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Video

Video is the technology of capturing, recording, processing, transmitting, and reconstructing moving pictures Film

Film is a term that encompasses motion pictures as individual projects, as well as the field in general.... 

, typically using magnetic tape Magnetic tape

Magnetic tape is a non-volatile [i] storage medium [i] consisting of a magnetic coa ... 

, electronic signals, or digital media, primarily for viewing on television Television

Television is a telecommunication [i] system for ... 

 or as video clip Video clip

Video clips are short clips [i] in video [i] format and predominantly found on the internet [i] ... 

s on computer Computer

A computer is a machine [i] for manipulating data [i] according to a list of instructions [i] ... 

 monitor Computer display

[i]s in the [[larynx]... 

s. It is to be differentiated from cinema Film

Film is a term that encompasses motion pictures as individual projects, as well as the field in general.... 

, which records images on celluloid film.

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Encyclopedia

Video is the technology of capturing, recording, processing, transmitting, and reconstructing moving pictures Film

Film is a term that encompasses motion pictures as individual projects, as well as the field in general.... 

, typically using magnetic tape Magnetic tape

Magnetic tape is a non-volatile [i] storage medium [i] consisting of a magnetic coa ... 

, electronic signals, or digital media, primarily for viewing on television Television

Television is a telecommunication [i] system for
... 

 or as video clip Video clip

Video clips are short clips [i] in video [i] format and predominantly found on the internet [i] ... 

s on computer Computer

A computer is a machine [i] for manipulating data [i] according to a list of instructions [i] ... 

 monitor Computer display

[i]s in the [[larynx]... 

s. It is to be differentiated from cinema Film

Film is a term that encompasses motion pictures as individual projects, as well as the field in general.... 

, which records images on celluloid film.

Description



The term video commonly refers to several storage formats for moving pictures: digital video formats, including DVD DVD

DVD is an optical disc [i] storage [i] media format that can be used for data storage, ... 

, QuickTime QuickTime

QuickTime is a multimedia framework [i] developed by Apple Computer [i], capable of handling various for ... 

, and MPEG-4; and analog videotape Videotape

Videotape is a means of recording television [i] pictures and accompanying sound onto magnetic tape [i] ... 

s, including VHS VHS

The Video Home System, better known by its abbreviation VHS, is a recording and playing standard f... 

 and Betamax Betamax

Sony [i]'s Betamax is the 12.7 mm home videocassette [i] tape recording format introduced in 1975 and de ... 

. Video can be recorded and transmitted in various physical media: in magnetic tape when recorded as PAL PAL

PAL, short for phase-alternating line, phase alternation by line or phase alternation lin... 

 or NTSC NTSC

NTSC is the analog television [i] system in use in Canada [i], Japan [i], South Korea [i], the United States [i] ... 

 electric signals by video cameras, or in MPEG-4 or DV DV

Digital Video is a video [i] format launched in 1996 [i], and, in its smaller tape form factor MiniD ... 

 digital media when recorded by digital cameras Digital camera

A digital camera is an electronic [i] device used to capture and store photograph [i]s elect ... 

.

Quality of video essentially depends on the capturing method and storage used. Digital television ' is a relatively recent format with higher quality than earlier television formats and has become a standard for television video. '

3D-video, digital video in three dimensions 3-D film

In film, the term 3-D is used to describe any visual presentation system that attempts to maintain o... 

, premiered at the end of 20th century. Six or eight cameras with realtime depth measurement are typically used to capture 3D-video streams. The format of 3D-video is fixed in MPEG-4 Part 16 Animation Framework eXtension .

In the UK United Kingdom

The United Kingdom of Great Britain and Northern Ireland is a country and sovereign state [i] tha ... 

, Australia Australia

Australia, officially the Commonwealth of Australia, is a country in the Southern Hemisphere [i] c ... 

, and New Zealand New Zealand

New Zealand is a country in the south-western Pacific Ocean [i] consisting of two large islands and many ... 

, the term video is often used informally to refer to both video recorders Videocassette recorder

The videocassette recorder, is a type of video tape recorder [i] that uses removable videotape [i] casse ... 

 and video cassettes Videotape

Videotape is a means of recording television [i] pictures and accompanying sound onto magnetic tape [i] ... 

; the meaning is normally clear from the context.

Characteristics of video streams


Number of frames per second

Frame rate, the number of still pictures per unit of time of video, ranges from six or eight frames per second for old mechanical cameras to 120 or more frames per second for new professional cameras. PAL PAL

PAL, short for phase-alternating line, phase alternation by line or phase alternation lin... 

  and SECAM SECAM

SECAM, also written SCAM , is an analog color television [i] system first used i ... 

  standards specify 25 fps, while NTSC NTSC

NTSC is the analog television [i] system in use in Canada [i], Japan [i], South Korea [i], the United States [i] ... 

  specifies 29.97 fps. Film is shot at the slower frame rate of 24fps, which complicates slightly the process of transferring a cinematic motion picture to video. To achieve the illusion of a moving image, the minimum frame rate is about ten frames per second.

Interlacing

Video can be interlaced Interlace

Interlace is a technique of improving the picture quality of a video [i] transmission without consuming ... 

 or progressive Progressive scan

Progressive or non-interlaced scanning is any method for displaying, storing or transmitting moving image [i] ... 

. Interlacing was invented as a way to achieve good visual quality within the limitations of a narrow bandwidth. The horizontal scan lines of each interlaced frame are numbered consecutively and partitioned into two fields: the odd field consisting of the odd-numbered lines and the even field consisting of the even-numbered lines. NTSC, PAL and SECAM are interlaced formats. Abbreviated video resolution specifications often include an i to indicate interlacing. For example, PAL video format is often specified as 576i50, where 576 indicates the vertical line resolution, i indicates interlacing, and 50 indicates 50 fields per second.

In progressive scan systems, each refresh period updates all of the scan lines. The result is a higher perceived resolution and a lack of various artifacts that can make parts of a stationary picture appear to be moving or flashing.

A procedure known as deinterlacing Deinterlacing

Deinterlacing is the process of converting interlaced [i] video into a non-interlaced form. ... 

 can be used for converting an interlaced stream, such as analog, DVD, or satellite, to be processed by progressive scan devices, such as TFT TV-sets, projectors, and plasma panels. Deinterlacing cannot, however, produce a video quality that is equivalent to true progressive scan source material.

Video resolution



The size of a video image is measured in pixel Pixel

A pixel is a single point in a graphic image.... 

s for digital video or horizontal scan lines for analog video. Standard-definition television is specified as 720/704/640×480i60 for NTSC and 768/720×576i50 for PAL or SECAM resolution. New high-definition televisions are capable of resolutions up to 1920×1080p60, i.e. 1920 pixels per scan line by 1080 scan lines, progressive, at 60 frames per second.

Video resolution for 3D-video is measured in voxels . For example 512×512×512 voxels resolution, now used for simple 3D-video, can be displayed even on some PDA Personal digital assistant

Personal Digital Assistants are handheld device [i]s that were originally designed as personal organisers, but ... 

s.

Aspect ratio




Aspect ratio Aspect ratio

The aspect ratio of a two-dimensional shape is the ratio of its longer dimension to its shorter dimensio... 

 describes the dimensions of video screens and video picture elements. The screen aspect ratio of a traditional television screen is 4:3, or 1.33:1. High definition televisions use an aspect ratio of 16:9, or about 1.78:1. The aspect ratio of a full 35 mm film frame with soundtrack is around 1.37:1.

Pixels on computer monitors are usually square, but pixels used in digital video have non-square aspect ratios, such as those used in the PAL and NTSC variants of the CCIR 601 digital video standard, and the corresponding anamorphic widescreen formats.

Color space and bits per pixel



Color model name describes the video color representation. YIQ YIQ

YIQ is a color space [i], formerly used in the NTSC [i] television [i] standard.... 

is used in NTSC television. It corresponds closely to the YUV YUV

The YUV model defines a color space [i] in terms of one luminance [i] and two chrominance [i]... 

scheme used in PAL television and the YDbDr YDbDr

YDbDr is the colour space [i] used in the SCAM [i] colour television [i] broadcasting standard, which is ... 

scheme used by SECAM television.

The number of distinct colours that can be represented by a pixel depends on the number of bits per pixel . A common way to reduce the number of bits per pixel in digital video is by chroma subsampling Chroma subsampling

Chroma subsampling is the practice of implementing more resolution for the luminance information than th... 

 .

Video quality

Video quality can be measured with formal metrics like PSNR or with subjective video quality using expert observation.

The subjective video quality of a video processing system may be evaluated as follows:
  • Choose the video sequences to use for testing.
  • Choose the settings of the system to evaluate .
  • Choose a test method for how to present video sequences to experts and to collect their ratings.
  • Invite a sufficient number of experts, preferably not fewer than 15.
  • Carry out testing.
  • Calculate the average marks for each HRC based on the experts' ratings.


Many subjective video quality methods are described in the ITU-T recommendation BT.500. One of the standardized method is the Double Stimulus Impairment Scale . In DSIS, each expert views an unimpaired reference video followed by an impaired version of the same video. The expert then rates the impaired video using a scale ranging from "impairments are imperceptible" to "impairments are very annoying".

Video compression method

A wide variety of methods are used to compress video streams. Video data contains spatial and temporal redundancy, making uncompressed video streams extremely inefficient. Broadly speaking, spatial redundancy is reduced by registering differences between parts of a single frame; this task is known as intraframe compression and is closely related to image compression. Likewise, temporal redundancy can be reduced by registering differences between frames; this task is known as interframe compression, including motion compensation and other techniques. The most common modern standards are MPEG-2, used for DVD DVD

DVD is an optical disc [i] storage [i] media format that can be used for data storage, ... 

 and satellite television Satellite television

Satellite television is television [i] delivered by way of communications satellite [i]s, as compared to ... 

, and MPEG-4, used for home video.

Bit rate

Bit rate is a measure of the rate of information content in a video stream. It is quantified using the bit per second unit or Megabits per second . A higher bit rate allows better video quality. For example VideoCD, with a bit rate of about 1 Mbit/s, is lower quality than DVD, with a bit rate of about 5 Mbit/s. HDTV has a still higher quality, with a bit rate of about 20 Mbit/s.

Variable bit rate  is a strategy to maximize the visual video quality and minimize the bit rate. On fast motion scenes, a variable bit rate uses more bits than it does on slow motion scenes of similar duration yet achieves a consistent visual quality. For real-time and non-buffered video streaming when the available bandwidth is fixed, e.g. in videoconferencing delivered on channels of fixed bandwidth, a constant bit rate  must be used.

Stereoscopic

Stereoscopic video requires either two channels — a right channel for the right eye and a left channel for the left eye or two overlayed color coded layers. This left and right layer technique is occasionally used for network broadcast, or recent "anaglyph" releases of 3D movies on DVD. Simple Red/Cyan plastic glasses provide the means to view the images discretely to form a stereoscopic view of the content. New HD DVD HD DVD

HD DVD is a next-generation optical [i] disc [i] format designed for high-den ... 

 and HD Blu-ray disk Blu-ray Disc

A Blu-ray Disc is a next-generation optical disc [i] format designed for high-density storage of high-definition video [i] ... 

s will greatly improve the 3D effect, in color coded stereo programs. The first commercially available HD players are expected to debut at the 2006 NAB National Association of Broadcasters

The National Association of Broadcasters is a US trade association that advocates on behalf of more than... 

 Show in Las Vegas in April. See articles Stereoscopy Stereoscopy

Stereoscopy, stereoscopic imaging or 3-D imaging is any technique capable of recording three... 

 and 3-D film 3-D film

In film, the term 3-D is used to describe any visual presentation system that attempts to maintain o... 

.

Video formats


See also

  • Generally
    • Audio Sound recording and reproduction

      Sound recording and reproduction is the electrical [i] or mechanical [i] re-creation and/or amplification [i] ... 

    • List of video topics
    • Video clip Video clip

      Video clips are short clips [i] in video [i] format and predominantly found on the internet [i] ... 




  • Video format
    • Film formats
    • Television Television

      Television is a telecommunication [i] system for

... 


    • Digital television
    • Satellite television Satellite television

      Satellite television is television [i] delivered by way of communications satellite [i]s, as compared to ... 

    • Interlaced video Interlace

      Interlace is a technique of improving the picture quality of a video [i] transmission without consuming ... 

    • Progressive video Progressive scan

      Progressive or non-interlaced scanning is any method for displaying, storing or transmitting moving image [i] ... 

    • Telecine transform Telecine

      Telecine is the process of transferring motion picture [i] film [i] into electronic form, or the ma ... 

    • Video codec
    • Timecode
    • Color space Color space

      A color model [i] is an abstract mathematical model describing the way color [i]s can be represented as ... 




  • Video usage
    • Video art
    • Closed-circuit television Closed-circuit television

      Closed-circuit television is the use of television [i] camera [i]s to transmit a signal to a specific, l ... 

    • Video projector Video projector

      A video projector takes a video [i] signal [i] and projects the corresponding image on a projection screen [i]... 

    • Video synthesizer Video synthesizer

      A Video Synthesizer is a device that electronically creates a video [i] signal.

... 


    • Video teleconference Videoconferencing

      A videoconference is a set of interactive telecommunication [i] technologies [i] which allow ... 

    • Video production
    • Optical feedback Optical feedback

      Optical feedback is the optical [i] equivalent of acoustic feedback [i]. ... 

    • Fulldome video


  • Video Screen Recording
    • Screencast