I Just discovered this very interesting project (that’s “beside” Shotcut crossplatform video editor) that claims:
MLT is an open source multimedia framework, designed and developed for television broadcasting. It provides a toolkit for broadcasters, video editors, media players, transcoders, web streamers and many more types of applications. The functionality of the system is provided via an assortment of ready to use tools, XML authoring components, and an extensible plug-in based API.
On Features page they also claim:
Small, clean API with minimal dependencies (POSIX and C99)
I honestly don’t know if it’s possible to port it to Haiku - for some features, such as JACK audio routing or WebVfx for HTML5-based graphics/animation generation could be impossible - but, as always, I strongly believe that a collaboration may benefit both.
Hope that inspires.