Version 2.4, February 09, 2011
Albert Graef <Dr.Graef@t-online.de>
This package contains software which makes it easier to use Faust DSPs with Pd and the Pure programming language. The main component is the faust2pd script which creates GUI wrappers for Faust DSPs. The package also includes a bunch of examples. The software is distributed under the GPL; see the COPYING file for details.
Note
This faust2pd version is written in Pure and was ported from an earlier version written in Pure’s predecessor Q. The version of the script provided here should be 100% backward-compatible to those previous versions, except for the following changes:
Also note that you can now run the script on 64 bit systems (Q never worked there).
As of version 2.1, the faust2pd script is now compiled to a native executable before installation. This makes the program start up much faster, which is a big advantage because most xml files don’t take long to be processed. You’ll need Pure 0.21 or later to make this work.
For Windows users, there’s an MSI package of Faust available at the Pure website, which also includes faust2pd.
Copyright (c) 2009-2010 by Albert Graef.
faust2pd is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
faust2pd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.
faust2pd is known to work on Linux and Windows, and there shouldn’t be any major roadblocks preventing it to work on other systems supported by Pure.
The faust2pd script is written in the Pure programming language and requires Pure’s XML module, so you need to install these to make it work. Install the latest pure*.tar.gz and pure-xml*.tar.gz packages and you should be set. (Pure 0.21 or later is required.) Also make sure that the LLVM base package is installed, as described in the Pure INSTALL file, some LLVM utilities are needed to make Pure’s batch compiler work.
To run the seqdemo example, you’ll also need the Pd Pure external (pd-pure*.tar.gz), also available at the Pure website.
To compile the examples, you’ll need GNU C++ and make, Pd and, of course, Faust. Make sure you get a recent version of Faust; Faust releases >0.9.8 include the puredata architecture necessary to create Pd externals from Faust DSPs.
Get the latest source from http://pure-lang.googlecode.com/files/faust2pd-2.4.tar.gz.
Run make and make install to compile and install the faust2pd program on your system. You can set the installation prefix by running make as make install prefix=/some/path. Default installation prefix is /usr/local, faust2pd is installed in the bin directory below that.
Optionally, you can also run make install-pd to copy the supporting Pd abstractions (faust-*.pd) to your lib/pd/extra directory, so that you can use the patches generated by faust2pd without copying these abstractions to your working directory. The Makefile tries to guess the prefix of your Pd installation, if it guesses wrong, you can specify the prefix explicitly by running make as make install-pd pdprefix=/some/path.
The included faustxml.pure script provides access to Faust-generated dsp descriptions in xml files to Pure scripts. This module is described in its own appendix below. It may have uses beyond faust2pd, but isn’t normally installed. If you want to use this module, you can just copy it to your Pure library directory.
Run make examples to compile the Faust examples included in this package to corresponding Pd plugins. After that you should be able to run the patches in the various subdirectories of the examples directory. Everything is set up so that you can try the examples “in-place”, without installing anything except the required software as noted in Requirements above. You can also run make realclean before make to regenerate everything from scratch (this requires faust2pd, so this will only work if you already installed the Pure interpreter).
Faust Pd plugins work in much the same way as the well-known plugin~ object (which interfaces to LADSPA plugins), except that each Faust DSP is compiled to its own Pd external. Under Linux, the basic compilation process is as follows (taking the freeverb module from the Faust distribution as an example):
# compile the Faust source to a C++ module using the "puredata" architecture
faust -a puredata.cpp freeverb.dsp -o freeverb.cpp
# compile the C++ module to a Pd plugin
g++ -shared -Dmydsp=freeverb freeverb.cpp -o freeverb~.pd_linux
By these means, a Faust DSP named xyz with n audio inputs and m audio outputs becomes a Pd object xyz~ with n+1 inlets and m+1 outlets. The leftmost inlet/outlet pair is for control messages only. This allows you to inspect and change the controls the unit provides, as detailed below. The remaining inlets and outlets are the audio inputs and outputs of the unit, respectively. For instance, freeverb.dsp becomes the Pd object freeverb~ which, in addition to the control inlet/outlet pair, has 2 audio inputs and outputs.
When creating a Faust object it is also possible to specify, as optional creation parameters, an extra unit name (this is explained in the following section) and a sample rate. If no sample rate is specified explicitly, it defaults to the sample rate at which Pd is executing. (Usually it is not necessary or even desirable to override the default choice, but this might occasionally be useful for debugging purposes.)
As already mentioned, the main ingredient of this package is a Pure script named “faust2pd” which allows you to create Pd abstractions as “wrappers” around Faust units. The wrappers generated by faust2pd can be used in Pd patches just like any other Pd objects. They are much easier to operate than the “naked” Faust plugins themselves, as they also provide “graph-on-parent” GUI elements to inspect and change the control values.
The process to compile a plugin and build a wrapper patch is very similar to what we’ve seen above. You only have to add the -xml option when invoking the Faust compiler and run faust2pd on the resulting XML file:
# compile the Faust source and generate the xml file
faust -a puredata.cpp -xml freeverb.dsp -o freeverb.cpp
# compile the C++ module to a Pd plugin
g++ -shared -Dmydsp=freeverb freeverb.cpp -o freeverb~.pd_linux
# generate the Pd patch from the xml file
faust2pd freeverb.dsp.xml
Please see Wrapping DSPs with faust2pd below for further details.
Note that, just as with other Pd externals and abstractions, the compiled .pd_linux modules and wrapper patches must be put somewhere where Pd can find them. To these ends you can either move the files into the directory with the patches that use the plugin, or you can put them into the lib/pd/extra directory or some other directory on Pd’s library path for system-wide use.
Also, faust2pd-generated wrappers use a number of supporting abstractions (the faust-*.pd files in the faust2pd sources), so you have to put these into the directory of the main patch or install them under lib/pd/extra as well. (The make pd-install step does the latter, see Installation above.)
The control inlet of a Faust plugin understands messages in one of the following forms:
Control names can be specified in their fully qualified form, like e.g. /gnu/bar/foo which indicates the control foo in the subgroup bar of the topmost group gnu, following the hierarchical group layout defined in the Faust source. This lets you distinguish between different controls with the same name which are located in different groups. To find out about all the controls of a unit and their fully qualified names, you can bang the control inlet of the unit as described above, and connect its control outlet to a print object, which will cause the descriptions of all controls to be printed in Pd’s main window. (The same information can also be used, e.g., to initialize GUI elements with the proper values. Patches generated with faust2pd rely on this.)
You can also specify just a part of the control path (like bar/foo or just foo in the example above) which means that the message applies to all controls which have the given pathname as the final portion of their fully qualified name. Thus, if there is more than one foo control in different groups of the Faust unit then sending the message foo to the control inlet will report the fully qualified name and value for each of them. Likewise, sending foo 0.99 will set the value of all controls named foo at once.
Concerning the naming of Faust controls in Pd you should also note the following:
Last but not least, there is also a special control named active which is generated automatically for your convenience. The default behaviour of this control is as follows:
The active control frequently alleviates the need for special “bypass” or “mute” controls in the Faust source. However, if the default behaviour of the generated control is not appropriate you can also define your own custom version of active explicitly in the Faust program; in this case the custom version will override the default one.
In the examples subdirectory you’ll find a bunch of sample Faust DSPs and Pd patches illustrating how Faust units are used in Pd.
The faust2pd script generates Pd patches from the dsp.xml files created by Faust when run with the -xml option. Most of the sample patches were actually created that way. After installation you can run the script as follows:
faust2pd [-hVbs] [-f size] [-o output-file] [-n #voices]
[-r max] [-X patterns] [-x width] [-y height] input-file
The default output filename is input-file with new extension .pd. Thus, faust2pd filename.dsp.xml creates a Pd patch named filename.pd from the Faust XML description in filename.dsp.xml.
The faust2pd program understands a number of options which affect the layout of the GUI elements and the contents of the generated patch. Here is a brief list of the available options:
| -h, --help | display a short help message and exit |
| -V, --version | display the version number and exit |
| -b, --fake-buttons | |
| replace buttons (bangs) with checkboxes (toggles) | |
| -f, --font-size | |
| font size for GUI elements (10 by default) | |
| -n, --nvoices | create a synth patch with the given number of voices |
| -o, --output-file | |
| output file name (.pd file) | |
| -r, --radio-sliders | |
| radio controls for sliders | |
| -s, --slider-nums | |
| sliders with additional number control | |
| -X, --exclude | exclude controls matching the given glob patterns |
| -x, --width | maximum width of the GUI area |
| -y, --height | maximum height of the GUI area |
Just like the Faust plugin itself, the generated patch has a control input/output as the leftmost inlet/outlet pair, and the remaining plugs are signal inlets and outlets for each audio input/output of the Faust unit. However, the control inlet/outlet pair works slightly different from that of the Faust plugin. Instead of being used for control replies, the control outlet of the patch simply passes through its control input (after processing messages which are understood by the wrapped plugin). By these means control messages can flow along with the audio signal through an entire chain of Faust units. (You can find an example of this in examples/faust/faustdemo.pd.) Moreover, when generating a polyphonic synth patch using the -n option then there will actually be two control inlets, one for note messages and one for ordinary control messages; this is illustrated in the examples/synth/synth.pd example.
The generated patch also includes the necessary GUI elements to see and change all (active and passive) controls of the Faust unit. Faust control elements are mapped to Pd GUI elements in an obvious fashion, following the horizontal and vertical layout specified in the Faust source. The script also adds special buttons for resetting all controls to their defaults and to operate the special active control.
This generally works very well, but you should be aware that the control GUIs generated by faust2pd are somewhat hampered by the limited range of GUI elements available in a vanilla Pd installation. As a remedy, faust2pd provides various options to change the content of the generated wrapper and work around these limitations.
Despite these limitations, faust2pd appears to work rather well, at least for the kind of DSPs found in the Faust distribution. (Still, for more complicated control surfaces and interfaces to be used on stage you’ll probably have to edit the generated GUI layouts by hand.)
For convenience, all the content-related command line options mentioned above can also be specified in the Faust source, as special tags in the label of the toplevel group of the dsp. These take the form [pd:option] or [pd:option=value] where option is any of the (long) options understood by faust2pd. For instance:
process = vgroup("mysynth [pd:nvoices=8] [pd:slider-nums]", ...);
Source options carrying arguments, like nvoices in the above example, can also be overridden with corresponding command line options.
Creating Faust plugins for use with Pd has never been easier before, so I hope that you’ll soon have much joy trying your Faust programs in Pd. Add Pd-Pure to this, and you can program all your specialized audio and control objects using two modern-style functional languages which are much more fun than C/C++. Of course there’s an initial learning curve to be mastered, but IMHO it is well worth the effort. The bottomline is that Pd+Faust+Pure really makes an excellent combo which provides you with a powerful, programmable interactive environment for creating advanced computer music and multimedia applications with ease.
Thanks are due to Yann Orlarey for his wonderful Faust, which makes developing DSP algorithms so easy and fun.
The faustxml module is provided along with faust2pd to retrieve the description of a Faust DSP from its XML file as a data structure which is ready to be processed by Pure programs. It may also be useful in other Pure applications which need to inspect description of Faust DSPs.
The main entry point is the info function which takes the name of a Faust-generated XML file as argument and returns a tuple (name, descr, version, in, out, controls) with the name, description, version, number of inputs and outputs and the toplevel group with the descriptions of the controls of the dsp. A couple of other convenience functions are provided to deal with the control descriptions.
Use the following declaration to import this module in your programs:
using faustxml;
For convenience, you can also use the following to get access to the module’s namespace:
using namespace faustxml;
The following constructors are used to represent the UI controls of Faust DSPs:
A button or checkbox with the given label.
A numeric input control with the given label, initial value, range and stepwidth.
Check for control description values.
Access functions for the various components of a control description.
This function returns a flat representation of a control group x as a list of basic control descriptions, which provides a quick way to access all the control values of a Faust DSP. The grouping controls themselves are omitted. You can pass the last component of the return value of the info function to this function.
Works like the controls function above, but also replaces the label of each basic control with a fully qualified path consisting of all control labels leading up to the given control. Thus, e.g., the label of a slider "gain" inside a group "voice#0" inside the main "faust" group will be denoted by the label "faust/voice#0/gain".
Extract the description of a Faust DSP from its XML file. This is the main entry point. Returns a tuple with the name, description and version of the DSP, as well as the number of inputs and outputs and the toplevel group with all the control descriptions. Raises an exception if the XML file doesn’t exist or contains invalid contents.
Example:
> using faustxml;
> let name,descr,version,in,out,group =
> faustxml::info "examples/basic/freeverb.dsp.xml";
> name,descr,version,in,out;
"freeverb","freeverb -- a Schroeder reverb","1.0",2,2
> using system;
> do (puts.str) $ faustxml::pcontrols group;
faustxml::hslider ("freeverb/damp",0.5,0.0,1.0,0.025)
faustxml::hslider ("freeverb/roomsize",0.5,0.0,1.0,0.025)
faustxml::hslider ("freeverb/wet",0.3333,0.0,1.0,0.025)