"The Big Judder Problem and the Overhyping of 24p"

skidu

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Came across this article the other day and figured it was worth sharing.

The Big Judder Problem and the Overhyping of 24p

I have to admit, I was also naive in thinking 24p would completely resolve juddering issues which are common when using a 3:2 pulldown but having tested it out on 3 different tv's now, they all exhibit the same issues. The only explanation I can think of is; either the PS3 doesn't handle 24p correctly or in fact, like the articles states 24p is just way too slow to resolve camera panning motion cleanly.

This also ties in nicely with 120hz, take Planet Earth for example. You would think running at 24p with Frame Interpolation on would result in completely smooth playback? (24 x 5 = 120), but infact on both the Samsung and Panasonic i still noticed hints of juddering and lost frames. It was only when i disabled 24p and ran at 60hz with Frame Interpolation on i achieved perfectly smooth pans.

Same with movies, 60hz with motionflow on low looks far more natural then 24hz with the same settings.

Just wondering what other peoples experiences are with 24p and if you prefer the cinematic 'juddery' look of for the artificial 'sped up' look with motionflow/frame interpolation on?
 
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Try a decent bluray player and see if the results are the same.
I see no judder at all running source direct from the Pioneer LX70A.

It would make an interesting comparison on your test setup :)
 
Wasn't Planet Earth shot at 1080i 50?

I've only scan-read the article, but shooting at morefps does seem to make sense. Cost has always been given as the main factor against that though - both cost of the actual film/digital storage, and in man-hours (ie when creating and rendering CGI).
 
Interesting article, but they're only looking at one part of the equation. It isn't just frame rate that dictates how smooth motion looks you also have to consider the display method and eyes response to different display methods.

Films in the cinema look smooth because of the shutter.....the image isn't on the screen 100% of the time so your eye/brain does the interpolation. Doubling the shutter speed (same frame twice) and switching off the room lights in a cinema is really to reduce the perceivable flicker.

Judder tends to look worse on LCD becasue unlike CRT and Plasma the image is on the screen continuously....there is no effective shutter so your eyes/brain can't do any interpolation. 100Hz tech is supposed to help this by generating so intermediate frames some that the image isn't fixed for quite so long. With CRT based tech (TV or projector) the image is scanned onto the screen allowing your eyes to iterpolate between frames....works a bit like the shutter on a cinema projector. I'm not totally sure how plasma works, but I think it's nearer to CRT tech than LCD.

The panasonic projector they quoted in the article is an LCD projector so it's not really suprising that it needs frame interpolation to make 24p look smooth. Although I don't have much direct experience with projectors I imagine that a DLP proctor would handle motion better due to the colour wheel thing that they use (I guess they must actually include a shutter or an effective shutter between colour wheel segments....can't understand how it would work otherwise).

I think that the articles suggestion of intentionally introducing 3:2 pulldown to help smooth out 24p judder sounds a bit mad....apart from anything else a good TV processor would be able to detect the 3:2 cadence and recover the original 24p signal anyway!! No harm in trying I suppose....it's still possible that some TVs out there don't process/display 24p properly anyway so it's always worth trying to see what looks best :)
 
I believe that LCD and Plasma both display the frame / image in one hit or blast many times a second (depending on frame rate) unlike CRT which builds it up from odd/even lines.

I assumed plasma had a slightly slower responce between puting each frame onscreen so you got a slightly smoother transition between frames compared to LCD.
 
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Totally agreed with that article. Had my TV (Toshiba Z)settings at what everyone theorised would be best for 24p input and found that it did a much better job with all the image processing options set to the complete opposite (on/high/smooth etc).
 
Tag

I'll post a response tomorrow


PS: 24p does matter, and yes, I can detect even pull-down (1:1, 2:2, 3:3 etc...) and uneven pull-down (2:3).
 
Film isn't judder free even in the cinema.

24fps is not enough in general. Film directors are trained to avoid certain panning speeds and types of shot although in many scenes it can still be apparent.

Its not just the cost that stops the speeding up though there is an association for many people that film=quality=art and video=television=rubbish. There has become a culture where the technically worse (low frame rate and film grain) has become associated with high value quality product (movies).

[Additional]

This is why some people choose to disable high frame rate modes for films to see it as it was intended. If it was just trying to achieve the closest to seeing the real image that was in front of the camera (infinite frame rate) the interpolation/frame rate would be high.
 
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Judde means uneven motion

anyway, I'll post semi-detailed post later
 
I believe that LCD and Plasma both display the frame / image in one hit or blast many times a second (depending on frame rate) unlike CRT which builds it up from odd/even lines.

I assumed plasma had a slightly slower responce between puting each frame onscreen so you got a slightly smoother transition between frames compared to LCD.

There is some kind of pre-charge period for Plasmas where each pixel has to be pre-charged before the illumination signal hits it.....it's the pre-charge that affects the black levels on plasmas and I guess it must allow a blank period or a phosphor decay period that acts as a virtual shutter. It's the lack of any blanking period that causes motion to look juddery on LCD.
 
just to field the DLP question as i own one that does 24hz properly & moves motion to 48hz / fp there is still judder. some movies dont suffer barely. but some including disapointingly some pixar stuff are really quite bad. the motion can be doubled, quadrupled but you will notice even on these sets (i owned a philps lcd with natural motion and really miss this option, on low setting) it still smears as the details are lost from the word go !

24fp/hz is simply too slow.


example, my HTPC can run 1080p 24hz on the vista desktop and the mouse judders and skips frames just the same, also when moving window panes.. its less at 50hz and almost perfect (well good enough i guess) and at 60hz its getting to the point where you would consider it smooth.


once again, all these speed up technologies actually really help, realistic or not but the side ways pan (thinks of spiderman on BD green goblin mask pan) even on the philips running full motion (96hz/100hz) with all its clever tech the motion is liquid smooth but the frame detail still isnt there.

dvd didnt seem as bad, although we have always accepted interlacing and motion effect up until recently where nearly all video gremlins are removed motion still remains or in the case of blueray has got worse, wasnt dvd 30fps and now we have 24fp ? that really is quite slow for our advanced eyes, wonder if some animals see even quicker maybe to htem the screens just flicker constantly


get used to it, until we have 120hz required for 3D we are stuck in the 1930`s.
 
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Judde means uneven motion
Yes you are technically correct but I think it is an issue that causes confusion when people can still notice stepped movement when they have 24p equipment.

We need another word for motion that isn't smooth caused by insufficient framerate. i.e. even but noticable changes between frames.

Visually this is similar but far less severe than judder.
anyway, I'll post semi-detailed post later
Looking forward to it.
 
Movies are shot in 24p and it will remain that way for a long time.

The user who wrote the article doesn't understand what judder is, which is quite sad really. By the looks of it, he spend so much time constructing it.


Judder refers to uneven motion. During 2:3 pull down (24>60), frame A is displayed twice and frame B is displayed three times and so on...

E.g. AA, BBB, CC, DDD, EE, FFF etc... which equals 60i/p.


This creates uneven motion (judder) and highly visible on panning scenes. However, most people are unconscious to this effect, unless you show them (just like phosphor trails on plasma).

24p was adopted by the CEA because it allowed consumers to view 24p contents natively without any motion errors. So each frame is displayed or repeated evenly.

What's surprising is that we've been enjoying this (even motion) for a long time cos 24p is accelerated to 25p and broadcasted at 50i. In DVDs, movies are stored in 25p and are displayed in 50i/p.

So 24p will not remove the choppy frame rate, but it will help to keep motion free of errors.

Also, the appearance of movies completely depend on the director. So on some movies, motion might appear smooth (soft), while on others, it's quote harsh (hard).


PS: I use the following term to describe motion (just to let you know ^-^):

Soft Motion: Low-motion with visible blur, which produces natural-smooth motion with minimal 'choppiness'. Best example, star wars EP3

Hard Motion: Low-motion with minimal or no visible blur, which creates highly visible choppy motion that at times hard to track/ focus on. Best example, saving private ryan

Judder: Low-motion contents with uneven motion. For example, the motion doesn't appear as smooth as the frames are skipped or display longer than the other. Best example, 24p on a 60i/p display.

Stutter: Low-motion and high-motion contents with random jumps in motion. This is common with computers (software based codes) and consoles. It occurs when frame are dropped or skipped to maintain sync. Best example, play a panning shot on you PC and find out LOL.
 
So I assume that most people who get this terminology wrong, are confusing judder with the issue of the lack of frame rates, is that a fair shout? For example, the last film I saw at the cinema was the new Bond film, and when the action heated up, and the camera panned fairly quickly, it was almost impossible to pick out any detail, as the motion obvioulsy lacked frames, and you could see that a greater frame rate was required. So is this what many people would mistake for judder, as this is exactly what you get when watching Blu-rays...? So is "judder" in the correct sense, not this blurry motion caused by lack of frame rates, but actually a jerky motion, which almost looks like the camera man has got the shakes when trying to film a smooth pan? :lesson: I've probably got this completely wrong, so please don't flame me! :rolleyes:
 
Toadus, you've actually got it more or less spot on.

In fact, when the whole jerky camera effect (or just a normal pan) isn't done correctly, it will look rubbish, and it's down to the director to try to stop that from happening. Indeed, when something like this happens, it's far more noticeable than 3:2 telecine judder in my opinion. But hey, it's part of the nature of film. It can be more noticeable on HDTVs due to sample-and-hold, mentioned earlier, as opposed to the flickering system used at the cinema.

Some films have been done with a 1/24 second shutter instead of 1/48 (Ali?) and, although I've not seen these movies, these tend to have more video-like motion which won't work for all material.

Also, using MCFI/Motionflow/100Hz technologies purely to reduce this effect is actually far more sensible than it was a year ago. Sony in particular (on W4500 and Z4500) have managed to be able to reduce this juddering without having too much of an impact on the film look or too many problems with processing artefacts. It's also rumoured that on Samsung's next range, there'll be separate controls for the smoothing and judder reduction elements of the Motion Plus technology. If that makes it to the finished product works well then we may not have to put up with this problem so much in the future. From everything I've seen, perfecting this kind of post-processing is a better option than changing the entire film industry to a higher frame rate.
 
I've never been clear on the term 'judder' and have always thought it to mean telecine judder, as in pulldown methods which cause a frame to drop every second or so. My last TV did this when the player (PS3) was set to 24hz on. The frame drop was evident everywhere, and not just on slow pans. When the player was set to 24hz off, I guess it played the disc at 50 or 60hz, which the TV could handle and no frames were dropped.
The other definition of judder which I think alot of people are usng, is when the picture looks as though it is constantly shaking, as if the material was filmed during a tiny earth quake. I'm not sure what the proper definition for this is as it doesn't sound like frame dropping or a pulldown issue. I'm wondering if this is due to electronic flicker and an individuals own sensiivity to it.
LCD screens have fluorescent tubes which flicker at 50hz, behind a screen of pixels which constantly open and close to let light through, over which a film is played which was filmed at 24hz, and displayed at 24hz or even 60hz. Wouldn't this pick and mix of different speed technlogies be visible to some people?
 
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Oh, excellent. :)

I'm not a fan of these motion features that come with the new LCD televisions, as IMO, they just don't work well... yet. I find there's two main issues with them: Unatural movement, making the film content look like it's been filmed with a home camcorder. And secondly, the artefacts when moving objects are displayed over non-moving objects.

I have a Samsung LEA656 which is a 100Hz set with motion malarky. It lets you choose the level of the motion enhancement which is a good thing, as if you set it to Low, it actually works fairly well with Blu-ray material. It seems as it only does it's thing when required, such as pan shots and what have you. If you turn it up a notch further, you get that laughable home camcorder look which is awful. I don't mind it on Pixar animation type stuff however. I cranked up the motion when Watching WALL-E and Ratatouille and when it worked, it actually looked quite stunning, but you have to put up with the artefacts, and lack of subtlety of when it "kicks in" and so forth.

Oddly enough though, when watching Blu-rays, I've never noticed Judder, in the correct sense, and that's without turning on 24p mode from my BD player...
 
The other definition of judder which I think alot of people are usng, is when the picture looks as though it is constantly shaking, as if the material was filmed during a tiny earth quake. I'm not sure what the proper definition for this is as it doesn't sound like frame dropping or a pulldown issue. I'm wondering if this is due to electronic flicker and an individuals own sensiivity to it.
LCD screens have fluorescent tubes which flicker at 50hz, behind a screen of pixels which constantly open and close to let light through, over which a film is played which was filmed at 24hz, and displayed at 24hz or even 60hz. Wouldn't this pick and mix of different speed technlogies be visible to some people?[/QUOTE]

This is what I have been refering to as judder and what I think is the biggest let down with Blu Ray.The image is fantastic but panning shots really suffer with this shaky motion.There's a scene in Casino Royale (mentioned in the article) where the camera slowly pans around the table creating a strobe like effect causing everything to flicker back and forth.The actual camera pan is smooth,it's whats on screen that judders.
 
So I guess this 24frame issue that shows up on fast panning shots/action is sort of 'frame lack' then?

Quite simply not enough frames per second to capture all the fast motion?

So with our fancy "full cinema 24p" modes now present on many TV's we're seeing it as it was intended, warts an' all!
 
WOW :) this is absolutely fascinating, I got the Samsung LE40A656 a week ago and was trying to understand all this 24fps 100hz motion plus techno babble and after reading this thread and the article it all slowly starts to make a little bit of sense

One thing though, would someone mind explaining in Lehman's terms what frame interpolation is and what this 2:3 pull down is please.

I can't get my head round it :confused:

Keep up the good work :clap:
 
Frame Interpolation is quite easy to explain actually. Obviously you are aware that video signals are lots of still pictures coming quickly enough to give an impression of motion. Frame interpolation, in this case, is basically looking at information from two frames and using it to create a new frame artificially between them, specifically in terms of moving objects.

3:2 pulldown is how you fit a 24Hz film source into a 60Hz broadcast for NTSC countries (North America/Japan). If you duplicate the first frame of the source twice, then the next three times, then repeat, it'll fit into 60Hz exactly, but since you're not duplicating the frames of the original source evenly, judder is introduced.
 
So judder will be there in any case if you chose to output 1080p/24Hz?

In terms of blur with fast action scenes, can lcd handle it like plasma with 24p output, or it wil be some blur on lcd due to lcd response time?
 
Hi

This 24fps really is old stuff, in fact very old stuff. My father, whose first job was a cinema projectionist, complained many times to the management about "flicker on the shutter" on the cameras - and that was in 1938!

I'm looking forward to when they ditch the mechanical 24fps cine cameras (100 year-old technology) and move on to high-speed digital capture.

Alan
 
wow, there are so many errors on this thread

I'll try and correct some, but I can't do everything myself lol
 
So judder will be there in any case if you chose to output 1080p/24Hz?

In terms of blur with fast action scenes, can lcd handle it like plasma with 24p output, or it wil be some blur on lcd due to lcd response time?

I would assume that there is LCD response time issues hence them trying to cover it up with all these 'fancy processing things'.
 
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