#Mephisto

#a Just-in-Time FAUST compiler embedded in an LV2 plugin

Write LV2 audio/cv instruments/filters directly in your host in FAUST DSP language without any need to restart/reload host or plugin upon code changes.

Use it for one-off instruments/filters, prototyping, experimenting or glueing stuff together.

Note: This will need a fairly recent libFAUST and/or bleeding edge GNU/Linux distribution.

Note: libFAUST 2.20.2 has a broken LLVM C-API and thus will be non-functional with this plugin.

#Packages

• ArchLinux

#Plugins

#Audio 1x1

1x1 Audio version of the plugin.

Prototype new audio filters and instruments in FAUST directly in your favorite running host, without the need to restart the latter after code changes.

#Audio 2x2

2x2 Audio version of the plugin.

Prototype new audio filters and instruments in FAUST directly in your favorite running host, without the need to restart the latter after code changes.

#Audio 4x4

4x4 Audio version of the plugin.

Prototype new audio filters and instruments in FAUST directly in your favorite running host, without the need to restart the latter after code changes.

#Audio 8x8

8x8 Audio version of the plugin.

Prototype new audio filters and instruments in FAUST directly in your favorite running host, without the need to restart the latter after code changes.

#CV 1x1

1x1 CV version of the plugin.

Prototype new CV filters and instruments in FAUST directly in your favorite running host, without the need to restart the latter after code changes.

#CV 2x2

2x2 CV version of the plugin.

Prototype new CV filters and instruments in FAUST directly in your favorite running host, without the need to restart the latter after code changes.

#CV 4x4

4x4 CV version of the plugin.

Prototype new CV filters and instruments in FAUST directly in your favorite running host, without the need to restart the latter after code changes.

#CV 8x8

8x8 CV version of the plugin.

Prototype new CV filters and instruments in FAUST directly in your favorite running host, without the need to restart the latter after code changes.

#Combo 44x44

4x4 Audio + 4x4 CV version of the plugin.

Prototype new CV filters and instruments in FAUST directly in your favorite running host, without the need to restart the latter after code changes.

#Dependencies

• LV2 (LV2 Plugin Standard)
• FAUST (Faust Programming Language >=2.14.4)
• OpenGl (OpenGl)
• GLEW (GLEW)
• VTERM (Virtual terminal emulator)

#Build / install

git clone https://git.open-music-kontrollers.ch/~hp/mephisto.lv2
cd mephisto.lv2
meson build
cd build
ninja -j4
ninja test
sudo ninja install

#UI

This plugin features a native LV2 plugin UI which embeds a terminal emulator which can run your favorite terminal editor to edit the plugin's FAUST source.

Currently, the editor has to be defined via the environment variable EDITOR:

export EDITOR='vim'
export EDITOR='emacs'

If no environment variable is defined, the default fallback editor is 'vi', as it must be part of every POSIX system.

Whenever you save the FAUST source, the plugin will try to just-in-time compile and inject it. Potential warnings and errors are reported in the plugin host's log and the UI itself.

On hi-DPI displays, the UI scales automatically if you have set the correct DPI in your ~/.Xresources.

Xft.dpi: 200

If not, you can manually set your DPI via environmental variable D2TK_SCALE:

export D2TK_SCALE=200

#Controls

The plugin supports up to 16 controls implemented as LV2 Parameters. To have access to them, simply use one of FAUST's active control structures with ordering indeces (monitonically rising starting from 0) in their labels in your DSP code:

cntrl1 = hslider("[0]Control 0", 500.0, 10.0, 1000.0, 1.0);
cntrl2 = hslider("[1]Control 1", 5.0, 1.0, 10.0, 1.0);
cntrl3 = hslider("[2]Control 2", 0.5, 0.0, 1.0, 0.1);

Read-only controls are also supported and will be shown as waveforms in the UI:

_ : hbargraph("[3]Probe 3", 0, 1);

#MIDI and polyphony

The plugin supports building instruments with MIDI polyphony. For this to work you have to enable the MIDI option and declare amount of polyphony (maximum polyphony is 64).

The plugin automatically derives the 4 control signals:

• gate (NoteOn vs NoteOff 0|1)
• freq (NoteOn-note + PitchBend), honouring PitchBend range RPN 0/0
• key (NoteOn vs NoteOff raw fractional value, honouring PitchBend range RPN 0/0)
• gain (NoteOn-velocity 0-1)
• vel|velocity (NoteOn-velocity raw value)
• pressure (NotePressure aka polyphonic aftertouch)

Additionally, the following MIDI ControlChanges are supported:

• SustainPedal
• AllNotesOff
• AllSoundsOff

Other MIDI events are not supported as of today and thus should be automated via the plugin host to one of the 16 control slots.

declare options("[midi:on][nvoices:16]");

freq = hslider("freq", 0, 0, 1, 0.1);
gain = hslider("gain", 0, 0, 1, 0.1);
gate = button("gate");
pressure = button("gate");
pressure = hslider("pressure", 0.0, 0.0, 1.0, 0.1);

cntrl1 = hslider("[0]Control 0", 500.0, 10.0, 1000.0, 1.0);
cntrl2 = hslider("[1]Control 1", 5.0, 1.0, 10.0, 1.0);
cntrl3 = hslider("[2]Control 2", 0.5, 0.0, 1.0, 0.1);

#OSC

OSC events are not supported as of today and thus should be automated via the plugin host to one of the 16 control slots.

#Time

The plugin supports LV2 time position events. To have access to them, simply use one of FAUST's active control structures with the corresponding time metadata in their labels in your DPS code and additionally enable the time option:

declare options("[time:on]");

barBeat = hslider("barBeat[time:barBeat]", 0.0, 0.0, 32.0, 1.0);
bar = hslider("bar[time:bar]", 0.0, 0.0, 400.0, 1.0);
beatUnit = hslider("beatUnit[time:beatUnit]", 1.0, 1.0, 32.0, 1.0);
beatsPerBar = hslider("beatsPerBar[time:beatsPerBar]", 1.0, 1.0, 32.0, 1.0);
beatsPerMinute = hslider("beatsPerMinute[time:beatsPerMinute]", 1.0, 1.0, 400.0, 1.0);
frame = hslider("frame[time:frame]", 1.0, 1.0, 400.0, 1.0);
framesPerSecond = hslider("framesPerSecond[time:framesPerSecond]", 1.0, 1.0, 96000.0, 1.0);
speed = button("speed[time:speed]");

#Issues/Patches

Please report issues to https://todo.open-music-kontrollers.ch/~hp/issues

Please submit patches to https://lists.open-music-kontrollers.ch/~hp/patches