Enhancement: Alternate display of GUI elements for 3D videos on a 3D display

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Many 3D videos are distributed in a side-by-side or above-below format, with 
the video's image for each eye being split in half and squished to half 
width/height as the name suggests. Most 3D televisions and monitors understand 
these formats and will display them in 3D correctly. When playing one of these 
videos, both halves of the display output will be stretched to double their 
width or height and displayed simultaneously with different light polarisations 
in a passive 3D display, or on alternate frames in an active shutter 3D 
display. However, gnome-mplayer's non-video elements (when playing in full 
screen, which you'd need to when using a 3D display) won't display properly 
when in these modes, the control bar popping up in side-by-side mode would 
result in the left half being stretched to double width and shown extending 
from the right of the left eye's image and vice versa. Similarly, subtitles 
will appear all wrong.

Therefore it would be really nice to have options in gnome-mplayer to make any 
display elements that aren't a part of the video itself (control bar, 
subtitles, media info toggled by the "i" button, etc.) to appear in a way that 
worked for side-by-side and above-below videos (half width and positioned in 
each horizontal half of the display for side-by-side, half height and 
positioned in each vertical half of the screen for above-below videos). Just to 
clarify, this isn't a request for any bino-style enhancements to the display of 
the actual videos, a modern 3D display doesn't need anything more than the 
video being played as-is, this is just a request for there to be options to 
make all non-video elements that are shown in full screen mode display in a 
manner suitable for side-by-side or above-below video playback on a 3D display. 
This probably wouldn't be too difficult to implement, especially as anything 
displayed in the exact same position on both halves of the screen would (3D 
depth-wise) appear at the absolute front, in front of everything else 
displayed, which would presumably be the most desirable Z-axis position for any 
GUI elements anyway. Obviously simply turning off the control bar is a 
workaround for the problem with the control bar itself, but turning off 
subtitles (or having their display mangled) means no support for deaf users.

I suppose if you wanted to be fancy about it, you could put sliders in the 
preferences for Z-axis position of subtitles, and (separately) Z-axis position 
of GUI elements... I'm not sure if "always in front" would necessarily be the 
best Z-axis depth for comfortable subtitle reading as I don't have a video 
player that can even display subtitles correctly in these 3D modes. Apparently 
3D Blu-rays are mastered with some kind of algorithm that dynamically adjusts 
the Z-axis of the subtitles so they appear in the middle of "the action" for 
each scene. However (while manual Z-axis sliders would also probably be pretty 
easy to implement, as you just have to have a small offset in position between 
the left and right eye images, and algorithms to automatically determine the 
best subtitle depth may be possible) this is really a secondary concern 
compared to getting non-video elements to simply display at all correctly in 
the first place.

Original issue reported on code.google.com by [email protected] on 27 Feb 2014 at 1:04

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Just a quick note to add... I incorrectly said in my report above that things 
like subtitles or GUI elements displayed at the same horizontal position in 
each half of the screen would appear at the extreme front of a 3D image. They'd 
actually appear in the middle depth-wise (not too close up, not too far away), 
which - now that I've had more chance to watch 3D media - would actually be 
better anyway than things being at the extreme front, as very close objects can 
be hard to focus on on a 3D display. Anyway, yes, if you didn't want the hassle 
of a depth slider or dynamic depth adjustment, putting GUI elements and 
subtitles in the horizontal exact middle of each half of the screen would work 
out just fine.

Original comment by [email protected] on 13 Mar 2014 at 12:15