How to properly decimate frames to make the video shorter on Virtual Dub 2?

[pernicio]

Hi yet again!

In a nutshell, the problem is that I would like to decimate every other frame, to make my video half the length (from 20 minute video to 10 minute video), without lowering the FPS. I tried to use the Virtual Dub 2 internal "Decimate 2" setting, but the video was 20 minutes long after processing, almost as if it either did not decimate every other frame, or it created a copy of every other frame for every decimated one.

1. What Avisynth+ settings/plugins or internal VirtualDub2 tools could I use to cut the video length in half by decimating frames?
2. How to ensure that the resulting video remains 60 FPS after the decimate process? (Important for future purposes, if I need to cut and glue timelapse videos together with normal speed video)

Thank you

[jagabo]

In VirtualDub select Video -> Frame Rate. At the top select "Change frame rate to (fps): 120. Then in the middle select Process every other frame (decimate by 2). In general, change the frame rate to N times the source video's frame rate, and decimate by N. So to 240 and 4, for example.

An AviSynth:

N = 2 # or whatever decimation value you want
AssumeFPS(framerate*N)
ChangeFPS(framerate/N)

[pernicio]

Thank you jagabo! now it worked as it should