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Discussion Starter · #1 ·
Ok so I have something that I would love to clarify but so far have not been able to get a proper answer, it seems that the deeper you get into trying to understand the complexity of film and frame rates the more clouded and shrouded in mystery the whole topic becomes. Ok so I have had my HTPC and associated equipment running for nearly 2 years now. However only lately I have started investing more into blu-ray movies. With this change in viewing I did lots of research into finding the optimal playback settings for blu-ray film.


The cumulative research showed that setting my HTPC to a refresh rate of 24hz, turning off any picture processing features (such as noise reduction, reverse pulldown, deinterlacing etc)of my video card and software player (TMT3) as well as that of my Amplifier should result in the cleanest, truest viewing form for blu-rays. The reality though is different...


With all post picture processing settings on my Samsung 120Hz LCD panel turned off, the blu-ray picture is a mess, stutters, grainy and blurry. Only after turning on the Auto Motion processor with a Judder Reduction setting between 4/5 do I get a more stable picture. Also I found that I had to set the Noise reduction setting to auto as while I don't mind some grain, with it off it was too grainy.


So now for my rant, why is it that without judder reduction on LCD panels (at least samsung's) is a bluray movie pretty much unwatchable?, when I know for a fact that the screen is being refreshed at 24Hz *5 and the bluray movie source is 24p and that no other processing is taking place that could be causing issues. Also to add insult to injury DVD's which require de-interlacing and inverse telecine to be displayed on a 120Hz panel play perfectly well when my screen refresh rate is 24Hz with less judder than blu-rays at the exact same settings used for viewing blu-rays.


I have gone through great lengths into trying to understand this, tried changing players, source content and countless configuration settings, the end result all pointed to the panels processor. Is it simply a case of a cheap processor on my TV a Samsung: LN52B610A5F?



Just to clarify my judder with the above configuration is very minimal, I'm the only one who notices it, but then again I'm picky.. but it still begs the question.
 

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Your 120Hz TV always refreshs it's screen 120 times a second with the contents of a separatly maintained software display buffer. If incoming or IVTC obtained film content 24fps is left in the display buffer for 1/24 of a second then 3:2 pulldown Judder will not occcur since 5x24= 120. When this funtion is invoked Frame interpolation motion compensation can not be used to maintain the contents of the display buffer.

The following link has more about this then you probably every need to know.

http://www.hdtvprimer.com/ISSUES/what_is_ATSC.html


The Info button on your TV states what frame rate the TV is receiving and not how it is being processed.
 

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Discussion Starter · #3 ·
Hello Walford,


Thank you for the link, I have used both the Info button on the TV as well as software to detect the contents of the film. Also to add more info, some films have less of an issue than others. The quote below gives a hint to the issue, which kinds of points back to my suspicion that its the quality of the components in the TV, and that most likely a higher end model could potentially not have this issue and that while the TV does support 24p it is not truly processing it correctly.


Quote:
120 Hertz technology


The best monitors show the image 120 times per second. 120 is an exact multiple of 24, 30, and 60. Thus in theory the monitor can show any program without introducing judder. But will the monitor actually do this? Consider the following questions:



1) When using the TV's internal receiver:

a) Can the monitor detect a 24p program and display it without judder?

b) Can the monitor detect a 24 frames/sec program transmitted in 1080 60i and reorganize it for display without judder?

c) Are motion compensated processing and judder-free display simultaneously possible?

2) When taking input from DVI or HDMI:

a) Can the monitor accept 24p and display it without judder?

b) Can the monitor detect a 24 frames/sec program transmitted in 1080 60i or 60p and reorganize it for display without judder?

c) Are motion compensated processing and judder-free display simultaneously possible?




The answer to question 2c is generally no. Since the motion vectors are not available to the monitor, the DVD player would have to do the motion compensated processing. But monitors that can accept 1080 120p are very rare, and 60p will introduce judder. You will likely have to choose either motion compensated processing or judder-free display, whichever looks better on your system.




120 Hertz technology is often touted as a fix for the slowness of LCDs. This is a dubious claim. The improvement is usually miniscule, often not discernable.
 

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3:2 pulldown Judder correction to 5:5 pulldown correction and concurrent 24fps motion compensation are not possible since on a 120hz display AFAIK you need a 240Hz or display to do both so that you can convert the 24fps input to 60 fps using 5:5 pulldown and then interporlate between each pair of 60fps frames.

The following link discuses how current generation TV sets convert 1080i/60 or 1080p/60 film based content bsack to 24fps so that they can apply 5:5 pulldown to eliminate 3:2 pulldown Judder.

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

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One more item may be in play here. Any film-based source video will have a varying amount of blur dependant upon how long of a shutter speed was used in the original photography, which in turn depends on how brightly the scene was lighted. (Now you know why intense lighting is used on movie sets - to minimize blur.)


It is possible to end up with display video that has LESS blur than the film source, but not on all HDTVs. The set must have implemented a "Pixel Swap" algorithym for blur reduction. This replaces the leading and trailing edges of a moving object with the same areas from the lagging and preceding frames respectively. The moving object ends up slightly shortened along the axis of motion, but with blurred edges replaced by unblurred background areas.


Unfortunately, they seldom tell you which algorithyms are implemented in an HDTV, or even what the various menu options for blur and judder reduction actually do to the video processing.


I don't know if pixel swap is implemented on your Samsung. It was in my vintage 2007 120Hz Samsung LN-T4669FX, but when I bough a second Samsung in 2009, they had switched video processors from a Micronas chipset to a Samsung in-house design, and had managed to break both the Reverse Telecine and Pixel Swap processing.


I know it's not very satisfying, but the best way to select a set is still to compare as many as possible and decide what pleases your own eyes. I spent 5 months selecting my last HDTV.


If you are presently dissatisfied, look for the "Official LNxxB610" thread in AVS, and see if someone else has figured out a menu setting to fix what bugs you, or if Samsung has released new firmware for your HDTV.
 
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