I need to build a ntsc dvd from a 25p movie. I've read about different solutions:
What is the most professional way without loosing any information?
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The least-lossy way should be to just stretch time, so your 25p becomes 24000/1001p. Then your video can go on a NTSC dvd with soft-telecining. The audio needs to be stretched to match, using a pitch-preserving method. (Soft TC means stored as progressive frames on the disc, with flags set to tell the player to apply a 3:2 pulldown if it needs to make 60i output (instead of 24p or 60p digital output)).
This is what British TV shows and movies typically do for their North American DVD releases. It changes the run-time of the show by 1.04%, which is annoying.
This soft-telecining (25p->24p) is what is described on that forum link you found about twixtor.
The alternative is to butcher your video frames into interlaced fields that are going to have to get put back together again into progressive frames if they're not going to look horrible on a non-CRT display. (This is the 25p->60i pulldown that Shin mentions. IDK the details either. And I wouldn't think it would ACTUALLY make motion look any smoother, because there's no motion-interpolation going on. You still only have a temporal resolution of 25p, which is what you'll get from a deinterlacer / pullup filter that can figure out how to reverse a hard 25p->60i pulldown.)
I think I remember reading that concert-recording DVDs (and other stuff where stretching the timescale is worse than bad video) might do something other than the usual 25p->24p. (like 25p->60i pulldown).
If you're making a Blu-Ray, it's worth researching if you can just put 25p content on a disc have have it play ok with North American equipment. Instead of dropping a frame every second on playback, you'd probably just get one frame shown for a different length of time than others. (Because the video output can be 60p, not 24p, even if the data on disc is 24 or 25p.)
I'm also not sure about DVDs, like what a North American dvd player would do with a 720x480p25 disc. (And it might be different for different players, and maybe only good for HDMI out, but bad for analog NTSC output).
Basically, I'm really hoping it's possible for the world to stop stretching / squishing video when sending it across the Atlantic. I know UK blu-ray releases of North American stuff are usually still 25p, though.
Anyway, whatever you decide to do, just be aware that one of these things is probably what actually happened. Have a look at the NTSC version you produce, with an eye for any problems that could have caused.
I personally would use media encoder and let it do the conversion. Convert it to a mpeg2-dvd format and pick a preset, you can adjust the preset to your liking. ME would do most of the heavy lifting. At this point I trust them to do the best job.
I find that nothing beats actually trying it though, you're not really out anything but time. And very little time at that. It's not like your encoding each frame by hand. :)