A webcam is a Caméra which is connected to the Ordinateur, via:

  • the port USB,
  • more rarely by the port FireWire,
  • or the parallel or series (old models, abandoned because of the too low flow),
  • on a network Ethernet (top-of-the-range, allows wire much longer) or wifi (without wire),
  • or thanks to a Carte of video intern or external acquisition with the PC,
  • via a analogical converter entered (cinch) digital display USB,
  • via a Video server entered analogical (cinch) digital display Ethernet.

The Caméra is of standard STAKE video-composite of the telegraphic type usual or Caméra without wire using the band of the 2,4 GHz (Bande L).

The finality of a webcam is not to produce a Vidéo high-quality, but to produce a Image basic, as well in definition (often less as the standard VGA, i.e. less 640×480 points), than of many images a second, making it possible to transmit the image by a network to low flow.

Some numerical cameras integrate a Webcam function. Those which do not have which it can be used as webcam if they have a video out, and that the computer has a Vidéo entry.

To ensure a rate of suitable cooling of image, it is preferable to have a broadband connection, for example ADSL.

Uses

It can film and thus to produce a traditional video stream, and to be used for the Visiophonie, or periodically capture an image. Its practical use often concerns the communication, in particular of the Visioconférence, as well as Vidéosurveillance, in particular of the detection of movement ensured by a program analyzing the differences between the successive images. One also finds Météocam, Astrocam, etc Certains models also integrate a Microphone.

The first webcam was connected at the department of computer sciences of the university of Cambridge in 1991 by James Quentin Stafford-Fraser and Paul Jardetzky (so that the members of the department data-processing can supervise the level of the coffee machine and to thus avoid moving for nothing) then connected to Internet in 1993 and cut the August 22nd 2001.

The use of the webcam for video-telephony is diffused very widely for the personal communications between Net surfers via cats, blogs, or via specific sites.

Software

A many software makes it possible to make forward video on the Net, in particular:

Technologies

The webcams have a sensor, which can be CCC, or CMOS, the webcams with sensors CMOS being generally less expensive and of quality less than a sensor CCC. To improve the image, the webcams are often coupled with a system Logiciel of interpolation, having for goal to post an image detailed starting from an image of low quality by creating Pixel S intermediaries whose Couleur is calculated by comparison with the adjacent pixels. Some webcams use infra-red diodes which allow a certain visibility in the complete black. The image is then in black and white. The interest of the infra-red diodes is that the produced light is invisible for the human eye. It thus does not dazzle the user.

Manufacturers, models, and difficulties of use

Contrary to other types of data-processing peripherals like key USB, the webcams were not equipped with standardized standards, and have pilot which are specific to each manufacturer and even often with each model, which makes difficult (but not impossible) their use on another Operating system (even another version of the same operating system) that for which the manufacturer planned a pilot.

This largely limited their deployment as well as the possible software applications, the acquisition of the images being often carried out through APIs various owners, often with the nonpublic specifications.

The images are often transmitted in the form of a flow JPEG, but this one is seldom standardized. The tendency is to use a standardized interface, in the course of deployment.

Use with Linux

Like all the peripherals, the use with Linux has a random side, no not providing manufacturer of pilot, nor, generally, of information making it possible to carry out one of them. What pushes the users and particularly the developers of Linux drivers for webcam to use the technique of the Retro-engineering (reverse engineering) to detail the electronics components of the webcam in order to program the good pilots.

In spite of that, a very great number of webcams function rather correctly with Linux. However, the general rule is that, even if the webcam functions rather well, certain advanced functions (automatic luminosity, etc) are not used, because of the lack of information.

Interactivity

Some webcams, in particular at Logitech, integrate interactive games or many functions intended to play with the image in real-time. Thus, it is possible to interact directly by the means of movements detected by the Capteur S present in the webcams. One thus can, for example, to control a Ballon by agitating the arm in front of the objective, or to even play plays by moving his body.

Logitech also developed in its version 5000 of the quickcam of the virtual accessories which adapt in real-time to your face, thus on messaging software such as MSN messenger. You can, consequently, change the color of your eyes or avoid you of a hat, a moustache or other accessories. If these tools remain for the moment relatively childish, it is that they were created to have an aspect of the type “cartoon”. They show, however, the possibilities of diversion of images and interactivity which a webcam offers.

It is besides damage which the developers general public do not create of more thorough and more serious software in order to be able as well as possible to exploit the exploitation of images in real-time.

Diversions

Considering their weak price, the webcams were often diverted of their primitive function. The most known application is it Astrocam , a webcam stripped of its optics and placed in a Telescope.

Simple: Webcam

Random links:1658 | Gisele (girl of Louis Piles) | Archdiocese of Ouagadougou | The lobster will not pass | He' S Back

© 2007-2008 speedlook.com; article text available under the terms of GFDL, from fr.wikipedia.org