A webcam is a video capture device connected to a computer or computer network, often using a USB port or, if connected to a network, ethernet or Wi-Fi.
The most popular use is for videotelephony, permitting a computer to act as a videophone or video conferencing station. This can be used in messenger programs such as Windows Live Messenger, Skype and Yahoo! messenger services. Other popular uses, which include the recording of video files or even still-images, are accessible via numerous software programs, applications and devices.
Webcams are known for low manufacturing costs and flexibility,[1] making them the lowest cost form of videotelephony.
The term 'webcam' may also be used in its original sense of a video camera connected to the Web continuously for an indefinite time, rather than for a particular session, generally supplying a view for anyone who visits its web page over the Internet. Some of these, for example those used as online traffic cameras, are expensive, rugged professional video cameras.
Contents |
History
First employed in 1991, a webcam was pointed at the Trojan room coffee pot in the computer science department of Cambridge University. The camera was finally switched off on August 22, 2001. The final image captured by the camera can still be viewed at its homepage.[2][3] The oldest webcam still operating is FogCam at San Francisco State University, which has been running continuously since 1994.[4]
One of the most widely reported-on webcam sites was JenniCam, started in 1996, which allowed Internet users to constantly observe the life of its namesake, somewhat like reality TV series Big Brother, launched three years later.[5] More recently, the website Justin.tv has shown a continuous video and audio stream from a mobile camera mounted on the head of the site's star. Other cameras are mounted at bridges, public squares and other public places, their output made available on a public Web page in accordance with the original concept of a "webcam".
Around the turn of the century, computer hardware manufacturers began building webcams directly into laptop and desktop screens, thus eliminating the need to use an external USB or Firewire camera. Gradually webcams came to be used more for communication between two people, or among a few people, than for offering a view on a Web page for an unknown public.
Video calling and conferencing
As webcam capabilities have been added to instant messaging, text chat services such as AOL Instant Messenger, one-to-one live video communication over the Internet has now reached millions of mainstream PC users worldwide. Improved video quality has helped webcams encroach on traditional video conferencing systems. New features such as automatic lighting controls, real-time enhancements (retouching, wrinkle smoothing and vertical stretch), automatic face tracking and autofocus assist users by providing substantial ease-of-use, further increasing the popularity of webcams.
Webcam features and performance can vary by program, computer operating system and also by the computer's processor capabilities. For example, 'high-quality video' is principally available to users of certain Logitech webcams if their computers have dual-core processors meeting certain specifications. Video calling support has also been added to several popular instant messaging programs.
Some online video broadcasting sites have taken advantage of this technology to create Internet television programs centered around two (or more) people "diavlogging" with each other from different locations. Among others, BloggingHeads.tv uses this technology to enable conversations between prominent journalists, scientists, bloggers, and philosophers.
Sign language communications via webcam
- Main articles: Video Relay Service, a telecommunication service for deaf, hard-of-hearing and speech-impaired (mute) individuals communicating with hearing persons at a different location, and Video Remote Interpreting, used where deaf/hard-of-hearing/mute persons are in the same location as their hearing parties
One of the first demonstrations of the ability for telecommunications to help sign language users communicate with each other occurred when AT&T's videophone (trademarked as the 'Picturephone') was introduced to the public at the 1964 New York World's Fair –two deaf users were able to freely communicate with each other between the fair and another city.[6] Various other organizations have also conducted research on signing via videotelephony.
Courtesy: SignVideo
Using such video equipment, the deaf, hard-of-hearing and speech-impaired can communicate between themselves and with hearing individuals using sign language. The United States and several other countries compensate companies to provide 'Video Relay Services' (VRS). Telecommunication equipment can be used to talk to others via a sign language interpreter, who uses a conventional telephone at the same time to communicate with the deaf person's party. Video equipment is also used to do on-site sign language translation via Video Remote Interpreting (VRI). The relative low cost and widespread availability of 3G mobile phone technology with video calling capabilities have given deaf and speech-impaired users a greater ability to communicate with the same ease as others. Some wireless operators have even started free sign language gateways.
Sign language interpretation services via VRS or by VRI are useful in the present-day where one of the parties is deaf, hard-of-hearing or speech-impaired (mute). In such cases the interpretation flow is normally within the same principal language, such as French Sign Language (FSL) to spoken French, Spanish Sign Language (SSL) to spoken Spanish, British Sign Language (BSL) to spoken English, and American Sign Language (ASL) also to spoken English (since BSL and ASL are completely distinct), etc.... Multilingual sign language interpreters, who can also translate as well across principal languages (such as to and from SSL, to and from spoken English), are also available, albeit less frequently. Such activities involve considerable effort on the part of the translator, since sign languages are distinct natural languages with their own construction, semantics and syntax, different from the aural version of the same principal language.
With video interpreting, sign language interpreters work remotely with live video and audio feeds, so that the interpreter can see the deaf or mute party, and converse with the hearing party, and vice versa. Much like telephone interpreting, video interpreting can be used for situations in which no on-site interpreters are available. However, video interpreting cannot be used for situations in which all parties are speaking via telephone alone. VRI and VRS interpretation requires all parties to have the necessary equipment. Some advanced equipment enables interpreters to remotely control the video camera, in order to zoom in and out or to point the camera toward the party that is signing.
Video security
Webcams are also used as security cameras. Software is available to allow PC-connected cameras to watch for movement and sound, recording both when they are detected; these recordings can then be saved to the computer, e-mailed or uploaded to the Internet. In one well-publicised case,[7] a computer e-mailed out images as the burglar stole it, allowing the owner to give police a clear picture of the burglar's face even after the computer had been stolen.
Input control device
Special software can use the video stream from a webcam to assist or enhance a user's control of applications and games. Video features, including faces, shapes, models and colors can be observed and tracked to produce a corresponding form of control. For example, the position of a single light source can be tracked and used to emulate a mouse pointer, a head mounted light would allow hands-free computing and would greatly improve computer accessibility. This can also be applied to games, providing additional control, improved interactivity and immersiveness.
FreeTrack is a free webcam motion tracking application for Microsoft Windows that can track a special head mounted model in up to six degrees of freedom and output data to mouse, keyboard, joystick and FreeTrack supported games. TrackIR is a commercial version of this technology utilising IR light, which has the advantage of being invisible to the naked eye, removing a distraction from the user.
The EyeToy for the PlayStation 2 (The updated PlayStation 3 equivalent is the PlayStation Eye) and similarly the Xbox Live Vision Camera and the Kinect AKA 'Project Natal' for the Xbox 360 and Xbox Live are color digital cameras that have been used as control input devices by some games.
Small webcam-based PC games are available as either standalone executables or inside web browser windows using Adobe Flash.
Aggregators
Due to the increasing number of webcams throughout the world, aggregator websites have arisen, allowing users to find live video streams based on location or other criteria. Aggregators provide collections of thousands of live video streams or up-to-date still pictures.
Technology
Webcams typically include a lens, an image sensor, and some support electronics. Various lenses are available, the most common in consumer-grade webcams being a plastic lens that can be screwed in and out to set the camera's focus. Fixed focus lenses, which have no provision for adjustment, are also available. As a camera system's depth of field is greater for small imager formats and is greater for lenses with a large f-number (small aperture), the systems used in webcams have sufficiently large depth of field that the use of a fixed focus lens does not impact image sharpness much. Image sensors can be CMOS or CCD, the former being dominant for low-cost cameras, but CCD cameras do not necessarily outperform CMOS-based cameras in the low cost price range. Most consumer webcams are capable of providing VGA-resolution video at a frame rate of 30 frames per second. Many newer devices can produce video in multi-megapixel resolutions, and a few can run at high frame rates such as the PlayStation Eye, which can produce 320×240 video at 120 frames per second.
Support electronics are present to read the image from the sensor and transmit it to the host computer. The camera pictured to the right, for example, uses a Sonix SN9C101 to transmit its image over USB. Some cameras, such as mobile phone cameras, use a CMOS sensor with supporting electronics "on die", i.e. the sensor and the support electronics are built on a single silicon chip to save space and manufacturing costs. Most webcams feature built-in microphones to make video calling and videoconferencing more convenient.
The USB video device class (UVC) specification allows for interconnectivity of webcams to computers even without proprietary drivers installed. Microsoft Windows XP SP2, Linux[8] and Mac OS X (since October 2005) have UVC drivers built in and do not require extra drivers, although they are often installed in order to add additional features.
Privacy
Many users do not wish the continuous exposure for which webcams were originally intended, but rather prefer privacy. Such privacy is lost when 'Trojan horse' programs allow malicious hackers to activate the camera without the user's knowledge, providing hackers with a live video feed.[citation needed] Cameras such as Apple's older external iSight cameras include lens covers to thwart this. Most other webcams have a built-in LED that lights up whenever the camera is active (such as Apple's newer internal iSight).
In mid-January 2005 some search engine queries were published in an on-line forum[9] which allow anyone to find thousands of Panasonic- and Axis-made high-end web cameras, provided that they have a web-based interface for remote viewing. Many such cameras are running on default configuration, which does not require any password login or IP address verification, making them visible to anyone.
Effects on modern society
Webcams allow for inexpensive, real-time video chat and webcasting, in both amateur and professional pursuits. They are frequently used in online dating. YouTube is a popular website hosting many videos made using webcams. News websites such as the BBC can also produce professional live news videos.[10]
On 23 March 2007, a man named Kevin Whitrick committed cyber suicide live on the internet in front of viewers in a chat room website.[11]
Videotelephony descriptive names & terminology
Videophone calls (or 'videocalls'), differ from videoconferencing in that they expect to serve individuals, not groups. However that distinction has becoming increasingly blurred with technology improvements such as increased bandwidth and sophisticated software clients that can allow for multiple parties on a call. In general everyday usage the term videoconferencing is now frequently used instead of videocall for point-to-point calls between two units. Both videophone calls and videoconferencing are also now commonly referred to as a 'video link'.
Webcams are popular, relatively low cost devices which can provide live video and audio streams via personal computers, and can be used with many software clients for video calls.[12]
A videoconference system is generally higher cost than a videophone and deploys greater capabilities. A videoconference (also known as a videoteleconference) allows two or more locations to communicate via live, simultaneous two-way video and audio transmissions. This is often accomplished by the use of a multipoint control unit (a centralized distribution and call management system) or by a similar non-centralized multipoint capability embedded in each videoconferencing unit. Again, technology improvements have circumvented traditional definitions by allowing multiple party videoconferencing via web-based applications.[13][14] A separate webpage article is devoted to videoconferencing.
A telepresence system is a high-end videoconferencing system and service usually employed by enterprise-level corporate offices. Telepresence conference rooms use state-of-the art room designs, video cameras, displays, sound-systems and processors, coupled with high-to-very-high capacity bandwidth transmissions.
Typical uses of the various technologies described above include videocalling or videoconferencing on a one-to-one, one-to-many or many-to-many basis for personal, business, educational, deaf Tele-Relay and tele-medical, diagnostic and rehabilitative use or services. New services utilizing videocalling and videoconferencing, such as personal videocalls to inmates incarcerated in penitentiaries, and videoconferencing to resolve airline engineering issues at maintenance facilities, are being created or evolving on an on-going basis.
No comments:
Post a Comment