using avisynth to convert 50fps to 25fps

[codemaster]

Source is 50 fps progressive (avi signpost). How do I convert it to 25 fps progressive in AviSynth, before serving the frames to x264.exe ?

AVISource("signpost.avi", audio=false).AssumeFPS(25,1)

I understand that AssumeFPS will alter playback speed. If source has 30 seconds, the result will have 60 seconds. But how do I drop all odd frames, or all even frames, with AviSynth ?

Is it better to set the Sony Vegas project at 25 fps ? Or to leave it at 50 fps in Vegas, and make it 25 fps in AviSynth ?

[poisondeathray]

SelectEven()

or

SelectOdd()

[jagabo]

or

SelectEvery(2,0)

or

ChangeFPS(25)

or

ConvertFPS(25)

or

Merge(SelectEven(),SelectOdd())

[codemaster]

Ok, I'll let the Vegas project at 50 fps, and add SelectEven() to AviSynth script.

SelectEven() and SelectOdd() seem to be the most appropriate functions for cutting framerate in half.