.  By default,	lines
	  are drawn along the frequency	axis.

     Line Width    [Toc]    [Back]
	  This menu item varies	the thickness of the line drawn. The default
	  is two pixel wide lines.

     Color    [Toc]    [Back]
	  Toggles between monochrome and color displays. Color is the default.

     Log Freq Scale    [Toc]    [Back]
	  Toggles between logarithmic and linear frequency scales. The default
	  is linear.

     Tmesh    [Toc]    [Back]
	  Toggles between wire frame and shaded	triangle mesh representations
	  of the power spectrum.  The default is wire frame.

     Wheel    [Toc]    [Back]
	  amesh	can simulate a wheel rolling over a rough surface under	the
	  influence of gravity.	 The frequency spectrum	forms the rough
	  surface, which moves past the	wheel.	The wheel jumps	off the
	  surface when it runs into a peak and then falls back due to gravity.
	  This menu option lets	you turn the visibility	of the wheel on	or off
	  and lets you change your viewpoint to	a "wheel's-eye"	view or	back
	  to normal.

									Page 1

amesh(6D)							     amesh(6D)

     FFT Size    [Toc]    [Back]
	  amesh	estimates the power spectrum by	performing a FFT on a fixed
	  number of consecutive	samples	from the input stream for each frame.
	  The number of	samples	is selected by the this	menu item.  The
	  default is 128 consecutive samples.

     Quit Quits	amesh.

Technical Notes    [Toc]    [Back]

     The power spectrum	is divided into	64 frequency bands evenly spaced
     between 0 Hz and (Sampling	Rate/2).  If the input is sampled at 8Khz the
     frequency bands go	up to 4Khz. If the input sampling rate is 22Khz	the
     top frequency band	is 11Khz etc.  amesh estimates the power spectrum by
     performing	a FFT on the consecutive number	of samples selected by the FFT
     Size menu (default	128). Thus the main loop of amesh looks	like:

	  while	(TRUE) {
	       Read all	available samples into the input buffer;
	       Perform FFT on the last 128 samples in the input	buffer;
	       Compute power spectrum for 64 frequency bands
	       from the	FFT output.
	       Plot the	most recent 25 power spectra using GL.

FILES    [Toc]    [Back]

     /usr/demos/General_Demos/amesh/data	wav sound files	used by	amesh

SEE ALSO    [Toc]    [Back]


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