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Reverberator Equalizer EQ Vibrato Tremolo Echo Tom Szilagyi LADSPA
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<font size="+2" color=#004060><b>TAP</b>-plugins</font><br>
<font color=#004060>Tom's Audio Processing plugins</font><br>
<font size="-1" color=#004060><i>for audio engineering on the Linux platform</i></font>
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<a href="../index.html">[ Home ]</a>
<a href="../ladspa.html">[ LADSPA plugins ]</a>
<a href="../reverbed.html">[ TAP Reverb Editor ]</a>
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<hr>
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<a href="install.html">[ Compiling & installing ]</a>
<a href="manual.html">[ User Manual ]</a>
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<br><br>
<font size="5">TAP Reverb Editor</font><br>
<font size="6"><b>User Manual</b></font>
<h2>Starting the program</h2>
<p>
If the program is <a href="install.html">correctly installed</a> on
your system, all you have to do is type
<code>reverbed</code>. However, there are a few command-line
parameters that are worth mentioning:
</p>
<ul>
<li><b>-a</b>: by default, the program does not connect its inputs and
outputs to any JACK port. When this option is used, the program will
try to connect its inputs to the first two hardware capture ports, and
its outputs to the first two hardware playback ports.</li>
<li><b>-i</b>: same as <b>-a</b>, but connect only the inputs to
hardware capture ports.</li>
<li><b>-o</b>: same as <b>-a</b>, but connect only the outputs to
hardware playback ports.</li>
<li><b>-c <i><client_name></i></b>: use
<i><client_name></i> instead of the default 'reverbED' when
registering to JACK. You need this option if you want to run more than
one instance of the program at the same time, since JACK client
programs must have unique client names.</li>
</ul>
<h2>The main window</h2>
<img src="editor1.png" alt="Editor window (1)">
<p>
The main window (as shown above) lets you do most of the work. It
consists of three areas: the top part provides controls for adjusting
global parameters of the reverberation unit, as well as three buttons
to launch additional windows (<i>Port Setup</i>, <i>Save / Export</i>,
<i>About</i>). The middle part (with the combo box and the <i>New</i>,
<i>Copy</i>, <i>Rename</i>, <i>Del</i> buttons) lets you manage your
Reverb Types by creating new ones from scratch or from an existing
one, as well as renaming and deleting them. Finally, the notebook
provides controls to adjust internal parameters of a chosen Reverb
Type. So let's describe them in detail.
</p>
<h2>Global parameters</h2>
<ul>
<li><b>Comb filters</b>: this toggle button switches processing of
comb filters on/off, the default being switched on. Comb filters
simulate the early reflections part of the reverb sound.</li>
<li><b>Allpass filters</b>: switches processing of allpass filters
on/off, the default being switched on. Allpass filters simulate the
dense 'tail' of the reverb; they add more depth to the reverberated
sound.</li>
<li><b>Bandpass filter</b>: switches the bandpass filter on/off, the
default being switched on. The bandpass filter has a low and high
cutoff frequency; the spectral content that falls outside this range
is attenuated. It processes the sound coming from the comb and allpass
filters, and makes the effect more natural by filtering out those
frequencies that normally do not occur in natural reverberation.</li>
<li><b>Enhanced Stereo</b>: adds spatial spread to the reverb sound,
largely adding to its depth and dimension. It sounds so great, it's
best to always leave this on. It does not consume extra CPU, just
changes the way internal parameters are calculated.</li>
</ul>
<p>
The <a href="../ladspa/reverb.html">TAP Reverberator</a> manual has
detailed advice about setting the following plugin parameters.
</p>
<ul>
<li><b>Decay</b>: adjusts a mostly important global parameter of the
whole effect. Larger values create depth, while smaller ones create
the feel of tighter, smaller spaces.</li>
<li><b>Dry Level</b>: adjusts the amount of the incoming dry signal in
the output signal.</li>
<li><b>Wet Level</b>: adjusts the amount of processed signal in the
output signal.</li>
</ul>
<p>
Some people will agree that the <b>BYPASS</b> button provides the most
useful feature of the program. ;-)
</p>
<h2>Managing Reverb Types</h2>
<p>
It's all about creating the perfect sounding reverb for your own use!
TAP Reverb Editor comes with a set of Reverb Types, but the whole
point is that you can create your own ones. Let's see what the program
provides to this end.
</p>
<ul>
<li>The <b>Reverb Type</b> selector combo box holds the name of all
currently available Reverb Types. Use it to select a Reverb Type to
listen to, or operate on.</li>
</ul>
<p>
These buttons provide functions for Reverb Type management:
</p>
<ul>
<li><b>New</b>: create a new Reverb Type from scratch. After you enter
the new name in the dialog that pops up when you press this button, an
'empty' Reverb Type with that name is created and inserted into the
list, so it will show up in the combo box. The new Reverb Type is not
completely empty: it has one comb filter and one allpass filter, with
their parameters set to default values. The bandpass low and high
cutoff frequencies are also set to default values.</li>
<li><b>Copy</b>: create a new Reverb Type, starting out as a copy of
the currently selected Reverb Type. Use this to enhance existing
Reverb Types while keeping the old version as well. Or create a
working copy of an already satisfactory Reverb Type for random
experimentations without spoiling the original.</li>
<li><b>Rename</b>: change the name of the currently selected Reverb
Type.</li>
<li><b>Delete</b>: remove a Reverb Type that you don't like.</li>
</ul>
<p>
Any changes you make to any Reverb Type (including creating, renaming
and deleting them) remains in memory until you explicitly tell the
program to save Reverb Types to file (more on saving later). So if you
mess something up, just exit the program without using the <i>Save /
Export</i> button, and all your changes will be gone.
</p>
<h2>Editing a Reverb Type</h2>
<p>
Reverberation is modelled by a set of comb filters, allpass filters
and a bandpass filter. The maximum number of comb filters is 20, and
the same limit applies to allpass filters. (It's easy to heighten this
limit in the source code, but that is beyond the scope of this
manual.)
</p>
<h3>Mastering the filters</h3>
<p>
The notebook pages <i>Comb Filters</i> and
<i>Allpass Filters</i> consist of a graphical display representing
each comb/allpass filter with a vertical line. There are controls to
cycle through all filters (<i>Next</i> and <i>Prev</i> buttons),
add/remove filters (<i>New</i>, <i>Del</i>) and adjust the parameters
of the currently selected filter (spin/slider controls at the bottom
of the page). The currently selected filter is highlighted in the
graphical display.
</p>
<p>
The reverb sound will immediately follow the changes you make to
filter settings. It is possible to set filters so hot that they start
operating as oscillators instead of filters (usually at extreme high
feedback <i>and</i> extreme low delay time settings). If this happens
while you are editing a Reverb Type, <b>don't panic</b>. Just hit the
BYPASS button -- that will zero out all internal buffers so everything
will cool down. While the effect is bypassed, move the filter
parameters that caused trouble back to the 'safe area', then re-enable
the plugin.
</p>
<h4>Comb filters</h4>
<p>
Comb filters are responsible for creating early reflections. They have
three parameters: <i>Delay</i>, <i>Feedback</i> and
<i>Freq. Response</i>. The delay time is proportional to the distance
the sound travels before it reaches your ear as an early
reflection. As each comb filter simulates a certain area where
acoustic reflection occurs (a wall or the ceiling for example, but
possibly other objects as well), the delay time you set determines the
virtual distance of this object from the sound source and the
listener. In the graphical display, the horizontal position of the
line representing the filter depends on this parameter.
</p>
<p>
Various kinds of materials reflect and absorb acoustic energy in
various degrees. The feedback parameter provides control of this
effect. For something that is a very good reflector (a flat brick-wall
for example) a reasonably high feedback value should be used. In the
graphical display, the length of the line representing the filter
depends on this parameter.
</p>
<p>
There is a secondary effect taken into account when simulating early
reflections: not only does the reflection ratio of acoustic surfaces
vary from one to another, but the reflection ratio of surfaces is also
frequency-dependent. Higher frequencies are attenuated more, thus high
frequency components decay in a shorter time. The <i>Frequency
Response</i> slider sets the amount of high attenuation for a given
comb filter. There is nearly no extra attenuation of high frequencies
when it is set to zero. In the graphical display, the color of the
line representing the filter depends on this parameter. Filters with
lower Freq. Response values (which mean smaller extra attenuation of
high frequencies) will be plot with a 'hotter' shade.
</p>
<h4>Allpass filters</h4>
<p>
Allpass filters are responsible for creating a reverb tail that makes
the reverberation thicker and more natural sounding. They have two
parameters, identical to the first two parameters of comb filters.
Note, however, that the maximum delay time of allpass filters is about
an order of magnitude lower than of comb filters. The graphical
representation of allpass filters is done in the same way as comb
filters, but here each line has the same color.
</p>
<h4>Bandpass filter</h4>
<p>
This notebook page provides two sliders to set the low and high cutoff
frequencies of the bandpass filter.
</p>
<h3>Impulse Response: a visual aid</h3>
<img src="editor2.png" alt="Editor window (2)">
<p>
A cornerstone of linear systems theory is that any linear system (such
as a complex digital filter like this reverb) is unequivocally
determined by its impulse response. Apart from this theoretical
curiosity, it may be useful to take a look at the impulse response of
a Reverb Type while inspecting or modifying it.
</p>
<p>
The <i>Length</i> slider below the plot lets you choose the end time
of the simulation (with the start point being at time zero). The time
needed to finish plotting is proportional to the time simulated. As
this is quite a CPU-demanding operation, it is never performed
automatically: you have to press the <i>Recalculate</i> button every
time you want to see a new plot of the currently active Reverb Type.
</p>
<p>
Please note that the simulation shows the impulse response of the
'clean' reverb: the settings of the dry and wet levels as well as the
BYPASS button are irrelevant. The decay time setting and the global
switches (Comb Filters, Allpass Filters, Bandpass Filter, Enhanced
Stereo) do affect the plot, though.
</p>
<h2>Port Setup</h2>
<img src="ports.png" alt="Port Setup dialog">
<p>
When you press the <i>Port Setup</i> button, a dialog similar to the
above pops up. It is very much like the input/output connections
dialog of a mixer-strip in Ardour, the only difference being that here
the input and output ports setup is performed in one dialog.
</p>
<p>
The upper half of the window handles connections to the input
ports. On the left, each input port has a list of its current
connections. By clicking on any list item, that connection will be
removed. The <i>Clear connections</i> button removes all connections
from the input ports.
</p>
<p>
The notebook on the right has a page for all client programs and
hardware devices available to the JACK server. By selecting a page,
you will see a list of that client's output ports. Clicking on a list
item connects the port to the currently selected input port (which has
a blue header). You can change the selected input port by clicking on
the unselected (grey) list header. When you add connections to the
input ports, the selection alters between the two inputs.
</p>
<p>
Connecting the outputs can be performed in the same manner. If you
start up another JACK client while the dialog is open, you may press
the <i>Rescan</i> button to make it appear in the notebooks on the
right. Closing and re-opening the dialog has the same effect, since
JACK ports are re-read and a new dialog instance is built every time.
</p>
<h2>Save / Export</h2>
<img src="export.png" alt="Save / Export dialog">
<h3>Saving your work</h3>
<p>
After you have had a good time messing around with Reverb Types, you
may want to leave everything as it was. In this case, just exit the
program and every change you made will be lost. However, there may be
times when you do have something to save: in this case, you will want
to make the changes permanent. So press the <i>Save / Export</i>
button, and the above dialog will appear.
</p>
<p>
Since there is quite a lengthy explanation included in this dialog,
things are pretty straightforward. The program stores everything there
is to Reverb Types in one file, and reads it every time you start the
program. The file read on program startup is always
<code>~/.reverbed</code> (a file called <code>.reverbed</code> in your
home directory), but you have the option to write to another file in
case you want to maintain different versions of the file.
</p>
<blockquote>
<h4><u>A request to all users</u></h4>
<i>The author of this program kindly asks you that if you develop any
new Reverb Type that you think would be of general interest, please
send him your </i><code>.reverbed </code> <i>file via e-mail, along
with your name (if your mail headers don't tell it all). Good Reverb
Types will be included in the next release (with due credit given to
the original author, that's why I need your name). This is a perfect
way to give something back for this software, and other users will
benefit from it as well. Thank you.</i> </blockquote>
<h3>Exporting to TAP Reverberator</h3>
<p>
Since this program is a JACK client, it cannot be automated from
within powerful hosts such as Ardour. However, if you created a good
Reverb Type, the program supports transferring its data into <a
href="../ladspa/reverb.html">TAP Reverberator</a>, which is a LADSPA
plugin for the same reverberation algorithm. It has the advantage of
being automatable on Ardour mixes, but it has no capabilities for
editing Reverb Types (that's why TAP Reverb Editor was created, after
all).
</p>
<p>
Exporting is the process of making the set of Reverb Types in TAP
Reverberator be identical to the set of Reverb Types in this
program. To do this, you have to export two files named
<code>tap_reverb_presets.h</code> and <code>tap_reverb.rdf</code> to
an arbitrary place on your computer storage. In the source code
directory of the TAP-plugins LADSPA plugin package you will find two
files with these names. Overwrite them with the newly exported ones,
and re-compile and re-install the TAP-plugins package. That's all, you
will have the same Reverb Types available in TAP Reverberator after
that. Pretty cool, eh?
</p>
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