AVISynth- "Stack" Frame Rates

[Alwyn]

I want to stack two videos to show the difference between 18fps and 50fps. The problem is that both videos must be the same frame rate, so I'm trying to make the 18fps video be 50fps. I can create this in my NLE: it just inserts duplicate frames to make up the frame rate to 50, but I'd like to do it with AVISynth or VDub.

As I see it, I can't use AssumeFPS (it speeds up the video) or FrameRateConverter/RIFE because they interpolate and create new unique frames, which I don't want.

I can't make VDub Video>Frame Rate achieve this.

I've attached an 18fps file.

How can I achieve this with AVISynth?

[Alwyn]

Search and ye shall find! D'oh, ChangeFPS(50) will do it.

[jagabo]

ChangeFPS() duplicates frames to increase the frame rate. ConvertFPS() adds blended frames -- though I don't think it will directly convert 18 to 50 fps. You might be able to call it twice using an intermediate frame rate.

[Alwyn]

Thanks Jagabo, I think "changefps" is what I want: insert duplicate frames to simulate the original fps of 18 so that I can put it into "stack" to match the RIFE 50 fps file. I did try "convertfps" but as you say, it blended in new frames so didn't achieve the comparison effect I was looking for.

My post above edited.