120Hz displays - does it matter that much? - AVS Forum
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post #1 of 26 Old 05-25-2007, 04:58 AM - Thread Starter
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Hi,
the 120Hz displays/120Hz driven panels coming to the market in the nearest future are said to introduce a new level of picture quality (at least that is what manufacturers claim).

Just one thing that I just don't get!?

I understand that having a 120Hz driven display will allow to have smooth 24/30/60 fps sources rendering - no jaggies and motion artifacts. But that's all!. It should help only in this regard as the logic tells me.

How these displays would pull out more source details/improve picture crisspness? Where's the hook?

Does driving the panels at 120Hz improve LCD/LCOS response time? The announced response time is supposed to stay at the same level I guess. Refereshing the pixel color information twice faster is good - agreed - if you have a more than 60 fps source (computer game) then you do not lose any frames. But how the 120Hz technology postpone on the picture quality other than eliminating motion jaggies? LCD/LCOS just don't work this way. Increasing panel's refereshing speed should be irrelevant unless it is lower than the panel's response time. That is why most LCD computer monitors have internal signal processing at 60Hz, sometimes even 50Hz. Nobody calls out for higher.

Am I missing something? And how the DLP adds up to this discussion?
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post #2 of 26 Old 05-25-2007, 05:20 AM
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I was under the impression that the 120Hz refresh rates wouldn't do anything for image quality except eliminate the judder that results from the usage of 3:2 pulldown on displays that can't refresh at some integer multiple of 24Hz. As far as motion artifacts, blurring, and jaggies - that sounds like more of an internal processing/source material issue than it does a panel refresh rate issue. I'm certainly no expert though so someone please pipe up if I'm missing something.

There are 10 types of people: those who understand binary, and those who don't.

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post #3 of 26 Old 05-25-2007, 07:42 AM
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If you want better image quality at this point you should look toward your source material.
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post #4 of 26 Old 05-25-2007, 11:08 AM
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120Hz mean 3D stereoscopic active projection - future of entertainment and gaming.
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post #5 of 26 Old 05-25-2007, 02:12 PM - Thread Starter
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Stereoscopic 3D is not possible with LCD/LCOS due to slow pixel response speeds. DLP will only benefit from 120Hz regarding 3D.

Please read this part from one of the press announcments:
"In a show of quality advancements, the largest LCD TV panel for mass production is also being demonstrated at the exhibition. Featuring proprietary 120Hz McFiTM (motion-compensated frame interpolation*) technology, the new 70 LCD display refreshes motion picture images at twice the speed of conventional 60Hz models. This doubles the number of frames per second, making moving images crystal clear".

Maybe it is all about frame interpolation algorithms? Then I doubt this will be a big improvement because the picture information is not in the source (Tryg - I agree, we should look for better sources).
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post #6 of 26 Old 05-26-2007, 02:12 AM
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Quote:
Originally Posted by Kobe View Post

Stereoscopic 3D is not possible with LCD/LCOS due to slow pixel response speeds. DLP will only benefit from 120Hz regarding 3D.

Please read this part from one of the press announcments:
"In a show of quality advancements, the largest LCD TV panel for mass production is also being demonstrated at the exhibition. Featuring proprietary 120Hz McFiTM (motion-compensated frame interpolation*) technology, the new 70 LCD display refreshes motion picture images at twice the speed of conventional 60Hz models. This doubles the number of frames per second, making moving images crystal clear".

Maybe it is all about frame interpolation algorithms? Then I doubt this will be a big improvement because the picture information is not in the source (Tryg - I agree, we should look for better sources).

I dont talk about LCD panel - this forum dedicated to FP.
I meant microdisplays: sxrd and dmd.

New version of Sony's SXRD panel offers a response of 2.5ms and increased framerate.
http://displaydaily.com/2007/04/23/s...xrd-projector/
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post #7 of 26 Old 05-26-2007, 05:49 AM
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Quote:
Originally Posted by vsv View Post

I dont talk about LCD panel - this forum dedicated to FP.
I meant microdisplays: sxrd and dmd.

New version of Sony's SXRD panel offers a response of 2.5ms and increased framerate.
http://displaydaily.com/2007/04/23/s...xrd-projector/

LCOS is the same concept as SXRD and 2.5ms response is still very, very slow relative to DLP 16 microsecond pixel response time.

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post #8 of 26 Old 05-27-2007, 08:35 AM
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At CES Olevia had an LCD 120HZ demo and aside from the image not having motion artifacts it also had a 3D like quality that I liked very much. I could only imagine how good that would look from a 1080P projector and a huge screen.
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post #9 of 26 Old 05-28-2007, 12:20 AM
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Hi Folks,
had a LCOS 120hz front projector setup at the Munich High end show hooked up with a Pioneer BR. The image was stunning.
Can't tell if it was the absend of juddder often recognized im movies, the better higher resoluton or maybe I#m driven by the numbers:1080p/24 input, 120Hz and 1920x1080 output

Best
Armin
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post #10 of 26 Old 05-28-2007, 12:43 AM
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Quote:


LCOS 120hz front projector

Sony Amethyst ?
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post #11 of 26 Old 05-28-2007, 01:37 AM
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Still Cinetron HD-900 latest revision
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post #12 of 26 Old 05-28-2007, 06:13 AM
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Current digital projectors suffer from the so called "sample-and-hold" effect, which adds a bit of motion blur. Getting rid of this is only possible by either:

(1) Increasing refresh rate and adding interpolated intermediate images.
(2) Breaking the "always on" system by either adding intermediate full black frames or by using a scanning light source (i.e. drawing the image line by line).

Going to 120Hz without either of the 2 mentioned additional changes doesn't help getting rid of the sample-and-hold effect. It may have other benefits, though, like avoiding the need to resync when switching from 24p based sources to 60p sources and back.

Here's a thread about the sample-and-hold effect:

http://www.avsforum.com/avs-vb/showthread.php?t=802850
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post #13 of 26 Old 05-28-2007, 09:07 AM
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Quote:
Originally Posted by Armin2 View Post

Still Cinetron HD-900 latest revision

I haven't heard much about the Cinetron since the pre-release information.

Is it available in the US?

Best Regards,
Doug
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post #14 of 26 Old 05-28-2007, 09:57 AM
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Doug,
don't know, but i'm selling it!

Best
Armin
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post #15 of 26 Old 05-28-2007, 10:29 AM
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Armin2, Cinetron HD-900 is able to display 3D stereoscopic pageflip video from PC same way as DepthQ(Infocus) projector? Thanks.
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post #16 of 26 Old 05-28-2007, 10:39 AM
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Quote:
Originally Posted by Armin2 View Post

Doug,
don't know, but i'm selling it!

Best
Armin


Any chance of this happening?
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post #17 of 26 Old 05-28-2007, 12:26 PM
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Quote:
Originally Posted by Armin2 View Post

Doug,
don't know, but i'm selling it!

Best
Armin

Thanks for the quick reply, and I hope it all goes well for you.

I searched a little bit more after posting the question, and I only found press releases announcing that it was coming. I guess it never got released here in the states.

Best Regards,
Doug
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post #18 of 26 Old 05-28-2007, 01:39 PM - Thread Starter
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Thanks madshi and all you guys for feedback. Now I get the whole idea behind 120 Hz.

However there are issues left worth discussing:
1) The intermediate frame interpolation technique seems to be ubiquitous among new 120Hz displays/projectors. Sony calls it MotionFlow and will equip VW60 and SXRD rear projectors with it, JVC calls it Clear Motion Drive and other so on. Many people who have seen these displays/projectors reported a great picture quality improvement. To be honest I don't like the idea of adding any extra information to the source. This must change the look of the primary image. I can imagine this might be good with sports video etc. but not with movies whereas the main characteristic of the filmlook is motion blur and low 24 fps rate. I don't want extra frames! Do you know if manufacturers will allow turning the frame interpolation off as an option?

2) I think in some time in future when backlight sources will be bright enough we will have scanning backlights to eliminate the sample-and-hold effect. I think it is a superior technique to the intermediate frame interpolation because it does nothing with the source image. They even might coexist. Scanning backlighting will resemble the way movie theater projectors display the image. Philips has this ongoing: http://www.lighting.philips.com/gl_e...n_news&lang=en

What do you think?

3) Do DLPs suffer from sample-and-hold effect to the same degree as LCD and LCOS/SXRD? 120 Hz DLPs will be great for 3D gaming (up to 60 frames for each eye). Do you know any 120 Hz DLP front projectors coming this year?

4) Computer games will be great on any 120 Hz display/projector. Up to 120 fps at full HD resolution is great. My old Sony CRT could do only 75 Hz at 1600x1200. I have a concern however if a 120 Hz display could take 120 Hz input from video card on a HDMI connector. Again the other thing is if this frame interpolation can be switched off. This must be a very time consuming processing and create gaming delay/lag. While this may help with blur and increase PQ on games with less fps, games that can run with up to 120 fps don't need any processing and the lag will make it unplayable.

5) I live in a PAL country. So the benefit of eliminating motion judders drops out. We in fact do not suffer from motion judders here. But having 120 Hz for BR/HD DVD 24p encoded movies is still great. I wonder how manufacturers will tackle the 50Hz issue. Will there be a separate *50Hz circuit to handle 50 Hz video sources? (extra costs)
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post #19 of 26 Old 05-28-2007, 05:43 PM
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Quote:
Originally Posted by HogPilot View Post

I was under the impression that the 120Hz refresh rates wouldn't do anything for image quality except eliminate the judder that results from the usage of 3:2 pulldown on displays that can't refresh at some integer multiple of 24Hz. As far as motion artifacts, blurring, and jaggies - that sounds like more of an internal processing/source material issue than it does a panel refresh rate issue. I'm certainly no expert though so someone please pipe up if I'm missing something.

Yup. The main advantage is to bypass the 3:2 (or more accurately, the 2:3) pull-down. Most current hdtv's are at 60Hz; so to display a 35mm film shot at 24 fps, it would have to display the film frames as 1,1,2,2,2,3,3,4,4,4, etc...(where 1, 2, 3 are frame 1, frame 2, etc...)

an hdtv at 120Hz can display 24fps at exact multiples of 5 (5:5 pulldown, if you will). It also has the advantage of displaying 30fps (digital movies are shot in 30fps) at multiples 4.

This is not all....as the SOURCE also matters. If you're watching 1080i/24 source and upconverting it to 1080p thru an hdtv @ 60Hz, not only does a 3:2 pull-down occurs, but the correct frames have to be matched up to display the picture as 1080p. If this does not happen correctly, then you'd end up with jaggies or judders or whatever.
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post #20 of 26 Old 05-28-2007, 06:20 PM
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Quote:
Originally Posted by Armin2 View Post

had a LCOS 120hz front projector setup at the Munich High end show hooked up with a Pioneer BR. The image was stunning.

No offense, but was that a private demo? Because I thought the public demo looked like crap. Some major problems with the demo. The source material was bad, I spotted major banding problems. Your demo guy blamed it on the mpeg2 codec, which we all know isn't true. I blame the encoding itself. Another problem, the player was set to output 1080i, leaving the deinterlacing to the D2. Again I spotted de-interlacing artifacts during The Fantastic Four. You should talk to the guy who did the demo, he said BDs video format is 1080i on the disc. I pointed out that BDs are usually encoded at 1080p24 and that it was more likely that only the player is set to 1080i (he showed me in the the setup options), which he didn't know. I talked a little to him about video formats, differences in encoding and so on before he left. He was a little surprised that 1080p could actually be stored on the discs.

- Stephan
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post #21 of 26 Old 05-28-2007, 11:54 PM
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Quote:
Originally Posted by reio-ta View Post

Where does this blur come from with sample and hold? I don't see it.

You would see it if you could turn it on/off and compare.

Quote:
Originally Posted by reio-ta View Post

Apparently super high speed cameras capable of doing "bullet time" don't see it either.

Correct, super high speed cameras don't see it, because the "sample-and-hold" motion blur is added by our eyes/brain. See the thread I linked to. There are some helpful pictures in there which explain why our eyes/brain add motion blur if a projector is "always on".

Quote:
Originally Posted by reio-ta View Post

I don't like the extra frames myself too! I also hope there is a way to turn that stuff off. How I see it, if your normal person thinks it's "better" doesn't mean it is. I actually see those additions as black flicker.

I think you're confusing black frame insertion and interpolated intermediate frame insertion. There is some flickering added with black frame insertion, that's true. But if you add interpolated intermediate frames, there's no flicker at all. However, there may be other artifacts, cause calculating real intermediate images is extremely difficult and calculation intensive.

But let me ask you: Do you see flickering in cinema? Cause those cinema projectors do shutter. That's something like black frame insertion. Although, I think the time where the screen is black is very small compared to how long frames are shown.

Quote:
Originally Posted by Kobe View Post

The intermediate frame interpolation technique seems to be ubiquitous among new 120Hz displays/projectors. Sony calls it MotionFlow and will equip VW60 and SXRD rear projectors with it

Are you sure that the VW60 will do intermediate frame interpolation? That's the first time I see it clearly stated as this.

Quote:
Originally Posted by Kobe View Post

I think in some time in future when backlight sources will be bright enough we will have scanning backlights to eliminate the sample-and-hold effect. I think it is a superior technique to the intermediate frame interpolation because it does nothing with the source image. They even might coexist. Scanning backlighting will resemble the way movie theater projectors display the image.

Samsung demonstrates both methods on shows. Don't know which they'll be using in the future. In the short run, black frame insertion is probably better, cause you can't do much wrong with it, but you'll lose brightness. In the long run intermediate frame interpolation might win. But I think it will take some time until it's really good enough for every kind of material...
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post #22 of 26 Old 05-30-2007, 08:00 AM
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Quote:
Originally Posted by reio-ta View Post

According to that PDF, Motionflow will be on 120hz SXRD micropanels. BFI is also mentioned. Is that part of MotionFlow, or a separate feature on panels that don't have MotionFlow?

Where is BFI mentioned? Didn't see that.
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post #23 of 26 Old 05-30-2007, 10:02 AM
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Quote:
Originally Posted by Tryg View Post

If you want better image quality at this point you should look toward your source material.

Tryg, it would help if you would define your position. Are you referring to something beyond BD and HDDVD?
This isn't the first time you have offered the same cryptic advice. Thanks.
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post #24 of 26 Old 05-30-2007, 02:52 PM
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Let me throw in a "non-professional" opinion and see if it muddies the waters a bit more. From reading this thread, it seems that many issues regarding 120hz is open to each person's visualization of the image. Let me explain in terms I am familiar with. At work, almost everyone leaves their monitors set in a standard way (1024x768 at 60hz). To me personally, I can see lots of flicker...especially on a white background (ie, when using Word). If I boost the refresh rate up to 72 or 75hz (which I have done to my personal workstation)...my sensitivity to "flicker" immediately goes away.

Could this be why some see a great pq improvement with 120 hz and others don't?

marcus

Our Personal Website with movie and music catalog pages.

Marcus & LaMona Home Theater
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post #25 of 26 Old 05-30-2007, 03:19 PM
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No, 120hz has nothing to do with flicker; in fact BFI tries to recreate the scanning CRT phenomenon on other technologies in order to reap one of the benefits of scanning displays - the clearing of image remnants by displaying black frames which cause your eye / brain to perceive less blur.
Other 120hz implementations use per pixel motion interpolation to create in between frames that also supposedly result in less blur. Both ideas seem like a bad thing to me, but I'm going to withhold judgment until I see the end results first hand.

The third option is to just repeat frames, which isn't a big step up from other LCOS and DLP implementations that take 24/48hz inputs and display them natively at 72 or 96hz which should be equally stutter free.
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post #26 of 26 Old 05-31-2007, 12:32 AM
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Quote:
Originally Posted by reio-ta View Post

"Similiar to BRAVIA LCD HDTVs, select BRAVIA 3LCD and SXRD TVs will
include MotionFlow 120Hz technology, x.v.Color, 10-bit processing, and
DMex capability, Full HD 1080p and BRAVIA TM Theatre Sync. Two Unique
Microdisplay HDTV features are Black Frame Insertion/Data Insertion,
which offer smooth, clear motion in fast moving scenes."

Thanks, somehow I missed this part. That's really strange. The other text clearly reads like interpolated intermediate images. But this reads like BFI. So which is Sony using now? Or maybe they're using both, depending on the model?
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