Provided by: jaaa_0.4.2-1ubuntu1_i386 bug


       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 :

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

          ·  by using the ’<’ or ’>’ buttons to decrement or increment,

          ·  by mouse gestures

   Frequency :
       If either of these is selected then

          ·  a horizontal Drag Left changes ’Min’,

          ·  a horizontal Drag Right changes ’Max’.

       If either of these is selected then

          ·  a horizontal Drag Left changes ’Cent’,

          ·  a horizontal Drag Right changes ’Span’.

   Amplitude :
       If either of these is selected then

          ·  a vertical Drag Left changes ’Max’,

          ·  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

       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.

       This  is  mainly  used to measure noise. The averaging lenght increases
       over time, to a maxumum of  1000  iterations.  Changing  the  input  or
       bandwidth resets and restarts the averaging.

       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.

       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
       marker.  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.