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Discussion Starter · #1 ·
Information in this thread is knowledge that was passed along to me, I do not have the engineering and design experience to claim any of this as 1st hand fact... so if this information is wrong... please correct it "IF" you are an Electrical Design Engineer who actually "knows". Not because you read it somewhere else on some other post, on some other website or on some review page done with biased opinions. I have yet to find an article on the "LCD vs. Plasma" debate that wasn't biased...


This has been a big debate on several threads across multiple forums. Everytime the subject of image blur and response time comes up, it seem everybody starts discussing this. So I did some digging and was able to speak wih an electrical engineer who works in this field (design, not a TV repair guy), and this is how he explained it to me....



From the begginning...


So the debate always revolves around Plasma vs. LCD, pixel response time and frame rate... (just paraphrasing the arguments here) Plasma has no blur due to pixel repsonse time, LCD has to introduce "tricks" to compete in this category... Refresh rates are not true... Plasma doesn't "need" any enhancements that have been introduced into the LCD market... on and on...

The rest of this is what I was told by an Electrical Engineering Design Major who works in AV field. Most of the advertising you see for ALL TVs is BS... It's marketing strategy to explain how it works to people who are shopping for a TV. Synchronizing frames of video with refresh rates of the TV simply does not happen...



Refresh Rates and video frames...


We are told by "advertising" that a 600Hz Plasma TV will take a 1080p/24 source and display each frame of video 25 times (24 x 25 = 600). And that a 240Hz LCD will take a 1080p/24 source and display each frame of video 10 times (24 x 10 = 240). This is a matter of coincidence ONLY. Let me explain.

For those who play video games on PC, you know that you can typically select an option to "sync every frame" of video with your display refresh rate to get smoother gameplay, and no tearing in the video frames. This is possible on a PC because the video card actually creates the video material AND controls the refresh rate, which means it can synchronize the two... A TV does not create the souce, it receives it from the Satellite, or Cable, or BluRay player or game system... or whatever other device that is sending the signal. The TV processes the video signal and displays the image to the screen. The advertising of each video frame being displayed "x" amount of times is simply marketing to explain to Joe Blow, what exactly a refresh rate is. Image processing and Refresh Rates are independant processes when it comes to TVs.

If you are watching a Blu-Ray, connected via HDMI, set to output 1080p/24... then the Blu-Ray player is sending 24 video frames per second (24Hz), and your TV is displaying 24 frames per second. If you are watching TV, the signal a 60Hz signal, and your TV is displaying 60 video frames per second, regardless of what material the original source was formatted. Now while your BluRay player is sending 24 video frames per second, and your TV is "processing" the signal of 24 video frames per second to be displayed, your TVs refresh rate is constantly operating to refresh the screen image that is processed by your TV. The two processes are not directly linked, they just work together in series to display a constant moving video image to your TV screen at what ever video frame rate happens to be sent to your TV. This is the standard, unmodified process with no Motion Smoothing or Interpolation.



What "is" the refresh rate of your TV??


If your LCD TV says 120Hz, then the refresh rate is 120Hz... If it says 240Hz, then it's 240Hz. And YES... even if it says 480Hz, the video screen (not processed image data) is refreshed at a rate of 480 times per second. The piece of hardware that controls "refresh rate" has no connection to the piece of hardware that sends the image data to the screen, other than the video data being sent "through" it, not "processed BY it". That being said, the refresh rate is a constant... you do not need to enable the "Motion Smoothing" on your LCD for it operate at 120Hz, 240Hz or 480Hz. This is simply more marketing because with the "Motion Smoothing" enabled, there is still less "blur" with this feature enabled regardless of the negative effects it may have on the picture.

For plasma it's a little different. EACH Idividual pixel is actually refreshed at 600Hz (YES 600 times per second). Effectively, that means the the entire video screen (not processed image data) is refreshed at a rate of 600Hz as well. Which is why Plasma does not need improvement in image "display" technology to address blur, because there is none. It litterally is already fast enough.



LCDs and Scanning backlights...


There is also a lot of information that says the 240Hz refresh rate of an LCD is acheived by combining 120 video frames and inserting black frames inbetween each video frame in each second. That's 120 video frames plus 120 black frames, to equal 240 frames per second (240Hz). Or 240 + 240 for 480Hz TVs. I was told that the scanning backlight is actaully a completely seperate process from the refresh rate. A 240Hz TV will refresh the actaul screen image 240 times per second wether that TV has scanning backlight technology or not. The explanation of intertwining the video frames and the "black frames" is simply another "advertising" explanation for Joe Blow. I did not ask him to explain the "scanning backlight", so I have no idea what it actauly does. But he said said it is a technology that actually has something to do directly with the "backlight" of the LCD TV, and nothing to do with the refresh rate (two seperate processes).



Are repsonse rate and refresh rate related? not really.


Plasma pixels are "refreshed" at 600Hz (1 / 600 = 0.00166666... sec, or 1.67ms) There are a few websites who say the pixel "response" time is 0.00167ms, which would equal 0.00000166666...sec). I read one of those and the author actually re-canted to state that he had a typo when stating 0.00167ms, and meant 1.67ms. By that logic, the pixels are refreshed as fast as they can respond, or change their state. Which also means that a Plasma pixel can change it's color 600 times per second. The engineer I spoke with confirmed 1.67ms, not 0.00167ms. Argue about it if you want, at either speed it doesn't really matter anyway.

The fastest LCDs are refreshed at 480Hz (1 / 480 = 0.002sec, or 2ms). However, the fastest pixel response (I've seen advertised) is 4ms, which would be closer to that 240Hz refresh rate. Can that be possible, 480Hz with a 4ms pixel response?... sure! It just means that the fastest Image change you will see on an LCD will be 240Hz. The state change (color change), or response of the pixel is seperate from the screen refresh rate of the LCD. So with a 4ms repsonse time, the most image changes possible would be 250 per second. And at a 480Hz refresh rate, the screen gets refreshed twice while the pixels are in the same state.

Remember, the video signal is displayed to the screen at the same rate it is delivered from the device (24Hz or 60Hz).



Motion Smoothing and Interpolation


It seems that early on in the development of 120Hz LCD TVs, these two technologies were viewd as one in the same. But recently they are two seperate processes. Motion Smoothing reduces the flicker caused by a true 24 frames per second display rate. Interpolation creates brand new video frames, which are estimated from the two adjacent video frames, in order to produce a "smoother" video playback (this creates the "video" or "soap opera" effect).

At true 24 frame per second, there is a visible flicker between the video frame changes which can be annoying for some people (including myself). Both LCD and Plasma TVs have "Motion Smoothing" technologies. Plasmas have Smoothing that runs at 48Hz, 72Hz, and 96Hz, to display each video frame 2, 3, and 4 times respectively to help reduce the flicker between the video frames. LCD TVs running at 240Hz, depending on the implementation, will process each video frame at 120Hz or 240Hz to display each video frame 5 or 10 times respectively to reduce the flicker between each video frame. This technology does NOT edit the original source video "data", it just refreshes each frame more often which reduces the amount of time the "black" frame flicker is seen, effectively creating a smoother video experience. (In my opinion, this works quite well in LCDs and Plasmas)

Inerpolation currently only exists in LCDs. This is the technology the take the 24 video frames per second, and uses a mathematical algorithm to create entirely new video frames to be added inbetween the original video frames. This effectively creates a smoother video effect by displaying more unique video frames per second which makes the video material seem smoother. This has two effects. The first is artifacting, or errors in the "newley created" video frames. This is mostly because the background image is estimated between the two frames... so it looks a little "off" when somebody walks across the screen. The second effect is that the movie now looks more like Video (60Hz) or a soap opera.

Both of these processes are handled by the video "image pocessing" of the TV. The video data is processes and delivered to the screen where the refresh rate make sre that the screen image i constantly displayed to the screen and the native refresh rate of 60Hz, 120Hz, 240Hz, 480Hz or 600Hz)



Conclusion


If there are any "Electrical Engineers" out there who are active in the field of AV design technology who can review this information, please clarify anything that is wrong and verify those things that are correct... Thanks!
 

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The stuff you talk about can be found on AVS or internet you do not need a engineer for that. You can do a search (or start a thread) on each subject, just don't try to get all the answers at once.
 

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Just curious: you really think electrical engineers that study these things, knows better than videophiles/ enthusiasts that LOVE these things?


I don't deny that there are people who chat stuff that they don't really understands, but once you are able to pinpoint who are in the know in these forums you can slowly learn from there.
 

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Discussion Starter · #4 ·

Quote:
Originally Posted by specuvestor /forum/post/20873773


Just curious: you really think electrical engineers that study these things, knows better than videophiles/ enthusiasts that LOVE these things?


I don't deny that there are people who chat stuff that they don't really understands, but once you are able to pinpoint who are in the know in these forums you can slowly learn from there.

Well... honestly, I think that's a 50/50 shot... Only because I've seen "experts" get schooled by "techs" or "engineers" in technical industries all the time. My brother is a PC enthusiast... But he doesn't know half of what I know about actually implementing hardware and software solutions to a large organization because I "am" an engineer who does this on a day-to-day basis... And after a little research, I typically find out that half of what he claims as fact comes from the same advertising schemes that I am questioning above... just a different field of discussion.


In any case, you're probably right, I did cover a lot of ground to be examined at a precise level. But turthfully, any clarification on ANY thing I listed would be nice....


like for example.... based on the most popular agreement amongst the most seemingly technical people on forums is that... for 120Hz, 240Hz, or 480Hz LCDs to operate in that mode, MEMC (Interpolation or "Motion Smoothing") MUST BE ENABLED...


However, I can tell you this from personal experience.... I have the Vizio XVT3D554SV TV (480Hz, 4ms). Vizio uses LG parts, so this one is probably based off the LG 55LX9500 (similar specs). Maybe different programming, but I would imagine they function the same at the basic hardware level of refresh rate and response time. On my 60Hz Sharp 32 inch TV, I can easily see the motion blur with everything we watch on that TV (blur-ray, DVD, TV, all at 1080P HD).


With the 55 inch Vizio, with all of the "motion smoothing" (MEMC) options turned OFF.... there is absolutely no blur.... If the TV was ONLY running at 60Hz.. Shouldn't I notice motion blur??? on a 55 INCH TV??? but there is none... That seems to back up the reasoning that the 480Hz (or 240Hz) is in effect all the time, regardless of the MEMC technology....


Ideas?


Input?
 

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Quote:
Originally Posted by RedJamaX /forum/post/20875901


Well... honestly, I think that's a 50/50 shot... Only because I've seen "experts" get schooled by "techs" or "engineers" in technical industries all the time.

I agree. IMO self proclaimed experts are all over internet forums and we have to be skeptical if no source is provided even when requested. Even further, a large majority of internet sites (media, encyclopedia, how things work) are full of misinformation. The best way to get information you can generally trust is through scientific journals and technical papers (and patents to some degree). Even these sources conflict once and a while. Or the poster may misinterpret them so having the source on hand is always a good thing.


IMO AVS is probably one of the best as many posters have and provide credible scientific sources when posted info is questioned.


Even so, there are a few posters here who post extremely well crafted and articulate explanations that turn out to be partial or complete BS and when asked for a credible source they tend to just state their credentials which is the worst thing to do IMO. Unfortunately many reading these posts take it as irrefutable fact.


If I don’t have a source and I am just describing what I think is going on I try and label it as opinion or theory. Otherwise I have a source available to back up what I post.


That being said here are a few points regarding your post:

Quote:
Originally Posted by RedJamaX /forum/post/0


For plasma it's a little different. EACH Idividual pixel is actually refreshed at 600Hz (YES 600 times per second). Effectively, that means the the entire video screen (not processed image data) is refreshed at a rate of 600Hz as well. Which is why Plasma does not need improvement in image "display" technology to address blur, because there is none. It litterally is already fast enough.

Subfield data is refreshed at 600Hz but the effective refresh rate (ie – fully compiled frames/second) remains at 60hz. 10 subfields compile into one full frame every 1/60th second.


And the reason why blur is small in PDP is because the 10 subfields used to compile one frame are sequenced in brightness weight. In other words only a few of the 10 subfields produce most of the light which creates a perceived short duty cycle (strobe effect) that reduces the hold time dramatically.


Quote:
Originally Posted by RedJamaX /forum/post/0


Plasma pixels are "refreshed" at 600Hz (1 / 600 = 0.00166666... sec, or 1.67ms) There are a few websites who say the pixel "response" time is 0.00167ms, which would equal 0.00000166666...sec). I read one of those and the author actually re-canted to state that he had a typo when stating 0.00167ms, and meant 1.67ms. By that logic, the pixels are refreshed as fast as they can respond, or change their state. Which also means that a Plasma pixel can change it's color 600 times per second. The engineer I spoke with confirmed 1.67ms, not 0.00167ms.

PDP response time depends on what process is measured and quoted. In PDP the gas discharge response time is microseconds or even nanoseconds. However, the photoluminescence is much slower in general. The blue phosphor response is in the microsecond range while the red and green both respond in the millisecond range (4-8ms with current technology).
 

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Discussion Starter · #6 ·

Quote:
Originally Posted by xrox /forum/post/20880089


Subfield data is refreshed at 600Hz but the effective refresh rate (ie – fully compiled frames/second) remains at 60hz. 10 subfields compile into one full frame every 1/60th second.


And the reason why blur is small in PDP is because the 10 subfields used to compile one frame are sequenced in brightness weight. In other words only a few of the 10 subfields produce most of the light which creates a perceived short duty cycle (strobe effect) that reduces the hold time dramatically.

Ok, still a little confused on this... Can you explain what exactly a "sub-field" is??? Is there a way to present a visual representation of it?? Or a link to a web site that has has already done so?


Quote:
Originally Posted by xrox /forum/post/20880089


PDP response time depends on what process is measured and quoted. In PDP the gas discharge response time is microseconds or even nanoseconds. However, the photoluminescence is much slower in general. The blue phosphor response is in the microsecond range while the red and green both respond in the millisecond range (4-8ms with current technology).

Now that makes more sense! But why are plasma pixel repsonse times always advertised as 2ms (1.67ms). If correct color requires the combination of the three sub-pixels, and two of those three can only change state at 4ms... then does not stand to reason that the actual "whole pixel" response rate is 4ms? Not that it matters to the human eye... but just for the sake of understanding...



btw... nice signature... I wish they would hit the studio, give us another album and go on tour again!
 

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Discussion Starter · #7 ·

Quote:
Originally Posted by xrox /forum/post/20880089


That being said here are a few points regarding your post:


Subfield data is refreshed at 600Hz but the effective refresh rate (ie - fully compiled frames/second) remains at 60hz. 10 subfields compile into one full frame every 1/60th second.


And the reason why blur is small in PDP is because the 10 subfields used to compile one frame are sequenced in brightness weight. In other words only a few of the 10 subfields produce most of the light which creates a perceived short duty cycle (strobe effect) that reduces the hold time dramatically.



PDP response time depends on what process is measured and quoted. In PDP the gas discharge response time is microseconds or even nanoseconds. However, the photoluminescence is much slower in general. The blue phosphor response is in the microsecond range while the red and green both respond in the millisecond range (4-8ms with current technology).

So...


I found this link:
http://www.best-3dtvs.com/guides/wha...ld-drive-mean/


With this explanation:


Sub Field Drive - Plasma Panel Basics

A Plasma panel display has near instantaneous response times on the order of 2 milliseconds. What this implies is that a plasma TV subpixel is only alight for a fraction of a second. Typically, most conventional Plasma TVs display video at 60fps (research has shown that the human eye cannot tell any significant difference in motion and smoothness of videos at higher frame rates). This implies that each frame has to be displayed for 1/60 or 17ms. However, the sub pixels of a plasma TV stay alight only for around 2ms when excited. Thus, to display a single frame for 1/60 seconds, the plasma panel excites the sub-pixels in pulses so as to keep all the pixels bright so that they can continuously display the desired frame.


Based on that description, the 600Hz is not really a "feature", but a "neccessity by design". In no way am I trying to take away from the plasma technology's ability to process motion on the screen.... Just trying to truly understand how the technology operates.
 

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Quote:
Originally Posted by RedJamaX /forum/post/20880384


Ok, still a little confused on this... Can you explain what exactly a "sub-field" is??? Is there a way to present a visual representation of it?? Or a link to a web site that has has already done so?

Think of a subfield as partial frame or partial video field. Most of the papers I have describe the subfield sequencing but it would be better to understand via a basic example first IMO.


Example: A video frame is sent to the display that depicts a bright white circle (video level 255) on a black background (video level zero). To display this frame the PDP must deconstruct and generate 10 "partial" frames each displaying a fraction of the 255 level. Each partial frame is called a "sub-field". For example:


subfield1 = 1

subfield2 = 2

subfield3 = 4

subfield4 = 8

subfield5 = 12

subfield6 = 16

subfield7 = 24

subfield8 = 32

subfield9 = 48

subfield10 = 108


Final Compiled image = 255


So in this very basic example there are 10 seperate partial frames (ie subfields) each displaying a circle on a black background displayed one after the other. Each partial frame has a fraction of the brightness of the final image. But because these images are displayed in such a short time our eyes integrate them together to form the original input frame (white circle of 255).


Now if this simple example helps then you will understand the following link from panasonic describing subfields much better.

www.blu-ray.com/doc/plasma3.ppt


Quote:
Originally Posted by RedJamaX /forum/post/20880384


But why are plasma pixel repsonse times always advertised as 2ms (1.67ms).

Without details we don't know.

Quote:
Originally Posted by RedJamaX /forum/post/20880384


btw... nice signature... I wish they would hit the studio, give us another album and go on tour again!

They will once APC is done touring.
 

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Quote:
Originally Posted by RedJamaX /forum/post/20881128


So...


I found this link:
http://www.best-3dtvs.com/guides/wha...ld-drive-mean/


With this explanation:


Sub Field Drive – Plasma Panel Basics

A Plasma panel display has near instantaneous response times on the order of 2 milliseconds. What this implies is that a plasma TV subpixel is only alight for a fraction of a second. Typically, most conventional Plasma TVs display video at 60fps (research has shown that the human eye cannot tell any significant difference in motion and smoothness of videos at higher frame rates). This implies that each frame has to be displayed for 1/60 or 17ms. However, the sub pixels of a plasma TV stay alight only for around 2ms when excited. Thus, to display a single frame for 1/60 seconds, the plasma panel excites the sub-pixels in pulses so as to keep all the pixels “bright” so that they can continuously display the desired frame.

I would say that information is incorrect and confusing. Read the following post describing how subfield weighting is the source of both flicker and good motion performance in PDP.

http://www.avsforum.com/avs-vb/showt...1#post19615951


And this graphic which shows how the light intensity vs time for one full frame of video on a PDP. You can see in this example there are 10-11 subfields and the phosphor decay of the blue and red is long creating a distinct shape to the intensity curve. This curve is the source of both flicker and good motion performance.

 

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Quote:
Originally Posted by RedJamaX /forum/post/20875901


Well... honestly, I think that's a 50/50 shot... Only because I've seen "experts" get schooled by "techs" or "engineers" in technical industries all the time. My brother is a PC enthusiast... But he doesn't know half of what I know about actually implementing hardware and software solutions to a large organization because I "am" an engineer who does this on a day-to-day basis... And after a little research, I typically find out that half of what he claims as fact comes from the same advertising schemes that I am questioning above... just a different field of discussion.


In any case, you're probably right, I did cover a lot of ground to be examined at a precise level. But turthfully, any clarification on ANY thing I listed would be nice....

Yes I was not referring to engineers that does video implementation on a day-to-day basis. There is also a big difference between those who study MBA and those who actually run companies



If you are keen to refresh rates you can refer to this not-so-long thread which has quite a lot of information:

http://www.avsforum.com/avs-vb/showthread.php?t=1285072


Hope that helps and you can clarify further here if you are really keen.
 

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Discussion Starter · #11 ·
Lots of great information there!! Thanks!


Based on those reading and pieces of information I have a few more questions... Maybe I'm just not fully understanding, or I didn't see this question answered...


In relation to Plasma TVs refresh rates of 48, 72, and 96Hz... I know the purpose of these refresh rates are meant to display 24p content at it's true frame rate.


But it seems that the default operation of plasma at it's full potential is based on a 60Hz refresh rate (10 subfields used to create "one" full picture which are fully combined at the rate of 1/60th of a second = 60Hz refresh rate). Are the higher refresh rates of 72Hz and 96Hz acheived by use of "weighted subfields"?? If so, does that reduce color quality... or brightness and contrast quality??? Or am I still missing something?
 

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Guess xrox has to explain this technicality on subfield
He's the man.


Like you said, the refresh rates you mentioned are a multiple of native 24fps so 48Hz is 2:2 pulldown, 72Hz is 3:3 pulldown and 96Hz is 4:4 pulldown. It's not manipulating the subfield but the frame. However if you've read the link that is not the case for LCD as pulldown is useless for LCD.


But personally I wouldn't be too concern about subfield anyway as anything above 85Hz is hardly perceptible (hence your 96Hz for plasma) except to know that 1)it reduces hold time and 2) response time of plasma is really fast



IMHO any marketing material above 120Hz, except backlight scanning which reduces hold time for LCD, is marketing, like you mentioned in the other thread.
 

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Discussion Starter · #13 ·
Not "concerned" really... not doing any kind of comparison. Just trying to understand how it all works...
I'm willing to bet that any effect from increaing the refresh rate would be visually negligable, just want to know how it does it.



Also, for LED screen sizes above 42"... I can see a big difference between 120Hz and 240Hz... but I also like "Smooth Motion" and Interpolation (I really hate flicker and judder).
 

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Discussion Starter · #15 ·

Quote:
Originally Posted by specuvestor /forum/post/20891102


Find out why there is a big difference between the 2 sets you saw, instead of succumbing to numerical heuristics

Just to elaborate... I actually played with the different motion smoothing and interpolation settings on two TVs (both were samsung), one was 120Hz, the other was 240Hz and there was a noticable "visual" difference in the performance between the two... both were 55" TVs. I ended up with the XVT 55" Vizio because of the better price, but I do beleive that all other things being equal (for motion smoothing), 240Hz is better with larger screen LCDs. I did not test it on a 40", but I'm guessing there would be less of a difference.
 
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