abaga129 / dplug-faust-example

Dplug Faust Example

This is an example plugin using Dplug with a Faust backend. It is a stereo reverb plugin using the Freeverb demo from the Faust library.

How to Build

Install the ldc2 D compiler.

Clone Dplug

git clone https://github.com/AuburnSounds/Dplug.git

Build dplug-build

# From Dplug repository
cd tools/dplug-build
dub --compiler ldc2

Add dplug-build to your path variable.

Clone this repo.

git clone https://github.com/ctrecordings/dplug-faust-example.git

Run dplug-build

dplug-build -c LV2 --compiler ldc2

You should now see the built LV2 plugin in builds/

You can copy this plugin to the folder on you PC that holds LV2 plugins.

If you are licensed to build VST2 or VST3 plug-ins you may also target those formats. See Dplug's documentation for more info on this.

How it Works

The faust DSP code is written in dsp/freeverb.dsp. Currently only one faust module can be supported in a single project.

In dub.json we specify a pre-build command to compile the faust code to Dplug format

"preBuildCommands": [
    "faust dsp/freeverb.dsp -lang dlang -a dplug.d -cn Freeverb -vec -o src/freeverb.d"
]

The faust architecture file for Dplug creates a complete gui-less Dplug plugin which has it's own entrypoints. We need to override these entrypoints so there is a version identifier provided to do this. In dub.json we add the faustoverride version.

"versions": ["futureMouseDrag", "faustoverride"],

Now we are able to import and inherit from the generated Dplug client.

final class ExampleClient : FaustClient

As well as define our own entry points

mixin(pluginEntryPoints!ExampleClient);

Linking params

When we specify our params enum, it is important that they are ordered to match what faust generates.

We can look at the buildUserInterface method of our generated freeverb.d to see the order.

Some code removed for conciseness.

	void buildUserInterface(UI* uiInterface) nothrow @nogc {
        ...
		uiInterface.addVerticalSlider("Damp", &fVslider0, cast(FAUSTFLOAT)0.5, cast(FAUSTFLOAT)0.0, cast(FAUSTFLOAT)1.0, cast(FAUSTFLOAT)0.025);
        ...
		uiInterface.addVerticalSlider("RoomSize", &fVslider2, cast(FAUSTFLOAT)0.5, cast(FAUSTFLOAT)0.0, cast(FAUSTFLOAT)1.0, cast(FAUSTFLOAT)0.025);
        ...
		uiInterface.addVerticalSlider("Stereo Spread", &fVslider3, cast(FAUSTFLOAT)0.5, cast(FAUSTFLOAT)0.0, cast(FAUSTFLOAT)1.0, cast(FAUSTFLOAT)0.01);
        ...
		uiInterface.addVerticalSlider("Wet", &fVslider1, cast(FAUSTFLOAT)0.3333, cast(FAUSTFLOAT)0.0, cast(FAUSTFLOAT)1.0, cast(FAUSTFLOAT)0.025);
        ...
	}

Alternatively we can add metadata to our controls by naming them like [paramIndex] Control Name. For example: [3] Wet. Although this example does not leverage this since it's using the freeverb demo.

So to match this we need to specify our params enum as follows:

enum : int
{
    paramDamp,
    paramRoomSize,
    paramStereoSpread,
    paramWet
}

The last step is to override processAudio so we can update our UI if needed.

override void processAudio(const(float*)[] inputs, float*[]outputs, int frames, TimeInfo info)
{
    assert(frames <= 512);
    super.processAudio(inputs, outputs, frames, info);

    if (ExampleGUI gui = cast(ExampleGUI) graphicsAcquire())
    {
        // update gui here.
        graphicsRelease();
    }
}