Add strobbing(blank frames) to videos

[Selur]

There's no native option for this?

No.

but it's about half the speed as it should be.

Enable "Filtering->Speed Change->Speed Settings->Change speed" and set it to 60fps.

About using the custom-option:
If you don't know how Avisynth/Vapoursynth works and how their scripts syntax works using the custom option is probably a bad idea.
Do look at the Avisynth/Vapoursynth Script View to see what Hybrid does with the custom addition you entered.

Also changing:

• the frame count will mess with the progress indication, file size calculation, etc.
  
• changing the resolution will cause Hybrid to crash or create invalid outputs
  
• changing the frame rate will have no effect
  

Here's the vapoursynth script for reference:

import vapoursynth as vs

core = vs.get_core()
clip = core.std.AssumeFPS(video_in, fpsnum=24)
blank = core.std.BlankClip(clip)
clip = core.std.Interleave(clips = [blank, clip, blank, clip, blank, clip])

clip.set_output()

that script naturally crashes since "video_in" is unknown.

simply using:

blank = core.std.BlankClip(clip, length=clip.num_frames)
clip = core.std.Interleave(clips = [blank, clip])

with Vapoursynth
or

blank = core.std.BlankClip(clip)
clip = core.std.Interleave(clips = [blank, clip])

with Avisynth,
both create proper outputs here.

Cu Selur

Ps.: side note: if you use vfr video that isn't converted to cfr during the processing will produce asynchronous output.