Some background...
AviSynth is a powerful, open-source, script-driven video editor that provides real-time, on-the-fly, frame-by-frame encoding and playback through certain players.
A script is generated with a text editor, and that script can be opened/run by other video tools such as editors or encoders like Avanti or FFmpeg, or players such as FFplay, Media Player Classic, or even Windows Media Player. I've seen mentioned on various sites that MPlayer will 'play' AVS files. Those programs feed the script to AviSynth (must be 'installed' on the machine) which then applies the script functions frame-by-frame to the video, and feeds it back, frame-by-frame, to the calling program.
AviSynth is better explained here...
http://avisynth.nl/index.php/Main_Pagehttps://en.wikipedia.org/wiki/AviSynthAvilable here...
http://sourceforge.net/projects/avisynt ... nth%202.5/Example 3-line script (save as script.avs). Simply drop the script on FFplay.exe ...
ColorBars(width=320, height=240, pixel_type="YV12")
Trim(0,200)
FadeOut(200, color=$b4b4b4, fps=24)
This script creates a small colorbar video that slowly fades out. Of course, any of the numerous AviSynth functions can be applied to an existing video to be played back, such as...
AVISource("inputvideo.avi")
Grayscale
FlipVertical()
This script would play back inputvideo.avi, converting it to grayscale and flipping it upside down as it does.
I hope this makes sense. I'm not sure what the required parameters are, or if SMPlayer simply passed the script to MPlayer if it would play.