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       jaaa -- JACK and ALSA Audio Analyser


       jaaa [-h]  [-C nchan]  [-J]  [-A   [-ddevice]    [-rrate]    [-pperiod]
       [-nnfraqs] ]


       jaaa is an audio signal generator and  spectrum  analyser  designed  to
       make accurate measurements.


       -h        Show summary of options.

       -C        Number of channels (1..8) [4

       -J        Use JACK

       -A        Use ALSA (with following options)

       -d device Alsa device [hw:0.0]

       -r rate   Sample frequency [48000]

       -p period Period size [1024]

       -n nfrag  Number of fragments [2]

       Either -J or -A must be given.


   Input :
       Select on of the four inputs.

   Frequency and Amplitude :
       These  two  sets  of  buttons  set  the display view.  One of these six
       buttons, or 'Bandw', 'Peak', or 'Noise' discussed below, has an  orange
       LED  at  its  left  side.   The  LED  indicates  the 'currenty selected
       parameter' that usually can be modified in three ways :

          o  by typing a new value into the text widget, followed by ENTER

          o  by using the '<' or '>' buttons to decrement or increment,

          o  by mouse gestures

   Frequency :
       Buttons 'Min' and 'Max' set the min and max displayed frequencies.   If
       either of these is selected then

          o  a horizontal Drag Left changes 'Min'

          o  a horizontal Drag Right changes 'Max'

       Button  'Cent'  is  the  frequency at the middle of the x-axis.  Button
       'Span' is 'Max' - 'Min', changing  this  value  preserves  'Cent'.   If
       either of these is selected then

          o  a horizontal Drag Left changes 'Cent'

          o  a horizontal Drag Right changes 'Span'

       Button  'Cent' can also be set by Clicking in the frequency axis scale.

   Amplitude :
       Button 'Max' is the maximum value on the y-axis.  Button 'Range' is the
       range of the y-axis.  If either of these is selected then

          o  a vertical Drag Left changes 'Max'

          o  a vertical Drag Right changes 'Range'

       So  for  the  last  four  mouse  gestures,  a Drag Left will scroll the
       display, while a Drag Right will zoom in or out.  Maybe I will add  and
       automatic  selection  of  the  axis based on the direction of the mouse

   Analyser :
       The analyser is based on a windowed FFT.   Actually  the  windowing  is
       performed   by   convolution   after   the   FFT,   and  combined  with
       interpolation.  The windowing and interpolation ensure  that  displayed
       peaks  will  be  accurate to 0.25 dB even if the peak falls between the
       FFT bins.  More accurate measurements can be  made  using  the  markers
       (see below).

       Button  'Bandw'  sets  the  FFT  length, and hence the bandwidth of the

       Depending on this value, the size of  the  display  and  the  frequency
       range, you may sometimes see two traces.

       This  happens  when  the  resolution of the analyser is better than the
       display, so that one pixel contains more than one analyser value.

       In that case, the blue trace is the peak value over the frequency range
       represented by each pixel, and the gray one is the average value.

       The  first  one  is  correct  for  discrete frequencies, and the latter
       should be used to read noise densities.

       There is no mouse gesture to change the bandwidth.

       Button 'VidAv'  or  video  average,  when  switched  on,  averages  the
       measured  energy over time.  This is mainly used to measure noise.  The
       averaging length increases over time, to a maxumum of 1000  iterations.
       Changing the input or bandwidth resets and restarts the averaging.

       Button  'Freeze'  freezes the analyser, but not the display, so you can
       still scroll and zoom or use the markers discussed below.

   Markers :
       Markers are used in order to accurately read off values in the display.
       There  can  be  up  to  two  markers,  set  by  clicking at the desired
       frequency inside the display.  When there are two markers,  the  second
       one will move with each click, while the first remains fixed.  Measured
       values for the two markers, and their difference in frequency and level
       are displayed in the upper left corner of the display.

       Button 'Clear' clears the markers.

       When  'Peak' is selected, clicking inside the display will set a marker
       at the nearest peak.

       The exact frequency and level of the peak are found  by  interpolation,
       so  the  frequency can be much more accurate than the FFT step, and the
       level corresponds to the true  peak  value  regardless  of  display  or
       analyser resolution.

       When  'Noise' is selected, clicking inside the display will set a noise

       The noise density (energy per Hz) is calculated and displayed.


       jackd (1)



       This manual page was written by  Philippe  Coval  for  the
       Debian  system  (but  may be used by others).  Permission is granted to
       copy, distribute and/or modify this document under the terms of the GNU
       General  Public  License,  Version 2 any later version published by the
       Free Software Foundation.

       On Debian systems, the complete text of the GNU General Public  License
       can be found in /usr/share/common-licenses/GPL.