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3D Stereoscopic Production & Delivery
Discuss 3D (stereoscopic video) acquisition, post and delivery.


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Old March 25th, 2010, 03:24 PM   #1
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Why do we need 3D monitors?

I'm not sure how 3D TVs work, but I know that RealD just flickers the left and right images one after another. I don't understand why a firmware update to one's bluray player, and some glasses wouldn't be able to playback a 3D bluray with an HDTV. Or even a computer for that matter. Could someone tell me why you need a whole new TV?
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Old March 25th, 2010, 03:27 PM   #2
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You need a new TV or monitor because it needs a refresh rate of 120hz. This allows 60 fields per second for each eye with active glasses. Anything much less than that and a flicker would be noticed.

There's nothing really 3D about the TV or monitor at all. Just a faster refresh rate.
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Old March 25th, 2010, 06:28 PM   #3
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Quote:
Originally Posted by Steve Shovlar View Post
There's nothing really 3D about the TV or monitor at all. Just a faster refresh rate.
That is just one type of 3D monitors, and not really the ideal type because it does not show video to both eyes at the same time.

A better way of doing it is using polarization. Every other row, or every other column, or in a checkerboard system both, uses the opposite type of polarization. That way both eyes see images at the same time, and only passive glasses are needed.

An even better way is by using two monitors and a see-through mirror. One monitor is watched through the mirror, the other is reflected by the mirror. Both monitors are polarized, so you just need polarized glasses.
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Old March 26th, 2010, 11:42 AM   #4
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So people have the option of either buying a 3D HDTV, or using ANY 120hz HDTV/monitor. And there are no real 3D options for a 60hz HDTV/monitor?
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Old March 26th, 2010, 03:36 PM   #5
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if you use time sequential 3D, any TV set can do it, but quality will vary with frame rate.
First 3D VHS were using the 60i interlaced signal to push 30L+30R, but it was acknowledged
to give headache if you look at it for more than few minutes.
but that was time sequential on interleaved frames on cathod ray tubes.
now with LCD, you can play only progressive picture. This technology would not work if you use the same old vhs tape.
You need to use a progressive picture, because if you use an interlaced one, there are big chances that the screen will try to deinterlace and mix left and right image at the same time.
Fortunately , progressive content can be easily created using 720p60 or 480p60.
But only blu-ray is able to play it, DVD is still limited to 480p30 (so you can try 15L+15R, but it will really flicker).
Trying time sequential format on an LCD TV set is like flipping the coin. You can not be sure what the electronic into the screen will do with your pictures, so before you buy the screen you had better to make some test.
3D enabled screen are probably more transparent and will have a 3D button to ensure that signal is fed to the LCD panel as it should be.

On the other end, you will get the line sequential format, that display both sides at the same time. quality wise, there is a small loss, since the vertical resolution is halved.
But technically speaking, it is easier to produce, since you just need to glue a polarized sheet on any LCD screen (provided the RGB pixels are arranged on a line).
These screen require nothing else than a cheap polarized glasses versus the expensive LCD shutter glasses + remote control electronic that time sequential needs.
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Old March 26th, 2010, 04:12 PM   #6
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Yes. Anaglyth. That type of 3D works on any monitor.
You will need a pair of cyan/magenta specs.
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Old March 27th, 2010, 12:02 PM   #7
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Giroud, would you say that the issue with time sequential 3D on a 60hz monitor is that quality will vary with things like frame rate, resolution, dimmed image etc...
or are you saying that sometimes it simply does not work at all?

If it is a question of lower resolution and mild flickering, I might argue that is a better option than a red and cyan anaglyph image.
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Old March 27th, 2010, 04:42 PM   #8
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the problem with time sequential is the screen to be only half of the solution.
You still rely on the electronic to drive the glasses and the glasses itself.
So you can can produce a 480p60 or 720p60 3D really easy. You can play it back from Bluray or PC or stand alone media player as well. Then rendering will depend the screen quality (plasma or lcd, power of backlight, contrast, speed of LCD), but today , most of the screen are building more or less the same picture, since the LCD panels ar emore or less all the same.
The difference would be in the electronic that drives the panels. High end screen are fiddling with the picture to give you "color/motion enhanced" that could be a problem with 3D.
Now , another factor is how well the glasses will interact with the screen.
basically, the vertical sync of the video will drive a IR led to send the pulse to the glasses.
the glasses will close/open each eye according to these pulses.
Since the only way to get the pulse is to get it before it enter the screen, there is always some parameters you will need to adjust (the start of the pulse and its length for the delay for the screen to build the picture for example and the time needed for the glasses to react). It is easy to build such electronic, few logical gates, cost nothing.
It will be harder to set it up correctly.
Ideally the IR emmiter should be self adjustable.
It would need a light sensitive diode that would read a recorded test signal (interleaved black/white frames), and calculate the delay and correct windows aperture.
again a cheap microprocessor would do that easily.
I think Xpand is selling that in their new X103 models (not yet available), advertised as self adjustable glasses. It is the same principle used in DLP-link technology.
If you do not care about getting the high end quality, just make some test, it will be probably ok in most case, since the timing are usually not so tight.
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