Are passive 3DTVs only half resolution? - AVS Forum
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Old 06-23-2012, 02:50 PM - Thread Starter
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I'm not so sure about that.
Here's why.
Take a typical passive 3D that has a refresh rate of 120 hertz.
Feed it a 3D blu-Ray at 1920 by 1080 @ 24P.
That would mean that the TV repeats the same frame 5 times
IF the TV shows the odd lines to the left eye and the even lines to the right eye for 120th of a second three times for each unique frame and then
alternates by doing the opposite the other two times then it is in fact showing the full resolution.
Perhaps it reverses this 3-2 pattern to a 2-3 pattern in alternating frames.
The only caveat is that the lines are in the wrong vertical position part of the time.
Is this in fact what they do? If not then why now?

Did IQ's suddenly drop sharply while I was away?
I enjoy 3D in spite of HDMI 1.4!
Full screen only 3D doesn't cut it!
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Old 06-23-2012, 03:50 PM
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AFAIK a 3D 120hz TV first uses 3:2 pulldown to convert the incoming 1080p 24fps frames to 1080p/60.
It then. displays data for the left eye 60 times a second which may always be on the odd lines and displays data for the right eye 60 times a second on the even lines The human mind then comnbines the left eye(1920x540) image and right eye(1920x540) data. just like on an old 480i CRT TV.
Many poptential passive TV purchasers are hoping that 240Hz/and/or 4K 3D passive models when they become available will be able to display full 1920x1080 3D frames for each eye.
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Old 06-23-2012, 05:51 PM - Thread Starter
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Quote:
Originally Posted by walford View Post

It then. displays data for the left eye 60 times a second which may always be on the odd lines and displays data for the right eye 60 times a second on the even lines
My point is that each eye may be getting all 1080 lines on a time multiplexed basis in that the 540 lines that each eye gets may alternate between the even and odd lines and the brain may see this as closer to 1080 then 540.
I'm currently conducting some experiments in an attempt to confirm this.

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I enjoy 3D in spite of HDMI 1.4!
Full screen only 3D doesn't cut it!
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Old 06-23-2012, 08:17 PM
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Quote:
Originally Posted by Frank View Post

IF the TV shows the odd lines to the left eye and the even lines to the right eye for 120th of a second three times for each unique frame and then
alternates by doing the opposite the other two times then it is in fact showing the full resolution.

I believe this is correct, this is LG's implementation on their newer displays. Technically you do get to see every pixel that's on the Blu-ray, so it's correct in a way to say it's not half resolution. The problem is you've taken a 1080p left eye image, broken it into two 540 interleaved halves, and then put one on top of the other. There's still the physical problem of only having 540 lines of pixels per eye. I would suspect this actually blurs the image by overlapping video data. You get all the pixels the on the Blu-ray, but in a very messy way.

I'd suggest spending less time trying to convince yourself there's no compromises with a 1080p passive display, and more time planning to buy a 4k passive display which will give full 1080p per eye with no tricks, compromises, or fuzzy math. wink.gif
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Old 06-23-2012, 08:35 PM - Thread Starter
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Originally Posted by Airion View Post


I'd suggest spending less time trying to convince yourself there's no compromises with a 1080p passive display, and more time planning to buy a 4k passive display which will give full 1080p per eye with no tricks, compromises, or fuzzy math. wink.gif
Why buy a 4K when I am simply trying to understand why my new LG passive looks as good as it does?
biggrin.gif

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Old 06-23-2012, 09:12 PM
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Fair enough. smile.gif
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Old 06-24-2012, 08:06 AM
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Hi Frank, sorry for my persistence.

In your previous thread, you were telling me that 1080p didn't really matter because of chroma 4:2:0 subsampling. Now here, you're wondering if full resolution 1080p is the reason your passive TV looks so good. The two don't seem to match up. Has your position evolved?

Also, how about my suggestion earlier that overlapping two 540p images per would just blur the image? It makes sense to me that it would do so. But, I'm not totally confident, which is why I think the question you're asking in this thread is very interesting.

Perhaps the reason your new display looks so good is due to reasons other than resolution trickery. Perhaps it just gets the fundamentals right, such as brightness or motion handling.
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Old 06-24-2012, 10:17 AM - Thread Starter
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Originally Posted by Airion View Post

Hi Frank, sorry for my persistence.
In your previous thread, you were telling me that 1080p didn't really matter because of chroma 4:2:0 subsampling. Now here, you're wondering if full resolution 1080p is the reason your passive TV looks so good. The two don't seem to match up. Has your position evolved?
Also, how about my suggestion earlier that overlapping two 540p images per would just blur the image? It makes sense to me that it would do so. But, I'm not totally confident, which is why I think the question you're asking in this thread is very interesting.
Perhaps the reason your new display looks so good is due to reasons other than resolution trickery. Perhaps it just gets the fundamentals right, such as brightness or motion handling.
I don't recall ever stating that "1080P doesn't matter."
Just pointing out a few seldom acknowledged limitations of the format, especially when it comes to the required 24 frames per second for "full 1080P per eye" (Which I learned to hate back in the 60s when I was shooting and editing super 8 movie film) It was even less then 24 FPS.eek.gif

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Old 06-24-2012, 01:32 PM
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Frank,
Is your new Passive TV as good as or better then your RP DLP or other 1080p 3D TV when playing q 2D Blu-Ray disk?
I look forwared to your 540 lines per eye test results.
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Old 06-24-2012, 01:44 PM - Thread Starter
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Originally Posted by walford View Post

Frank,
Is your new Passive TV as good as or better then your RP DLP or other 1080p 3D TV when playing q 2D Blu-Ray disk?
I look forwared to your 540 lines per eye test results.
I don't know how it does with a 2D Blu-Ray disk. So far I use it as a large computer monitor for various projects including CAD, video editing, internet browsing, live HD 3D viewing, and so on including typing this while watching for an eagle in a tree in my live 3D window.
I'm sure my wife will want to watch a 2D BluRay on it soon and I can report then.

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Old 06-26-2012, 08:05 PM - Thread Starter
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I just got some Snellen eye charts today and did some preliminary resolution testing and the first tests yielded some interesting results.
Let me just say that it's pretty apparent that the effective resolution of my LG passive TV is not half in 3D mode.smile.gif

Did IQ's suddenly drop sharply while I was away?
I enjoy 3D in spite of HDMI 1.4!
Full screen only 3D doesn't cut it!
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