AviSynth is available free from its homepage at http://www.avisynth.org/, where you can also find the full documentation and additional filters!
To set up AviSynth:
.exe(executable) extension. That will redirect you to a list of mirrors from which you can select one near you. Be careful not to download an alpha version as those are only available for testing purposes and are likely to be unstable.
Before we serve frames with AviSynth, we need to familiarize ourselves with the scripting ...