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

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

Postby mirkosp » Wed Sep 15, 2010 10:35 am

Actually, all the anime blurays I have ripped so far were either 23.976 progressive or 59.94 interlaced with MBAFF and a lot of annoying stuff to deal with...
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Snowcrash » Wed Sep 15, 2010 12:09 pm

mirkosp wrote:Actually, all the anime blurays I have ripped so far were either 23.976 progressive or 59.94 interlaced with MBAFF and a lot of annoying stuff to deal with...

Damned :(
I suppose 23.976 progressive is not a bad deal but what is 59.94 interlaced with MBAFF ?
And do you rip a blu-ray with a specific software ?
Actually I think the Blu-Ray ripping shoud have another thread ^^
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby mirkosp » Wed Sep 15, 2010 1:43 pm

MBAFF is a kind of interlace that AVC streams can have. Basically the image is separed into blocks, and each block could be either progressive or interlaced. So in the same stream you could have content telecined to 29.97, progressive at 29.97, interlaced at 59.94, and even combinations of two or more in the same frame, considering the block division. It is possible to find vfr material on DVD, however on DVDs you don't have different content separed into blocks (you can have telecined content with full field interlaced content on top, though, and that isn't nice :roll: ), so it's easier to deal with. OTOH, if you find content a section in a MBAFF stream that has both progressive and interlaced blocks in the same frame, you have to either do a lot of fancy stacking to keep the progressive footage as progressive and treat the interlaced/telecined content properly, or just nuke the whole thing, which could lead to a loss of quality in the progressive parts of the image. There probably exist some filters that can recognize progressive content and leave it alone while dealing with the interlaced content, but I'm not sure which/how good they are. IIRC I was told that some versions of tempgauss_mc can do that, but there are over 9000 versions of it around so it's kinda hard to know which do and which don't, if any version actually does...
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Mister Hatt » Thu Sep 16, 2010 12:55 am

Bluray has a few standards. By far the most common is 1920x1080p24, but 1920x1080i60 and 1440x1080i60 are common enough as well. Note that all those rates are at the 1% reduced rate. So basically 23.976fps progressive or 29.970fps interlaced. As mirko said, sometimes you get (actually nobody else I know gets them, mirko just has INCREDIBLY bad luck and encodes shitty shows anyway) the evil shit called MBAFF. Don't ever try to deal with it, instead send an angry email to the producer.

As for simplifying framerate problems around the world, digital televisions aren't required to have a default framerate, they just interpolate the served frames to whatever their refreshrate is (usually 120Hz, so it works well with p much everything, or 200Hz for dumb companies that think it looks better with motion failure) so it really makes no difference what the source rate is. Only analogue TV's are restricted by rate in what they can show and that's only because of the electrical power frequency in the electron gun of the CRT. PAL countries use 50Hz powerlines, NTSC countries use 60Hz powerlines. That's where the rates came from for field refreshing. So with HD, there are none of these issues, as the display has a much higher refresh rate and just interpolates (usually they just dumb-duplicate tho) and gives you a clean 120Hz image. For example, 24-1% video gets duplicated 5x per frame, while 30-1% gets duplicated 4x. 60fps gets doubled. Most displays are progressive and deinterlace with <methods> so that you end up not refreshing by field but if you choose to, there are ways to work with that too.

tl;dr MBAFF sucks ass and you should never use it ever because it's just annoying and stuff. Even YATTA has issues with it. Framerate standardisation on HD is irrelevant.
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Snowcrash » Mon Sep 20, 2010 3:00 am

I think this thread was very instructive for me (and other people I hope) about framerates and other stuff. It's really more clear for me anyways (between the framerate and refreshrate, etc...)

About HD, I understand it's easier to get downloaded source instead a Blu-Ray rip apparently :roll:

But I am thinking about a recent HD AMV made by Bauzi. According what you said, Blu-ray are 23.976 fps or 29.97 fps (and not really 24 fps actually).

Mister Hatt wrote:Bluray has a few standards. By far the most common is 1920x1080p24, but 1920x1080i60 and 1440x1080i60 are common enough as well. Note that all those rates are at the 1% reduced rate. So basically 23.976fps progressive or 29.970fps interlaced.

But the framerate of the video of Bauzi is 24 fps and not 23.976 fps. Did he do something wrong with the fps ?
Here is the link of his thread : viewtopic.php?f=3&t=101478
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Mister Hatt » Mon Sep 20, 2010 5:38 am

Yes, he did it wrong. I know for a fact what framerate those sources he had were animated at and he has indeed rounded up for no good reason other than possibly math for scenematching, which I doubt.
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby Scintilla » Mon Sep 20, 2010 7:01 am

Was he editing in Adobe Premiere pre-CS3 (or -CS2?) and did it at 24 because the NLE doesn't support 23.976 properly and forgot (or chose not) to change it back afterwards?
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Re: Why do we have to convert 25 fps to 23.97 fps ?

Postby mirkosp » Mon Sep 20, 2010 9:37 am

He's using premiere and after effects CS5.
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