
========
pd-faust
========

Version 0.4, |today|

Albert Graef <Dr.Graef@t-online.de>

pd-faust is a dynamic environment for running Faust dsps in Pd. It is based on
the author's :doc:`faust2pd<faust2pd>` script, but offers many small
improvements and some major additional features:

* Faust dsps are implemented using two Pd objects, ``fsynth~`` and ``fdsp~``,
  which provide the necessary infrastructure to run Faust synthesizer and
  effect units in Pd, respectively.

* In contrast to faust2pd, the Pd GUI of Faust units is generated dynamically,
  inside Pd. While pd-faust supports the same global GUI layout options as
  faust2pd, it also provides various options to adjust the layout of
  individual control items.

* pd-faust recognizes the ``midi`` and ``osc`` controller attributes in the
  Faust source and automatically provides corresponding MIDI and OSC
  controller mappings. OSC-based controller automation is also available.

* Perhaps most importantly, Faust dsps can be reloaded at any time (even while
  the Pd patch is running), in which case the GUI and the controller mappings
  are regenerated automatically and on the fly as needed.

.. _faust2pd: faust2pd

Copying
=======

Copyright (c) 2011 by Albert Graef

pd-faust is distributed under the GNU LGPL v3+. Please see the included
COPYING and COPYING.LESSER files for details.

This package also includes the faust-stk instruments which are distributed
under an MIT-style license, please check the examples/dsp/README-STK file
and the dsp files for authorship information and licensing details pertaining
to these. The original faust-stk sources can be found in the Faust
distribution, cf. http://faust.grame.fr/.

Installation
============

You'll need Faust_ and Pd_, obviously. Fairly recent versions of these are
required. Faust versions 0.9.46 and 2.0.a3 and Pd version 0.43.1 have been
tested.

The pd-faust objects are written in the Pure_ programming language, so you'll
also need an installation of the Pure interpreter (0.51 or later), along with
the following packages (minimum required versions are given in parentheses):
:doc:`pd-pure<pd-pure>` (0.15), :doc:`pure-faust<pure-faust>` (0.8),
:doc:`pure-midi<pure-midi>` (0.5) and :doc:`pure-stldict<pure-stldict>` (0.3).

Finally, gcc and GNU make (or compatible) are required to compile the helper
dsps and the example instruments; please check the Makefile for details.

.. _Faust: http://faust.grame.fr/
.. _Pd: http://puredata.info/
.. _Pure: http://pure-lang.googlecode.com/

For a basic installation run ``make``, then ``sudo make install``. This will
install the pd-faust objects in your lib/pd/extra/faust folder. Add this
directory to your Pd library search path (``-path`` option or
``Preferences/Path`` in Pd) and you should be set. The ``make`` command also
compiles the Faust dsps included in the distribution, so that the provided
examples will be ready to run afterwards as well (see Examples_ below).

The Makefile tries to guess the installation prefix under which Pd is
installed. If it guesses wrong, you can tell it the right prefix with ``make
prefix=/some/path``. Or you can specify the exact path of the lib/pd directory
with ``make pdlibdir=/some/path``; by default the Makefile assumes
``$(prefix)/lib/pd``.

It is also possible to specify an alternative flavour of Pd when building and
installing the module, by adding a definition like ``PD=pd-extended`` to the
``make`` command line. This is known to work with pd-extended_ and pd-l2ork_,
two popular alternative Pd distributions available on the web.

.. _pd-extended: http://puredata.info/downloads/pd-extended
.. _pd-l2ork: http://l2ork.music.vt.edu/main/?page_id=56

The pd-faust objects are installed both in source form (so you can customize
them for your own purposes) and in binary form as a Pd object library which
can be loaded with Pd's ``-lib`` option. The latter substantially reduces
startup times and is thus the recommended way to run pd-faust if you don't
need to customize the pd-faust objects on the fly. To these ends, after
completing installation and setting up ``Preferences/Path`` in Pd, simply add
``pdfaust`` to your preloaded library modules in Pd's ``Preferences/Startup``
dialog.

.. note:: The ``pdfaust`` module must come *after* the ``pure`` entry which
   loads pd-pure, otherwise you'll get an error message. In any case the
   pd-pure loader will be required to run these objects, so it should be
   configured accordingly; please check the :doc:`pd-pure<pd-pure>`
   documentation for details.

Some further build options are described in the Makefile. In particular, it is
possible to compile the Faust dsps to LLVM bitcode which can be loaded
directly by the Pure interpreter, but for that you'll need a special Faust
version (see the Faust2_ website for how to get this version up and running)
and an LLVM-capable C/C++ compiler such as clang or gcc with the dragonegg
plugin (please check the Makefile and the LLVM_ website for details).

.. _LLVM: http://llvm.org/
.. _Faust2: http://www.grame.fr/~letz/faust_llvm.html

If you have the required tools then you can build the bitcode modules by
running ``make bitcode`` after ``make``. If you run ``make install``
afterwards, the bitcode modules will be installed along with the "normal"
Faust plugins. In addition, a second object library called ``pdfaust2`` will
be built and installed, which can be used as a drop-in replacement for
``pdfaust`` and lets you run the bitcode modules. (Note that in the present
implementation it is not possible to load both ``pdfaust`` and ``pdfaust2`` in
Pd, you'll have to pick one or the other.)

Usage
=====

Working with pd-faust basically involves adding a bunch of ``fsynth~`` and
``fdsp~`` objects to a Pd patch along with the corresponding GUI subpatches,
and wiring up the Faust units in some variation of a synth-effects chain which
typically takes input from Pd's MIDI interface (``notein``, ``ctlin``, etc.)
and outputs the signals produced by the Faust units to Pd's audio interface
(``dac~``).

For convenience, pd-faust also includes the ``midiseq`` and ``oscseq`` objects
and a corresponding ``midiosc`` abstraction which can be used to handle MIDI
input and playback as well as OSC controller automation. This useful helper
abstraction is described in more detail under `Operating the Patches`_ below.

.. note:: pd-faust interprets MIDI, OSC and Faust dsp filenames relative to
   the hosting Pd patch by default. It will also search the ``midi``, ``osc``
   and ``dsp`` subfolders, if they exist, for the corresponding types of
   files. Failing that, it finally searches the directories on the Pd library
   path (including their ``midi``, ``osc`` and ``dsp`` subfolders). To disable
   this search, just use absolute pathnames (or pathnames relative to the
   ``.`` or ``..`` directory) instead.

The fdsp~ and fsynth~ Objects
-----------------------------

The ``fdsp~`` object is invoked as follows::

  fdsp~ dspname instname channel

* ``dspname`` denotes the name of the Faust dsp (usually this is just the name
  of the .dsp file with the extension stripped off). Please note that the
  Faust dsp must be provided in a form which can be loaded in *Pure* (not
  Pd!), so the ``pure.cpp`` architecture included in recent Faust versions
  must be used to compile the dsp to a shared library. (If you're already
  running Faust2_, you can also compile to an LLVM bitcode file instead; Pure
  has built-in support for loading these.) The Makefiles included in the
  pd-faust distribution show how to do this.

* ``instname`` denotes the name of the instance of the Faust unit. Multiple
  instances of the same Faust dsp can be used in a Pd patch, which must all
  have different instance names. In addition, the instance name is also used
  to identify the GUI subpatch of the unit (see below) and to generate unique
  OSC addresses for the unit's control elements.

* ``channel`` is the number of the MIDI channel the unit responds to. This can
  be 1..16, or 0 to specify "omni" operation (listen to MIDI messages on all
  channels).

.. note:: Since the ``fdsp~`` and ``fsynth~`` objects are written in Pure,
   their creation arguments should be specified in Pure syntax. In particular,
   both ``dspname`` or ``instname`` may either be Pure identifiers or
   double-quoted strings (the former will automatically be translated to the
   latter). Similarly, the ``channel`` argument (as well as the ``numvoices``
   argument of the ``fsynth~`` object, see below) must be an integer constant
   in Pure syntax, which is pretty much like Pd syntax but also allows the
   integer to be specified in hexadecimal, octal or binary.

The ``fdsp~`` object requires a Faust dsp which can work as an effect unit,
processing audio input and producing audio output. The unit can have as many
audio input and output channels as you like (including zero).

The ``fsynth~`` object works in a similar fashion, but has an additional
creation argument specifying the desired number of voices::

  fsynth~ dspname instname channel numvoices

The ``fsynth~`` object requires a Faust dsp which can work as a monophonic
synthesizer. This typically means that the unit has zero audio inputs and a
nonzero number of audio outputs, although it is possible to have synths
processing any number of audio input channels as well. (You can even have
synths producing zero audio outputs, but this is generally not very useful.)
In addition, pd-faust assumes that the Faust unit provides three so-called
"voice controls" which indicate which note to play:

* ``freq`` is the fundamental frequency of the note in Hz.

* ``gain`` is the velocity of the note, as a normalized value between 0 and 1.
  This usually controls the volume of the output signal.

* ``gate`` indicates whether a note is currently playing. This value is either
  0 (no note to play) or 1 (play a note), and usually triggers the envelop
  function (ADSR or similar).

pd-faust doesn't care at which path inside the Faust dsp these controls are
located, but they must all be there, and the basenames of the controls must be
unique throughout the entire dsp. Otherwise the synth will not work as
expected.

Like :doc:`faust2pd<faust2pd>`, pd-faust implements the necessary logic to
drive the given number of voices of an ``fsynth~`` object. That is, it will
actually create a separate instance of the Faust dsp for each voice and handle
polyphony by allocating voices from this pool in a round-robin fashion,
performing the usual voice stealing if the number of simultaneous notes to
play exceeds the number of voices. Also note that an ``fsynth~`` operated in
omni mode (``channel = 0``) automatically filters out messages on channel 10
which is reserved for percussion in the General MIDI standard.

The ``fdsp~`` and ``fsynth~`` objects respond to the following messages:

* ``bang`` outputs the current control settings on the control outlet in OSC
  format.

* ``write`` outputs the current control settings to external MIDI and/or OSC
  devices. This message can also be invoked with a numeric argument to toggle
  the "write mode" of the unit; please see `External MIDI and OSC
  Controllers`_ below for details.

* ``reload`` reloads the Faust unit. This also reloads the shared library or
  bitcode file if the unit was recompiled since the object was last loaded.
  (Instead of feeding a ``reload`` message to the control inlet of a Faust
  unit, you can also just send a ``bang`` to the ``reload`` receiver.)

* ``addr value`` changes the control indicated by the OSC address ``addr``.
  This is also used internally for communication with the Pd GUI and for
  controller automation.

In addition, the ``fdsp~`` and ``fsynth~`` objects respond to MIDI controller
messages of the form ``ctl val num chan``, and the ``fsynth~`` object also
understands note-related messages of the form ``note num vel chan`` (note
on/off) and ``bend val chan`` (pitch bend). In either case, pd-faust provides
the necessary logic to map controller and note-related messages to the
corresponding control changes in the Faust unit.

.. note:: Like pd-pure, pd-faust also remaps Pd's ``menu-open`` command so
   that it lets you edit the Faust source of an ``fdsp~`` or ``fsynth~``
   object by right-clicking on the object and choosing ``Open`` from the
   context menu.

GUI Subpatches
--------------

For each ``fdsp~`` and ``fsynth~`` object, the Pd patch should also contain an
(initially empty) "one-off" graph-on-parent subpatch with the same name as the
instance name of the Faust unit::

  pd instname

You shouldn't insert anything into this subpatch, its contents (a bunch of Pd
GUI elements corresponding to the control elements of the Faust unit) will be
generated automatically by pd-faust when the corresponding ``fdsp~`` or
``fsynth~`` object is created, and whenever the unit gets reloaded at runtime.

As with faust2pd, the default appearance of the GUI can be adjusted in various
ways; see `Tweaking the GUI Layout`_ below for details.

The relative order in which you insert an ``fdsp~`` or ``fsynth~`` object and
its GUI subpatch into the main patch matters. Normally, the GUI subpatch
should be inserted *first*, so that it will be updated automatically when its
associated Faust unit is first created, and also when the main patch is saved
and then reloaded later.

However, in some situations it may be preferable to insert the GUI subpatch
*after* its associated Faust unit. If you do this, the GUI will *not* be
updated automatically when the main patch is loaded, so you'll have to reload
the dsp manually (sending it a ``reload`` message) to force an update of the
GUI subpatch. This is useful, in particular, if you'd like to edit the GUI
patch manually after it has been generated.

In some cases it may even be desirable to completely "lock down" the GUI
subpatch. This can be done by simply *renaming* the GUI subpatch after it has
been generated. When Pd saves the main patch, it saves the current status of
the GUI subpatches along with it, so that the renamed subpatch will remain
static and will *never* be updated, even if its associated Faust unit gets
reloaded. This generally makes sense only if the control interface of the
Faust unit isn't changed after locking down its GUI patch. To "unlock" a GUI
subpatch, you just rename it back to its original name. (In this case you
might also want to reinsert the corresponding Faust unit afterwards, if you
want to have the GUI generated automatically without an explicit ``reload``
again.)

Examples
--------

The examples folder contains a few example patches which illustrate how this
all works. Having installed pd-faust as described above, you can run these
from the examples directory, e.g.: ``pd test.pd``. (You can also run the
examples without actually installing pd-faust if you invoke Pd from the main
pd-faust source directory, e.g., as follows: ``pd -lib lib/pdfaust
examples/test.pd``.)

Here are some of the examples that are currently available:

* test.pd: Simple patch running a single Faust instrument.

* synth.pd: Slightly more elaborate patch featuring a synth-effects chain.

* bouree.pd: Full-featured example running various instruments.

For your convenience, related MIDI and OSC files as well as the Faust sources
of the instruments and effects are contained in corresponding subdirectories
(midi, osc, dsp) of the examples directory. A slightly modified version of
the faust-stk instruments from the Faust distribution is also included, please
check the examples/dsp/README-STK file for more information about these.

The MIDI files are all in standard MIDI file format. (Some of these come from
the faust-stk distribution, others can be found on the web.) The OSC files
used by pd-faust for controller automation are plain ASCII files suitable for
hand-editing if you know what you are doing; the format should be fairly
self-explanatory.

Operating the Patches
---------------------

The generated Pd GUI elements for the Faust dsps are pretty much the same as
with :doc:`faust2pd<faust2pd>` (which see). The only obvious change is the
addition of a "record" button (gray toggle in the upper right corner) which
enables recording of OSC automation data.

In each example distributed with pd-faust you can also find an instance of the
``midiosc`` abstraction which serves as a little sequencer applet that enables
you to control MIDI playback and OSC recording. The usage of this abstraction
should be fairly obvious, but you can also find a brief description below.

.. note:: If you use the ``midiosc`` abstraction in your own patches, you
   should copy it to the directory containing your patch and other required
   files, so that MIDI and OSC files are properly located. Alternatively, you
   can also set up Pd's search path as described at the beginning of the
   Usage_ section.

The first creation argument of ``midiosc`` is the name of the MIDI file,
either as a Pure identifier (in this case the .mid filename extension is
supplied automatically) or as a double-quoted string. Similarly, the second
argument specifies the name of the OSC file. Both arguments are optional; if
the second argument is omitted, it defaults to the name of the MIDI file with
new extension .osc. You can also omit both arguments if neither MIDI file
playback nor saving recorded OSC data is required. Or you can leave the first
parameter empty (specify ``""`` or ``0`` instead) to only set an OSC filename,
if you don't need MIDI playback. The latter is useful, in particular, if you
use ``midiosc`` with an external MIDI sequencer (see below).

The abstraction has a single control outlet through which it feeds the
generated MIDI and other messages to the connected ``fsynth~`` and ``fdsp~``
objects. Live MIDI input is also accepted and forwarded to the control outlet,
after being translated to the format understood by ``fsynth~`` and ``fdsp~``
objects. In addition, ``midiosc`` can also be controlled through an external
MIDI sequencer connected to Pd's MIDI input. To these ends, `MIDI Machine
Control`_ (MMC) can be used to start and stop OSC playback and recording with
the transport controls of the external sequencer program. To make this work,
the external sequencer must be configured as an MMC master.

.. _MIDI Machine Control: http://en.wikipedia.org/wiki/MIDI_Machine_Control

At the bottom of the abstraction there is a little progress bar along with a
time display which indicates the current song position. If playback is
stopped, you can also use these to change the current position for playback,
recording and a number of other operations as described below. Note that if
you drive ``midiosc`` from an external MIDI sequencer instead, then it is a
good idea to load the same MIDI file in ``midiosc`` anyway, so that it knows
about the length of the MIDI sequence. This will make the progress bar
display the proper position in the file.

Here is a brief rundown of the available controls:

* The ``start``, ``stop`` and ``cont`` controls in the *first* row of control
  elements start, stop and continue MIDI and OSC playback, respectively. The
  ``echo`` toggle in this row causes played MIDI events to be printed in the
  Pd main window.

* The gray "record" toggle in the upper right corner of the abstraction
  enables recording of OSC controller automation data. Note that this toggle
  merely *arms* the OSC recorder; you still have to actually start the
  recording with the ``start`` button. However, you can also first start
  playback with ``start`` and then switch recording on and off as needed at
  any point in the sequence (this is also known as "punch in/out" recording).
  In either case, pushing the ``stop`` button stores the recorded sequence for
  later playback. Also note that before you can start recording any OSC data,
  you first have to arm the Faust units that you want to record. This is done
  with the "record" toggle in the Pd GUI of each unit.

* The "bang" button next to the "record" toggle lets you record a static
  snapshot of the current parameter settings of all armed units. This is also
  done automatically when starting a fresh recording. The "bang" button lets
  you change the starting defaults of parameters of an existing recording. It
  is also useful if you just want to record a static snapshot of the current
  parameter settings without recording any live parameter changes. Moreover,
  you can also set the parameters at any given point in the piece if you first
  position the progress bar or the time display accordingly; in this case you
  may first want to recall the parameter settings at the given point with the
  ``send`` button described below. In either case, recording must be enabled
  and playback must be *off*. Then just arm the Faust units that you wish to
  record, set the playback position as needed, change the controls to what you
  want their values to be (maybe after recalling the current settings), and
  finally push the "bang" button.

* There are some additional controls related to OSC recording in the *second*
  row: ``save`` saves the currently recorded data in an OSC file for later
  use; ``abort`` is like ``stop`` in that it stops recording and playback, but
  also throws away the data recorded in this take (rather than keeping it for
  later playback); and ``clear`` purges the entire recorded OSC sequence so
  that you can start a new one.

* Once some automation data has been recorded, it will be played back along
  with the MIDI file. You can then just listen to it, or go on to record more
  automation data as needed. Use the ``echo`` toggle in the second row to
  print the OSC messages as they are played back. If you save the automation
  data with the ``save`` button, it will be reloaded from its OSC file next
  time the patch is opened.

* The controls in the *third* row provide some additional ways to configure
  the playback process. The ``loop`` button can be used to enable looping,
  which repeats the playback of the MIDI (and OSC) sequence ad infinitum. The
  ``thru`` button, when switched on, routes the MIDI data during playback
  through Pd's MIDI output so that it can be used to drive an external MIDI
  device in addition to the Faust instruments. The ``write`` button does the
  same with MIDI and OSC controller data generated either through automation
  data or by manually operating the control elements in the Pd GUI, see
  `External MIDI and OSC Controllers`_ below for details.

* There's one additional button in the third row, the ``send`` button which
  recalls the recorded OSC parameter settings at a given point in the
  sequence. Playback must be off for this to work. After setting the playback
  position as desired, just push the ``send`` button. This sets the controls
  to the current parameter values at the given point, for *all* parameters
  which have been recorded up to (and including) this point.

Please note that ``midiosc`` is merely an example which should cover most
common uses. If you don't need all the fancy functionality it provides, your
patches may simply feed control messages directly into ``fdsp~`` and
``fsynth~`` objects instead. On the other hand, if you need even more
elaborate input/output interfacing than what ``midiosc`` provides, ``midiosc``
can be used as a starting point for your own input/output abstractions driving
the ``fdsp~`` and ``fsynth~`` objects in your patch.

External MIDI and OSC Controllers
---------------------------------

The ``fsynth~`` object has built-in (and hard-wired) support for MIDI notes,
pitch bend and MIDI controller 123 (all notes off).

Other controller data received from external MIDI and OSC devices is
interpreted according to the controller mappings defined in the Faust source
(this is explained below), by updating the corresponding GUI elements and the
control variables of the Faust dsp. For obvious reasons, this only works with
*active* Faust controls.

An ``fdsp~`` or ``fsynth~`` object can also be put in *write mode* by feeding
a message of the form ``write 1`` into its control inlet (the ``write 0``
message disables write mode again). For convenience, the ``write`` toggle in
the ``midiosc`` abstraction allows you to do this simultaneously for all Faust
units connected to ``midiosc``\ 's control outlet.

When an object is in write mode, it also *outputs* MIDI and OSC controller
data in response to both automation data and the manual operation of the Pd
GUI elements, again according to the controller mappings defined in the Faust
source, so that it can drive an external device such as a MIDI fader box or a
multitouch OSC controller. Note that this works with both *active* and
*passive* Faust controls.

To configure MIDI controller assignments, the labels of the Faust control
elements have to be marked up with the special ``midi`` attribute in the Faust
source. For instance, a pan control (MIDI controller 10) may be implemented in
the Faust source as follows::

  pan = hslider("pan [midi:ctrl 10]", 0, -1, 1, 0.01);

pd-faust will then provide the necessary logic to handle MIDI input from
controller 10 by changing the pan control in the Faust unit accordingly,
mapping the controller values 0..127 to the range and step size given in the
Faust source. Moreover, in write mode corresponding MIDI controller data will
be generated and sent to Pd's MIDI output, on the MIDI channel specified in
the creation arguments of the Faust unit (0 meaning "omni", i.e., output on
all MIDI channels).

The same functionality is also available for external OSC devices, employing
explicit OSC controller assignments in the Faust source by means of the
``osc`` attribute. E.g., the following enables input and output of OSC
messages for the OSC ``/pan`` address::

  pan = hslider("pan [osc:/pan]", 0, -1, 1, 0.01);

.. note:: In contrast to some other architectures included in the Faust
   distribution, pd-faust only allows literal OSC addresses here. That is,
   glob-style OSC patterns are not supported as values for the ``osc``
   attribute.

Also note that while the necessary infrastructure to support OSC input and
output is already provided by pd-faust, the OSC input and output facilities
themselves which are needed to make this actually work are not implemented in
the default version of the ``midiosc`` abstraction distributed with pd-faust.
That's because Pd doesn't provide any built-in objects for OSC input and
output, although a few different solutions exist and are included in
Hans-Christoph Steiner's Pd-extended_ distribution, such as Martin Peach's
`OSC externals`_.

.. _OSC externals: http://puredata.info/Members/martinrp/OSCobjects

The distribution includes a version of the ``midiosc`` abstraction which
implements OSC input and output using Martin Peach's objects in the
midiosc-mrpeach.pd file. You most likely have to edit this abstraction for
your purposes; at least you'll have to change the network addresses so that it
works with the OSC device or application that you use.

Tweaking the GUI Layout
-----------------------

As already mentioned, pd-faust provides the same global GUI layout options as
:doc:`faust2pd<faust2pd>`. Please check the faust2pd documentation for details.
There are a few minor changes in the meaning of some of the options, though,
which we consider notable improvements after some experience working with
faust2pd. Here is a brief rundown of the available options, as they are
implemented in pd-faust:

* ``width=wd``, ``height=ht``: Specify the maximum horizontal and/or vertical
  dimensions of the layout area. If one or both of these values are nonzero,
  pd-faust will try to make the GUI fit within this area.

* ``font-size=sz``: Specify the font size (default is 10).

* ``fake-buttons``: Render ``button`` controls as Pd toggles rather than
  bangs.

* ``radio-sliders=max``: Render sliders with up to ``max`` different values as
  Pd radio controls rather than Pd sliders. Note that in pd-faust this option
  not only applies to sliders, but also to numeric entries, i.e., ``nentry``
  in the Faust source. However, as with faust2pd's ``radio-sliders`` option,
  the option is only applicable if the control is zero-based and has a
  stepsize of 1.

* ``slider-nums``: Add a number box to each slider control. Note that in
  pd-faust this is actually the default, which can be disabled with the
  ``no-slider-nums`` option.

* ``exclude=pat,...``: Exclude the controls whose labels match the given glob
  patterns from the Pd GUI.

In pd-faust there is no way to specify the above options on the command line,
so you'll have to put them as ``pd`` attributes on the *main* group of your
Faust program, as described in the faust2pd documentation. For instance::

  process = vgroup("[pd:no-slider-nums][pd:font-size=12]", ...);

In addition, the following options can be used to change the appearance of
individual control items. If present, these options override the corresponding
defaults. Each option can also be prefixed with "\ ``no-``\ " to negate the
option value. (Thus, e.g., ``no-hidden`` makes items visible which would
otherwise, by means of the global ``exclude`` option, be removed from the
GUI.)

* ``hidden``: Hides the corresponding control in the Pd GUI. This is the only
  option which can also be used for group controls, in which case *all*
  controls in the group will become invisible in the Pd GUI.

* ``fake-button``, ``radio-slider``, ``slider-num``: These have the same
  meaning as the corresponding global options, but apply to individual control
  items.

Again, these options are specified with the ``pd`` attribute in the label of
the corresponding Faust control. For instance, the following Faust code hides
the controls in the ``aux`` group, removes the number entry from the ``pan``
control, and renders the ``preset`` item as a Pd radio control::

  aux = vgroup("aux [pd:hidden]", aux_part);
  pan = hslider("pan [pd:no-slider-num]", 0, -1, 1, 0.01);
  preset = nentry("preset [pd:radio-slider]", 0, 0, 7, 1);

Remote Control
--------------

Also included in the sources is a helper abstraction faust-remote.pd and an
accompanying elisp program faust-remote.el. These work pretty much like
pure-remote.pd and pure-remote.el in the :doc:`pd-pure<pd-pure>` distribution,
but are tailored for the remote control of Faust dsps in a Pd patch. In
particular, they enable you to quickly reload the Faust dsps in Pd using a
simple keyboard command (``C-C C-X`` by default) from Emacs. The
faust-remote.el program was designed to be used with Juan Romero's Emacs
`Faust mode`_; please see etc/pure-remote.el in the pd-faust source for usage
instructions.

.. _Faust mode:  https://github.com/rukano/emacs-faust-mode

Caveats and Bugs
================

Some parts of this software might still be experimental, under construction
and/or bug-ridden. Bug reports, patches and suggestions are welcome. Please
send these directly to the author, or post them either to the Faust or the
Pure mailing list.

In particular, please note the following known limitations in the current
implementation:

* Passive Faust controls are only supported in ``fdsp~`` objects.

* The names of the voice controls in the ``fsynth~`` object (``freq``,
  ``gain``, ``gate``) are currently hard-coded, as are the names of the
  ``midi``, ``osc`` and ``dsp`` subfolders used to locate various kinds of
  files.

* Polyphonic aftertouch and channel pressure messages are not supported in the
  MIDI interface right now, so you'll have to use ordinary MIDI controllers
  for these parameters instead. Coarse/fine pairs of MIDI controllers aren't
  directly supported either, so you'll have to implement these yourself as two
  separate Faust controls.

Also, please check the TODO file included in the distribution for other issues
which we are already aware of and which will hopefully be addressed in future
pd-faust versions.
