Kinect with Linux

OpenKinect and OpenNI

The Adafruit contest had been hosted on a GitHub site called libfreenect. Once the contest had been won, Josh Blake and some others founded a community called OpenKinect. From their Web site (see Resources):

OpenKinect is an open community of people interested in making use of the amazing Xbox Kinect hardware with our PCs and other devices. We are working on free, open-source libraries that will enable the Kinect to be used with Windows, Linux and Mac.

The OpenKinect community consists of over 2,000 members contributing their time and code to the Project. Our members have joined this Project with the mission of creating the best possible suite of applications for the Kinect. OpenKinect is a true "open source" community!

Our primary focus is currently the libfreenect software. Code contributed to OpenKinect where possible is made available under an Apache20[sic] or optional GPL2 license.

Around the same time, a number of companies with interests in commercializing natural interfaces formed a group called OpenNI. According to their Web site (see Resources):

The OpenNI organization is an industry-led, not-for-profit organization formed to certify and promote the compatibility and interoperability of Natural Interaction devices, applications and middleware. One of the OpenNI organization's goals is to accelerate the introduction of Natural Interaction applications into the marketplace.

OpenNI offers its software under several different licenses—LGPL for the open-source bits and just binaries for some proprietary parts (like skeletal identification). The founders of OpenNI include:

• PrimeSense, Inc., the company that supplied Microsoft with the technology for "Project Natal", which became the Kinect.

• Willow Garage, a company focused on hardware and software for personal robotics.

• SideKick, a game software company that develops motion-based games.

• ASUS, the computer OEM, who is selling a different 3-D depth sensor based on PrimeSense technology called X-tion Pro.

In general, OpenKinect appears to be approaching NUI from the bottom up, starting with the libfreenect driver and building on top of that, all strictly open source. OpenNI has more of an architectural vision for how NUI devices from different vendors can interoperate. There's plenty of room for the two organizations to work together.

Try It Yourself

The drivers and demo software for Kinect are readily available, both from OpenNI and from openkinect.org (see Resources). Installation on Ubuntu 10.10 is particularly easy, as both organizations provide prebuilt packages. If you're running a different Linux distro, RPMs and debs also are available, along with ample build instructions, so you shouldn't have a problem.

With the OpenKinect packages, you get some demo programs that show the depth perception and color image capability of the Kinect. Utilities are included to record the Kinect data stream and to emulate a Kinect so the software can be used without having the hardware connected. There also are language interfaces in various stages of development for the following:

• Python.

• Synchronous C interface (functions instead of callbacks).

• ActionScript.

• C++.

• C#.

• Java JNI.

• Java JNA.

• JavaScript.

• Common Lisp.

The OpenNI package has similar capabilities, and it includes detailed documentation of the C/C++ interface to the underlying layers. The OpenNI documentation and sample code is oriented toward Visual Studio, but most of it also is applicable to gcc.

Reality Bites

Okay, wrong movie, but there are some not-so-obvious realities to using Kinect with Linux. They might or might not affect your explorations:

1. The USB connector on the Kinect device is nonstandard. That's okay if you buy the Kinect as a standalone device. It comes with a power supply and an adapter to use standard USB. If you buy the Kinect as part of an Xbox bundle, you will need to buy the power supply/adapter separately.

2. The depth perception technology in Kinect works best at distances of 6–8 feet. It's not a mouse-and-keyboard distance interface, it's a stand-across-the-room-and-wave interface.

3. The Kinect software is able to determine body position and infer the positions of arms and legs, but it isn't able to do things like individual finger resolution. That makes it difficult to do things like sign-language interpretation.

Let the Games Begin

So, now for $150 you can have open-source access to hardware that would have cost you $30,000 a few years ago. What clever ideas can you come up with for NUI?

Resources

OpenKinect: http://www.openkinect.org

OpenNI: http://www.openni.org

Kinect Teardown: http://www.technologyreview.com/video/?vid=644