Xbox kinetic how does it work

Microsoft is projecting that it will sell 5 million units between now and Christmas. We'll have more details and a review of the system soon, but for now it's worth taking some time to think about how it all works.

Kinect's camera is powered by both hardware and software. And it does two things: generate a three-dimensional moving image of the objects in its field of view, and recognize moving human beings among those objects. Older software programs used differences in color and texture to distinguish objects from their backgrounds.

PrimeSense, the company whose tech powers Kinect, and recent Microsoft acquisition Canesta use a different model. The camera transmits invisible near-infrared light and measures its "time of flight" after it reflects off the objects.

Time-of-flight works like sonar: If you know how long the light takes to return, you know how far away an object is. Cast a big field, with lots of pings going back and forth at the speed of light, and you can know how far away a lot of objects are. Using an infrared generator also partially solves the problem of ambient light. Since the sensor isn't designed to register visible light, it doesn't get quite as many false positives.

PrimeSense and Kinect go one step further and encode information in the near-IR light. As that information is returned, some of it is deformed -- which in turn can help generate a finer image of those objects' 3-D texture, not just their depth.

With this tech, Kinect can distinguish objects' depth within 1 centimeter and their height and width within 3 mm. Story continues At this point, both the Kinect's hardware -- its camera and IR-light projector -- and its firmware sometimes called "middleware" are operating.

The Kinect has an on-board processor which is using algorithms to process the data to render the three-dimensional image. The Kinect sensor is a flat black box that sits on a small platform, placed on a table or shelf near the television you're using with your Xbox Newer Xbox s have a Kinect port from which the device can draw power, but the Kinect sensor comes with a power supply at no additional charge for users of older Xbox models.

For a video game to use the features of the hardware, it must also use the proprietary layer of Kinect software that enables body and voice recognition from the Kinect sensor [source: Rule ]. A further look at the technical specifications for Kinect reveal that both the video and depth sensor cameras have a x pixel resolution and run at 30 FPS frames per second. The specifications also suggest that you should allow about 6 feet 1. The Kinect hardware, though, would be nothing without the breakthrough software that makes use of the data it gathers.

Leap forward to the next page to read about the "brain" behind the camera lens. Sign up for our Newsletter! The dots are arranged in a pseudo-random pattern that is hardwired into the sensor. You can see some of the pattern in Figure Figure The dot pattern on the sofa arm. A pseudo-random sequence is one that appears to be random, but it is actually mechanically generated and easy to repeat. It can then compare the image from the camera with the pattern it knows it is displaying, and can use the difference between the two to calculate the distance of each point from the sensor.

To understand how the Kinect does this, you can perform a simple experiment involving a darkened room, a piece of paper, a flashlight, and a helpful friend. Now, get your friend to stand about 5 feet 1. Ask your friend to hold the paper to the front of you, holding the torch in your left hand, shine the torch dot onto the piece of paper.

Now ask your friend to move forward toward you. As the person comes closer, you will see that the dot on the paper moves a little to the left because it now hits the paper before it has traveled quite as far to the right.

Figure shows how this works. If you know the place you are aiming the dot, you can work out how far away your friend is by the position of the dot on the paper. The impressive thing about the Kinect sensor is that it performs that calculation for thousands of dots, many times a second.

Figure Showing how the Kinect distance sensor works. This technique is interesting because it is completely different from the way that humans see distance. Each human eye gets a slightly different view of a scene, which means that the closer an object is to a human, the greater the difference between the images seen by each eye. The brain identifies the objects in the scene, determines how much difference there is between the image from each eye, and then assigns a distance value to each object.

The Kinect sensor also contains four microphones arranged along the bottom of the bar. You can see them in Figure : two on the left and right ends, and two more on the right side of the unit. The Kinect uses these microphones to help determine from where in a room a particular voice is coming. This works because sound takes time to travel through air. Sound travels much more slowly than light, which is why you often hear a thunderclap long after seeing the corresponding bolt of lightning.

When you speak to the Kinect sensor, your voice will arrive at each microphone at different times, because each microphone is a slightly different distance away from the sound source. Software can then extract your voice waveform from the sound signal produced by each microphone and—using the timing information—calculate where the sound source is in the room.

From a control point of view, when a program knows where the speech is coming from perhaps by using the distance sensor , it can direct the microphone array in that direction, essentially creating a software version of the directional microphones that are physically pointed at actors to record their voices when filming motion pictures.