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What is "Pulldown"?

PanthersFan
06-03-2008, 04:36 PM
I've noticed in shopping for a new HDTV that the descriptions of the displays have some terminology now that says something like "2:3 Pulldown".

The heck does that mean?

borromini
06-03-2008, 04:55 PM
http://en.wikipedia.org/wiki/2:3_pulldown

mobiushky
06-03-2008, 04:59 PM
I've noticed in shopping for a new HDTV that the descriptions of the displays have some terminology now that says something like "2:3 Pulldown".

The heck does that mean?

It helps to know that movies are all filmed at a rate of 24 frames per second and that tv is filmed at 30 frames per second. (It's actually much more complicated, but for sake of simplicity I'll avoid that). Nearly every TV on the market is made to operate at 60 Hz (or frames per second). SO, they took 30 and show every frame twice and viola you get 60. It's easy to show TV on a TV since 60 is a nice multiple of 30. But when you double 24 you get 48. Triple it and you get 72. Not very nice. So what happens when you try to show a movie recorded at 24 fps on a tv that has to have 60 fps? The solution was 3:2 or 2:3 pull down (same thing). Frames are shown inequal numbers of times. Say you have frames A, B, C, D, etc.... 3:2 would look like this:

AAA-BB-CCC-DD-EEE-FF-GGG...... first frame "flashed" 3 times, then twice, then three, etc.

Doing this introduces errors into the image such as judder and even motion blur. Most people are used to it since all DVDS are processed using 3:2 pulldown.

rm00k
06-03-2008, 05:45 PM
This is also where 120hz TVs play a part. 24 x 5 = 120, makes it easy to implement anti-judder processing without 2:3 pull down.

erict
06-04-2008, 05:32 AM
This is also where 120hz TVs play a part. 24 x 5 = 120, makes it easy to implement anti-judder processing without 2:3 pull down.


Great info on how to understand pulldown. Does a plasma tv seem to escape this problem:confused:

pappylap
06-04-2008, 07:38 AM
The only displays that properly show 24 fps are the Pioneers... just another reason why they cost more.......:banana:

Jim Bob Jones
06-04-2008, 02:31 PM
Check here (scroll down page a little) for clear and explicit information:http://www.sptimes.com/2004/09/05/Floridian/Real_Florida__Red_fac.shtml

1080PsF
06-06-2008, 08:43 AM
It helps to know that movies are all filmed at a rate of 24 frames per second and that tv is filmed at 30 frames per second. (It's actually much more complicated, but for sake of simplicity I'll avoid that). Nearly every TV on the market is made to operate at 60 Hz (or frames per second). SO, they took 30 and show every frame twice and viola you get 60. It's easy to show TV on a TV since 60 is a nice multiple of 30. But when you double 24 you get 48. Triple it and you get 72. Not very nice. So what happens when you try to show a movie recorded at 24 fps on a tv that has to have 60 fps? The solution was 3:2 or 2:3 pull down (same thing). Frames are shown inequal numbers of times. Say you have frames A, B, C, D, etc.... 3:2 would look like this:

AAA-BB-CCC-DD-EEE-FF-GGG...... first frame "flashed" 3 times, then twice, then three, etc.

Doing this introduces errors into the image such as judder and even motion blur. Most people are used to it since all DVDS are processed using 3:2 pulldown.You’re pretty close on this but not totally correct. First off not all films are shot in 24 some in Europe are shot in 25. NTSC video is not 60 frames per second but 29.97 frames per second and each frame is made up of two fields the first being the odd lines and the second being the even lines so there are 59.94 fields per second (okay I’ll give you that the progressive monitors are 59.94 frames per second, but the incoming video isn’t, except for 720p). 3:2 / 2:3 being the same thing is some what correct but the cadence is different and everything now is a 2:3 pull-down because everything needs to start on an “A” frame for the editors. So the cadence goes AABBBCCDDDAABBBCCDDD…there are just the A, B, C, and D frames of film. When the 2:3 pull-down is done in fields it is not as noticeable as it is when it is done in frames for the progressive monitors. It does induce judder but not motion blur and it has been used long before DVD’s.

When we transfer film shot at 24 to either NTSC or 1080i/59.94 a 2:3 needs to be added. With the addition of color to the video signal the frame rate had to be changed from 30fps to 29.97fps so there in turn the film had to be slowed down to 23.976fps (it’s still shot at 24 only transferred at 23.976) to keep it equal to 25% slower than the video signal, that way the 2:3 pull-down could be added to make the output video 29.97fps. Each frame of film is scanned and then it is color corrected then is outputted as either two fields or three fields of video to the videotape machine in the cadence noted above. It is very important that the cadence stays correct through the entire show or movie (this was not that important in years past but with the new encoders and decoders it is very important now).

Now when we transfer 24-frame film to HD video that is either 23.98 or 24 we transfer it frame to frame and then the videotape machine inserts the 2:3 pull-down on the output.

So to the op it is just a way to make film run at a frame rate that could be used on must TV’s.

mobiushky
06-06-2008, 11:32 AM
You’re pretty close on this but not totally correct. First off not all films are shot in 24 some in Europe are shot in 25. NTSC video is not 60 frames per second but 29.97 frames per second and each frame is made up of two fields the first being the odd lines and the second being the even lines so there are 59.94 fields per second (okay I’ll give you that the progressive monitors are 59.94 frames per second, but the incoming video isn’t, except for 720p). 3:2 / 2:3 being the same thing is some what correct but the cadence is different and everything now is a 2:3 pull-down because everything needs to start on an “A” frame for the editors. So the cadence goes AABBBCCDDDAABBBCCDDD…there are just the A, B, C, and D frames of film. When the 2:3 pull-down is done in fields it is not as noticeable as it is when it is done in frames for the progressive monitors. It does induce judder but not motion blur and it has been used long before DVD’s.

When we transfer film shot at 24 to either NTSC or 1080i/59.94 a 2:3 needs to be added. With the addition of color to the video signal the frame rate had to be changed from 30fps to 29.97fps so there in turn the film had to be slowed down to 23.976fps (it’s still shot at 24 only transferred at 23.976) to keep it equal to 25% slower than the video signal, that way the 2:3 pull-down could be added to make the output video 29.97fps. Each frame of film is scanned and then it is color corrected then is outputted as either two fields or three fields of video to the videotape machine in the cadence noted above. It is very important that the cadence stays correct through the entire show or movie (this was not that important in years past but with the new encoders and decoders it is very important now).

Now when we transfer 24-frame film to HD video that is either 23.98 or 24 we transfer it frame to frame and then the videotape machine inserts the 2:3 pull-down on the output.

So to the op it is just a way to make film run at a frame rate that could be used on must TV’s.

I know. Remember that I mentioned:

"It's actually much more complicated, but for sake of simplicity I'll avoid that."

The question I would ask is that you speak from the stand point of video editors regarding 2:3 pull down, whcih makes sense for video transfer into the DVD realm. However, when a TV takes a 24Hz signal in, does it need the same A frame reference for the editors? Since the two terms seem to be used interchangeably in the TV world (not video editing world), does every TV do 2:3, or 3:2, or some do one some do the other?

PanthersFan
06-06-2008, 02:38 PM
Wow... way more goes on than I was ever aware of.

So... if the video source (DVD) is already doing 2:3 pulldown, why does the display need to do it?

rm00k
06-07-2008, 08:19 AM
Wow... way more goes on than I was ever aware of.

So... if the video source (DVD) is already doing 2:3 pulldown, why does the display need to do it?

Right, why would any TV need to do 3:2 pulldown if the input signal is never 24fps - TV video comes in at either 30 or 60 hz depending if its interlaced or progressive and DVD's are encoded at 30?

1080PsF
06-07-2008, 02:04 PM
Wow... way more goes on than I was ever aware of.

So... if the video source (DVD) is already doing 2:3 pulldown, why does the display need to do it?With a 2:3 there will be mixed video frames so progressive monitors need to remove the 2:3 so the frames can be restored back to how they should look, but since the monitor is still 60Hz it still needs to add the 2:3 back in so the monitor can display the picture, but the monitor adds the 2:3 in frames and not fields so it's more noticeable.

pappylap
06-08-2008, 01:48 AM
Right, why would any TV need to do 3:2 pulldown if the input signal is never 24fps - TV video comes in at either 30 or 60 hz depending if its interlaced or progressive and DVD's are encoded at 30?

24p on DVD
DVDs, however, are capable of storing the native 24p frames. Every Hollywood movie is laid to disc as a 24p (actually 23.976p – see below) stream. With a progressive-scan DVD player and a progressive display, such as an HDTV, only the progressive frames are displayed and there is no conversion to an interlaced format – eliminating the appearance of any interlace or de-interlacing artifacts. When displayed on a standard NTSC TV (which only display 60i) the DVD player will add 3:2 pulldown to the signal.

In traditional television broadcast and VHS, the video stream has 3:2 pulldown added. This material cannot be displayed progressively without the resolution loss of de-interlacing, unless the de-interlacer has accurate cadence detection.


24p video production
Increasingly, 24p is used to acquire video. The most prolific use of this has been with HDTV and digital cinema such as the Star Wars prequel trilogy.

In 2002, Panasonic released the Prosumer DV camera AG-DVX100 (followed by the updated models AG-DVX100A in 2003 and AG-DVX100B in 2005). This camera was the first DV camera that could switch between different frame rates, including 60i, 30p, and 24p with a choice between the 2:3:3:2 or 3:2 pulldown schemes. The 24p feature on the camera produces film-like video that is preferred by many narrative filmmakers. Canon soon followed suit with the Canon XL-2, offering the same frame rates and pulldown choices as the DVX100.

Following the success of the DVX100, in December, 2005, Panasonic released the Panasonic AG-HVX200, which offers 24p HD at the sub-$10,000 level. Basically an HD version of the DVX100 series, it heavily targets independent filmmakers, as HD has a much higher resolution than DV and will generally look superior on a film blow-up. It is also noteworthy that the camera records HD footage, complete with clip information, to static P2 memory cards instead of tape. This could potentially signify a radical change in the video editing workflow.

For recording 24p to tape in formats which typically do not support 24p, such as DV, options include PsF, 2:3 Pulldown and advanced pulldown.

Some music videos and television series today are shot with 24p video instead of 35 mm or Super 16 mm film.