According to its website and author,
VapourSynth is an application for video manipulation... written in C++ and a Python module to
allow video scripts to be created. Inspired hardly by AviSynth, it has more features and
advantages than its predecessor, like multithreading, less memory leaks, more colorspaces, variable
frame rate, etc.
VapourSynth can be extended via plugins and scripts. And there are a lot of them.
Do you want to know more about VapourSynth and how to use it? If you're an AviSynth freak, please visit my blog (in Spanish), where I can help you to migrate to VapourSynth without lots of effort. Also you can visit the VapourSynth's Documentation, it's very generous and detailed.
L-SMASH-Works is a video provider for AviSynth and VapourSynth. It can open every format supported by FFmpeg (or the compiler).
Unfortunately, the author doesn't provide an official DLL for Windows, only the source code.
These are my first trying to compile useful DLLs which can be loaded into the "core" and "core64" VapourSynth directories. These DLLs were compiled against most recent FFmpeg and L-SMASH git versions (October 2018).Get L-SMASH-Works for VapourSynth for Windows (x86/x64)