amesh(6D)

NAME
     amesh - audio spectrum analyzer

SYNOPSIS
     amesh

DESCRIPTION
     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
          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
          This menu item varies the thickness of the line drawn. The default
          is two pixel wide lines.

     Color
          Toggles between monochrome and color displays. Color is the default.

     Log Freq Scale
          Toggles between logarithmic and linear frequency scales. The default
          is linear.

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

     Wheel
          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.
     FFT Size
          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
     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
     /usr/demos/General_Demos/amesh/data        wav sound files used by amesh

SEE ALSO
     apanel(1)