This is (most directly) in reference to a "problem" slomo clip that Jim Simon was dealing with when doing 60i->24p conversions. This workflow and the required tools are nearly identical, so please read
this thread if you have no idea what I'm talking about here. Also go
here if you have don't know what AviSynth is or how it works.
I'm posting a solution I created for creating speed-adjusted 50i or 60i clips for normal SD editing. I figured others could benefit from this also, independent of doing NTSC Film conversions.
I was never quite satisfied with the quality of slow motion or speeded up motion in PPro or AfterEffects. I'm unable to really control the frame blending (well, I can in After Effects but it is real pain.)
The other route to go is with "Pixel Motion" instead of frame blending. I'll admit, it does get nice results (sometimes) but it is extremely slow.
The time effects in these programs fail horribly on interlaced material for the simple fact that neither has a capable built-in deinterlacer. I also remember reading a complaint from a user on this forum about the way Premiere interlaces the output in "timelapse" sequences.
In any case, one should be able to do a "near-perfect" 50% speed progressive output from an interlaced clip. This can't be done with Premiere alone, for want of said HQ deinterlacer.
I have written a function for AviSynth specifically for the purpose of making speed alterations to interlaced clips. It has both "traditional" blending and motion-compensated modes -- and can combine both.
With my function, you can get interlaced from progressive and vice-versa. There is a choice of several deinterlacing engines, varying in quality vs. speed. It works identically with both PAL and NTSC sources and always renders to the same format/framerate of the source, but with more or less frames.
1.) Requires AviSynth 2.5.7.
2.) The contents of the .zip go in the AviSynth plugins folder.
3.) Script examples are included in the timelapse.txt file.
4.) You can open your script with Virtual Dub and save as an .AVI or use the Premiere AviSynth Import filter.