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Old 3rd March 2018, 11:01   #1428  |  Link
r0lZ
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Join Date: Jul 2003
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LG TVs (HD and UHD) use always passive glasses that filter the polarized light. That means that they emit half the pixels with a particular polarization, and the other half with the opposite polarization. As far as I know, all LG TVs are based on the same model. One line of pixel contains the pixels for the left view, the next one for the right view and so on. (I have read somewhere that LG is now able to offer full resolution for the two eyes, but theoretically, it's impossible.) Therefore, it seems logical to use Half-TAB instead of Half-SBS, as there is exactly the same number of line for the left and right eyes in the encoded video and in the screen. You encode 1920x540 and you see exactly that. If you use Half-SBS, half the pixels are not at the right position and are useless. You see a 960x540 image.

However, if that logic is correct for Half-TAB, IMO there is absolutely no reason to prefer Full-TAB over Full-SBS or FS. Since the video resolution is full anyway, the passive HD TV will throw away half the resolution regardless of the 3D frame packing. But the habit to prefer TAB over SBS is well anchored, and there are certainly many web sites that continue to pretend, probably wrongly, that Full-TAB gives a better quality with all kind of LG TVs.

I don't know how 3D UHD LG TVs react to Half-TAB or Half-SBS. IMO, the quality loss when using Half-SBS is probably minimal, if not completely absent, but I'm not sure.

On the other hand, Half-SBS is largely considered better for active 3D TVs. I don't know why, as with active glasses, all pixels are used to display the left and right views. But it is a fact that Half-TAB gives less good results on my Samsung HD TV. Again, I think that Full-SBS/TAB/FS are strictly equivalent.
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Last edited by r0lZ; 3rd March 2018 at 11:25.
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