# 120 Hz Refresh rate for a HD TV make any difference?



## rasmasyean (Jul 29, 2011)

What exactly does a 120Hz refresh rate help with...that is noticable?

And do you need a special HDMI output to be able to do 120 Hz like a blue ray player...or perhaps a HTPC with a monster graphics card? Does TiVo output at 120 Hz?


----------



## dianebrat (Jul 6, 2002)

This is the 2nd post that you've posted that really should have gone in Happy Hour, not Tivo Coffee House. I'm not saying that no one here will answer, but that Happy Hour is a better place for non-Tivo discussions.


----------



## atmuscarella (Oct 11, 2005)

rasmasyean said:


> What exactly does a 120Hz refresh rate help with...that is noticable?
> 
> And do you need a special HDMI output to be able to do 120 Hz like a blue ray player...or perhaps a HTPC with a monster graphics card? Does TiVo output at 120 Hz?


You need to go find a site that explains LCD refresh rates. Your questions show you have no understanding of what it means. Do a Google search for something like "60hz vs 120hz" and go from there.

Good Luck,


----------



## jrm01 (Oct 17, 2003)

As mentioned above, this type of question should not be in this Forum, but hey, I've got nothing better to do so let me throw in my 2-cents worth. 60 hz TVs refresh the image on the screen 60 times per second. This has been the LCD standard for years. However, one of the drawbacks of LCD TVs has been that when there is fast motion on the screen there is a slight blur in the video. They now have 120 hz sets that display the image twice as often, thus reducing the blur considerably.

The 120 hz action is completely handled by the TV and does not require any special HDMI cables (no matter what your retailer tells you) nor special source equipment.

Now, if you're talking about 120 hz with 3D source, that's another matter - but I've already said enough (maybe too much).


----------



## lrhorer (Aug 31, 2003)

Yeah, I'm afraid not. 120Hz is the least common multiple of both 24 and 60. The human eye cannot usually see any flicker from a source delivering more than 24 frames per second, but the problem its it can sometimes notice flicker and jitter from a source that has been converted from 24 fps, which is typical for film and some 1080p content, to 60 fps, or vice-versa. A 120Hz native refresh rate can handle both without flicker or jitter. No video signals of which I am aware employ a 120Hz frame rate, but a 120Hz screen can display both 30 / 60 Hz and 24 Hz without artifacts. It's true such artifacts are more readily seen in a fast-moving video.


----------



## rasmasyean (Jul 29, 2011)

Where do you get a 24 FPS video feed? From a cable channel playing "old movies"? From a VCR? From a DVD player?


----------



## lessd (Jan 23, 2005)

rasmasyean said:


> Where do you get a 24 FPS video feed? From a cable channel playing "old movies"? From a VCR? From a DVD player?


A BD player (Blue Ray)


----------



## aaronwt (Jan 31, 2002)

The streaming services have 1080P24 encodes(also720P24/480P24) . If you have a device that can output them in their native format.


----------



## Jonathan_S (Oct 23, 2001)

lessd said:


> A BD player (Blue Ray)





aaronwt said:


> The streaming services have 1080P24 encodes(also720P24/480P24) . If you have a device that can output them in their native format.


And that's because movies are filmed in 24 frames per second.

So the Blu ray or streaming service is providing you unaltered frame rates. (But if you've got a 60 Hz TV then it's doing conversion to get from 24 to 60 and that conversion can cause motion artifacts.)


----------



## rasmasyean (Jul 29, 2011)

What happens when you have a HTPC play a blue ray disc or stream Netflix? Do you get 24 FPS? Or does it "vary the FPS" like what you see in games' FPS guages?


----------



## Jonathan_S (Oct 23, 2001)

rasmasyean said:


> What happens when you have a HTPC play a blue ray disc or stream Netflix? Do you get 24 FPS? Or does it "vary the FPS" like what you see in games' FPS guages?


It shouldn't vary because its playing from a pre-rendered source, not struggling to keep up with on the fly rendering of 3D geometry like in a video game. But I'm guessing the actual output FPS would probably depend on the video card, drivers, and probably playback software used by the HTPC.

I don't know if most video cards support 24 (or 120 FPS) over DVI/HDMI or if the drivers & video software would be smart enough to configure them in that mode when playing from a 24 FPS source.
(Hopefully someone more knowledgable can answer)


----------



## rasmasyean (Jul 29, 2011)

Jonathan_S said:


> It shouldn't vary because its playing from a pre-rendered source, not struggling to keep up with on the fly rendering of 3D geometry like in a video game. But I'm guessing the actual output FPS would probably depend on the video card, drivers, and probably playback software used by the HTPC.
> 
> I don't know if most video cards support 24 (or 120 FPS) over DVI/HDMI or if the drivers & video software would be smart enough to configure them in that mode when playing from a 24 FPS source.
> (Hopefully someone more knowledgable can answer)


Well a the computer monitor has a "native" refresh it seems (mine is 60 Hz). But I'm not sure if that's actually a max or what. Because I'm pretty sure I've seen like "90 FPS" as well as "20 FPS" in the built-in game guage. So perhaps the rendered video is one thing...and the actual monitor output is another...unless 60 Hz is just for the Windows UI and "full-screening" allows computer monitors to go faster/slower with some sort of computer monitor specific electronics.

So "Netflix" will go through some 3:2 pulldown on my 60 Hz monitor at least in Windowed mode. But will full screening bump the monitor refresh down to 24 Hz? 48 Hz? Or focusing on the NetFlix Window?


----------



## [email protected] (Dec 1, 2007)

jrm01 said:


> As mentioned above, this type of question should not be in this Forum, but hey, I've got nothing better to do so let me throw in my 2-cents worth. 60 hz TVs refresh the image on the screen 60 times per second. This has been the LCD standard for years. However, one of the drawbacks of LCD TVs has been that when there is fast motion on the screen there is a slight blur in the video. They now have 120 hz sets that display the image twice as often, thus reducing the blur considerably.


Unfortunately, it doesn't do a thing to reduce blur if what you have to display is a 60Hz signal, which is the best you can get from a 60Hz source such as TV transmissions (if you are lucky - some are only 30Hz) or a DVD. The blur is often visible in a single frame (pause your TV signal and take a look at it).

120Hz helps slightly, for two reasons. One is inherent in human vision; displaying the same image twice in succession (with a very short gap in between), then displaying the next image twice, and so on produces a perceived effect of smoother motion than simply displaying each image once for twice as long. The other effect comes from the fact that some TVs will actually interpolate a new image in between the two transmitted frames. This generally works quite well, although there are occasional artifacts created by this process.


----------



## [email protected] (Dec 1, 2007)

rasmasyean said:


> What happens when you have a HTPC play a blue ray disc or stream Netflix? Do you get 24 FPS?


For Blu-Ray, that depends on your hardware. I have a PS3 for my Blu-Ray player, and a TV (and home theatre system) that support 1080p24. This means that when I watch a Blu-Ray I get 24fps.

I don't think Netflix stream anything at that rate (yet ...).


----------



## smbaker (May 24, 2003)

rasmasyean said:


> So perhaps the rendered video is one thing...and the actual monitor output is another..


I'm pretty sure the games are talking about the frame rate of the data being updated in the frame buffer (i.e. rendering), not display refresh rate. I just checked an old asteroids 3D game that I wrote many years ago on much older hardware, and it claims to be rendering at over 2500 fps on my modern hardware when set to immediate render mode.

In the old days you used to lock the refresh rate to the display rate to reduce tearing (i.e. so you don't see half of a new screen and half of an old screen when the monitor refreshes). Not sure if they do something different these days, such as double/triple buffering.


----------



## Jonathan_S (Oct 23, 2001)

[email protected] said:


> The other effect comes from the fact that some TVs will actually interpolate a new image in between the two transmitted frames. This generally works quite well, although there are occasional artifacts created by this process.


For what it's worth I personally don't care for that motion smoothing / interpolation effect and turned it off on my TV...


----------



## larrs (May 2, 2005)

Jonathan_S said:


> For what it's worth I personally don't care for that motion smoothing / interpolation effect and turned it off on my TV...


I'll second that. In fact, many people (me included) feel it makes everything look like a cheap direct-to-video production. I keep it turned off on my sets that have it.


----------

