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

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

Postby Snowcrash » Fri Aug 27, 2010 2:52 am

Hi there,

I edit already for 2 years now. But I still read the excellent guide of Ermac, AbsoluteDesitiny and Zarxarx.

Like I am from Europe where the standard is PAL, I got few question about the 25 fps framerate. Apparently it seems that this framerate is “difficult” for AMV-makers. But why?
According to the guide, we should deinterlace first, and then convert 25 fps to 23.97 fps with the script MRestore().

You can read the guide's part concerning PAL here:
Spoiler :
If you have a full field blended source, which is usually the case with PAL footage, you will probably just deinterlace. Another option you have with PAL footage is a function called MRestore. MRestore should ONLY be tried if you have PAL footage with a framerate of 25 fps. MRestore will attempt to convert the material back to its original framerate of 23.976 fps while removing blended frames. MRestore can be used like so:

MPEG2Source("C:\yourfolder\blah.d2v")
TDeint(mode=1)
Mrestore()

MRestore may often look worse than simply deinterlacing though, but it doesn't hurt to give it a shot and see if you like how it turns out. It has some settings that you can tweak, so in order to get the most out of it, you should read it's documentation.


But honestly when I am working with my DVD:
1/ I just deinterlace my source with a simple filter (sometimes not if the DVD source is progressive).
2/ I keep the framerate at 25 fps, why I should change it? 25 fps is the standard of Europe.
3/ What is the interest to get back the original fps of an anime?

And I always get a good source for the editing.

Does someone have few answers to help me understanding this concept of 25 fps to 23.97 ? ^^
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Mister Hatt » Fri Aug 27, 2010 3:14 am

You don't have to at all and anyone who says you do is wrong. However, most anime is 24-1% and is converted badly to 25fps in which case it does need to be reversed. Luckily for lazy people such as myself, it's impossible to get 99% of PAL stuff back to original FILM rates and you are better off buying the R2j DVD instead.
Spoiler :
Doing an AMV with a PAL DVD is just stupid. Even if your country uses PAL, if you care enough to at least read the guide or think about conversion, then you should also know not to use PAL in the first place. You say you get a "good source" but if your source is PAL, then either you're blind or you don't speak English well enough to know what "good" means.

Somewhat related, the guide is old, outdated, and wrong.

[Kariudo: Personal attacks /off topic stuff hidden]
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby mirkosp » Fri Aug 27, 2010 7:25 am

Hatt is sadly right, PAL footage is generally bad and you should be looking elsewhere (japanese import is a nice solution quality wise but decidedly expensive as far as prices go ─ american import is lower quality but should be more affordable). There are 2 cases in which working with PAL is fine:
1) If it was directly sped up to 25. You can slow it back down to 23.976.
2) If it was euro telecined, be it hard or soft (if soft you're luckier, though). In this case it's just about doing an inverse telecine.
Unfortunately, unless you're dealing with a rather old source (in which case you'll find yourself dealing with case 1), very few sources fall into either of these categories, as blend decimate/random field drop are the most common behaviour in hardware encoders ─ or at least the cheapest/oldest ones that tend to be used.
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Zarxrax » Fri Aug 27, 2010 8:12 am

Yes, obviously the solution is to tell him to throw his dvds away and buy new ones /sarcasm

The reason that it is suggested that you try to convert to 23.976 fps, is because that is how it was originally designed. Anime comes from Japan which uses the NTSC standard rather than pal. In it's native format, anime is typically 23.976 fps, and then telecined up to 29.97 fps.
When its converted to PAL, they typically take that telecined 29.97fps version and convert the framerate to 25fps (as mirko explains above). This makes it a complete mess.
Using mrestore is an attempt to undo that mess. (though probably it wont help much)
Deinterlacing is conceding that nothing can be done about the mess.
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby mirkosp » Fri Aug 27, 2010 9:08 am

Zarxrax wrote:Using mrestore is an attempt to undo that mess. (though probably it wont help much)

I've got better results with srestore than with mrestore, but it still is far from being able to use a clean copy...
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Snowcrash » Fri Aug 27, 2010 9:41 am

Thanks for your replies.

Actually I understand what you said : anime is originally in 23,97 fps, then converted in 29,97 fps (because NTSC is the standard in Japan).
So the purpose to get a good DVD source is getting back to the original framerate.

But for example, I will ask for 2 videos I made :




In the two cases I kept the framerate at 25 fps (it's not a problem for Android Love because Renaissance is a PAL movie), but for Appleworld I use the PAL DVD of Appleseed.

I just deinterlaced the video and kept the framerate at 25 fps. And so ? What is the problem ? Does the video look like bad (in term of video quality) ?
I don't understand why it's such a big deal to get back at the original framerate (furthermore we can see now few videos at 59,97 or 60 fps). I read the guide of zarxrax (yes Mister Hatt I can't read english and I am blind :p)
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Athena » Fri Aug 27, 2010 10:34 am

Appleworld seems very blurry to me. The aspect ratio is also slightly wrong.

This being said, I actually liked the video, and it's a keeper.
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Zarxrax » Fri Aug 27, 2010 12:46 pm

In the case of appleworld, I don't see any blended frames, so this is apparently one of the few cases where the conversion to PAL was handled quite well.
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Zarxrax » Fri Aug 27, 2010 1:00 pm

To expand on that, the majority of PAL anime is going to look like this after you deinterlace it: http://a.imageshack.us/img413/7928/hamtalol.png

Which is why pal anime is bad.
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby mirkosp » Fri Aug 27, 2010 1:04 pm

Thinking about it again, I should have named it SadEuropeanHamster.png ( ゚∀゚)アハハ八八ノヽノヽノヽノ \ / \/ \
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Snowcrash » Sat Aug 28, 2010 4:11 am

Zarxrax wrote:In the case of appleworld, I don't see any blended frames, so this is apparently one of the few cases where the conversion to PAL was handled quite well.

Zarxrax wrote:To expand on that, the majority of PAL anime is going to look like this after you deinterlace it: http://a.imageshack.us/img413/7928/hamtalol.png

Which is why pal anime is bad.


Oh I see. But perhaps the Appleseed DVD is not considered as anime but 3D film ? Maybe it's not a problem when we deinterlace ?

Another case : I have the Animatrix DVD and the frames are originally progressive. So I suppose this kind of DVD is ideal for AMV-maker because we don't need to deinterlace the source. We just got a 25 fps rate.
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby mirkosp » Sat Aug 28, 2010 6:28 am

Even when progressive, PAL is not optimal. 3 are the cases of progressive PAL:
1) It was blended to 25: worst case, you can save less than what you could attempt to save when you have a field blended source. Admittedly, this case is luckily rare to nonexistant in my experience (I think I read about it but never found it myself).
2) A frame was added every 24: in this case, the frame could either be a duplicate or a blend of the two frames close to it. I have found this case a few times, it is the most common for progressive PAL in my experience. All you have to do is tdecimate(cycle=25) and hope tdecimate is smart enough to remove the duplicate/blended one. Alternatively you can use an ovr file in tdecimate or try a selectevery to decide which frame is the duplicate/blended one that you should be getting rid of. After you restore the 24.00fps stream like this, you can assumefps to ntcs_film.
3) There was a direct speedup to 25fps: in this case you just assumefps back to ntcs_film. You could still edit at 25fps if you wish, but in some places you might notice that the motion is funnily faster than it should be: a common case is when there's someone walking in a somewhat robotic way due to being accelerated like that. Generally however speedups aren't common in progressive PAL because when the source did go through a speedup, it generally is a source dealt with in the 70s/80s, and at the time they generally did full field interlacing with the TV airing in mind, so they just picked the source, dropped the audio, did the speedup, and interlaced, with the dub done at the new speed. The only progressive PAL DVD that went through a speedup that I have in mind is the Italian release of The Sky Crawlers by Dall'Angelo Pictures (not that it matters, they also did the BD at 23.976, so I got that :asd: ).
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Mister Hatt » Sun Sep 05, 2010 8:27 am

The best PAL fixing filter I have seen, rather than mrestore and srestore, is actually restore24. Sadly it still isn't ideal. No filter will be. Think about what they are doing: recreating frames which no longer exist and then IVTC'ing them. Obviously there is no good way to do that.

One other thing: mirko has said that you should only be ok with PAL under certain conditions but left out the most important and obvious one: WHEN IT IS ACTUALLY ANIMATED AT 25FPS IT IS OK TO USE PAL.
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby mirkosp » Sun Sep 05, 2010 8:43 am

Mister Hatt wrote:One other thing: mirko has said that you should only be ok with PAL under certain conditions but left out the most important and obvious one: WHEN IT IS ACTUALLY ANIMATED AT 25FPS IT IS OK TO USE PAL.


Right, I keep forgetting because japanese animation at 25fps is rare... I guess the only one I can think of is First Squad, but that was 24.00 maybe, I can't recall as all I have is second hand info.
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Mister Hatt » Mon Sep 06, 2010 5:57 am

It's one of my hobbies to find weird and interesting footage!
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