Capture midi messages in Processing during playback

The 2nd midi in Processing example will use the Receiver interface to capture all the midi messages during the playback of a midi file. The program uses the custom GetMidi class to implement the Receiver interface. During the playback, it will display the NOTE_ON message with information of channel, octave and note.

The source code of the example is also in the Magicandlove GitHub repository.

Sample Processing screen during midi playback

Using midi in Processing for playback

This is my first use of midi in Processing. I do not use the MidiBus library for Processing. Instead, I try to use the standard midi package in Java. The SE8 standard Java package also contains the javadoc documentation.

Screenshot of the Processing sketch

The Processing source code and sample midi files are in the Magicandlove GitHub repository. The midi example files are downloaded from the midiworld website.

The code basically needs a Synthesizer class to render midi instruments into audio and a Sequencer class to playback the midi sequence.

Synthesizer synth = MidiSystem.getSynthesizer();
Sequencer player = MidiSystem.getSequencer();
synth.open();
player.open();

All the midi music files are in the data folder of the Processing sketch. To playback each piece of midi music, we need to convert each into a Java File object and use the following code to playback it. The variable f is a File object instance containing the midi file in the data folder.

Sequence music = MidiSystem.getSequence(f);
player.setSequence(music);
player.start();

First try of P5 and OpenCV JS in Electron

This is my first try of the p5.js together with the official release of OpenCV JavaScript. I decided not to use any browsers and experimented with the integration in the Electron environment with Node.js. The first experiment is a simple image processing application using Canny edge detector. The IDE I choose to work on is the free Visual Studio Code and which is also available in multiple OS platforms. I have tested both in Windows 10 and Mac OSX Mojave. In Mac OSX, I first install the Node.js with Homebrew.

brew update
brew install node

Then I install the Electron as a global package with npm.

npm install -g electron

For the Visual Studio Code, I also include the JavaScript support and the ESLint plugin. The next step is to download the p5.js and p5.dom.js code from the p5.js website to your local folder. I put them into a libs folder outside of my application folders. For OpenCV, it actually includes the pre-built opencv.js from its documentation repository. The version I used here is 3.4.3. The only documentation I can find for OpenCV JS is this tutorial.

For each of the Node.js application, you can initialise it with the following command in its folder. Alternately, you can also do it within the Terminal window from Visual Studio Code. Fill in the details when prompted.

npm init

In Visual Studio Code, you have to add a configuration to use the electron command to run the main program, main.js, rather than using the default node command. After adding the configuration, it will generate the launch.json file like the following,

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "type": "node",
            "request": "launch",
            "name": "Electron Main",
            "runtimeExecutable": "electron",
            "program": "${workspaceFolder}/main.js",
            "protocol": "inspector"
        }
    ]
}

For the programming part, I used a main.js to define the Electron window and its related functions. The window will load the index.html page. It is the main webpage for the application. It will then call the sketch.js to perform the p5.js and OpenCV core functions. The p5.js and OpenCV communicate through the use of the canvas object. The GUI functions, imread() and imshow() are used for such communication. This example will switch on the default webcam to capture the live video and perform a blur and Canny edge detection.

Source code is now available at my GitHub repository.