Developing

The best way to learn LV2 is by example. The documentation and example projects mentioned below are good starting points. If you're writing a plugin in C, copying one of the example plugins in LV2 as a template is recommended.

What not to do: If you are new to LV2, do not look at the specifications and API references first! These references provide detail, but not necessarily a clear high-level view. Start with the suggestions below, and check the references later when you need specifics.

Implementing Plugins

LV2 includes several well-documented example plugins which are simple demonstrations of various plugin types. If you prefer to read source code, they are in the plugins directory of the LV2 distribution.

There is also a "book" generated from the literate source code of these plugins (work in progress):

Programming LV2 Plugins

After writing a plugin, be sure to validate the data to check for typos and invalid constructs.

Implementing Hosts

LV2 hosts use a library to handle all the details of plugin discovery, investigation, and instantiation. Lilv is the standard library for hosts:

Lilv API Reference

Plans are currently underway to incorporate simple and thoroughly documented hosts into LV2, along the lines of the plugin examples. Until then, several external projects serve as useful examples:

lv2apply is a very simple program included with Lilv which applies an LV2 plugin to an audio file. Start here to learn the basics of loading an LV2 plugin.
Jalv is real-time Jack host which supports MIDI, embedded GUIs, presets, state saving, and other features.

Reference

Most LV2 specifications have two parts: code and data. The "specification" documentation comes from the data, and defines/documents the various concepts involved. Start there to better understand an extension's purpose.

The API reference is generated from Doxygen, and serves the usual purpose. Go there for documentation about a specific function, struct, or define.

Distribution and Packaging

Contributing to LV2

Both LV2 itself and this site are stored in git:

git clone https://gitlab.com/lv2/lv2.git
git clone https://gitlab.com/lv2/site.git

There are also mirrors at lv2plug.in and Github.

Contributions are most welcome. If you plan to implement something significant, it is a good idea to discuss it with the community on the mailing list to be sure you're headed in the right direction. Feel free to get creative, but note that all released LV2 APIs are permanently stable, so changes that break them can not be accepted.

A good entry point for beginners is writing new example plugins (using an existing example as a template) to demonstrate some functionality in the simplest possible way.

Happy hacking!

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