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Discussion Starter · #1 ·
Hi,

I an thinking about buying a Philips tv model 6704. However, I have been unable to find out any info if the 120Hz refresh is able to be turned off. I've seen 120hz in action and just don't like the way it makes movies look.
 

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You can't turn it off. A 120HZ panel is always going to refresh at that rate. You can only change how the video processor doubles the 60HZ output.
 

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Discussion Starter · #4 ·

Quote:
Originally Posted by display veteran /forum/post/18143527


You can't turn it off. A 120HZ panel is always going to refresh at that rate. You can only change how the video processor doubles the 60HZ output.

So I can change the the processor speed on the 6k series Philips tvs?
 

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Quote:
Originally Posted by nitespark /forum/post/18144215


So I can change the the processor speed on the 6k series Philips tvs?

I see that I am going to have to generate a post on what happens from the video inputs to the panel. There is quite a bit of misunderstanding about this. Stay tuned.
 

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You can turn it off on most displays. Its usually called auto motion plus or something like that. Unfortunately those guys are not correct. 120 hz IS frame interpolation. Do some research and youll see what I mean.
 

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Quote:
Originally Posted by BWDinc /forum/post/18150354


You can turn it off on most displays. Its usually called auto motion plus or something like that. Unfortunately those guys are not correct. 120 hz IS frame interpolation. Do some research and youll see what I mean.

No, you cannot turn it off. Do some research with the folks who design these panels instead of the fly-by-night people who think they know it all.
 

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Quote:
Originally Posted by BWDinc /forum/post/18151516


ok, well turn off the frame repeating "feature" and see how much better the picture gets.

That doesn't change the fixed refresh rate of the panel. It only changes the interpolation method.
 

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Quote:
Originally Posted by display veteran /forum/post/18165373


No, you cannot turn it off. Do some research with the folks who design these panels instead of the fly-by-night people who think they know it all.

the update rate of an LCD panel is most certainly not fixed. i've proved this before and have seen it first hand.


talk about the update rate of a TV is really pointless though so to answer the OP's original question as display vet and others have said 95% of TV's with motion enhancers can have it turned off and often also adjusted to your liking at a lower setting.


120hz is simply an enabler and whether or not a certian model allows you to turn off 120hz completely is mostly pointless because with normal TV use 120hz all by itself does not produce the effect your seeing and dislike, its just a needed instrument to enable better motion enhancement


back on the to the other subject with display vet. some TV models like for example the Toshiba xv645u's actually have a separate option in their menu for 120hz (on/off) as well as the motion enhancer (off/normal/smooth)


having had this display connected to my PC as a monitor i did lots of tests on it's performance blurring wise and with 120hz off it performed poorly and had excessive smearing with dark images because the TV switched the mode the TCON was in to a less aggressive timing. this had the positive effect for reducing input lag considerably making it very good for gaming but had terrible pixel blurring making it bad for games with dark images. turning 120hz on halved the pixel lag trail down to level more acceptable but still not as good as my current Panasonic 37" S1 60hz LCD TV.


the simple fact that my 60hz LCD is able to out perform a 120hz Toshiba LCD when in 120hz just goes to show how bad pixel response time still can be with today's TV's and how it totally contributes to blurring on many LCD TV's


The higher end current LCD TV's like sony and samsung models employ even more aggressive RTC (response time compensation or overdrive as its has been called on PC monitors) to make up for the poor pixel response time of the VA panels used in their TV's but this is also what makes them have even more input lag and make them nearly worthless for gaming on for many gamers out there today.


the RTC technique can also bring other undesirable side effects like reversal of the way the pixels respond to changes in the image. to first give you some background on how VA panel type LCD's typically respond naturally (without RTC) are as follows


low large transition times (white to black/black to white aka on off response)

slight transition times are however terrible and this is much more common esp. with TV use


RTC buffers the incoming video frames, analyzes them and then applies just the right amount of extra voltage to the needed pixel transistors to get them to change state faster without overshooting their desired position which would result in inverse ghosting, something that was very common on the first LCD monitors that came out for the PC market with RTC.


RTC is directly related to a panels update rate and without it it would make 120hz completely pointless. it is 100% possible to turn off or turn down RTC on an LCD as evidenced by LCD TV's like the Toshiba i mentioned as well as the A series Samsung TV's of 2008. they all used this to reduce their input lag down to PC monitor usability levels.


Changes in update rate are also proven possible by Sony and LG TV as well as others i'm sure that are 60hz and allow for a 24p input mode and when they get it rather than adding judder via a 3:2 pulldown they switch the panel to a 48hz mode and do a 2:2 pulldown. LG actually advertises this feature as a 2:2 pulldown while sony does not but I owned one and can 100% guarantee you that it did exactly that with a 24p input as evidenced by the lack of judder seen in movies (most notably in the rolling credits)


bottom line here is LCD's do not have a refresh rate, they have an update rate. its determined by the Timing controller and TCON's can be made to be flexible these days to switch update rates as well as turn RTC on and off or reduce RTC


see this photo for a graphic example of pixel response of an LCD with and without RTC as well as the voltage signal graph difference

 

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Display Veteran,

From you and others I beleive that the TCON circuitry does not change the actual refresh rate being used by an LCD panel to refresh the screen from the output frame buffer it is refreshing from. However, the software and firmware that control the content of the output buffer can but does not have to change the buffer's content.

If this is a correct understanding and the TCON refresh rate is 120hz then a faster fps could not be achieved but slower fps rates such as 60 fps, 30 fps, or 24fps could.

Another way to say this is that if you do not change the frame in the output buffer for 1/60th of a second it will be displayed twice. And if you wanted to create 3:2 pulldown from 24fps content you would leave half the frames in the output buffer for 1/40th of a second and the other half of them in for 1/60th of a second. And for 5:5 pulldown you would leave each frame of 24fps content in the output buffer or 1/24th of a second.


frito,

This concept may be what Sony uses to eliminate judder and reduce motion blur of 24fps content on 60Hz systems and why your Sony is so smooth. I have seen a Sony reference to " 2:2 pulldown plus compensation" as an alternative to 3:2 pulldown but until now I had not idea what it meant. I now think that Sony may be leaving each frame of 24fps content in the ouput buffer for 1/60th of a second and inserting an emply frame after each pair of frames. For lack of a better name I might call this " 2:2:blank" pulldown.
 
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