29.97fps Debate

[JodoKaast]

My friend and I are having an argument on something right now, and I believe that I am correct and he doesn't know what he's talking about.

He says he likes to leave movies at their original fps, like 29.97fps. I tell him that it's a retarded thing to do since it's 29.97fps because of a telecining process to just add extra frames to fit with NTSC standards.

He is addament about the fact that he has encoded all his movies at 29.97fps, but I tell him either he didn't do that or it's just a simple waste of space.

Would a movie even look right if you didn't do any IVTCing of any sort? He's been using xmpeg, and I'm afraid I don't know very much at all about the program, but I figure it must be doing the IVTC automatically for him or something...

So what's the verdict? Who's a (bigger) moron?

[brett]

Well, there ARE movies that are 29.97fps... just not many of them. Mostly just lower-budget straight to video movies and porn are 29.97fps. So, unless your friend is encoding a lot of NTSC porn, he's probably doing it the wrong way :)

I'm going to assume you're not talking about PAL DVD's, so I won't even get into that, but you seem to be correct about everything you've said. I've never used XviD, but I glanced at Doom9's XviD guide, and you still have to create a DVD2AVI project and us Forced Film mode to change it to 24FPS then use GKnot.

There is no legitimate excuse for leaving a regular 24fps film in 29.97fps when encoding DivX. The only way you could possibly justify it would be if you thought you were saving time, and that's not true. Using Forced Film doesn't take any time, and leaving the source as 29.97fps means you have more frames, and the codec has to work harder on each frame because it's interlaced, so your encoding will go much slower.

If your friend is legally blind and wants to rip DivX at 320x240, it doesn't make much difference, but at higher resolutions you need to do some sort of deinterlacing to rip 29.97fps, in which case your results will be much worse than 24fps. Even if you did want to rip in 320x240, the really fast way would be an Avisynth script that threw out the odd fields and then used Decimate, which would give you 24fps.

[manono]

Hi-

The movies were originally shown in the movie theater at 23.976fps. They were telecined to 29.97fps when mastered for DVD. If your friend has kept his at 29.97fps, then they either have the interlacing, and they are unwatchable, or he has just deinterlaced and they play with a stutter since the duplicate frames weren't removed. Not to mention the poorer quality resulting from the deinterlacing and trying to cram more frames into the same amount of space. Your friend's an idiot (or maybe just ignorant). He should come here and read some of the guides.

Hi brett-you beat me to it.:)

Edit Again-Movies are played at 24fps in a movie theater. It's after television rears its ugly head that IVTC brings it down to 23.976. Thanks for the heads up NeVeRLiFt (the Nicky Link).

[NeVeRLiFt]

These links should help your friend understand it, get your friend to go there and read up on it ;)

http://www.lukesvideo.com/telecining.html

http://www.divx-digest.com/articles/vhs_capture2.html

http://nickyguides.digital-digest.com/interlace.htm

[JodoKaast]

Sweet! Thanks for the info and the links!

[jggimi]

One more really good -- but awfully technical -- explanation of the standard 3:2 telecine process: www.doom9.org/synch.htm -- look under the 35mm Film to NTSC Video Conversion section.

The frames aren't exactly duplicated. The "extra" frames are blends of the frame ahead and behind, interlaced together. If you look at the raw 29.97 frames in frame-by-frame fashion in Gknot or Vdub, and you come to one of the "extra" frames at a scene change...you'll see it very clearly.