JAPA-0.9.4 -- Release notes  27/11/2021
___________________________

Maintenance update.
Added more display options.


JAPA-0.9.2 -- Release notes  25/08/2018
___________________________

Maintenance update.
Improved noise generator.


JAPA-0.8.4 -- Release notes  02/07/2013
___________________________

Maintenance update.

Replaced libclalsadrv with libzita-alsa-pcmi


JAPA-0.6.0 -- Release notes  14/03/2010
___________________________

Maintenance update.

Added -s option to select Jack server.
Added -C and -P otions to enable use of split ALSA devices.
Compiles without warnings using gcc-4.4.3.


JAPA-0.4.0 -- Release notes
___________________________

Some bugfixes.
E-mail address updated.
Removed itypes.h, using standard int types.
Pink and white noise generators now output
exactly -20dB ref. the RMS value of a full
scale sine wave.


JAPA-0.2.0 -- Release notes
___________________________

Some bugfixes.
Added white and pink noise generators.


JAPA-0.1.6 -- Release notes
___________________________


This the first official release.

Changes w.r.t. the 0.0.1-alpha release:

 - now uses anti-aliased fonts (via Xft/fontconfig)
 - added /etc/japa.conf 
 - added 80dB range
 - added 440Hz log scale
 - some bugfixes

Many thanks to the alpha testers, in particular Lukas Erni.

See INSTALL for build instructions (it's simple).

Run JAPA without any options to get some help. All options
can also be put in:

/etc/japa.conf     System wide defaults, mostly for binary
                   packages that must not modify any home
                   directory when installed.

~/.Xdefaults       User preferences for all instances.
                   Normally used only to override colors
                   and fonts, but all options can be put
                   here.

~/.<xxx>rc         User preferences for instance started
                   with -name <xxx>. The default name is
                   "japa". If this file exists, even empty,
                   then /etc/japa.conf will not be used.


Description
-----------

JAPA is a 'perceptual' or 'psychoacoustic' audio spectrum
analyser. This means that the filters that are used to
analyse the spectrum have bandwidths that are neither
constant (as in JAAA), nor proportional to the center
frequency (as in a 1/3 octave band analyser), but tuned
to human perception. With the default settings, JAPA uses
a filter set that closely follows the Bark scale.

In contrast to JAAA, this is more an acoustical or musical
tool than a purely technical one. Possible uses include
spectrum monitoring while mixing or mastering, evaluation
of ambient noise, and (using pink noise), equalisation
of PA systems.

JAPA allows you to measure two inputs at the same time,
compare them, store them to memory and compare them to
stored traces. It offers a number of resolutions, speeds,
and various display options.



Quick Manual
------------

Display controls

The controls below the spectrum window modify only the way
things are presented, and not the actual measurement.

   Range: Vertical display range, 20, 40, 60 or 80 dB. There
   are two scales. The one at the left is used for absolute
   displays. The one at the right always has 0 dB at half
   scale and is used when comparing two signals.

   Scale: Controls the frequency scale. Grid lines are one
   octave apart, minor ticks are 1/3 octave. The default
   scale is logarithmic with ticks the standard 1/3 octave
   frequencies. There are two alternatives:
   
     440 Hz log scale (click <-). This has the grid lines
     exactly on the A in each octave. Minor ticks are C#
     and F.

     Warped scale. (click ->) This follows the filter
     bandwidths, i.e. all filters will have the same
     width on the screen. The exact layout of this
     scale depends on the "warp factor" (see below).

   Resp: The normal frequency response is flat in the
   sense that it will correctly indicate the level of a
   sine wave at all frequencies. The Prop setting adds
   a correction that is inversely proportional to the
   relative bandwidth of each filter. This will give
   a flat display when the input is pink noise.


Input controls

There are two channels, called 'A' and 'B'. Each of
them can be connected to one of four inputs, or
switched off (this conserves CPU cycles - switching
off the corresponding trace display does not).
 
Below the input selection is the gain control. Input
gain can be set in steps of 5 dB. There are two more
buttons:

   Auto: Sets the gain based on the current signal
   level. This a momentary action.

   Lnk:  The second channel's gain can be linked to
   the first for stereo operation. This includes the
   Auto function.


Analyser controls

   Resol: Resolution of the filter bank. This sets
   the FFT size to 128, 256, or 512. The number of
   filters effectively used is almost equal to this
   number (japa interpolates between FFT bins to
   give correct amplitudes at all frequencies).

   Warp: JAPA uses a 'warped FFT' to analyse the
   spectrum.  Frequency warping is done by replacing 
   each delay element in the digital processing by
   an all-pass filter. This control allows you to
   set the warp factor, and this in turn determines
   how the filter bandwidths change as a function of
   the center frequency. You can see the warped
   scales by selecting the 'Warp' option in the
   'Scale' display control. The default setting
   corresponds closely to the Bark scale. Higher
   values give more detail in the lower frequency
   range at the expense of the higher.
   
   Speed: This controls the averaging filters that
   follow the spectrum analyser. The Low setting
   is mainly for noise measurement.


Memory store controls

Each channel has a peak hold function. Note that
this operates *after* the averaging done in the
analyser and set by the Speed controls.   
There are two memories called 'X' and 'Y'. The 
current data for each channel can be stored to
either memory. When the peak hold function is
active, the current peak values are stored.

Note: the peak hold function and the two memories
are reset when either the Resolution or Warp factor
are changed. This may change in future versions.

Note: the gain controls are shown as part of the
input blocks, but in reality the gain is applied only
much later: when a trace is displayed or stored to
memory. The result is that the peak hold function
is not disturbed by changing the gain.


Trace display controls

Four traces can be displayed at any time, and
each row controls one of them. Options of the
form 'A/B' compare two inputs or memories. This
means that the difference in dB between them 
is displayed rather than the actual levels.


Enjoy !

-- 
FA

