Passive 3DTV - Side by side (SBS), or top and bottom (TAB)? (1 Viewer)


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  • July 18, 2008
    Australia Australia
    Hi guys.

    I am wondering how to can get the most resolution out of a 3D BluRay backup through a passive-3D TV.

    My passive 3DTV outputs the left and right eye frames at the same time (unlike active which switches each eye). To achieve this with only 1920x1080 pixels to work with, the TV polarises the first row of pixels for one eye, then polarises the second row for the other, this alternation continues all the way down the length of the display. Therefore, the TV is outputting 1920x540 pixels for each eye.

    I can store a straight ISO of a BluRay and use frame packing to playback (the official BluRay 3D way), but I always reencode because the storage becomes ridiculous. So I've been reading online and there seems to be two methods: side by side and top and bottom (SBS & TAB).

    So the final resolutions for each eye becomes:
    SBS: 960x1080
    TAB: 1920x540

    But the /final/ output on a passive 3DTV (P-3DTV) means halving the vertical pixels again, so:
    P-3DTV -SBS: 960x540
    P-3DTV -TAB: 1920x270

    270 pixels vertically is so lossy it surely becomes visible. Therefore the best method appears to be SBS.

    But here's my thinking. If I store data using the TAB method, I end up with each frame having 1920 pixels of horizontal resolution, and 540 pixels of vertical resolution -exactly the output resolution of my passive 3DTV. If I do TAB, are the passive 3DTVs smart enough to alternate the vertical pixels so as to not lose resolution?

    Another way to look at it is this, if you get clever with the encoding, you could theoretically encode a 1920x1080 frame that has its first row of pixels coming from the left frame of the source, then the second row coming from the right frame of the source, then alternate the whole way through.

    This way you could send the 2D frame to your TV and it should appear 3D when you don the glasses. This would mean storing 1920x1080, and ending up with 1920x540 each eye. Ideal. This would only be possible if the TV /always/ polarises the light. Perhaps it doesn't for 2D content, I dunno. Notice that storing TAB is effectively the same thing as this, but instead of alternating yourself you simply stack the frames on top of one another and let the TV do the job. But does it do the clever thing? Or does it halve the vertical resolution? I don't actually get the telly until tomorrow.

    Any thoughts?
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