Top-Bottom 3D vs. Side-by-Side on Passive Display - Page 5 - AVS Forum
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post #121 of 124 Old 08-17-2014, 08:13 AM
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Originally Posted by Jedi2016 View Post
HOU works on paper for passive displays, but not in practice. The loss of vertical resolution is noticeable, and the overall image appears much softer than HSBS.
Whilst I haven't actually watched HOU 3D, I have viewed the 2D frames which make it up and I must say they do look softer than the SBS versions. Perhaps the conversion is inadvertently softening the image, such as scaling 1080p to 540p instead of selecting a field.

Although HOU works on paper and should be the best presentation method for passive displays, we do not know what the TV is doing in converting to the interlaced presentation method and whether filtering is being applied. In addition, I understand that the human eye is more sensitive in the vertical direction than in the horizontal.

As you say, the true test would be to make an interlaced composite of the left and right eye views using a single field from each view and watch in 2D but with the 3D glasses, although I'm not sure if any software exists to create that type of video.
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post #122 of 124 Old 08-17-2014, 10:24 AM
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Whilst I haven't actually watched HOU 3D, I have viewed the 2D frames which make it up and I must say they do look softer than the SBS versions. Perhaps the conversion is inadvertently softening the image, such as scaling 1080p to 540p instead of selecting a field.

Although HOU works on paper and should be the best presentation method for passive displays, we do not know what the TV is doing in converting to the interlaced presentation method and whether filtering is being applied. In addition, I understand that the human eye is more sensitive in the vertical direction than in the horizontal.
Exactly. I think the TV's upscaling of the 540p image, and then the splitting into interleaved fields is what's causing it. The TV isn't smart enough to simply "spread" the lines across the interleaves without futzing with it first. Back in CRT days, vertical resolution was absolutely more visually noticeable. Again, on paper, it probably wouldn't make a difference with these HD displays we're all using, but it does still seem to matter in some respect as far as how our eyes are interpreting it. Perhaps it boils down to our eyes being side-by-side instead of top-and-bottom, where they're more easily able to "fill in the gaps" horizontally using both eyes, but have more trouble with it vertically.

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Originally Posted by IanD
As you say, the true test would be to make an interlaced composite of the left and right eye views using a single field from each view and watch in 2D but with the 3D glasses, although I'm not sure if any software exists to create that type of video.
I've done enough work with interlaced video in the past, I think I can do it using some of my VFX and editing software. In fact, I know my VFX software can do it, I've created interleaved 3D video before (scratch-built stuff, mostly just fiddling around to see what I can do). But that's not ideal for an entire feature film, that software's meant for single shots or very short segments. I imagine something like VirtualDub could do it if you could figure out what settings to use. I haven't bothered with that program in years, though.

Welcome to Rivendell, Mister Anderson.
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post #123 of 124 Old 08-17-2014, 07:52 PM
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Exactly. I think the TV's upscaling of the 540p image, and then the splitting into interleaved fields is what's causing it. The TV isn't smart enough to simply "spread" the lines across the interleaves without futzing with it first.
It is most likely a combination of the encoders scaling 1080p to 540p instead of choosing a field when processing the original frame packed source; the TV futzing with the 540p when expanding it into a 1080i field; and the fact that a frame has twice as much horizontal information as vertical, so the vertical is the one least able to support being reduced further.

I expect something like Avisynth could be used to easily process the 3D source into an interleaved frame for subsequent encoding with x264.

The main downside that I can see is that 3D TVs are setup to handle frame packed, SBS, HOU and sometimes checkerboard 3D in special modes that allow them to adjust 3D effect, but if you send a 2D frame with interleaved 3D I don't think there is a special mode to be able to adjust 3D effect so you are stuck with what you get. It is important therefore to get the left and right eye orientations correct as I doubt you would be able to switch except in 3D mode.

The other downside is that interleaved 3D is probably harder to compress without losing detail, so I'm guessing the file sizes will be larger than normal (as they tend to be with interlaced versus progressive frame compression).
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post #124 of 124 Old 08-17-2014, 08:31 PM
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I tend to never adjust the effect. If it's a film, I'm content with whatever the director and DP thought was good. If it's a game or something, I can usually adjust the effect in software. Otherwise, it's content I create myself, so I know it's right to begin with. So that wouldn't be much of a hindrance. You're right about the compression, though. The files I usually work with are pretty small, so it's not much of a consideration. I've never tried it on something feature-length.

If I'm not mistaken, the FPR layers are fixed, right? So the lines assigned to the left eye will always be the left eye, regardless of what type of TV it is. This has got me wanting to put something together, to see if I can render it that way, send it to my TV and have it display correctly.

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