[vlc-devel] OpenHMD branch?

Lomax lomax at clickworkorange.com
Mon May 20 01:16:41 CEST 2019

Sending another screenshot[1], showing more clearly what the problem is; 
here I have dropped out of full screen, paused and zoomed the video to 
1/4. As you can see, the video which actually contains two over/under 
360 panoramas is not shown as two L/R "squircles" as expected, but as a 
~16:9 mono crop. This cropped view follows the rotational movements of 
the Rift (both vertically and horizontally).


1: https://i.imgur.com/il6CJUi.jpg

On 2019-05-19 23:57, Lomax wrote:

> Hello again,
> I've just tried cleanly rebuilding everything once more, this time 
> using a manual build of vlc/contrib/libplacebo. The shipped verion 
> (allthough the same version number) does not seem to include shaderc 
> support, so I downloaded/built/installed that first, then libplacebo, 
> then VLC. I'm basically trying to retrace every step I took on the 
> previous Celeron/Intel UHD machine, where it did work (albeit at 
> slideshow speeds). Alas, this seems to have made no difference. I'm 
> almost beginning to suspect that the change of GPU is the root of my 
> problem... Some concrete questions:
> Does VLC-HMD require libplacebo built with shaderc support?
> What is the role of libplacebo?
> What is the role of assimp?
> Are the VirtuaTheatre files needed for stereoscopic 360 playback?
> Are the following runtime errors possibly related to my problem?
> - chain filter error: Too high level of recursion (3)
> - main filter error: Failed to create video converter
> - main vout display error: Failed to create video converter
> - main vout display error: Failed to adapt decoder format to display
> - main video output error: video output creation failed
> - main decoder error: failed to create video output
> I suspect not, because I do remember seeing them before - and there 
> *is* video output, just not in the right format.
> Is there any debugging method I can use to find out more - e.g. should 
> I build VLC with some debugging option?
> And finally, the main question: What might be the reason that the video 
> displays as a rectangular mono panorama instead of the expected side by 
> side stereo "squircles"?
> To be fair, I am putting these questions as much to myself, while 
> hoping those who know the ins & outs of VLC can provide some further 
> insight.
> Doggedly,
> Lomax
> On 2019-05-19 17:26, Lomax wrote:
> Hi Alexandre,
> Thank you for spending time on this - don't worry about my long 
> rambling post from Friday; if there's any useful information there then 
> great, but the questions are not so important. In answer to your 
> questions re. usage, I'm working on a public exhibition at a "marine 
> knowledge centre" in Sweden (a registered non-profit), where the staff 
> are involved also in practical science - including diving to document, 
> sample and survey the marine life and seabed conditions. They have a 
> very nice stereoscopic 360 underwater camera (not sure of the model but 
> can check if you want) but they have no means to show its footage to 
> the museum visitors - which is where I come in: amongst other things* 
> I've been tasked to build a permanent exhibit with which visitors can 
> view this material. I chose, perhaps foolishly, to use the Oculus Rift 
> CV1, thinking it was a well established product with plenty of support. 
> Only afterwards did I find out that it was nothing of the sort, and 
> that indeed the whole area of stereoscopic 360 video is severely 
> underdeveloped. Only proprietary (Windows/MacOS) applications seem to 
> be available, which would be unsuitable for use in an exhibition; no 
> user interaction should be required to launch the video, nor should the 
> computer, or any OS or application GUI elements be visible, and the 
> system needs to be reliable - we just want the video to play in a 
> continuous loop from when the computer is switched on until it's 
> switched off, and nothing else. This, and the fact that it is open 
> source, is why I went with VLC - thinking the command line interface 
> should make it easy to get it to start playing on boot (and it was), 
> and that we could tweak anything else we might want to adjust in the 
> source if needed. So our application is basically as simple as could 
> be; there's no interactivity, no audio, and no motion tracking beyond 
> rotation, and the material is pretty "standard" (at least as far as any 
> standards are established). But I've now spent 50hrs+ on this, and 
> EUR1500+ on hardware, yet have nothing to show, which means I'll have 
> some tough explaining to do...
> I've taken some quick snaps of what I see[1-4] - please let me know if 
> there's any specific information I can provide which may help getting 
> to the bottom(!) of this.
> Cheers,
> Lomax
> *) For example, I've also built a remote controlled submerged camera 
> out in the water, based on an Axis PTZ PoE camera, which can be 
> controlled with an analogue joystick from inside a mock "submarine". 
> This is 2D HD and works beautifully on a Pi3 connected to a curved 27" 
> monitor.
> 1: https://i.imgur.com/WGzfcY4.jpg
> 2: https://i.imgur.com/bAy39Wy.jpg
> 3: https://i.imgur.com/jWTbBxn.jpg
> 4: https://i.imgur.com/SswgW8T.jpg
> Hi, I'll answer to your bigger previous post later, but first, thank
> you for your comprehensive testing of this branch and the report you
> did.
> The code is extracting lenses properties from OpenHMD to match the
> projection with the way the headset works. If there is no HMD, there
> is no projection. The "circle-like" effect is a colour and pixel
> transformation (using panotools parameters) to match the lenses used
> by the headset, which is needed because of the low distance between
> the eyes and the screen in the headset.
> What is your setup, do you have screenshot of the issue ? This code was
> taylored for headset demos so there are probably a lot of different
> hacks and mostly only headset playback is probably correctly handled in
> this version.
> I can try to provide you a version with some fixes for the demo if you
> want and if it's not too much time consuming, but I would like to know
> the exact use case for your demo. You can ping me as "unidan" on irc if
> you need some help on the build itself.
> Greats,
> --
> Alexandre Janniaux,
> VideoLabs

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