[Doom9]

@Rash: Alright, I finally managed to properly play an AviSynth script on my work PC. Rendering the script in Graphedit yields the following Graph, which I believe to be the standard (it rings a bell seeing it.. unlike the Moonlight one, this one looks very familiar).

AviSynth Video -> AVI Decompressor -> Color Space Converter -> Video Renderer. Both filters in the middle are standard Windows filters, filename is quartz.dll. I guess they'll also do the decoding in MeGUI.

I also tried setting ffdshow to not decode AviSynth (no change), then enable support for all supported raw output (no change), changing it to decode raw YV12 (now I have the same graph as you have), but in all cases MeGUI still opened the video.