libuvc-based camera support

[d235j]

This is necessary for Mac OS X and Linux (for cross-platform camera access).

I have patched up libuvc to work correctly at https://github.com/d235j/libuvc but I have not yet had a chance to integrate libuvc support into OSVR-Core. The changes in #284 should make this easier.

[rpavlik]

I assume you mean OS X (not Mac since I was recently informed there is no such thing) and Linux...

[WiedemannD]

I assume OSVR-Core with libuvc support is mandatory for the HDK Camera to work/track position on OS X at all? If yes, I would up vote this, if I could!

[godbyk]

There's work in progress in the uvc-camera branch.

[gustavklopp]

[ChristophHaag]

I looked a bit at the code and so far it seems like the VideoBasedTracker plugin gets the image and extracts some points without much trouble and the debug window looks nice enough, but most of the leds are all labeled -3 most of the time and when dumping to csv most of the positions show -nan.

Can you describe what needs to be done there? Is it normal that the LEDs are flickering in that video? Are they not synchronized to the camera yet? Or is it something else?

https://www.youtube.com/watch?v=Be9PGokKSBI

[Conzar]

The numbers should be green. See this video for the correct behavior.
https://youtu.be/0faUZWFu6-E

[ChristophHaag]

Thanks for the reference video. Note that the Video Tracker Calibration Utility is only available for windows, and that in my video you see the output from this code

OSVR-Core/plugins/videobasedtracker/VideoBasedTracker.cpp

Line 209 in 3a449d7

if (m_params.debug) {

instead.

I take from your video that the flashing" effect is normal, so thanks for that.

It was a bit hard to see while flickering so I added some code to show ? for unidentified LEDs and ID: <led.getOneBasedID()> for identified LEDs and it looks like it's just identifying random LEDs as random numbers: https://www.youtube.com/watch?v=KEj_pv8p-QI
So my guess is still that the LEDs are not properly synchronized to the video framerate.

[Conzar]

How are you running VideoBasedTracker?

[ChristophHaag]

Well, it is run by the default osvr_server_config.HDK20ExtendedLandscape.sample.json. If you mean the window, it is shown when you edit this config file, go to the com_osvr_VideoBasedHMDTracker section and set showDebug to true.

[rpavlik]

So if you are in the show debug mode, and press B for blobs view, then you'll see both reprojected locations (if you get a lock) as well as the beacon ID values: negative are sentinel values. -3 means enough frames to identify but no pattern matched: I'd imagine this is a frame duplication or drop. (-1 is not enough data associated with a continuous blob).

There should be some pulsing, but not flickering, if you have the sync cable connected. (The video calibration tool, view cam, etc are just windows only because I kept the code brief and didn't abstract out the factory - should be easy to tweak.)

But yes, to get it to work, we do need every single frame, with some reliable amount of world to plugin latency.

[ChristophHaag]

So I have been playing with libuvc settings a bit: ChristophHaag@9d377e5

Nothing seemed to really help (and much is undocumented in the driver at https://github.com/ktossell/libuvc/blob/master/src/ctrl-gen.c so I ended up putting in a time measure every time libuvc calls the callback with a new frame:

7.869802ms since last frame = 127.068000 fps
11.954927ms since last frame = 83.647520 fps
7.986380ms since last frame = 125.213175 fps
11.984378ms since last frame = 83.441961 fps
7.908881ms since last frame = 126.440137 fps
12.015909ms since last frame = 83.223000 fps
7.863718ms since last frame = 127.166310 fps
11.998185ms since last frame = 83.345939 fps
7.970222ms since last frame = 125.467020 fps

So that's not smooth 100fps. Perhaps libuvc is batching/buffering stuff? Could this be the reason that it's not working properly?