VapourSynth installation issue

[Axymeus]

I'm trying to migrate to VapourSynth but I'm getting a ton of errors setting it up. Python 3.10.9 is installed, VapourSynth as well. I managed to use vsrepo to install FFMS2, so far so good. I then start VapourSynth Editor and tried to load a mp4 video with FFMS2, "can't open" it says. Well fine, I now test the most basic script possible:

from vapoursynth import core
my_clip = core.std.BlankClip(width=1920, height=1080, length=1000, fpsnum=24, color=[255, 0, 0])
my_clip.set_output()

And hit the preview... nothing.

Failed to convert to RGB:
Resize error: Invalid format id.
Couldn't create preview node for output number 0.

What am I doing wrong?

[_Al_]

Looks like it is not vapoursynth error, why don't you give it specifically format=vs.RGB24, and if it works, then go into settings and look around, give it matrix settings (even if it is not needed in your case)
It's quite stupid advice, but I'd start with that.

[poisondeathray]

What version of vapoursynth, what version of vapoursynth editor ?

[Axymeus]

Thank you, but the error remains exactly the same with RGB24 as format. I've tried using FFMS2 with a mkv video, and I'm getting the same error (and MP4's still can't be read). I don't understand what is going on, I usually use AviSynth+ just fine too.

[Axymeus]

What version of vapoursynth, what version of vapoursynth editor ?

Everything was installed today so it's all up-to-date, that's VS R61 and VSEdit R19.

[poisondeathray]

vapoursynth API4 (r56 and newer) needs the vsedit mod version , is that the one you're using ?
https://github.com/YomikoR/VapourSynth-Editor/releases

[Axymeus]

Ah. Well, that's much better, thank you. I was following this guide http://www.vapoursynth.com/doc/installation.html#basic-program but this particularity wasn't mentionned.