This is frei0r - a minimalistic plugin API for video effects.
The main emphasis is on simplicity - there are many different applications that use video effects, and they all have different requirements regarding their internal plugin API. And that's why frei0r does not try to be a one-in-all general video plugin API, but instead an API for the most common video effects: simple filters, sources and mixers that can be controlled by parameters.
It's our hope that this way these simple effects can be shared between many applications, avoiding their reimplementation by different projects.
On the other hand, this is not meant as a competing standard to more ambitious efforts that try to satisfy the needs of many different applications and more complex effects.
If you are new to frei0r, the best thing is probably to have a look at the frei0r header, which is quite simple.
After that, you might want to look at the frei0r functions in more detail.
When developing a new frei0r effect, you have to choose