Interlace and 3:2 pull down

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Interlace and 3:2 pull down

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max777

Junior Member

2. January 2004 @ 11:36

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Is there ever a reason to do a 3:2 pull down on a 24fps progressive AVI? The AVI to DVD guide on here basically lead me to do this and now I'm waiting 30 hours for my MP2 to render. I'm hoping it will turn out ok. Why it needs to turn it into a 30fps interlaced movie is beyond me.

But anyway, now I'm totally confused about interlace and which FPS to use. I was hoping someone could direct me to some info or enlighten me on these subjects?

As my basic understanding goes, interlace is a way to create better quality video on TV, while using less space than progressive. And if you were to de-interlace everything, you end up with slightly less sharper picture quality.

24FPS is only used to fit more on a DVD, possibly increasing the picture quality.

24FPS interlace is not possible.

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Minion

AfterDawn Addict

2. January 2004 @ 14:45

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OK..I"ll try to explain interlaced Video and 3:2 pulldown in a Very Basic Way...The NTSC Standard Has to be 29.97fps/30fps interlaced because this is what our TV are Meant to display, But Movies are Shot on Film which is 23.976fps/24fps Progressive so to make the Progressive 24fps Film Conform to the NTSC Standard they use a Thing called 3:2 Pulldown Which Splits some of the Frames into Fields and Blends Fields from one Frame with Fields from another Frame so it can Make up the Extra Frames and be interlaced... 3:2 Pulldown is usually implememnted by adding Flages to the Mpeg stream that the DVD Player reads and it does the 3:2 pulldown based on the Flags in the Video Stream...I find it better to encode My DVD Compliant Files to 23.97fps/24fps and then use a seperate Program to add the 3:2 Pulldown Flags instead of letting the encoder add the 3:2 Pulldown flags..The Program I use for this is Called "Dopulldown" which is Freeware and can be found on the Net...Well I hope this explains it a Bit, ....Cheers

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max777

Junior Member

2. January 2004 @ 15:44

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I get all that, but what I don't understand is for what purpose do you do all this? If DVD compliant works ok at 24fps Progressive, then why convert it to 30fps interlace? The commercial DVD pirates of the carribean is at 24fps Progressive (NTSC). Looks awesome. So if I try to copy it should I turn it into 30fps?

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Minion

AfterDawn Addict

2. January 2004 @ 16:27

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It is because they developed the NTSC Broadcast standard Long before they ever thought they would be putting Movies on to TV..The the Pirates of the Caribean and 99% of all DVD"s are Not 24fps ,They are 23.986/24fps with 3:2 Pulldown so you should do the same..ALL NTSC Film DVD"s have 3:2 Pulldown so the can conform with the NTSC Broadcast standard...So if you have a 23.976fps/24fps Progressive AVI file and you want to put it on DVD then you encode it as 23.976/24fps with 3:2 Pulldown..The File is still 23.97fps/24fps Progressive ,the 3:2 Pulldown is just so your DVD Player/TV can Properly display it....It is a Hard to grasp concept which is even harder for me to explain ,This artical explains it better than I can :
http://www.dlpstore.com/techguide/pulldown_1.asp?page=2

But Basicly Just encode the File as a 24fps file with the 3:2 Pulldown Flags because this is the way ALL NTSC Film DVD"s are Made.....Cheers

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vurbal

Staff Member

2 product reviews

2. January 2004 @ 20:27

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The Progressive output looks great on your monitor because computer monitors are Progressive scan displays, which is also why interlaced material that looks fine on a TV can look like crap on a monitor. A normal TV doesn't actually display Progressive frames. They have to be changed into interlaced fields. And as Minion said, that's just the way it's done.

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