Ok so posting this here too for the YT thread, the meta data that the YT help guide is referring to isn't
what you can scan with a media info reader, this is what's built into the files themselves as they're rendered and more complex than showing the layout type which can be added to the media info. At least that's what I've learned from a little research. That help guide suggests using a NLE like Vegas Pro or Go Pro studio, so the 3D info is already built into them into those renders same as always and you don't need to add anything later.
You can add 3D layout type with something like mkvtoolnix and maybe that does something for certain media players possibly to trigger the display, I really don't know for sure. But I've tested my display on YT videos without that added and it auto triggers with using the built in app just fine in display. Auto sensing is really for smart devices that grab the file and process it internally. I think for media players (in a PC) sent to screen then it's up to the media player to send that trigger to the display so that may be what that's for.
So playing 3D from a computer right now, unless you can load Flash in a browser you don't have access to the 3D options that were there before and at least for me using Chrome browser I only see 2D and anaglyph options, no side by side. This can only be by design, they just don't have Chrome and YT setup to link to the side by side file, it defaults to the 2D or anaglyph so that's what they set it up for.
Safari browser I can still use Flash which has all those options before or I can disable Flash which is fine too and get the raw side by side file in HTML 5 player.
I took a look at what video files YT stores on one of my videos to see if there's a new anaglyph file but there isn't, it just has different resolutions saved in mp4, webm and vpx files for playback depending on what the user selects. The 2D and anaglyph versions are converted by the player on the fly which isn't really that intensive so it doesn't require a separate file for it stored. BTW, I think this is why PDVD is broken because it's not getting access to the raw files, same as Chrome browser. It must use HTML 5 player and therefore 2D and anaglyph only.
The comment below the 3D checkbox indicates the 3D box is going away soon so if that's true then you will need to upload in the 3D format(s) you want to show and if you want 2D you'll need another upload for that too. On a few videos I added annotations with the text: click here to view this video in 2D which disappeared after a few minutes and also put one on the 3D version with link to 2D. (However, I just looked and annotations feature is now gone replaced with end screens
so I need to look at that. You can no longer edit or add annotations have to use the new end screen feature.)
So YT's solution to 3D is anaglyph only at least for now. This is short lived if the 3D checkbox is going away so it would seem this problem will resolve itself shortly. I suspect again, this is why PDVD doesn't work, because it's forcing 2D and anaglyph and PDVD either hasn't been updated or it can't access the source files like I can with Safari browser with HTML 5.
So might as well stop checking the 3D box and plan on what 3D format you want to use. I say top/bottom should be standard just because it equals the resolution on passive and active, but there's editors that might not have top/bottom like PD so there's that issue.
The other question is what will happen with all the videos that are 3D and the 3D checkbox is selected? I think some support is going to be lost. You should be able to play the raw file and all the smart devices with 3D out there won't have a problem with that but they won't be able to select 2D or anaglyph or other conversions unless you still have Flash support in your browser. So if you have 3D uploads and no 2D you may need to upload 2D versions. The 3D versions should be fine because they'll just be in the format you uploaded.