120hz explained

[stockstar1138]

I already posted this in another thread, i put a lot of work into it and dont want to have it overlooked.

i have been hearing a lot of complaints about the 120hz tvs looking "too smooth" in the past i have complained about it to. i was ignorant to how these 120hz actually worked, below is a description on what is causing the "too smooth" look that people are complaining about and that these tvs do not have this problem if the settings are correctly set.


here is the problem you guys are seeing with the 120hz tvs.

they got these motion enhancer settings on and it tries to interpolate changes in the pictures for all 120 frames per second. in other words if i got 2 frames of a movie and the image of the move in one frame is here:



and the next frame is here

xxxxxxxxx

a tv that is set to display the native 1080p24 signal will do this (this is having motion settings set to low or off)

1st frame repeated 5x (24 x 5 = 120)








notice all similies are on the same spot horizontally on the screen as the same image is simply repeated 5 times in a row.

2nd frame
xxxxxxxxxx
xxxxxxxxxx
xxxxxxxxxx
xxxxxxxxxx
xxxxxxxxxx



the motion looks realitively smooth on the screen as all frames are repeated on screen an equal amount of times and the image is exactly how it is encoded vs. a 60hz tv will do this

1st frame





2nd frame
xxxxxxxxxxx
xxxxxxxxxxx

notice that all frames are not repeated equal amounts which creates uneven judder (note: judder is a natural part of 24p film, uneven judder, caused by a 3:2 pulldown is not). to arrive at this a hdtv does something called a 3:2 pulldown.

a 120hz tv with motion enhancers on is going to take a 1080p24 signal and display each frame 5 times, however instead of just displaying the image as encoded it is going to try to interpolate where the image will be at in between frames and is going to go like this
is

1st frame

xx
xxxx
xxxxxx
xxxxxxxx



2nd frame
xxxxxxxxxxx
xxxxxxxxxxxxx
xxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxx

with a 120hz tv with motion settings on "on" or high" every single frame (for 120 frames) will show a different image, even though the film should only be showing 24 different frames per second (each repeated 5 times) when being displayed at native 1080p24 signal. with motion enhancers on it will not repeat the native 1080p24 signal instead it will try to guess what the 4 frames would look like between what the blu-ray player is telling it to display. this is what gives it the ridiculous smoothness look. i hope this clears things up. nothing beats a native 1080p24 signal which you can get with a 120hz tv, but not a 60hz tv. all 120hz tvs should be able to have these motion enhancers turned off.

all those xxxxs were added as space fillers and mean nothing.

[seto]

Nice work on the guide. This makes things a bit easier to understand.

[york weir]

Are the two threads the same?

[dobyblue]

Unfortunately not all 120Hz sets work like Sony's motionflow sets do.

A lot will take the 24Hz signal, use 3:2 pulldown to get to 60Hz, then use 2:2 pulldown to get to 120Hz.

[Grif32]

Originally Posted by york weir

Are the two threads the same?

There are 3 now

[stockstar1138]

what the hell is going on. i only posted this once

[york weir]

Originally Posted by stockstar1138

what the hell is going on. i only posted this once

LOL, your finger trembling?

On topic, my brother-in-law bought a Samsung LN-T5271F and hated the 120hz feature and turned it off. Is it really only good for material recorded in 24hz?

[stockstar1138]

props to dobyblue for this post

"Unfortunately not all 120Hz sets work like Sony's motionflow sets do.

A lot will take the 24Hz signal, use 3:2 pulldown to get to 60Hz, then use 2:2 pulldown to get to 120Hz."

these are the sony's (xbr4 and xbr5) im talking about in the OP. im pretty sure that the samsungs 71 do what doby is complaining about, i was not aware of this until now.

[nhaase]

I would like to add that the line of Pioneer Kuro plasmas display 24p material in a different way. They will display 24p material at 72Hz, or "3:3 pulldown," if you want to use a familiar term. 3:2 pulldown means what stockstar said, so 3:3 pulldown means each frame is repeated only 3 times, instead of 5. Another way to do the same thing.

Stockstar, this is a very good, straight-forward explanation. I guess there are three of these threads because it's just that good!

[whippersnapper]

Originally Posted by stockstar1138

what the hell is going on. i only posted this once

what the hell is going on.

The forum must be doing thread interpolation.

[devils3023]

Originally Posted by york weir

LOL, your finger trembling?

On topic, my brother-in-law bought a Samsung LN-T5271F and hated the 120hz feature and turned it off. Is it really only good for material recorded in 24hz?

As he stated above it negatively effects a 1080p24fps signal and should be turned to off/low when watching a blu-ray. For cable tv you can turn in to on/high if you prefer.

[stockstar1138]

Originally Posted by york weir

LOL, your finger trembling?

On topic, my brother-in-law bought a Samsung LN-T5271F and hated the 120hz feature and turned it off. Is it really only good for material recorded in 24hz?

no. 120hz is the magic number.

tv broadcasts are done in 60 frames per second.

so a blu-ray encoded at 1080p24, the tv will take the image and repeat 5 times

and a broadcast broadcasted at 720p60, the tv will take the image and repeat 2 times.

120hz is so great because both 60 (tv) and 24 (blu-ray) are factors of the number.

both tv and blu-ray are shown in their native forms.

[york weir]

Originally Posted by stockstar1138

no. 120hz is the magic number.

tv broadcasts are done in 60 frames per second.

so a blu-ray encoded at 1080p24, the tv will take the image and repeat 5 times

and a broadcast broadcasted at 720p60, the tv will take the image and repeat 2 times.

120hz is so great because both 60 (tv) and 24 (blu-ray) are factors of the number.

both tv and blu-ray are shown in their native forms.

My brother-in-law said it was jerky and just didn't feel right to his eyes. I need to get to his house and watch it first hand though he doesn't have any 1080p24 material.

[stockstar1138]

Originally Posted by york weir

My brother-in-law said it was jerky and just didn't feel right to his eyes. I need to get to his house and watch it first hand though he doesn't have any 1080p24 material.

well thats most likely because of what dobyblue stated. the samsung 71 series takes a 1080p24 encode, uses the 3:2 pulldown to arrive at 1080p60 and then multiplies that by 2. so instead of a normal 60hz tv doing this

1st frame





2nd frame

xxxxxxxxx
xxxxxxxxx

the 71 series does this

1st frame








2nd frame

xxxxxxxxxx
xxxxxxxxxx
xxxxxxxxxx
xxxxxxxxxx


it just multiplies the 3:2 pull down two times.

[crunchywyte]

I bought a 52" Sharp LCD in Nov., towards the end of Dec. I went into a Best Buy and saw how the Sony XBR4 played back Blu-rays at their native 24hz and now I can not even watch Blu-ray's on my Sharp any longer, I am working on getting the Sharp sent back and I am in the process of buying the 46" XBR4, I read somewhere..."Once you see video in 24p, you won't be able to view it any other way"....for me this has been very true. I cannot believe how it just looks as though you are looking through a window at the movie like you are there.

[stockstar1138]

Originally Posted by crunchywyte

I bought a 52" Sharp LCD in Nov., towards the end of Dec. I went into a Best Buy and saw how the Sony XBR4 played back Blu-rays at their native 24hz and now I can not even watch Blu-ray's on my Sharp any longer, I am working on getting the Sharp sent back and I am in the process of buying the 46" XBR4, I read somewhere..."Once you see video in 24p, you won't be able to view it any other way"....for me this has been very true. I cannot believe how it just looks as though you are looking through a window at the movie like you are there.

i know what you mean. i had no problem with my samsung 65 series til i saw the xbr4 and now its really hard to watch sometimes. im going to avoid looking at the xbr4 for a while and see if i forget about how smooth it looked to make my blu-ray experience more enjoyable.

you know what though, thats the thing with tech, its always getting better.

those people who spent thousands on 720p hdtvs kicked themselves when 1080p came out, we kick ourselves when 120hz tvs came out, those people will kick themselves when oled is affordable, those people will kick themselves when 3d comes out and the process just keeps going on and on and on. we as consumers can never be satisfied unless we are willing to spend a ton of money on upgrades every few years.

[jkwest]

i have the 50A3000...and I can tell you 120Hz is weird....it looks great on naturelike shows and sports...but, on movies..ehh, I'm not a fan...makes movies look like soap operas..

[owa]

Thanks for the mini-guide. I've been wondering what they do that makes it look "different" from my current TV (that I hope to replace soon with a 120hz set).

[Carmien]

Nicely done.

My perspective as a 52" XBR5 owner.

I have the option with Motionflow (120Hz) of off/on/high.

When I turn it to on things look smooth. I have Blade Runner (which is 24p) on Blu and I have to say that it is an AMAZING visual to behold. It is like sex for the eyes.

If I turn Motionflow to High then I get that ultra-smooth look. The explanation given is a good one. It really comes down to the TV guessing what will happen but not all guesses are good. This becomes particularly apparent in fast action scenes such as chases. The motion is unnatural but the colours and lines are very vivid.

I've watched Planet Earth with Motionflow on high and enjoyed it. I also think that Motionflow for sports is fantastic. The comment about TV broadcasting meaning on a repeat of 2 frames IMHO results in a very clear capture of motion.

As someone who is both a movie fan and a sports fan I really do get the best of both worlds. I get to enjoy 24p movies with Motionflow on low mode, and for sports I crank it up to high and my eyes get to feast.

[bilbravo]

I still don't understand why you want 1080p/24. Why not 1080p/60? I assume the 24/60 are fps.

For example, video games run at 60fps (hopefully). They look better than something that runs at 30fps.

Please explain why I would want less frames per second. And "because that's how it is encoded" is not what I'm looking for, because my next question would be : why not shoot/encode it at more frames per second?