Creating a VSTi with GUI in Crystal: Setting up the Project

Welcome to this tutorial on how to write a Virtual Studio Technology instrument (VSTi) with a graphical user interface (GUI) using the Crystal programming language. VSTis are software plugins that can be used to add audio effects or synthesize sounds within a digital audio workstation (DAW). They are a popular choice among music producers and audio engineers, as they offer a high level of flexibility and customization.

In this tutorial, we will demonstrate how to write a VSTi with a GUI using Crystal, a statically-typed, compiled programming language that is similar to Ruby. We will be using the JUCE library, which is a cross-platform C++ framework for developing audio applications, to handle the low-level audio processing and GUI creation.

Here is an overview of the steps we will be following:

1. Install the necessary dependencies
2. Set up the project structure
3. Implement the audio processing code
4. Implement the GUI code
5. Compile the VSTi

Let’s get started!

1. Install the necessary dependencies

The first step is to install the necessary dependencies for developing a VSTi with Crystal and JUCE. You will need to install the following:

• Crystal: You can install Crystal by following the instructions on the Crystal website (https://crystal-lang.org/).
• JUCE: You can download and install JUCE by following the instructions on the JUCE website (https://juce.com/).
• A DAW: You will need a DAW to test your VSTi. Some popular options include Ableton Live, FL Studio, and Logic Pro.

2. Set up the project structure

Once you have installed the necessary dependencies, you can set up the project structure for your VSTi. The project structure will consist of the following files:

• shard.yml: This file will contain the project dependencies and build configuration.
• src/main.cr: This file will contain the main entry point for the VSTi.
• src/audio_processor.cr: This file will contain the audio processing code for the VSTi.
• src/gui.cr: This file will contain the GUI code for the VSTi.

Here is an example of the shard.yml file for our VSTi project:

name: vsti
version: 0.1.0

dependencies:
  juce:
    github: crystal-community/juce

build_targets:
  vsti:
    main: src/main.cr
    dependencies:
      - juce
    cflags: -I/path/to/JUCE/modules

Make sure to update the cflags to point to the correct path for your JUCE installation.

3. Implement the audio processing code

Next, we will implement the audio processing code for our VSTi. This code will be responsible for generating or processing the audio signals that will be passed to the DAW.

We will start by creating the AudioProcessor class in the src/audio_processor.cr file. This class will inherit from the juce::AudioProcessor class and will override the prepareToPlay, processBlock, and releaseResources methods to handle the audio processing.

Here is an example of how we might implement the AudioProcessor class:

require "juce"

class AudioProcessor < Juce::AudioProcessor
  def initialize
    super
  end

  def prepare_to_play(sample_rate, block_size)
    # Initialize audio processing here
  end

  def process_block(buffer, midi_messages)
    # Process audio here
  end

  def release_resources
    # Clean up audio processing resources here
  end
end

4. Implement the GUI code

Next, we will implement the GUI code for our VSTi. This code will be responsible for creating the user interface that allows the user to control the audio processing parameters.

We will start by creating the Gui class in the src/gui.cr file. This class will inherit from the juce::AudioProcessorEditor class and will override the resized method to handle the layout and placement of the GUI elements.

Here is an example of how we might implement the Gui class:

require "juce"

class Gui < Juce::AudioProcessorEditor
  def initialize(processor)
    super(processor)
    
    # Create and add GUI elements here
  end

  def resized
    # Set the bounds and layout for the GUI elements here
  end
end

5. Compile the VSTi

Finally, we can compile our VSTi by running the crystal build command with the --release flag. This will build the VSTi binary and output it to the bin directory.

crystal build --release src/main.cr -o bin/vsti.so

You can then load the VSTi into your DAW and test it out.

That’s it! You now have a working VSTi with a GUI written in Crystal. You can customize the audio processing and GUI code to create your own unique VSTi.