Skeltrack - Open Source Skeleton Tracking
Joaquim Rocha, IgaliaGUADEC 2012 - A Coruña
Igalia's Interactivity Team was on to investigateimmersive applications using FOSS
These applications representnew/different ways of interaction for users
Those can go from entertainment to more serious applications
The Kinect
Microsoft's Kinect was the first camerawith a price affordable to the public
The USB connection is open and thus hackable
This originated Open Source projects like the libfreenect,a library to control the Kinect device and get its information
We created a GLib wrapper for libfreenect called GFreenect
GFreenect offers asynchronous functions (and some synchronous aswell) and makes it easy to use with other GNOME technologies
GObject Introspection opens these technologies for users ofPython, Javascript, Vala, etc.
The Kinect has a structured light camera which gives depth information
But that's raw information... values from 0-2048
libfreenect/GFreenect can give those values in mm
Still...
It does NOT tell you there is a person in the picture
Or a cow
Or a monkey
Let alone a skeleton and where its joints are!
For this you need a skeleton tracking solution
Skeleton Tracking
Three proprietary/closed solutions exist:
Microsoft Kinect SDK: non-commercial only
OpenNI: commercial compatible
Kinect for Windows: commercial use allowedbut incompatible with the XBox's Kinect
Conclusion: There were no Free solutions toperform skeleton tracking... :(
So Igalia built one!
Enter Skeltrack
What we wanted:✩ A shared library, no fancy SDK✩ Modular (do one thing)✩ Device independent✩ No pattern matching, no databases✩ Easy to use (everybody wants that!)
Not as easy as it sounds!
The current version tracks up to 7 joints:✩ Head;✩ Shoulders;✩ Elbows;✩ Hands.
Smoothing is implemented usingHolt's Double Exponential formulas
Smoothing and heuristics usedcan be tweaked using GObject properties
There are still some things missing...
Future work
Hands from elbows: If one of the extremas is an elbow, weneed to infer where the hand is
Robustness: Use restrictions to ignore objects that are notthe user
Multi-user: Track more than one person at a time
And of course, get the rest of the joints: hips, knees, etc.
How to use it?
First reduce the depth buffer's dimension
Reducing the buffer's dimension will make things faster
While at it, it's wise to also apply a depth threshold
Asynchronous API
SkeltrackSkeleton *skeleton = SKELTRACK_SKELETON (skeltrack_skeleton_new ());skeltrack_skeleton_track_joints (skeleton, depth_buffer, buffer_width, buffer_height, NULL, on_track_joints, NULL);
Synchronous API
SkeltrackJointList list;list = skeltrack_skeleton_track_joints_sync (skeleton, depth_buffer, buffer_width, buffer_height, NULL, NULL);
Skeleton Joint:
ID: HEAD, LEFT_ELBOW, RIGHT_HAND, ...x: X coordinate in real world (in mm)y: Y coordinate in real world (in mm)screen_x: X coordinate in the screen (in pixels)screen_y: Y coordinate in the screen (in pixels)
Join us!
https://github.com/joaquimrocha/Skeltrack
Nifty Tools for Development:
GFreenect: https://github.com/elima/GFreenect
GFreenect Utils: https://github.com/joaquimrocha/gfreenect-utils
GFreenect Python Example
Tool: depth-file-viewer
Tool: record-depth-file
Demo?
Warning: Might go wrong!
Questions?
Creative Commons pictures from flickr:Kinect: Auxo.co.krMonkey: nothingtosayKid Playing: Rob WelshSkeleton: Dark Botxy
Other non CC images:Doctor: http://research.microsoft.com/en-us/projects/touchless/Minority Report:http://www.ovelf.com/2010/04/14/oblong-tan-g-speak-arttirilmis-gerceklikte-hareketlerin-3-boyutta-yorumlanmasi/
