What is 3:2 pulldown?

[Antoneo]

I see this on the specifications of tvs these days... what exactly is it? It is related to anamorphic dvds?

 

[pulse8]

Basically, 3:2 pulldown is what they do to get 24fps film to 29.97fps interlaced video.

 

[Valhalla1]

nm

 

[BDawg]

Pulse8 has it pretty right.

To save film, movies are shot at 24 frames per second (NTSC TV is ~30).

Progressive scan DVD players de-interlace the interlaced video signal to create 1 progressive frame from 2 interlaced field. If the video is 30fps, everything is well and the images are recombined correctly. If it's a 24fps film, de-interlacing can create problems like combining two fields that are unrelated (from a scene change etc.)

With 3:2 pulldown, the de-interlacer recognises film content and does the proper conversion from 24 fps to 30 while de-interlacing.

If you want more detail than that, just ask.

 

[pulse8]

<< To save film, movies are shot at 24 frames per second (NTSC TV is ~30). >>

It has nothing to do with saving film. It has to do with seeing smooth motion and persistance of vision.

Any slower and you'd see the frame changing and any faster is just unecessary.

This is a good link with a diagram.

The term mostly refers to the process of converting film to video.

 

[BDawg]

<< It has nothing to do with saving film. It has to do with seeing smooth motion and persistance of vision. >>



I always heard it was about film costs. Just like encoding Dolby Digital on the film instead of a seperate media.

 

[pulse8]

<<

<< It has nothing to do with saving film. It has to do with seeing smooth motion and persistance of vision. >>



I always heard it was about film costs. Just like encoding Dolby Digital on the film instead of a seperate media. >>

These days it may be the reason they still do it rather than filming made-for-tv-movies at 29.97 instead of 24fps, but the original idea behind the speed is for smooth motion.

Also, the faster the projector and camera have to run, the easier it is to have them screw up.

 

[BD2003]

Ive got two questions about dvds....somewhat related.

Whats the use of a progressive scan dvd when our tvs are interlaced to begin with? Just for HDTVs I suppose?

AFAIK, DVDs are encoded at 720x480. But most are widescreen, so that cuts it nearly in half. Since it appears theres only 300 or so lines of actual data, what happens when you view it on a widescreen TV? Will it just stretch it out and make it look like a glorified VHS with only 300 lines of resolution, or is there more in there than we can see on TVs?

If so why can't we see that on PCs using pixel doubling for the extra vertical lines, and even encode it into divx? Am I missing something here?

 

[Antoneo]

Hmmm ok, I currently have a regular old 27 inch tv. The dvd player I am looking at (the pioneer dv440) does not mention 3:2 pulldown and is not progressive scan. So is my understanding that 3:2 pulldown is only for people who own a progressive scan capable tv set?

 

[pulse8]

<< Hmmm ok, I currently have a regular old 27 inch tv. The dvd player I am looking at (the pioneer dv440) does not mention 3:2 pulldown and is not progressive scan. So is my understanding that 3:2 pulldown is only for people who own a progressive scan capable tv set? >>

3:2 pulldown is not the same thing as progressive scan. A progressive scan DVD player will reverse the 3:2 pulldown that's put in place when the film is transferred to video, bringing it back to it's original 24fps frame rate.