Pyle wrote:
How do you activate the .dll file that Avisynth comes in?
You install it, and the installer registers AVISynth as a media handler for *.avs files.
As a simple example, think of AVISynth scripts as programs, AVISynth as an interpreter, and VirtualDub(Mod) as a front-end. You load the script via the front-end; the front-end passes the script to the interpreter. The interpreter executes the script and passes the results back to its caller, i.e. VirtualDubMod, which gives the results back to you.
Or, even easier, you can think of AVISynth as a programmable codec: you feed it scripts, it decodes those scripts and gives you video data back. It's not quite technically correct, but from the perspective of manifested behavior, it works.