TV judder. 100hz to blame?

Iuvatar

Standard Member
Ok here is whats up.

Last week i bought a philips 32pfl5606 tv. Its a full hd led 100hz tv that has a great picture quality BUT there is a fault. When compared to my non led, non 100hz hdtv the philips' picture seems to be a bit less smooth and prone to slight juddering (my brother says he cant see a thing but i see it clearly). Now this kinda defies the whole 100hz thing. Isnt 100hz technology ment to elimitane judder? How come a non 100hz tv is smoother then a 100hz one in both sd and hd tv?
Oh and the judder is there when watching sd tv and hd tv via hdmi. When i stream films from my pc i can make the pc output 24hz so the judder in that case is gone (or at least i cant spot it). But 24hz is only from blu ray and hd content. When watching dvd and other random video files i have the PC set at the default 60hz and teh judder is there.

Can the reason for this be hte 100hz that somehow manages to expose every single imperfection in the quality of the video that is non detectable with a tv with a slower response time?

Help!
 

mikej

Well-known Member
i have the PC set at the default 60hz and teh judder is there.

I thought UK TV's were set up for 50Hz (Freeview etc) or 24Hz (BluRay) and not 60Hz.. at least not natively.

A PC monitor would accept a 60Hz signal without a problem, but perhaps UK TVs cannot ?

Can you set your PC to output 50Hz ? IIRC, there is a very similar recent post around here somewhere where this solved the problem.
 

AndyCob

Well-known Member
The original idea of 100Hz was to reduce flicker on CRT TVs and not judder at all, plus it had the always desirable larger number bigger is better factor to attract the non tech savy public to buy.

UK TV is based on a 50Hz signal (there is loads more but I don't propose going into the drifferences between interlaced and progressive etc here a search will get you tons of threads). By flashing the screen twice as fast (essentially showing each picture twice) it reduced the flicker some people noticed as CRT screens started to get larger. This was feature of the technology in CRT screens in that an electron beam scans across the phosphor coating on the back of the screen to generate light so the image essentially flashes up brightly then dims all of which happens very fast and by doing it twice it evened out the image brightness. LCD and plasma flat panles work differently as the pixels stay constantly lit until changed.

Later manufacurers realised there were possible improvements with motion in that you could interpolate (make up) extra images to go in between the broadcast images by processing consecutive images to creat an extra one to go inbetween. While this is a heavily marketed feature to most customers in many cases it really doesn't work that well. As simply flashing the image twice would be of no benefit on a plasma or LCD where the pixel is always fully lit, this became the reason for 100Hz on plasma/LCD. No one wanted to go back to 50Hz because then it wouldn't sound as good as 100Hz to those people that just look for bigger numbers as an indicator that it must be better.

Many screen setup guides begin with turn any motion handling/image smoothing feature off and as you have noticed it frequently is worthless or even detrimental and can result in all sorts of undesirable effects. It can be a good thing but it depends a lot on how it was implemented and the nature of the source/screen etc.

The things to try are adjusting the screen settings for whatever motion handling your screen may have which may reduced the judder.

Also since your TV is 50/100Hz feeding it 60Hz from the PC is a recipe for disaster as your PC will be converting 50Hz material to 60Hz then your TV will be convertiong it back to 50Hz which will probably cause all sorts of judder so set your PC display refresh for the output to the TV at 50Hz if possible. For Blu-ray content in 24p you want your PC/BD player outputting at 24Hz and for SD UK TV or UK PAL DVDs 50Hz, only use 60Hz if playing US 60Hz material such as a US DVD.
 

HaRd2BeAr

Distinguished Member
Also since your TV is 50/100Hz feeding it 60Hz from the PC is a recipe for disaster as your PC will be converting 50Hz material to 60Hz then your TV will be convertiong it back to 50Hz which will probably cause all sorts of judder so set your PC display refresh for the output to the TV at 50Hz if possible. For Blu-ray content in 24p you want your PC/BD player outputting at 24Hz and for SD UK TV or UK PAL DVDs 50Hz, only use 60Hz if playing US 60Hz material such as a US DVD.

Most tvs can accept and display 60hz as that is what game consoles run at.
 

AndyCob

Well-known Member
They can accept it as an input but the results of how they then convert it back to 50Hz to process and display can be most undesirable and judder is at leat one major consequence very few that I aware of will actually display 60 as 60 but will convert it. Most if not all UK consoles ought to output at 50Hz if set to do so.

I beleive the TV I currently have actually displays 60Hz as 60Hz or even 120Hz if motion smoothing is enabled but this is not a documented feature of the set but likely a hang up from the fact that like many UK TVs it is based in part on a US model. The TV is officially 50/100Hz but my read of it's service docs indicate it not only accepts 60Hz as many/most do these days (as well as 24,48,50,60) but actually displays it at 60Hz and even has support for motion smoothing 60Hz to 120Hz rather then converting 60 to 50 then processing to 100 but this is not stated anywhere officially that I can find. The closest thing in the manufacturer stated spaecs comes from the set being marked as 100Hz+, something I believe was done to avoid confusing most buyers by mentioning the support for 60/120 which most would neither use or understand.
 

HaRd2BeAr

Distinguished Member
They can accept it as an input but the results of how they then convert it back to 50Hz to process and display can be most undesirable and judder is at leat one major consequence very few that I aware of will actually display 60 as 60 but will convert it. Most if not all UK consoles ought to output at 50Hz if set to do so.

I beleive the TV I currently have actually displays 60Hz as 60Hz or even 120Hz if motion smoothing is enabled but this is not a documented feature of the set but likely a hang up from the fact that like many UK TVs it is based in part on a US model. The TV is officially 50/100Hz but my read of it's service docs indicate it not only accepts 60Hz as many/most do these days (as well as 24,48,50,60) but actually displays it at 60Hz and even has support for motion smoothing 60Hz to 120Hz rather then converting 60 to 50 then processing to 100 but this is not stated anywhere officially that I can find. The closest thing in the manufacturer stated spaecs comes from the set being marked as 100Hz+, something I believe was done to avoid confusing most buyers by mentioning the support for 60/120 which most would neither use or understand.

As stated before modern lcds/plasmas etc will accept and display 60hz properly. There is an option for 1080p @ 50hz but i imagine this is for cheap brands as every tv i have looked at recently has stated support of 1080p @ 60hz.

In fact my 3 year old Samsung 32B450 will accept and display 1080p @ 60hz with no judder (obviously it is only 1366 * 768) and even if i select the 50hz option it switches to 60hz. Every other source is 50hz.

Remembering that the Xbox 360 is American and the games are developed for use with a console that displays 50hz.

I don't know all the in and outs though.

Anyway back to topic :)
 

Iuvatar

Standard Member
Ok guys thanks for the detailed replies.
So basically the 100hz of the tv itself cannot be blamed for the judder since 100hz refers to the flicker rate and not the actual movement of the images i.e. picture?
I was at the store today comparing the TV with another LG right next to it. The LG was a normal LED tv (no 100hz) and cheaper too, but i noticed that it had a smoother picture. Both tvs were hooked up to sky sport HD and were showing a football game and like i said the LG was smoother. How is this possible? Is it just that the LG is a better TV then the philips even tho it is cheaper and a non 100hz?

I guess that you explained the biggest question that was gnawing at me. Can the 100hz make a picture (either hdtv, sdtv or blu ray) worse in aspect of judder and non-smoothness. The answer is no? (sorry i just want to be super sure)
And i found a program called reclock. Can this help me to solve at least the PC judder part of my problem? As for the television broadcast, i guess im stuck with a juddery picture (tho i will try turning off all effects in the pixel plus HD menu, but my hopes are low of that improving anything, *sigh*)

P.S. If someone has the same model tv please leave your impressions. So that was philips 32pfl5606.

Cheers.

P.P.S
AndyCob

The tv manual says to set the pc to 60hz when conecting the tv to it. When i connect the tv with teh PC and go to the display options of my ati graphic cad i have a choice of lots of resolutions from 23 to 60 hz. (i have 25hz twice for some reason).
 
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AndyCob

Well-known Member
Sorry I have confused things slighly for you I think by bringing up the origin of 100Hz on CRTs. The 100Hz on LCD/plasma can indirectly be responsible for the judder in some circumstances (it wasn't on old CRTs). I say indirectly because it is actully the process of conversion or interploation for generating extra intermediate frames that tends to cause the judder becasue of the differing frame rates, simply flashing the same image twice for example would not cause much if any judder, but interpolating an extra frame inbetween can if the process isn't done well as can dropping frames or other odd conversions for getting from 60 to 50/100. Converting 60Hz to 50 or 100 doesn't convert simply, 50 to 100 is easy at it's most basic it's just x2 as is 60 to 120 but to go from 60 to 50 or 100 you need to drop frames or do a lot of fancy interpolation that can create judder. The actual quality of the result though is very dependant on the specific implementation even converting 50 to 100

Usually there will be a menu option that controls what your screen is doing with regards motion handling and how it converts 50 to 100. I don't know what it is on your TV but my Sony for example has 4 seperate options plus off of the 4 options 2 are terrible, one is good and one is very good and off is best for BD. Go through your manual/settings and try the options you may well find you can correct the problem with the right setup.

As to the difference between the TVs you observed it's impossible to say, one may have a better convsersion system or been setup differently.

Can 100Hz make a picture worse?
The answer is a definite yes if the conversion is done badly, it can also make it better if done well and there is also a matter of personal preference and the nature of the source material which differs between film and TV.

In short try feeding your PC to the TV at 50Hz not 60Hz, you should be able to do that in Windows display properties or your video drivers without resorting to any extra software. Is the entry in the manual for connecting by VGA or HDMI, if you connecting by HDMI from PC to TV I would definitely ignore the manual and try 50Hz, just like setting it to 24Hz for blu-ray means you are feeding 24p material at 24Hz, if you are feeding UK TV or DVD that is 50Hz at source so connect at 50Hz. You may find some of those framrates that appear twice are 25i/25p this relates to interlaced or progressive but it probably isn't worth getting into the differences, just pick 24Hz or 24p for BD and 50Hz or 50p for UK TV/DVD, only use 60Hz for US DVD or if viewing your actual PC desktop or games etc that expect 60Hz.

That and try altering the relevant TV settings, I don't know them for your TV but they can be hidden all over the place under all sorts of names.
 
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Iuvatar

Standard Member
Allrighty then, thanks a lot for breaking things down for me AndyCob.
Strangely i do not have an "turn 100hz off" on my tv, so i cant change it. But i was able to get good quality playback when setting the tv at 24 hz for bray and 25 for dvd. Its too bad that i always have to change the hz to match the material im viewing but i suppose it cant be helped.

Over and out.
 

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