DSSI

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What is DSSI?

DSSI (pronounced "dizzy") is an API for audio processing plugins, particularly useful for software synthesis plugins with user interfaces.

DSSI is an open and well-documented specification developed for use in Linux audio applications, although portable to other platforms. It may be thought of as LADSPA-for-instruments, or something comparable to VSTi.

DSSI consists of a C language API for use by plugins and hosts, based on the LADSPA API, and an OSC (Open Sound Control) API for use in user interface to host communications. The DSSI specification consists of an RFC which describes the background for the proposal and defines the OSC part of the specification, and a documented header file which defines the C API.

DSSI is Free Software. The DSSI header file is provided under the GNU Lesser General Public License.

Status

The DSSI API is currently at version 1.0. The API itself is now considered stable -- any further development will retain backward compatibility with previous versions. A host or plugin that implements the 1.0 API can expect to be compatible with other DSSI plugins or hosts well into the future.

The current DSSI distribution, version 1.1.0, contains the most recent release of the DSSI header file, documentation, reference host, and example plugins.

Currently available hosts (as of March 2012) which provide complete or nearly-complete DSSI support include:

• jack-dssi-host, which is a reference implementation included in the DSSI 1.1.0 distribution.
• The Rosegarden MIDI and audio sequencer.
• ghostess, a host with a simple GTK+ interface, based on jack-dssi-host.
• dssi~, a Pure Data external which hosts DSSI plugins.
• Aldrin, the tracker and modular synth inspired by Buzz. Full support for DSSI OSC/UIs requires Aldrin 0.13 and Armstrong 0.2.6.
• Qtractor, an audio/MIDI multi-track sequencer.
• The MusE sequencer added full DSSI support with version 1.0.
• Renoise, a tracker-based digital audio workstation, supports DSSI as of version 2.6.
• Carla, a host for multiple plugin standards, including DSSI, LADSPA, LV2 and VST. Carla is part of the KXStudio applications suite.

Hosts which provide partial or specialized DSSI support include:

• cli-dssi-host, a command-line tool for producing a single note from a DSSI plugin, and saving the resulting audio to a file. Does not include OSC or user interface support.
• simplehost, a minimal host for driving a single DSSI plugin via JACK MIDI. Does not include OSC or user interface support. The included DSSI C++ classes are intended to be reusable.
• GNU Classpath can host DSSI plugins with its Synthesizer class. Does not include OSC or user interface support.
• Jost, which can host DSSI, LADSPA, and linux-native VST plugins in a directed graph. Provides its own UI for controlling DSSI plugin parameters, but does not (as of version 0.5.5) support DSSI UIs.
• The DSSI-to-LV2 bridge in NASPRO provides partial DSSI support (as of version 0.4.0, no support for MIDI programs, UIs, or run_multiple_synths()).
• Csound5. Csound 5.12.1 contains some support for DSSI and LADSPA plugins.
• The Wired music production and creation system has some support for DSSI in its 0.7.0 release.

Currently available plugins include:

• FluidSynth-DSSI, a FluidSynth soundfont-playing plugin.
• Xsynth-DSSI, an analog-style (VCAs-VCF-VCO) synth plugin.
• dssi-vst, a wrapper plugin enabling the use of many Windows VST plugins.
• hexter, a Yamaha DX7 modeling plugin.
• ll-scope, a GTK+ oscilliscope plugin.
• Sineshaper, a waveshaping synth plugin.
• dssi_convolve, a DSSI wrapper around libconvolve, providing a friendly convolution plugin for reverb effects (among other uses).
• xy-controller-dssi, a GUI controller plugin which translates mouse input into X-Y control outputs, and xy-gravity, which includes gravity and damping simulations.
• WhySynth, a synth plugin featuring four oscillators per voice, multiple oscillator, filter, and envelope modes, effects, and more.
• nekobee, a synth plugin that emulates the sound of the TB-303 Bassline.
• nekostring is an emulation of a 70s-era string ensemble.
• The Calf audio plugin pack contains a monophonic analog-style synth and a versatile organ/pad synth.
• HOLAP contains both DSSI and standalone versions of horgand, an FM-based organ synth, and the Holharm smart harmonizer DSSI plugin. (There's also an intriguing start to another FM synth that uses FLTK for the GUI.)
• amSynth now includes a DSSI plugin in current git (it is not included in the 1.3.0 release.)
• ZynAddSubFX can be built as a DSSI plugin (with limited GUI support as of version 2.4.1).
• ls16 is a convenience DSSI plugin offering a limited front-end to the LinuxSampler library. It works better with certain hosts than others; see the ls16 website for details.
• The LibModSynth Plugin Suite currently includes Ray-V, an analog-style lead synthesizer, a sampler, and several effects plugins, including filters, delay, and distortion plugins.
• sfxr-dssi, a simple DSSI version of the sfxr sound effect generator.
• Three simple example plugins, and two simple-but-useful monotimbral sampler plugins, are included in the DSSI distribution.

The following development tools support DSSI:

• Faust is a functional programming language specifically designed for real-time signal processing. The Faust compiler can produce a variety of output formats, including DSSI plugins (without GUIs).
• FLAM (Front-ends for Linux Audio Modules) is a collection of tools for designing and running graphical control interfaces. Currently, it produces custom Qt DSSI GUIs for LADSPA plugins. (Note that only some hosts support loading DSSI UIs for LADSPA plugins; ghostess, MusE, and Rosegarden are among those that do.)
• LibModSynth, in addition to containing several DSSI plugins, aims to be a complete system for designing DSSI plugins. It includes tools for rapid plugin development, and a library of audio DSP modules.
• ocaml-dssi provides OCaml bindings for DSSI, allowing OCaml code to load DSSI plugins.

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