Additional Depth Modes: Subpixel, LR-check, extended-disparity support

[Luxonis-Brandon]

Start with the why:

The additional depth modes available in our framework are useful in certain scenarios, including:

• Supporting closer-in minimum depth (by a factor of 2): Extended disparity
• Eliminating shadowing from running disparity in only one direction: left/right check (runs disparity in both directions)
• Allowing further maximum distance, and better accuracy w/in given range: subpixel support

Move to the how:

Analyze the memory/resource use of enabling these modes through the API, and implement such that limits are placed on other resources appropriately (e.g. fewer SHAVES available for neural compute).

Move to the what:

Support the following additional depth modes:

• Subpixel
• LR-check
• Extended disparity

[Luxonis-Brandon]

Initial LR-check implementation is in #178

[Luxonis-Brandon]

And see #184 for more of the why of what subpixel is useful for.

[Luxonis-Brandon]

We have an initial implementation of this now, including a point-cloud projector: https://github.com/luxonis/depthai-experiments#gen2-subpixel-and-lr-check-disparity-depth-here
Go to the repo depthai-experiments , check out the branch gen2_stereo and run:

cd gen2-camera-demo
python3 -m pip install -r requirements.txt
python3 main.py 

It is configured with LRcheck + Subpixel by default.
I will also add command line options, but for now please edit the script to change the config:

lrcheck  = True 
extended = False
subpixel = True 

Note that as of now there is no median filtering when any of the lrcheck, subpixel, or extended disparity are enabled. So that is why it looks a bit grainy.
And there’s some error when doing the point cloud projection where a bunch of valid depth points (maybe 1/2 of them?) don’t get projected. So the quality is actually better than what is shown here.

[Luxonis-Brandon]

And here is an example of my floor with subpixel and LR check enabled:

And side view of a face with shelves in the background for subpixel and LR check enabled:

[Luxonis-Brandon]