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2:3 pulldown explained??

post #1 of 31
Thread Starter 
I have a few questions in regards to 2:3 pulldown.

To my understanding.....(and please, please, please correct if/when I'm wrong) biggrin.gif
Flat panel TV's today are natively 59.94Hz or 60Hz displays
Video(i.e. Satelite, Cable, Antenna) is shot in 29.97fps or 30fps
Film(movies) are created in 24fps

When and where is the 2:3 pulldown implemented? Does this have anything to do with satelite, cable and air TV, or is the 2:3 pulldown only in reference to film(movies)?

Thanks all!
post #2 of 31
Today, HD video is shot in either 1080x60i or 720x60P so there is no 2:3 pulldown necessary for a 60Hz HDTV. Those also happen to be the 2 HD broadcast formats used by CBL/SAT/TELCO/OTA

If a station is showing a movie that was originally shot in 24 fps, they will have already done the 2:3 pulldown because they are broadcasting in the above two HD formats

Blu-ray disc is recorded at 24P. There you need the 2:3 pulldown to get to 60Hz
post #3 of 31
Thread Starter 
Am I correct then in thinking that FPTV's natively display @ 59.94 or 60Hz?
post #4 of 31
Thread Starter 
In response to my last post,

I just re-read @ Lee Stewarts post and therefore withdrawal my last post. biggrin.gif

Why is HDTV broadcast in 1080/60i? Bandwith issue?
post #5 of 31
Quote:
Originally Posted by hoozthatat View Post

Am I correct then in thinking that FPTV's natively display @ 59.94 or 60Hz?

It depends on the projector. Probably a cheap one would be. All of the good ones have multiple scan rates. Having a 120Hz scan rate means you can do 1080x60i or 720x60P and also 1080x24P without having to use 2:3 pulldown. 1080x24P x 5 -= 120Hz. They show each frame 5 times. In the case of 720x60P - 2 times. The same for 1080x60i (i = interlaced) so they have to deinterlace first.
post #6 of 31
Quote:
Originally Posted by hoozthatat View Post

In response to my last post,
I just re-read @ Lee Stewarts post and therefore withdrawal my last post. biggrin.gif
Why is HDTV broadcast in 1080/60i? Bandwith issue?

Yes. Each channel is 6Mhz - that is in accordance with the FCC (for OTA). 1920x1080x60i takes up the same bandwidth as 1280x720x60P.
post #7 of 31
Thread Starter 
@ Lee Stewart... I have a question about de-interlacing, does it refer to just in the resolution of the image or does it refer to the Hz as well?
I.E. If I'm watching a 1280x720/60p is my HDTV de-interlacing the image if it's native display resolution is 1920x1080?
Edited by hoozthatat - 9/14/12 at 8:50pm
post #8 of 31
Quote:
Originally Posted by hoozthatat View Post

@ Lee Stewart... I have a question about de-interlacing, does it refer to just in the resolution of the image or does it refer to the Hz as well?
I.E. If I'm watching a 1280x720/60p is my HDTV de-interlacing the image if it's native display resolution is 1920x1080?

1920x1080x60i is an interlaced format. All television before HDTV was 480x60i. What the i means (interlaced) is that a frame which consists of say 1920x1080 is broken up into fields. 2 fields = 1 frame. 1 field will be the odd number vertical lines while the other field will be the even numbered vertical lines. This saves bandwidth. When an HDTV deinterlaces, it is combining the 2 fields to create 1 frame which it then shown on the flat panel display because flat panel displays show 1 frame at a time. 1280x720x60P - the P = progressive. Progressive means showing content at one frame at a time. The 720P format shows 60 frames/sec. No deinterlacing is done. 1920x1080x60i shows 60 FIELDS/sec. Deinterlacing is required. BD's 1920x1080x24P is 24 frames/sec. Again no deinterlacing done.

If you are watching 1280x720x60P on an HDTV that has a native resolution of 1920x1080x60P then your TV is going to have to convert the 720P to 1080P. This is called upscaling. It has to make an educated guess as to what the additional pixels will be. 720P = 921,600 pixels. 1080P = 2,073,600 pixels. It uses special algorithms to make this educated guess when it has to create the missing 1,152,000 pixels per frame

If you had a 720P HDTV and fed it a 1080 signal, then the opposite happens. It has to throw away 1,152,000 pixels per frame

Computer monitors have been progressive for decades. It is difficult to read text if shown in an interlaced format but very easy with a progressive format.
Edited by Lee Stewart - 9/14/12 at 9:34pm
post #9 of 31
Thread Starter 
Quote:
Originally Posted by Lee Stewart View Post

1920x1080x60i is an interlaced format. All television before HDTV was 480x60i. What the i means (interlaced) is that a frame which consists of say 1920x1080 is broken up into fields. 2 fields = 1 frame. 1 field will be the odd number vertical lines while the other field will be the even numbered vertical lines. This saves bandwidth. When an HDTV deinterlaces, it is combining the 2 fields to create 1 frame which it then shown on the flat panel display because flat panel displays show 1 frame at a time. 1280x720x60P - the P = progressive. Progressive means showing content at one frame at a time. The 720P format shows 60 frames/sec. No deinterlacing is done. 1920x1080x60i shows 60 FIELDS/sec. Deinterlacing is required. BD's 1920x1080x24P is 24 frames/sec. Again no deinterlacing done.
If you are watching 1280x720x60P on an HDTV that has a native resolution of 1920x1080x60P then your TV is going to have to convert the 720P to 1080P. This is called upscaling. It has to make an educated guess as to what the additional pixels will be. 720P = 921,600 pixels. 1080P = 2,073,600 pixels. It uses special algorithms to make this educated guess when it has to create the missing 1,152,000 pixels per frame
If you had a 720P HDTV and fed it a 1080 signal, then the opposite happens. It has to throw away 1,152,000 pixels per frame

So then am I correct in thinking that broadcast HDTV is played back at 30fps? If 2 fields = 1 frame?
post #10 of 31
I don't want to mix you up but there is something you should know . . .

When we say 1920x1080 - that is the H & V count of the visible image we see. But it is not the total signal. 1920x1080 is really 1920x1125. The other 45 lines of vertical resolution you never see. Or at least you shouldn't. They perform "housekeeping" functions. Sometimes a station will mess up and you will see what looks like dots and dashes at the top of your image. These are part of the 45 "housekleeping" vertical lines.
post #11 of 31
Thread Starter 
Quote:
Originally Posted by Lee Stewart View Post

I don't want to mix you up but there is something you should know . . .
When we say 1920x1080 - that is the H & V count of the visible image we see. But it is not the total signal. 1920x1080 is really 1920x1125. The other 45 lines of vertical resolution you never see. Or at least you shouldn't. They perform "housekeeping" functions. Sometimes a station will mess up and you will see what looks like dots and dashes at the top of your image. These are part of the 45 "housekleeping" vertical lines.

So then broadcast HDTV doesn't necessarily have a set fps? And it's just all rated to 60Hz?
post #12 of 31
Quote:
Originally Posted by hoozthatat View Post

So then am I correct in thinking that broadcast HDTV is played back at 30fps? If 2 fields = 1 frame?

Yes - many call 1080x60i 1080x30P. But in actuality it isn't 60i or 30P. It's really 59.94i and 29.97P. Keep in mind that when you are deinterlacing, artifacts can come about that can affect the images. This is removed with the progressive formats
post #13 of 31
Thread Starter 
Quote:
Originally Posted by Lee Stewart View Post

Yes - many call 1080x60i 1080x30P. But in actuality it isn't 60i or 30P. It's really 59.94i and 29.97P. Keep in mind that when you are deinterlacing, artifacts can come about that can affect the images. This is removed with the progressive formats

So then where do Hz play in? Purely how many times per second the screen refreshes? IE on the TV itself, nothing to do with broadcast and such?
post #14 of 31
Quote:
Originally Posted by hoozthatat View Post

So then broadcast HDTV doesn't necessarily have a set fps? And it's just all rated to 60Hz?

Broadcast TV has a set number of HD formats it can broadacst at:

1920x1080x60i

1920x1080x60P*

1280x720x60P

* for the future. Some SAT channels are broadcast at this format. No OTA yet. It is in the specs.
post #15 of 31
Quote:
Originally Posted by hoozthatat View Post

So then it's essentially better to display at 30 or 29.97p rather than 59.94i? Can you adjust your TV or source (like directv hd receiver) to push or display (depending if you're adjusting the TV or the satellite box) at either 60i or 30p?
I've never seen an adjust such as that in an FP

You can usually set the box to three choices:

1080
720
Native - whatever the signal is - that is what the box will pass.

It depends on which device is doing the better job of upscaling - the box or your HDTV as to what setting you choose.

The TV itself can only show it's native resolution (720, 766 or 1080) in a progressive format. You have no control over that. But you do have control on many TVs as to what the frame rate will be if you have a 120 or 240 or even 480 Hz HDTV
post #16 of 31
Quote:
Originally Posted by hoozthatat View Post

So then am I correct in thinking that broadcast HDTV is played back at 30fps? If 2 fields = 1 frame?
No, not necessarily. 60i (US broadcast standard) can be de-interlaced by the TV to 60p.
Quote:
Flat panel TV's today are natively 59.94Hz or 60Hz displays
Quite a few of the latest are 120Hz or more (eg. 240Hz).
post #17 of 31
Quote:
Originally Posted by Lee Stewart View Post

The other 45 lines of vertical resolution you never see. Or at least you shouldn't. They perform "housekeeping" functions. Sometimes a station will mess up and you will see what looks like dots and dashes at the top of your image. These are part of the 45 "housekleeping" vertical lines.

....or if you have your tv's aspect set to 1:1 pixel matching so that you are viewing everything that is being broadcast (no pixel stretching at all), you will see the housekeeping vertical lines at the top but that's mostly on commercials, at least for OTA.
post #18 of 31
Quote:
Originally Posted by Lee Stewart View Post

I don't want to mix you up but there is something you should know . . .
When we say 1920x1080 - that is the H & V count of the visible image we see. But it is not the total signal. 1920x1080 is really 1920x1125. The other 45 lines of vertical resolution you never see. Or at least you shouldn't. They perform "housekeeping" functions. Sometimes a station will mess up and you will see what looks like dots and dashes at the top of your image. These are part of the 45 "housekeeping" vertical lines.

Don't forget the horizontal blanking. The actual full raster is 2200x1125 for a 1080i@29.97 fps HD-SDI stream. HD vertical blanking never contains any data in the active portion. If you're seeing dots and dashes, it's always from an improperly aligned SD upconvert.

Here's an image where things have been shifted so that you can see the blanking. Number 1 is VITC data that's in both the vertical and horizontal blanking area. Number 2 is four channels of digital audio. Number 3 is the SAV (start of active video) code.

blanking1.png

Ron
post #19 of 31
Quote:
Originally Posted by Lee Stewart View Post

Today, HD video is shot in either 1080x60i or 720x60P so there is no 2:3 pulldown necessary for a 60Hz HDTV. Those also happen to be the 2 HD broadcast formats used by CBL/SAT/TELCO/OTA

If a station is showing a movie that was originally shot in 24 fps, they will have already done the 2:3 pulldown because they are broadcasting in the above two HD formats

Blu-ray disc is recorded at 24P. There you need the 2:3 pulldown to get to 60Hz

I have Google Fiber Gigabit Internet and TV for a week now. I had been watching U-verse TV for the prior seven years. Someone posted on the official Fiber forum that he was getting film based panning judder and speculated about a 24P bug. I've also noticed a severe film based panning judder at times. Don't recall seeing it so much on U-verse. From what you say, apparently this would have nothing to do with the Google Fiber TV box, but is a broadcast source issue. Can you please confirm this? TV is Panasonic 65VT50. Thank you.
post #20 of 31
Quote:
Originally Posted by hoozthatat View Post

When and where is the 2:3 pulldown implemented? Does this have anything to do with satelite, cable and air TV, or is the 2:3 pulldown only in reference to film(movies)?
Film is shot at 24fps. In NTSC regions, this is slowed down to 23.976fps. (24/1.001)

This allows you to encode 23.976fps frames into 59.94Hz (NTSC is 60/1.001)
Using a 3:2 encoding scheme, 5x 23.976 = 119.88.. = 2x 59.94

With hardware that can reverse this 3:2 encoding scheme, you can extract the original 23.976fps video, and play it back at 24Hz.
If your hardware cannot do this, the video will judder due to the uneven frame encoding.

Of course this only applies to content which was originally shot at 24fps.


In PAL regions where the legacy format is 50Hz rather than 60/1.001, films are typically sped up from 24fps to 25fps, and encoded using a 2:2 scheme.
With Blu-ray discs, the releases are often at the original 24fps framerate, rather than the slower 23.976fps - though sometimes they are still 23.976fps if they just use the same source as the US release.
post #21 of 31
@Chronoptimist, you said, "If your hardware cannot do this, the video will judder due to the uneven frame encoding." To clarify, the hardware you are referring to is the cable provider box? If the cable box can't/shouldn't do the processing, then can/should the TV do it? Your response seems to contradict what I quoted from Lee Stewart. Sorry, but I'm still a bit confused.

As far as what is shot at 24fps, my understanding is that would be all movies and all film-based TV shows, such as say Law & Order, but not videotape such as sports or news, etc. Thanks.
post #22 of 31
Quote:
Originally Posted by BIC2 View Post

@Chronoptimist, you said, "If your hardware cannot do this, the video will judder due to the uneven frame encoding." To clarify, the hardware you are referring to is the cable provider box? If the cable box can't/shouldn't do the processing, then can/should the TV do it? Your response seems to contradict what I quoted from Lee Stewart. Sorry, but I'm still a bit confused.

As far as what is shot at 24fps, my understanding is that would be all movies and all film-based TV shows, such as say Law & Order, but not videotape such as sports or news, etc. Thanks.
I'm not sure if your cable box will switch to using a 24Hz output - it may need to be your television that handles this. Not much hardware has proper 3:2 support.
post #23 of 31
Quote:
Originally Posted by BIC2 View Post

@Chronoptimist, you said, "If your hardware cannot do this, the video will judder due to the uneven frame encoding." To clarify, the hardware you are referring to is the cable provider box? If the cable box can't/shouldn't do the processing, then can/should the TV do it? Your response seems to contradict what I quoted from Lee Stewart. Sorry, but I'm still a bit confused.

As far as what is shot at 24fps, my understanding is that would be all movies and all film-based TV shows, such as say Law & Order, but not videotape such as sports or news, etc. Thanks.

Film for episodic TV is basically dead. Since 2010 most production is using digital file based systems. Now they still run at 24P. 1080/24p IS the standard for episodic TV production these days. 1080/60i is used mostly for live and taped shows such as GMA, TODAY show, The View, etc.

Though not used much anymore, in the early 2000s some shows used 24P video cameras to video tape. This has mostly been replaced with file based cameras.

Note 24P also means 23.976.

The whole idea of 24P HD is the ability to have a single universal master. For 1080/60i (and 59.94), just add 3/2 as was done with film. For 1080/50i just speed it up 4%, again just as was done with film for 50hz television. And of course 1080/24p can be down converted to 525/60 or 625/50 without the artifacts from standards conversion - again just as we did in the film days. Many European broadcasters will not accept 60hz conversions. 24P video solves this problem.
Edited by Glimmie - 9/5/13 at 6:30pm
post #24 of 31
What about telecine judder? Is that different from 2:3 judder? If so, how do I tell the difference while watching? Should I set TV box for 1080i or 1080p out? I have Google Fiber TV box and Panasonic 65VT50. Thank you.
post #25 of 31
Quote:
Originally Posted by BIC2 View Post

What about telecine judder? Is that different from 2:3 judder?
Same thing.
Quote:
If so, how do I tell the difference while watching? Should I set TV box for 1080i or 1080p out? I have Google Fiber TV box and Panasonic 65VT50. Thank you.
It depends on which device, the fiber box or the TV, has a better 3/2 detector. Try both combinations and choose the one that looks best to you.
post #26 of 31
Just to clarify, since the cable TV is broadcast in 1080i, if I leave the cable box on 1080i out, the TV does the 3:2 processing; if I leave the cable box on 1080p out, the cable box does the 3:2 processing. Is that correct? The cable box also has a 720p out option. Although probably not worth the trouble to keep changing, I assume it might be preferable to switch the output to 720p for ABC & Fox or doesn't matter as TV will upconvert to 1080p anyway? Thanks.
post #27 of 31
Quote:
Originally Posted by BIC2 View Post

Just to clarify, since the cable TV is broadcast in 1080i, if I leave the cable box on 1080i out, the TV does the 3:2 processing; if I leave the cable box on 1080p out, the cable box does the 3:2 processing. Is that correct?
Yes.
Quote:
The cable box also has a 720p out option. Although probably not worth the trouble to keep changing, I assume it might be preferable to switch the output to 720p for ABC & Fox or doesn't matter as TV will upconvert to 1080p anyway? Thanks.
Yes again.
post #28 of 31
Quote:
Originally Posted by BIC2 View Post

Although probably not worth the trouble to keep changing, I assume it might be preferable to switch the output to 720p for ABC & Fox or doesn't matter as TV will upconvert to 1080p anyway? Thanks.

Depends ... the chances are that the scaler in your TV is probably better than the on in the cable box. Also, many cable boxes have a "native" format option which would probably be "best" with most modern TVs, so long as you can stand the few extra seconds it might take for the TV to re-sync when changing channels.
post #29 of 31
Sorry, my technical knowledge is not at the level of some on this post.

I have a 2012 Panasonic 65VT50 plasma, a top of the line TV. If I set the Google Fiber TV Box on 1080i out, on the TV setting for 3:2 pulldown is Auto and 24p DirectIn is grayed out at 60Hz. Both movie and video look OK.

If I set TV Box to 1080p out the TV 3:2 is grayed out set to Off and the 24p stays same 60Hz grayed out. Both movie and video seem OK.

If I set TV Box to 1080p/24 out, the TV 3:2 changes to Off and the 24p gives me the option of 48, 60 or 96Hz (I have it set at 96). Both movie and video look a bit weird. Movie motion has artifacts and video seems a bit cartoonish. These same settings on Blu-ray are fine.

The TV manual says the 3:2 only works with Non-HDMI sources. All my sources are HDMI. What settings should I use? Thank you.
post #30 of 31
Quote:
Originally Posted by BIC2 View Post

Sorry, my technical knowledge is not at the level of some on this post.

I have a 2012 Panasonic 65VT50 plasma, a top of the line TV. If I set the Google Fiber TV Box on 1080i out, on the TV setting for 3:2 pulldown is Auto and 24p DirectIn is grayed out at 60Hz. Both movie and video look OK.

If I set TV Box to 1080p out the TV 3:2 is grayed out set to Off and the 24p stays same 60Hz grayed out. Both movie and video seem OK.

If I set TV Box to 1080p/24 out, the TV 3:2 changes to Off and the 24p gives me the option of 48, 60 or 96Hz (I have it set at 96). Both movie and video look a bit weird. Movie motion has artifacts and video seems a bit cartoonish. These same settings on Blu-ray are fine.

The TV manual says the 3:2 only works with Non-HDMI sources. All my sources are HDMI. What settings should I use? Thank you.

It sounds like that box isn't doing a very good job with inverse telecine (IVTC); hence the artifacting. Which apparently is what you're doing when displaying TV content (29.97 fps) with that 1080p/24 setting. For video content originally shot at 29.97 frames per second, attempting to do IVTC is a bad idea anyway, since it wasn't telecined in the first place. For telecined movies originally shot at 24 fps it might be okay, though it's possible the box will get the pattern wrong. The pattern won't necessarily be consistent throughout the program. Blu-Ray of course will look fine, as it's 24 fps (actually 23.976 fps for TV display, but that's a quibble). Really I dunno why your box has that option. Maybe someone can explain.

And I hope I've understood correctly what your settings do. As to that last bit from your manual, I confess I dunno what to make of that. tongue.gif

I'd set it to 1080i or 1080p. It won't much matter which, as the TV will convert 1080i to 1080p internally because that's what the panel can display. If any true 1080p content is available to you (other than Blu-Ray), set the box to 1080p. (I understand DirectTV, for instance, offers ppv movies in 1080p). I presume if you set your Blu-Ray player to 1080p/24 output, your TV will display that correctly at 48, 72, or 96 Hz. Mine does, at 120 Hz. (Even multiples of 24, you see).

Telecine, or pulldown, is done two ways, which are functionally equivalent: 2:3 pulldown or 3:2 pulldown. It just refers to the pattern in which fields are repeated to bring up film content (24 fps) to TV broadcast standard (29.97 fps).

This little picture might help you visualize how it's done, although it's a bit old and refers to NTSC:


Edited by fritzi93 - 9/10/13 at 10:36pm
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