

Ask HN: 120hz is all that is needed for a TV to be 3d Compatible? - lakeeffect

True or False?  This is what my buddy was telling me, but i have no way to verify this info.  Anybody know for sure.  I find it hard to believe that a "3d TV" is just a marketing initiative.<p>Also side question, does anyone know if Google TV boxes come with Component, HDMI, or Cable wire connections.
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Kliment
To display 60hz stereo images, you need a 120hz image and synchronized shutter
glasses. Each frame is shown twice, once to the left eye and once to the
right. These are interleaved in time and synchronized with the shutters on the
glasses that alternately close the left and right eye. To display stereo
images, you not only need a 120hz display device, you also need a way to
synchronize the glasses with the image. There are some methods that patch into
the video stream and use the vsync there, there are some that plug into the
television itself and are triggered by actual frame changes. Note that
progressive scan LCDs tend to be terrible for stereo, because not all of the
image updates at once, and thus each eye sees some of the image meant for the
other eye (and you get blurring and the stereo illusion breaks).

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sev
I watched a 3d movie on a lcd screen that's not 120 hz (it's less but i'm not
sure what hz it was). I saw the 3d image, but it was horrible. It was not
pleasing to watch at all. I'm guessing this was due to the "each eye sees some
of the image meant for the other eye" idea you pointed out. So this is what 3d
tv's are meant to do...improve 3d viewing capabilities, not necessarily create
it?

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Kliment
Watching 30fps stereo on a DLP projector running at 60hz is a pleasure. It's
not so much the framerate as the fact that an LCD screen does not update the
entire image at once, but scans through it one line at a time. This way you
don't have a single time point where the entire image is just left or just
right. Updating the entire screen at once, at 120fps, is what 3d televisions
(and DLP projectors) do, in addition to providing an external sync trigger
signal for shutter glasses to latch onto. That is what makes a display device
3d compatible, not the frame rate in itself.

That said, if you have a high enough framerate on an LCD you can simulate the
global screen change effect by just showing each frame longer, for example
running a 120hz screen at 30fps stereo (60 fps total), and showing each frame
twice, giving the screen time to update.

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fragmede
Not exactly.

For a computer monitor to be compatible with Nvidia's 3D shutter glasses, all
it needs is for it to be 120Hz. The connected computer has a USB dongle which
the 3D glasses sync with. For a TV to really 3D capable, it has to have the
dongle built in, and be able to interpret a 3D signal (HDMI 1.4a[1]). What
confuses the issue is that most TV's and computer monitors these days have
both HDMI and DVI ports on them.

[1] <http://www.hdmi.org/press/press_release.aspx?prid=120>

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redcap
Do you mind if I side-track a little and ask people's opinion of 3D in
general?

I've seen two movies in 3D in the past year - Avatar and Toy Story 3. While
Avatar was fun, and Toy Story 3 exception, I didn't feel that the 3D really
added much to the experience. In particular, the colour for Toy Story 3 seemed
dimmer than normal. I also where glasses, so I sometimes had reflections
obscuring the picture.

I understand that 3D is being hyped as the next big thing to get after a big
flatscreen TV, so I'd be interested to hear what people here think of it.

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mooism2
I've seen 3 movies in 3D. With Avatar and How To Train Your Dragon, I felt the
3D added something worthwhile to the experience. With Alice In Wonderland, it
didn't.

I don't think I'd want a 3D TV though, not while you need special glasses to
see the picture properly. It's one thing wearing them when you've made the
effort to go to the cinema, quite another when you're just casually watching
at home; they become something else to lose, like the remote only not as
useful.

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rick_2047
Also I think 3D glasses would mean no proper TV to people who have spectacles.

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wfjackson3
120 Hz is ambiguous. Are you referring to the display refresh speed? Was the
discussion in the context of a specific physical display technology?

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lakeeffect
Is my 600 hz Plasma 3d Ready?

~~~
lakeeffect
[http://www.tvlampsnbulbs.com/2009/03/what-does-600hz-
subfiel...](http://www.tvlampsnbulbs.com/2009/03/what-does-600hz-subfield-
motion-mean/)

