mep

Introduction

mep is a scriptable midi event processor.

It uses koto scripts to process incoming midi events.

I/O

Every instance of mep introduces a new virtual midi-in and a virtual midi-out port for the incoming messages to be processed and the processed messages to be sent out.

The default naming for these virtual ports are mep_in and mep_out.

If multiple instances of mep are running, every additional instance's virtual ports are suffixed with an increasing number such as mep_in #2,mep_out #2,mep_in #3,mep_out #3 and so on..

One can name an instance's port by using the --port <port name> option when running mep.

For example, mep --port wakkanai would create wakkanai_in and wakkanai_out virtual ports.

Scripts

mep would check for .mep folder in your home directory and shows you an enumerated list of all files (scripts) in the folder with the extension of .koto.

If no .mep folder is found on startup, it will create one and fill it with bunch of example scripts.

If .mep folder exists but empty, mep will notify you about this, ask you to add some scripts and exit.

As soon as you select a script from the enumerated list by entering the index number and pressing enter, the virtual ports will be created and the event processing will begin.

Editing

When an instance of mep is running. .mep folder is being watched for changes. Editing your scripts will be reflected immediately.

Look for info in the koto main repository to see if there is syntax highlighting available for your editor.

Some answers to possible questions

• What are koto scripts?

  Koto is a simple, expressive, embeddable programming language, made with Rust.

  Please visit the main repository for more information.

• How to process midi with koto?

  I've written a midi library (toolkit) for koto. Koto scripts which are run by mep have access to this library.

  In the example scripts you will notice import midi statement in the begining.

• Are there any examples?

  Please check the example_scripts in the repository to see some working examples.

• How may I see what is available in koto_midi library to use?

  Currently if you visit the repository and follow the instructions to run tests, a complete API will be printed to stdout. You can take this as a reference. For sure in the future a more ergonomic way will be introduced.

• How may I debug my scripts?

  Errors in your scripts would navigate you to a new screen and show you the koto error. mep will let you know which script caused the error and wait for changes.

  After you fixed your erroring script in ~/.mep folder, it will move to the screen where you can choose your scripts again.

  Please check todo section for some exceptions to this behavior.

Building

Building mep is as simple as running cargo build or cargo build --release if you have rust in your system installed.

mep uses the nightly channel or rust.

Running

To run mep after building you may run cargo run if you have rust in your system installed. You may add command line options by running cargo run -- <your-command-line-options>. To see the list of available command line options you may run cargo run -- --help.

Alternatively if you run cargo build and then navigate to <repository-root>/target/debug you may find the mep binary and run it or if you run cargo build --release then the binary will be in <repository-root>/target/release.

Extra

mep also exposes random library from koto. You may visit koto main repository to understand how to use it.

You may bring it in scope by writing import random in koto scripts.

Last words

Currently mep is in early development stage and not stable. A release will be made when required stability is achieved.

Todo

• Do not panic in runtime_error! macros. Fall back to watcher and notify user to fix the script.
• Improve code quality.
• Add tests where possible.