Light alloy videoplayer + frame rate conversion scripts

Im used with potplayer to load avisynth/vapoursynth scripts. Also for MPV.
Light alloy is an old videoplayer that also implement avisynth... so you can use scripts. But I have a question if someone here is used to it (the forum of that video player is gone now).

In potplayer I use ffdShow_source() or potplayer_source() at the begining of the script to load the video that have to be processed.

Im not able to use ffdShow_source() in Light alloy.

Anyone know the trick to load the video that have to be used with the script? I cannot find clear documentation to do it.