Explain checkerboard and interlaced 3D pls

[Freke1]

I can't understand what the unused pixels do.
Like in the US 3D HD TV's, the Zalman 3D monitor and interlaced 3D videos.

If this is a side-by-side 3D video (frame sequential):
Left eye sees (16*5 pixel):
LLLLLLLLLLLLLLLL
LLLLLLLLLLLLLLLL
LLLLLLLLLLLLLLLL
LLLLLLLLLLLLLLLL
LLLLLLLLLLLLLLLL
while right eye is black.
Then right sees:
RRRRRRRRRRRRRR
RRRRRRRRRRRRRR
RRRRRRRRRRRRRR
RRRRRRRRRRRRRR
RRRRRRRRRRRRRR
while left eye is black.

How does this look on a checkerboard TV, and how does a interlaced video look on a framesequential monitor (like the 22" Samsung) pls?

[cybereality]

Technically the unused pixels should display nothing (aka black) however it doesn't appear this way in practice. If you were to run interlaced on a CRT with shutters then the image appears darker (like it has black interlaced lines, cause it does). However on the Zalman it appears to be like a full resolution (almost) image with no black lines. Sometime I try to look for the lines and you don't see them at all. I am not sure what kind of magic makes it work, but it does.

[DmitryKo]

There are no "checkerboard TVs" which are able to display checkerboard format as native. As of now, the checkerboard pattern is a just packing format which allows transmitting 1080p stereo signal in 60 Hz bandwidth. After unpacking, the empty pixels in the checkerboard image need to be interpolated from the neighbours in a process known as quincunx sampling.

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   *
*  +  *
   *

The pixel in the center gets its color value by linearly or bilinearly interpolating from the color values of its 4 neighbouring pixels (less pixels are available at the edges); in a simpler wording, the center pixel is the average of color values of its neighbours. There are variations of the checkerboard format, such as RealD side-by-side with checkerboard which offers more pixel coherency between the views.


As for line interleaved formats, there is no need to interpolate anything on a passivee polarized display device which uses different micropolarizers on each alternating line; the line interleaved and line interlaced formats will fit the native pixel layout of such device.

In theory, a passive polarized display could as well use the checkerboard pattern for micro-polarizers instead of line-alternative pattern, but as of now there are no such devices on the market.


Frame sequential TVs with active glasses should be able to accept line-interleaved or line-interlaced signal as well, since it's just another form of packing the stereo signal into standard 60 Hz video bandwidth; they would need to interpolate the missing lines or deinterlace, since they are inherently progressive displays, then display the frames in a sequence as usual. Such interpolation however would give you a sub-optimal picture in comparison with checkerboard sampling.
(A 120 Hz CRT display could probably accept interlaced signal as it is, but it would need to digitally process line-interleaved signal to extract two separate sub-frames and then either display it as interlaced singal or deinterlace to full progressive frames)

Similarily, passive polarized TVs with line-interleaved polarizing pattern should be able to accept checkerboard, they would interpolate it as usual then drop the lines as necessary.

Did I answer all of your questions? 8)

[Freke1]

Yes thank You.

[taz291819]

Similarily, passive polarized TVs with line-interleaved polarizing pattern should be able to accept checkerboard, they would interpolate it as usual then drop the lines as necessary.

Or do it the easy way and integrate the new Sigma Designs SoC into the display. It can convert all popular methods to another other method.

[DmitryKo]

do it the easy way and integrate the new Sigma Designs SoC into the display

I was trying to explain the principle, not prepare "how to" guide to designing your own stereo television

[wbloos]

There are no "checkerboard TVs" which are able to display checkerboard format as native.

well this is not correct - therefore you need to know how the 3D ready DLP TVs work - in fact all 3D rearprojection TVs have a special DLP chip which in fact has no 1920*1080 pixels - it has only half of the pixels aranged in a special order. Here is how these piyels (mirrors on the DLP chip) are setup:

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row    1 2 3 4 5 6 7 8 9
line 1 /\  /\  /\  /\  /\
line 2 \//\\//\\//\\//\\/
line 3 /\\//\\//\\//\\//\
line 4 \//\\//\\//\\//\\/
line 5 /\\//\\//\\//\\//\
       \/  \/  \/  \/  \/

The pixels are rhombis not squares (hope one can see it above) - then there is a wobble unit which shifts the light 1/2 pixels horizontal (right after the DLP chip) at 120Hz
Now if you have a closer look at this pattern you will see that this is a checkerboard pattern - each view is shown once during one wobble period - the second view is shifted and uses all DLP mirrors

Two days ago I had the chance to test a Samsumg Plasma 3D ready TV using cherboard playbyck from my laptot - surprisingly if watchin the picture without glasses it was not flickering (changing the view between left and right) - in fact the TV still displayed the checkerboard pattern - it seem this TV just switches the one view to black while displaying the other view

Werner

[DmitryKo]

in fact all 3D rearprojection TVs have a special DLP chip which in fact has no 1920*1080 pixels - it has only half of the pixels aranged in a special order. then there is a wobble unit which shifts the light 1/2 pixels horizontal (right after the DLP chip) at 120Hz

Since the shift is horizontal and not diagonal, I don't really see how checkerboard is related to wobulation.

What you describe would require diagonal movement and that would only be possible with double wobulation, which would work in both vertical and horizontal dimensions thus making diagonal movement possible. So far only horizontal-wobulating DMD devices have been released on the market.

if watchin the picture without glasses it was not flickering (changing the view between left and right) - in fact the TV still displayed the checkerboard pattern - it seem this TV just switches the one view to black while displaying the other view

What "other view"? Frame sequential method works by displaying only one view at a time, it would be quite absurd to display both frames simultaneously as in undecoded checkerboard source, and I don't think they skip the interpolation step and leave black pixels in the extracted sub-frames, that would be immediately noticeable.

As for flickering, you wouldn't notice it on a plasma display because it uses pulse-width modulation to change brightness of the pixels, so they can blink at up to 123 kHz (120 frames * 1024 brightness levels).

[iondrive]

DmitryKo,

You're pretty smart for your age judging by your picture.



http://www.dlp.com" onclick="window.open(this.href);return false; used to have some good pdf's about the checkerboard 3d format but now I don't see them there anymore. That's too bad.

[DmitryKo]

http://www.dlp.com used to have some good pdf's about the checkerboard 3d format but now I don't see them there anymore

The links are still there, see http://www.dlp.com/hdtv/dlp-features/3d-hdtv.aspx, section Technical links and documents; the content is currently missing though.

You're pretty smart for your age judging by your picture

Yeah, my IQ can only be expressed with imaginary numbers

[Freke1]

Damn I had forgotten about imaginary numbers ¯\(°_o)/¯
Those are annoying.

[DmitryKo]

see http://www.dlp.com/hdtv/dlp-features/3d-hdtv.aspx, section Technical links and documents; the content is currently missing though

The documents have been uploaded.