24fps or 29.97fps ???

[RodNichols5]

I have been capturing for about a year now, thanks for all the help in this excellent site, but there is something that puzzles me. I understand that film is typically 24 fps and that TV is typically 29.97 fps (or something close to that) I also know that when a film shot at 24 fps is converted to TV at 29.97 fps, that you get 3:2 telecine. I have noticed that just about all of my captures of TV programs seem to have the 3:2 telecine problem. I am thinking mainly of Star Trek The Next Generation, X Files, and Babylon 5. Are all/most of the TV shows filmed in the last several years filmed in 24 fps, and then when they are broadcast they are converted to 29.97 fps ? Or could it be my capture card ? I am using an ATI 7500 AIW and using Virtual Dub for the captures. I don't mind the results I get but I have wondered, if I am capturing a TV program, shouldn't all of the frames be clear, rather than 3 clear followed by 2 with interlacing then 3 clear, etc. ?? Any insight would be most appreciated !!

Thanks to all !!

[SLK001]

ALL films originally presented in a theater are 24fps. To display on TV, these films are telecined to 29.97fps (2:3 pulldown).

All of your captures will be 29.97fps, because to be viewed on TV, they had to either be telecined, or filmed at 29.97fps.

Now your question about if "all/most of the TV shows filmed in the last several years filmed in 24 fps" is a tougher question. Live shows, like sports events and "oprah" shows are filmed at 29.97fps (by filmed, I mean videotaped). Most (if not all) soaps are also taped at 29.97fps. Episodes of Star Trek TNG and Babylon 5 are usually hybrids, in that the main scenes with people in them are filmed at 24fps, while the CGI scenes are usually taped at 29.97fps. These are combined post production, with the film parts receiving a 2:3 pulldown (telecine).

In a nutshell, you need to "know" your source.

[Vejita-sama]

A surprising number of TV shows are shot at 23.976fps actually. And then telecided (it's actually 2:3 pulldown, 3:2 pulldown is a little different check the glossary for more info).

However if you capturing you ALWAYS capture at 29.97fps, it MIGHT then be possible to run an IVTC (inverse telecide) process on that capture to generate the original 23.976fps source, encode, and then telecide again. But all things being equal IVTC processes on capture sources can be 'tricky'.

[Gazorgan]

Stay 29.97 . The hybrid special effects will kill you trying to go 'back' to a non-existant 23.97 'film'. Let's not even consider Brittish/Europeon shows in the US.

[non-linear]

If you're capturing from any broadcast source; it doesn't matter what the actual show was shot in, it's still broadcast in 29.97fps (any show shot in 24fps or another frame rate would already be converted to 29.97 before it goes to air). Whether you're recording from a VCR or off cable, satellite, or over the air, it's already 29.97fps (for countries that broadcast NTSC). That doesn't change.

There's no need to run IVTC when capturing, unless you're actually capturing something running at 24fps (if you have a film projector patched into your capture card, but not many people would be doing that).

[nymph4444]

They say film is 24fps and then telecided puldown to 29.97fps for TV creen.

But if you shoot at 24 fps how do they up convert the fps? 29.97 fps is more then 24 fps so they are not adingd frames are they?

And why do they call it pull down it sould be pullup?

[edDV]

They say film is 24fps and then telecided puldown to 29.97fps for TV creen.

But if you shoot at 24 fps how do they up convert the fps? 29.97 fps is more then 24 fps so they are not adingd frames are they?

And why do they call it pull down it sould be pullup?

I agree with most of the above. They convert 24p (23.976p) to 29.97 with telecine (extra pad fields) as follows:



If you want more explanation ask more.

[LightWeightProducer]

24 FPS is slowed to 23.976, then fields are repeated (the 3:2 pattern often mention) to achieve a field rate of 59.94 for broadcast / other analogue systems.

Uhhh, like he said ^^^

[jagabo]

There are no frames in interlaced analog video, only fields, 59.94 fields per second. When it's digitized pairs of fields are woven together into frames, 29.97 frames per second.

[edDV]

I have the "Max Headroom" series on advanced order. Can't wait to look at frame/field rates.

Maybe they deinterlaced it all. Maybe it's original mixed.

[Nelson37]

Much depends on the source, but as a general rule removing the pulldown, or IVTC can result in better visual quality and definitely a smaller filesize or more efficient bitrate allocation.

The card you have is capable of doing this on the fly, with results comparable to software filters used in post-processing, again depending on the source.

The best source for this would be full-length movies, broadcast in HD, and captured thru the S-video output on the box. Star Trek Enterprise on HDNet also worked very, very well.

[Nelson37]

Holy crap the OP is long gone! 2003!

[nymph4444]

When you say the pad the feild to ad frames do you meen they just ad Copies of Frames?

[edDV]

When you say the pad the feild to ad frames do you meen they just ad Copies of Frames?

In the drawing you will see an extra field is added for frames 1 and 3 to make 29.97 telecine. For inverse telecine, those fields are removed.

[nymph4444]

One thing are you getting these drawlings from a site?

And I don't get this if I shoot a Film 24 fps and put it right up on Projector it shows 24 frames per sec and you can see it ok.

But if I show that same 24 frame film on a TV screen it wont look right?
Is it because the CRT draws faster then 24 fps?

[edDV]

I got the original off a Google image search for "telecine". I drew the right half myself.

One thing are you getting these drawlings from a site?

And I don't get this if I shoot a Film 24 fps and put it right up on Projector it shows 24 frames per sec and you can see it ok.

No projectors don't run 24fps. If they did it would be a flickery mess. You couldn't watch it.

Film projectors have a 2x or 3x gate. The gate advances the film, locks the frame still, then a shutter passes the bulb light twice or three times per frame. A 2x gate flashes the film at a 48 fps rate, a 3x gate flashes the film at a 72 fps rate. This results in less flicker to the human eye.

Film projectors for interlace TV broadcast have special gates that alternately flash 3 fields on one frame, then 2 fields on the next frame at a 59.94 field per second rate.

But if I show that same 24 frame film on a TV screen it wont look right?
Is it because the CRT draws faster then 24 fps?

A CRT TV runs at a fixed 59.94 field per second rate. The 24 fps film must go through the telecine process to be converted to 59.94 fields per second.

[nymph4444]

So when they shoot Movies on Film they and up with 24 frames per sec.

Then they Develap it and they still have 24 frames per sec.

When it is in the movie projector I thought all that film just ran right through the projector.

So I did not get what you told me?
Do they do something to the frames before they run throught the projector to make them seem like there are more?

[jagabo]

So when they shoot Movies on Film they and up with 24 frames per sec.

Then they Develap it and they still have 24 frames per sec.

When it is in the movie projector I thought all that film just ran right through the projector.

So I did not get what you told me?
Do they do something to the frames before they run throught the projector to make them seem like there are more?

No, it's done as the film passes through the projector:

http://www.movingimage.us/sprockets/filmproj.swf

Displaying the film at 24 fps flickers very badly. So modern projectors display each frame 2 or 3 times (48 fps or 72 fps).

[edDV]

And film projectors for TV broadcast have special gates that are synchronized to video 59.94 field per second rate. This gate exposes the camera sensor three times per film frame (to three TV fields) alternating with two times per film frame (for two TV fields) then three again. The result is the telecine field pattern shown in the diagram above.

There is a second type of film projector for TV called a flying spot scanner, but I'll wait to discuss that until you understand a classic film projector.

[edDV]

So when they shoot Movies on Film they and up with 24 frames per sec.

Then they Develap it and they still have 24 frames per sec.

When it is in the movie projector I thought all that film just ran right through the projector.

So I did not get what you told me?
Do they do something to the frames before they run throught the projector to make them seem like there are more?

The spool of film does have 24 frames per second. When shown in a cinema, the shutter-gate flashes each frame multiple times for a 48 fps or 72 fps rate to the screen. A TV projector gate flashes the film at 59.94 field per second rate.

Progressive TV sets operate similar to cinema projectors. If you play a "24p" (23.976 fps) Blu-Ray movie, the TV will repeat frames 2-3-2-3-2-3 for "60Hz" TV sets or 5-5-5-5-5-5 for "120Hz" TV sets.

The frame repeat process is very similar to flashing a single film frame several times in a cinema projector.

[nymph4444]

Now if I understand the video I just saw on Projectors you gave the link.

The top real gives the film and it goes down to the other real that winds it and pulls it I get this.

But am I right the film goes passed the shuter that is spinning and the shuter has two open spot and two salid spod.
And the Lamp is behind the shuter and when the spins to an open spot the Light can pass through and onto the film I get this.

Now doe the Light keep going through the film and then into the Lens and out the Projector.

[edDV]

Yes, think of a film projector as a photon gun. The lamp is on but blocked by the shutter. When the shutter opens, the light photons are released and shoot through the film to the screen as a flash.

If this is a TV projector, the shutter opens 3 times for one film frame, then two times for the next film frame. Instead of a screen, the photons are shot into a TV camera lens. The result is telcine interlace video.

[edDV]

Here is another graphic of how a 2x gate works.


http://en.wikipedia.org/wiki/Movie_projector


PS: the shutter graphics seem reversed to me but the idea is right.

[nymph4444]

So you have the Flash Lamp then infront of that you have the Shutter then infront ot that hangs the Film and on the other side of the Film in the Lens?

[jagabo]

No, the lamp is on continuously. The spinning shutter determines when the light passes through to the film.

[edDV]

So you have the Flash Lamp then infront of that you have the Shutter then infront of that hangs the Film and on the other side of the Film in the Lens?

Yes... id goring the gate. The gate limits what the viewer sees. Does that pose a question?

The "flash Lamp" is not flashing, it is full on but inhibited by 1st the gate, then the shutter.

[nymph4444]

I am soory I have my Parts a little mixed up.

Going from the back out to the Lens

First you have a round Merror then infront of it is the Lamp the Merror makes it even Brighter.
Infronnt of the Lamp is the Spinnning Gate Shutter and two spot are open and two spots are solid.
Infront of the WShuter is the Film and as is move down across the Shuter and the Film is in Sync with the Shuter so when the Shuter is at an open spot the Light goes throught and the Film stops and the Light goes through the Film and to the Lens.

Am I off on any of this?

[edDV]

Mirror - Lamp - Spinning Shutter - Gate (holds the film frame still then advances film to to next frame) - lens ..... screen or TV camera lens.

In the case of a 2x gate, the gate holds the film frame still for two shutter flashes.

In the case of a 3x gate, the gate holds the film frame still for three shutter flashes.

In the case of a TV gate, the gate holds the film frame still for three shutter flashes, advances to the next frame, then holds the second film frame still for two shutter flashes.This repeats 3-2-3-2. The gate/shutter are synchronized to the same vertical sync as the camera so that each flash occurs during an active field scan.

[nymph4444]

Does the film move down to the pickup real I ask because I saw on youtube they put the big film reals on a flat bed table and I thought how can they be projected if they are sideways?

[edDV]

Most 35mm film formats used for TV use a vertical feed orientation. Some motion picture production process film and IMAX use the sideways feed.


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