AviSynth was designed to be a very very powerful tool for video post-production. It provides almost unlimited ways of editing and processing videos. AviSynth works as a frameserver, providing instant and very fast editing without the need for temporary files.
AviSynth itself does not provide a graphical user interface (GUI) but instead relies on a script system that allows advanced non-linear editing. While this may at first seem tedious and unintuitive, it is remarkably powerful and is a very good way to manage projects in a precise, consistent, and reproducible manner.
Because text-based scripts are human readable, projects are inherently self-documenting. The scripting language is simple yet powerful, and complex filters can be created from basic operations to develop a sophisticated palette of useful and unique effects.

What's New in This Release:
Additions:
· Added support for argument passing and EAX return value to SoftwireHelper.
· Added "Global OPT_VDubPlanarHack=True" to flip YV24 and YV16 chroma planes for old VDub's.
· Added ContinuedDenominator/ContinuedNumerator(f[]i[limit]i) script functions. [undocumented]
· Tweak: fix MaskPointResizing + put back Dividee ISSE code (use sse=true, can't use all settings in that case). [undocumented]
· Added ChromaPlacement and ChromaResample options to planar colour conversions.
· Added MaskHS.
· Minor tweaks to get ready for VC8.
· Add Y8 for DevIL, planarize EBMP.
· Planar support for many filters.
· Added Info() time indicator on audio length and video (current frame & total). (2.5.8)
· Added UtoY8 and VtoY8.
· Added more info to Info(). (2.5.8)
· ColorYUV: Added all adjustment parameters as conditional variables "coloryuv_SETTING". Enable by setting conditional=true. [undocumented]
· ConditionalReader: Added support for type String. [undocumented]
· ConditionalReader: Added offset keyword to offset all frame...