Why do we have to convert 25 fps to 23.97 fps ?

This forum is for questions and discussion of all the aspects of handling your footage. If you have questions about capturing/ripping footage, AviSynth, or compression/encoding/converting, look here.

Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby mirkosp » Mon Sep 13, 2010 1:59 pm

This is how I know things, so chances are I am wrong to very wrong, but throwing it out there, worst case there'll be laughs and corrections. So well, from my understanding...
The main animator does the keyframes of the animation, and might also fully animate the most important sequences. Then inbetweeners draw some extra frames to make the animation smoother for the scenes of which the animator only did the main keyframes. At this point you don't have a real "animation" yet, since the drawings are on their own, and they are put together and animated at the PC. Once there, generally you get the actual animation done at 7~13fps, with some of the most important scenes that might actually be animated at 23.976 (these things are depending on the budget too). And since this all is put together in NLEs/post-processing software with a 23.976 timeline (or potentially something else, read on), the pans/zooms and other computer-aided effects and animations go at 23.976, whereas the drawings have a lower framerate. That should be how it's done. Then again, depending on the series, you might be getting a VFR thing which has parts going at 23.976, others at 29.97, others at 59.94 (as in, fully interlaced with each field unique), etc... there are many kinds of footage. Luckily these days finding 23.976 progressive on BDs (or 29.97 telecines, on DVDs) seems to be the most common situation, but there still are a few exceptions... which tend to be the hardest and most annoying ones to deal with, especially if there happen to be things going at different speeds in the same sequence (eg: the animation was 23.976, telecined to 29.97, and it has full field interlaced credits rolling at 59.94 on top).
Hopefully I mostly got it right, so now to wait for Hatt to correct the rest...
Image
User avatar
mirkosp
MODkip
 
Joined: 24 Apr 2006
Location: Gallarate (VA), Italy
Status: (」・ワ・)」(⊃・ワ・)⊃

Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby post-it » Mon Sep 13, 2010 2:03 pm

Mister Hatt wrote:
post-it wrote:.. converting files and wondered .. !
120fps is a hack used for faking VFRaC ..

Thx 8-)
This is perfect;
.. one very long thought .. sorry for the lengthy scope:
This is right at the heart of a question I had for almost five years.

My Overview (background of logic/understanding) of this problem:
. I grasp the concept of Variable-Length Video Frames and how that
would make video-files smaller in size while keeping the Video-Audio-Sync
alignment look/seem natural-looking. ( the ART of Illusion -- as it is sometimes referred to. )

My question:
. Is there a computer program and/or piece of video editing equipment currently made/created
which can separate the video frames and fields one-by-one without duplicating any fields and/or frames?


reason for question being asked:
. I'm looking for a program which will give me things frame-by-frame
without any-duplicates -- reguardless if the Audio matches or not!
(( a frame-by-frame sequencer to which video fields are NOT the editing factor. ))

? what would this solve ?
. if I were going to piece things together and Freeze-Frame something, it should be
the Editors choice as to how-long "that frame" remains on the screen - not the choice
of the original encoding programmer.

. What I'm looking for is something "which can bring things back to its origins",
back to the created scene's. Is there a program out-there which will do such a
thing
as I am describing?

-- just curious 8-)
User avatar
post-it
 
Joined: 17 Jul 2002
Status: Audio: bass remains; if else, 3D

Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby mirkosp » Mon Sep 13, 2010 2:08 pm

Avisynth can do that just fine, actually.
Image
User avatar
mirkosp
MODkip
 
Joined: 24 Apr 2006
Location: Gallarate (VA), Italy
Status: (」・ワ・)」(⊃・ワ・)⊃

Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby post-it » Mon Sep 13, 2010 2:22 pm

mirkosp wrote:Avisynth can do that just fine, actually.

0_0 .... ^_________^ .... please show
me this magical, totally "really-needed"
script which alludes me to "no-end!"

Student Ready, Willing, and clueless in scripting :up:

:book: If you would be soo kind, mirkosp-sama
User avatar
post-it
 
Joined: 17 Jul 2002
Status: Audio: bass remains; if else, 3D

Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Kazend » Mon Sep 13, 2010 2:34 pm

Hi there,

http://i25.servimg.com/u/f25/11/05/55/21/bd_pal10.jpg

[MOD258: Image converted to link due to excessive height.]
User avatar
Kazend
 
Joined: 17 Mar 2007
Location: France - Picardie

Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby mirkosp » Mon Sep 13, 2010 2:39 pm

Well, deleteframe and duplicateframe are probably the things you're looking for if I'm understanding correctly what you asked. If you want to keep the audio sync then you'd be using freezeframe instead. But generally, all the internal filters for timeline editing will be useful depending on what you're trying to do exactly. As for the separating fields without duplicating them, I assume you're referring to something like separatefields? Although perhaps you're referring to bob. OTOH, if what you wanted to do was making a VFR encode, then just have a read here ─ dealing with vfr isn't hard if you don't have to splice clips together in a NLE.
Image
User avatar
mirkosp
MODkip
 
Joined: 24 Apr 2006
Location: Gallarate (VA), Italy
Status: (」・ワ・)」(⊃・ワ・)⊃

Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby post-it » Mon Sep 13, 2010 3:12 pm

beginning reading ... I'm not worried about the Audio Portion, I can encode that later.
What I need is something which can ignore which video field it is ( as long as the heart of the scene is not being duplicated. )

That is what I'm looking for is a frame-by-frame sequencer that will not "keep" any duplicate images.
( all of the frame "displaying-length's" should all be the same. [[ this is usually a control within the Codec itself. ]] )
Image
That's what I'm looking for. ( in theory, sound simple enough. ) 8-)
User avatar
post-it
 
Joined: 17 Jul 2002
Status: Audio: bass remains; if else, 3D

Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby mirkosp » Mon Sep 13, 2010 3:20 pm

Then you probably want to look into the 2pass vfr with tivtc... just don't use the timecodes file it'll create. I think that should give you the result you're looking for.
Image
User avatar
mirkosp
MODkip
 
Joined: 24 Apr 2006
Location: Gallarate (VA), Italy
Status: (」・ワ・)」(⊃・ワ・)⊃

Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby post-it » Mon Sep 13, 2010 4:48 pm

hmmm . . something seems to be missing .. maybe it hasn't been made yet.
Actually, I'm looking for a filter which will EraseDuplicateFrame(s) and leave the
original single frame relating to a sequence of events along a non-sync-time-line
leaving "only" the sequence of events.
( sorta like a Frame Comparer that deletes Duplicate Frame regardless of the Audio sync.
( The Audio is not part of the equation in my line of work. ))

. An example would be ..
1) you have video coverage of an accident.
2) you need the sequence of events.
. . what you do not need are frame repeats; I waist waaay to much time trimming those frames from the "events"

Its hard enough to write an Actuarial Profile of a scene and then have to correct things frame-by-frame "not only
adjusting for jitter" but actually noticing "if that frame is a duplicate to the one before it" within those
corrections! I guess what I'm looking for is a Scene-Detection-that-Compares-Frames-and-Deletes-Repeats filter.

.. T_T .. does that description make any sense in English?
( I know it sound correct when I say it and someone repeats it back to me. )
.. Does this kind of filter even sound plausible?
User avatar
post-it
 
Joined: 17 Jul 2002
Status: Audio: bass remains; if else, 3D

Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby mirkosp » Mon Sep 13, 2010 5:14 pm

Yes, I know what you mean. You can't do this thing directly (or rather, I don't know how, if there is a way), hence why you'd be doing a 2pass like if you were to do a VFR encode. Making a VFR encode will effectively delete the duplicate frames, it'll just remember in a timecode file for how long they are to be shown, but if you ignore the timecode file, you can just get the output you want.
Image
User avatar
mirkosp
MODkip
 
Joined: 24 Apr 2006
Location: Gallarate (VA), Italy
Status: (」・ワ・)」(⊃・ワ・)⊃

Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Mister Hatt » Mon Sep 13, 2010 9:48 pm

Sn0wcrash wrote:But as you said before, you get a lot of stuff shot at 23.97 fps. Are you talking about anime ?
Usually, an animator has to create whole frames manually (for traditionnal animation). So how can you get a original material video at 23.97 fps (for anime) ?
Apparently old animes was animated at 12 fps (and after the frames were doubled to get a 24 fps rate).
But now do they their work at 24 fps or what ?
This might come as a shock but you're making the incorrect assumption that a scene is animated by the second. 23.976fps might be a fractional rate by the second but for a standard you will find that it's usually about 35,000 frames. Animators work by the number of frames, not the rate they are played at. If they believe that a scene needs to be smoother, they will give it more frames and a higher rate. Nobody animates saying "I want it to be this rate" though; it's just that for a decent motion range they know how many frames to throw over a period of time so that you end up with 23.976fps as a baseline. I hope this clears it up a bit.

As far as frameserving without nulls, avisource("your-video-with-null-frames.avi") will do it. If however your encoder sucked and encoded non-nulls by actually duplicating the frames and hard encoding, then getting it back to normal is considerably harder and I can't think of an easy way to do it consistently well. So if you need 120fps, do it properly in the first place; Tritical wrote a cool toy for doing it, part of avi_tc_package IIRC.
Mister Hatt
 
Joined: 25 Dec 2007
Status: better than you

Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Snowcrash » Tue Sep 14, 2010 2:18 am

Mister Hatt wrote:Nobody animates saying "I want it to be this rate" though; it's just that for a decent motion range they know how many frames to throw over a period of time so that you end up with 23.976fps as a baseline. I hope this clears it up a bit.

Thanks a lot. It's effectivelly more clear for me ;)
So the animators do their frames and after they end up at the target framerate on the baseline.
But isn't it easier to end up at 29.97 fps (or 25 fps) instead 23.97 to get directly the right framerate for NTSC (or PAL) standard (depending if the anime is done in NTSC or PAL country) ?

And Kazend :

:rofl:
PAL will win ! XD
Image
User avatar
Snowcrash
 
Joined: 19 Jun 2008
Location: France
Status: Looking for a job T_T

Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby post-it » Tue Sep 14, 2010 5:11 pm

mirkosp wrote:.. Making a VFR encode will effectively delete the duplicate frames, it'll just remember in a timecode file for how long they are to be shown, but if you ignore the timecode file, you can just get the output you want.
^_^ I was over-thinking the problem; soo close to the answer that I missed it X_X

THx 8-) That did it ^_^
User avatar
post-it
 
Joined: 17 Jul 2002
Status: Audio: bass remains; if else, 3D

Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Mister Hatt » Tue Sep 14, 2010 11:59 pm

Sn0wcrash wrote:But isn't it easier to end up at 29.97 fps (or 25 fps) instead 23.97 to get directly the right framerate for NTSC (or PAL) standard (depending if the anime is done in NTSC or PAL country) ?
No, because they have to draw more, and converting between standards is a lot easier when your baseline is FILM. Not to mention that NTSC and PAL are standards for SD only and most stuff is HD now. As for older stuff, it was often made for display in cinemas and whatnot so using FILM rates made sense, along with the aforementioned standards conversion point.
Mister Hatt
 
Joined: 25 Dec 2007
Status: better than you

Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Snowcrash » Wed Sep 15, 2010 10:20 am

Ok I think I got all the explanations I want ^^

Just a last thing. Now with the HD video (blu-ray), it seems the framerate of this support is commonly 24 fps. Is it a will to simplify the problem of different framerate around the world ?
Image
User avatar
Snowcrash
 
Joined: 19 Jun 2008
Location: France
Status: Looking for a job T_T

PreviousNext

Return to Footage Help

Who is online

Users browsing this forum: No registered users and 0 guests