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Discussion Starter · #1 ·
Help!


For 2 weeks I have read a staggering amount of contradictory and misleading information regarding the way that both plasma and LCD TVs attempt to handle this issue. From what I have read, I surmise that:


Because of the sample and hold (pixel swap) nature of LCD tech, LCD TVs cannot reproduce 24fps.


Even LCDs with 120 or 240hz refresh rates are only adding variations of motion blur or frame interpolation to address the issue. This seems to be the most confusing area, as many (most? all?) LCD sets with refresh rates as multiples of 24 still use frame interpolation of one kind or another rather than a strict 4:4 or 5:5 pulldown, perhaps because of the above mentioned nature of their technology.


The above information may possibly be untrue. Its possible that some LCD TVs also employ a timing function (TCOD I think) that swaps the whole frame at a specific rate rather than on a pixel by pixel basis as normal (stepped down to 24 or 48hz from 60) in order to achieve 24p. Perhaps Sony's "True Cinema" is an example of this.


Although Plasma TVs don't have this issue, of the 2009 models, only the Panaonic V10 was able to play back 24p correctly without frame interpolation or 2:3 because of its 96hz refresh rate.


Of the 2010 models only the Panaonic VT series and maybe only the VT25 will have the 96hz refresh necessary for true 24p playback. Its possible that other plasmas have this capacity as well, but if so, I haven't found any.


I don't have a bias one way or the other. I'd just like some hard technical answers to these questions before I plunk my cash down. Anybody?
 

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Yes - Via Blu-Ray Player with 24P passed through as has been tested over and over . . .


You do understand that 24P is not the same thing as the measured Hz don't you? Don't confuse them.


Read my link on the importance of 1080P.


Here's an extensive list that identifies the panels that have been tested and includes most HT not just LCD.

http://forums.highdefdigest.com/home...rame-rate.html
 

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Quote:
Originally Posted by westa6969 /forum/post/18236471


Yes - Via Blu-Ray Player with 24P passed through as has been tested over and over . . .


You do understand that 24P is not the same thing as the measured Hz don't you? Don't confuse them.


Read my link on the importance of 1080P.


Here's an extensive list that identifies the panels that have been tested and includes most HT not just LCD.

http://forums.highdefdigest.com/home...rame-rate.html

The list appears outdated. The Sony Z5100 series is not listed, and DOES accept and display 1080p/24p signals with no 3:2 pulldown.
 

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Discussion Starter · #4 ·
Thanks westa6969. I had seen your list. And yes, I do understand the difference between frame rate and hz. Since we shoot on film and project on film and everything in between is done digitally, we have to grapple with this issue constantly. And we've worked with Apple and AVID for decades to keep abreast of the compression and decompression scenarios, which have become even more complicated now with the advent of 24p cameras.


My confusion stems from contradictory information about the nature of LCD technology itself. On one hand, I have your very useful list of 24p compatible devices, and on the other, a dozen posts from various (very knowledgeable sounding) members that contradict the information you've provided. These are the ones I mention that talk about the way the sets handle refresh (by changing individual pixels rather than entire frames). I'm not doubting you myself per se. But if this is true, then an LCD set will never display true 24 frames per second, because even though it is refreshing at a variable of 24, it is holding onto pixels that it believes are not changing enough to warrant a refresh.
 

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Discussion Starter · #5 ·
this quote from that article


"Now 24fps experience is possible at home, thanks to the Z5100's 24p Cinema Playback. But wait! There's still one more piece the puzzle, and that's how 240Hz technology affects 24p playback. For 24Hz (24p) video signals, Motionflow 240Hz adds 9 newly created frames that are inserted between the original 24 frames, which also totals out to 240 frames per second (24 x 10). This reduces the affects of telecine judder."


seems to indicate that you need to have the interpolated frames created by the 240 hz processing in order to avoid telecine judder. That's exactly what I don't want. Either the motion blur OR the judder. If a film is shot at 24fps, and played back at 24fps, then there is no telecine or inverse telecine happening. Judder is what happens when you have a mismatch of timing between the frame rates. A true 24p playback devive would incorporate neither.
 

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The problem is LCD's Sample and Hold induced blur as well as pixel level poor response speed.


120/240hz LCD's attempt to remove this problem by decreasing pixel response time and repeating frames when the motion enhancer is turned off, the latter has zero effect on how 24fps looks due to sample and hold blur which is caused by your eyes.


LCD's never blank the image, it is always there, scanning backlights can help but they are not enough not correct the problem due to pixel lag and the fact that a scanning backlight does not fully blank the screen like a CRT does. so manufactures resort to motion enhancers to achieve a smoother overall picture.


LCD's look very fluid however to the human eye when true frame rates of anywhere from 60-120 fps are displayed as evidenced by video games played on LCD monitors and TV's. the main problem with them is handling low framerate video like 24 fps film and 30 fps video sources


Plasma does not have these issues because of its sub filed refresh design where every other frame is a different part of the video image i believe it refreshes chroma then luma back and forth rapidly but i may be wrong its something like that though


if you record a plasma with a high speed camera and slow down the playback you can see each individual frame is not in full color but they appear to be to your eyes due to the high speed at which these frames alternate (600 times a second on current plasma models) this is also the cause for the flicker some people notice with bright/white images on plasma
 

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Bram...,

A 120Hz LCD TV refresh the contents of each display 120 times a second and it does so by refreshing it from the contents of a output buffer. And yes the display itself shows and holds the conten untill the next refresh 1/120th of a second later. The effective refresh rate of video itself is controlled by how often the content of the output buffer is changed. If the TV has 60fps second content and leavs each frame of it in the output buffer then each frame will be displayed twice resullting in a effective 60f fps refresh rate.

If the TV has 24fps content and leaves each frame of it the output buffer for 1/24th of a second then the effective refresh rate is 24fps which is know as 5:5 pulldown.

The 600fps subfield refresh rate in some Plasma TVs is not the same since the frame content of the display never changes faster then 60fps , each frame of content is being displayed 10 times to reduce pixel fade.
 

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Quote:
Originally Posted by brambler /forum/post/18236914


Judder is what happens when you have a mismatch of timing between the frame rates. A true 24p playback devive would incorporate neither.

Judder is not a result of 2:3 pulldown. Hitching is a side effect of the uneven 2,3,2,3,2,3... film cadence. Judder is an inherent quality of material shot in 24fps. A 60Hz LCD that can also refresh at 48Hz or a 120Hz or 240Hz LCD with all motion interpolation features turned off can properly do 2:2, 5:5, or 10:10 pulldown, respectively. Judder cannot be eliminated without motion interpolation and doing so will make film look like video and very unnatural.
 

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The "Hitching" that you refer to is also known as 3:2 Pulldown judder which is different from 24fps Judder that can occur during filming a movei. See some of the links in the following search results:

http://www.bing.com/search?q=3%3A2+j...form=QBLH&qs=n


Unlike Plasmas LCD's are not designed to have multiple refresh rates so you can not put a 60Hz LCD into 48Hz mode like you can do with some plasmas to eliminate frame rate Judder using 2:2 pulldown.

I have seen posts that imply that some TV vendors use 2:2 Puilldown and scanning backlights (Frame Insertion) to add an extra frame after each pair of frames on a 60Hz LCD to eliminate frame rate Judder and to reduce motion blur caused by the "Show and hold" characteristic of LCD displasys
 

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Discussion Starter · #10 ·
thanks all for chiming in. although it seems my confusion is to continue!


on one hand, we have Frito saying that the LCD technology is such that it cannot faithfully play back 24p content and must resort to motion enhancers to achieve a more fluid look. this is what i understood from the research i have done.


on the other, Walford states that the picture buffer is able to refresh the entire screen in multiples of 24, whether it be 4:4 or 5:5. this contradicts what i have read but is what i hope for, as it would allow me to buy an LCD instead of a plasma and see my films played back correctly.


I hope i understand these 2 posts accurately. If not, forgive me. Its a bit new to me.


As for the semantic issues. I won't debate the terminology. When I say judder, what I mean is the unnatural motion you see as a result of the mismatched frame rates. The issue that occurs when you actually film something i can live with, as it is inherent to the content. My goal is not to see a perfectly smooth picture, but to see the films as they truly are, with as little or no modifications as possible.
 

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Discussion Starter · #11 ·
Walford,


A side question. Are there 2 different versions of LCD TVs. Some that have a native 120hz refresh rate, and some that are in fact 60hz TVs with an optional 120hz motion "enhancement"?


And if so, would it then follow that the native 120hz TVs could properly display 24p content by completely firing the frame buffer at 5:5, but that the latter would be using the motion enhancement to compensate for the mismatch between 60 and 24.


(dizziness ensuing)
 

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Quote:
Originally Posted by brambler /forum/post/18236394


For 2 weeks I have read a staggering amount of contradictory and misleading information regarding the way that both plasma and LCD TVs attempt to handle this issue. From what I have read, I surmise that:


• Because of the sample and hold (pixel swap) nature of LCD tech, LCD TVs cannot reproduce 24fps.
Simply not true with a display that has a refresh rate divisible by 24. The pixels will change every 1/24th of a second when fed 24p.

• Even LCDs with 120 or 240hz refresh rates are only adding variations of motion blur or frame interpolation to address the issue. This seems to be the most confusing area, as many (most? all?) LCD sets with refresh rates as multiples of 24 still use frame interpolation of one kind or another rather than a strict 4:4 or 5:5 pulldown, perhaps because of the above mentioned nature of their technology.
Only if the motion interpolation is active. It can be turn off on most models to achieve unaltered 5:5 pulldown.


These are the ones I mention that talk about the way the sets handle refresh (by changing individual pixels rather than entire frames). I'm not doubting you myself per se. But if this is true, then an LCD set will never display true 24 frames per second, because even though it is refreshing at a variable of 24, it is holding onto pixels that it believes are not changing enough to warrant a refresh.

Digital compression encoding will hold pixels to the next frame. The display with all motion interpolation off, shouldn't be acting like an encoder.


If by "true 24 fps", you mean that you want to see each original unaltered film frame, you will need to go to the movies or purchase a film projector and screen. Once a film is digitized and/or compressed, it will not be exactly like the original film frames, on any type of display.
 

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Quote:
Originally Posted by walford /forum/post/18240467


The "Hitching" that you refer to is also known as 3:2 Pulldown judder which is different from 24fps Judder that can occur during filming a movei. See some of the links in the following search results:

http://www.bing.com/search?q=3%3A2+j...form=QBLH&qs=n


Unlike Plasmas LCD's are not designed to have multiple refresh rates so you can not put a 60Hz LCD into 48Hz mode like you can do with some plasmas to eliminate frame rate Judder using 2:2 pulldown.

I have seen posts that imply that some TV vendors use 2:2 Puilldown and scanning backlights (Frame Insertion) to add an extra frame after each pair of frames on a 60Hz LCD to eliminate frame rate Judder and to reduce motion blur caused by the "Show and hold" characteristic of LCD displasys

yes they can do this


it's been proven quite a few times on these forums


60hz LG's do it via 48hz 2:2 pulldown


60hz Sony's do it via 48hz 2:2 pulldown


some 120hz LCD TV's allow turning off 120hz completely, the Toshiba xv645u allowed this for its game mode.


it had some really adverse side effects though and so does the 48hz mode and thats why you don't see people bragging about them or manufactures pushing these modes.


on the 48hz LCD's setting them to this mode is much like a plasma at 48hz with a 2:2 pulldown except the whole screen does not flicker like plasma does only the moving edges flicker at a high rate and it looks worse to the eyes than watching it at 60hz with some judder


on the Toshiba disabling 120hz via game mode also reduced the amount of RTC performed in the timing controller and this resulted in visible smearing of dark images because its pixel response time at that point was not capable of keeping up with 60fps under every possible color transition, something that *VA Panels are very well known to be bad at naturally is pixel response time, RTC is the only way to fix it and it has to buffer incoming frames to work at its best and that right there is why *VA panels are terrible for gaming, if they even allow you to reduce or disable RTC like that Toshiba did you get visible pixel smearing and major color banding problems


i'm sure there are plenty of TV's out there today that do not allow you to change their refresh rates but saying an LCD cannot change their refresh rates is wrong.


most current LCD TV's do not allow it and that is the reason for all the false ideas and confusion on the matter
 

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Quote:
Originally Posted by brambler /forum/post/18240930


thanks all for chiming in. although it seems my confusion is to continue!


on one hand, we have Frito saying that the LCD technology is such that it cannot faithfully play back 24p content and must resort to motion enhancers to achieve a more fluid look. this is what i understood from the research i have done.


on the other, Walford states that the picture buffer is able to refresh the entire screen in multiples of 24, whether it be 4:4 or 5:5. this contradicts what i have read but is what i hope for, as it would allow me to buy an LCD instead of a plasma and see my films played back correctly.


I hope i understand these 2 posts accurately. If not, forgive me. Its a bit new to me.


As for the semantic issues. I won't debate the terminology. When I say judder, what I mean is the unnatural motion you see as a result of the mismatched frame rates. The issue that occurs when you actually film something i can live with, as it is inherent to the content. My goal is not to see a perfectly smooth picture, but to see the films as they truly are, with as little or no modifications as possible.

Yep I've owned and viewed many 120hz TV's as well as a 60hz Sony that did display 24p natively via a 48hz 2:2 pull down as well as via a reverse 3:2 pulldown method that could also employ a motion enhancer to smooth it out and also own a plasma and a 1080i CRT RPTV


film looks worse on any of these LCD's than it does on a plasma or CRT display because the normal moving edge flicker/blur although is completely normal for 24fps content due to its low frame rate. looks visibly much worse on any LCD if the LCD is not using a motion enhancer to compensate for the low frame rate. Plasma and CRT produce the most film like experience without going to a theater watching it on a real film projector. this is one of the main reasons why if you read the CRT front projector section its still the preferred projector system over DLP and LCD/LCoS projectors for home theater rooms and Plasma is the preferred flat panel display for Films as well, even with 2:3 judder present in a film a plasma still looks better to many people myself included than LCD's with no 2:3 judder and motion enhancers on or off


120hz LCD can produce a good viewing experience to most people via motion enhancement but some people dislike even mild motion enhancement and faster pans and movements still have plenty of irritating edge flicker when a motion enhancer is set to a low level. plus they can still produce artifacts and distortions when a complicated scene is displayed and the enhancer gets confused and messes up.
 

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Quote:
Originally Posted by frito /forum/post/18241217


Yep I've owned and viewed many 120hz TV's as well as a 60hz Sony that did display 24p natively via a 48hz 2:2 pull down as well as via a reverse 3:2 pulldown method that could also employ a motion enhancer to smooth it out and also own a plasma and a 1080i CRT RPTV


film looks worse on any of these LCD's than it does on a plasma or CRT display because the normal moving edge flicker/blur although is completely normal for 24fps content due to its low frame rate. looks visibly much worse on any LCD if the LCD is not using a motion enhancer to compensate for the low frame rate. Plasma and CRT produce the most film like experience without going to a theater watching it on a real film projector. this is one of the main reasons why if you read the CRT front projector section its still the preferred projector system over DLP and LCD/LCoS projectors for home theater rooms and Plasma is the preferred flat panel display for Films as well, even with 2:3 judder present in a film a plasma still looks better to many people myself included than LCD's with no 2:3 judder and motion enhancers on or off


120hz LCD can produce a good viewing experience to most people via motion enhancement but some people dislike even mild motion enhancement and faster pans and movements still have plenty of irritating edge flicker when a motion enhancer is set to a low level. plus they can still produce artifacts and distortions when a complicated scene is displayed and the enhancer gets confused and messes up.

24p content looks no better or worse on Plasma than it does on LCD. 2:3 pulldown will always look worse than 2:2, 4:4, 5:5 pulldown, and so on. Motion blur is more pronounced on an LCD in fast moving scenes but this is separate from 24fps judder. LCDs don't need any motion interpolation settings active to display film true to the source material.


Once again, the only negative about an LCD motion-wise is motion blur. If you turn on any motion interpolation features, then you will lose the natural look of motion on an LCD.
 

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I fear that I am normally saying LCD refresh rate instead of Frame rate which is controlled by the panels TCON circuit instead of Refresh rate(fps) which is controlled by the TV's Video processing circuits.

The following link I founcd helpfull in understanding that there are several different ways that the TV's video processing circuits can modify the refresh rate.

http://www.edom.com.tw/en/index.jsp?m=viewblock&id=201


More then you ever wanted to know about how video processing circuits create the output buffer for the actual panel.

http://www.hotchips.org/archives/hc2...C20.25.241.pdf


I have read some links that imply that LCD panels that support the Display Port interface may have the capability to change the frequency(HZ) of the TCON circuit. I have not been able to find any links for LCD TVs that have TCON circuits that can run at more then one frequency.
 

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Quote:
Originally Posted by brambler /forum/post/18240992


Walford,


A side question. Are there 2 different versions of LCD TVs. Some that have a native 120hz refresh rate, and some that are in fact 60hz TVs with an optional 120hz motion "enhancement"?


And if so, would it then follow that the native 120hz TVs could properly display 24p content by completely firing the frame buffer at 5:5, but that the latter would be using the motion enhancement to compensate for the mismatch between 60 and 24.


(dizziness ensuing)

No, when motion interpolation such as AMP on Samsungs is turned completely off you get 5:5 pulldown. When such features are on, you get interpolated frames that add something to the image that wasn't there in the source material to begin with. As such, motion interpolation must be off to get the natural film look from a BD or DVD movie.
 

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Quote:
Originally Posted by PlasmaPZ80U /forum/post/18242403


No, when motion interpolation such as AMP on Samsungs is turned completely off you get 5:5 pulldown. When such features are on, you get interpolated frames that add something to the image that wasn't there in the source material to begin with. As such, motion interpolation must be off to get the natural film look from a BD or DVD movie.

this is correct.


in my own personal experience though viewing movies this way on a friends Samsung 46B630 and on a Toshiba 40xv645u that i owned briefly vs my Panny 50X1 plasma and my same friends Panny 50S1 plasma, due to sample and hold induced motion blur as well as typical LCD pixel blur normal film edge flicker/blur is extremely apparent on an LCD vs a Plasma


Sample and hold induced perceived blur has been scientifically shown in testing done by companies to be the major factor causing problems with low frame rate material on LCD's and it is created by your eyes not the LCD
 

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Quote:
Originally Posted by walford /forum/post/18242299


I fear that I am normally saying LCD refresh rate instead of Frame rate which is controlled by the panels TCON circuit instead of Refresh rate(fps) which is controlled by the TV's Video processing circuits.

The following link I founcd helpfull in understanding that there are several different ways that the TV's video processing circuits can modify the refresh rate.

http://www.edom.com.tw/en/index.jsp?m=viewblock&id=201


More then you ever wanted to know about how video processing circuits create the output buffer for the actual panel.

http://www.hotchips.org/archives/hc2...C20.25.241.pdf


I have read some links that imply that LCD panels that support the Display Port interface may have the capability to change the frequency(HZ) of the TCON circuit. I have not been able to find any links for LCD TVs that have TCON circuits that can run at more then one frequency.


Display port is just another method of transmitting a digital video signal to a digital display much like HDMI/DVI


all 3 types are capable of any resolution and refresh rate provided it does not exceed the bandwidth limits of the cable/connector.


once this signal gets to a display, the display must convert it to a signal that the TCON understands.


the internal workings of an LCD display are what determines what refresh rates or update rates if you will that this display can use, there are many LCD PC monitors out there that support 60hz as well as higher refreshes like 72,75,85,100 and 120hz.


how it is handled depends on the monitor specifically. if you look into it you will find that some monitor will display higher refreshes natively and others will just drop frames and it will cause horizontal tearing in test images/moving images on the screen just like computer games cause horizontal tearing if you turn off V-Sync and the framerate exceeds your displays refresh rate
 

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Discussion Starter · #20 ·
So if I understand correctly:


a 120hz LCD can faithfully reproduce 24p content using 5:5 pulldown with its motion enhancers off (no frame interpolation). Its still refreshing its images at 120x per second, but not adding any in between frames to smooth the motion. However, with these settings off, the motion blur inherent in the LCD technology yields a slightly less than desirable look (to some). This motion blur is not the typical effect you see when looking at projected film, but an artifact of the television's tech itself.


I know to those of you who understand this (or think you do!) this must feel like flogging a dead horse, but I am just trying to make sure I have it clearly. All of the new LCDs seem to have their own terminology for how they support 24p, but the language is clearly intended for sales purposes and seems often misleading.
 
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