Movit is the Modern Video Toolkit and aims to provide an open-source library with high-quality video filters running on the GPU.
The Movit library is providing basic video filtering with all work being offloaded to the graphics processor. Currently supported GPU-based video filters include scaling, blur, sharpening, overlaying, color grading, and more. Movit itself is just a video library but integration work is ongoing to support this GPU-based library using GLSL within Kdenlive.
Steinar H. Gunderson spoke last weekend at FOSDEM about the Modern Video Toolkit so if this interests you and missed out on the presentation, the PDF slides can be viewed here
and there's the Movit project site