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Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) systems, which, in turn, were replaced by flat-panel displays of several types.
Video systems vary in display resolution, aspect ratio, refresh rate, color capabilities, and other qualities. Analog and digital variants exist and can be carried on a variety of media, including radio broadcasts, magnetic tape, optical discs, computer files, and network streaming.
Etymology
The word video comes from the Latin verb video (I see).
History
Analog video
Video developed from facsimile systems developed in the mid-19th century. Early mechanical video scanners, such as the Nipkow disk, were patented as early as 1884, however, it took several decades before practical video systems could be developed, many decades after film. Film records using a sequence of miniature photographic images visible to the eye when the film is physically examined. Video, by contrast, encodes images electronically, turning the images into analog or digital electronic signals for transmission or recording.
Video technology was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) television systems. Video was originally exclusively live technology. Live video cameras used an electron beam, which would scan a photoconductive plate with the desired image and produce a voltage signal proportional to the brightness in each part of the image. The signal could then be sent to televisions, where another beam would receive and display the image.Charles Ginsburg led an Ampex research team to develop one of the first practical video tape recorders (VTR). In 1951, the first VTR captured live images from television cameras by writing the camera's electrical signal onto magnetic videotape.
Video recorders were sold for $50,000 in 1956, and videotapes cost US$300 per one-hour reel. However, prices gradually dropped over the years; in 1971, Sony began selling videocassette recorder (VCR) decks and tapes into the consumer market.
Digital video
Digital video is capable of higher quality and, eventually, a much lower cost than earlier analog technology. After the commercial introduction of the DVD in 1997 and later the Blu-ray Disc in 2006, sales of videotape and recording equipment plummeted. Advances in computer technology allow even inexpensive personal computers and smartphones to capture, store, edit, and transmit digital video, further reducing the cost of video production and allowing programmers and broadcasters to move to tapeless production. The advent of digital broadcasting and the subsequent digital television transition are in the process of relegating analog video to the status of a legacy technology in most parts of the world. The development of high-resolution video cameras with improved dynamic range and color gamuts, along with the introduction of high-dynamic-range digital intermediate data formats with improved color depth, has caused digital video technology to converge with film technology. Since 2013,[update] the use of digital cameras in Hollywood has surpassed the use of film cameras.
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 (frame/s) for old mechanical cameras to 120 or more frames per second for new professional cameras. PAL standards (Europe, Asia, Australia, etc.) and SECAM (France, Russia, parts of Africa, etc.) specify 25 frame/s, while NTSC standards (United States, Canada, Japan, etc.) specify 29.97 frame/s. Film is shot at a slower frame rate of 24 frames per second, which slightly complicates the process of transferring a cinematic motion picture to video. The minimum frame rate to achieve a comfortable illusion of a moving image is about sixteen frames per second.
Interlaced vs. progressive
Video can be interlaced or progressive. In progressive scan systems, each refresh period updates all scan lines in each frame in sequence. When displaying a natively progressive broadcast or recorded signal, the result is the optimum spatial resolution of both the stationary and moving parts of the image. Interlacing was invented as a way to reduce flicker in early mechanical and CRT video displays without increasing the number of complete frames per second. Interlacing retains detail while requiring lower bandwidth compared to progressive scanning.
In interlaced video, the horizontal scan lines of each complete frame are treated as if numbered consecutively and captured as two fields: an odd field (upper field) consisting of the odd-numbered lines and an even field (lower field) consisting of the even-numbered lines. Analog display devices reproduce each frame, effectively doubling the frame rate as far as perceptible overall flicker is concerned. When the image capture device acquires the fields one at a time, rather than dividing up a complete frame after it is captured, the frame rate for motion is effectively doubled as well, resulting in smoother, more lifelike reproduction of rapidly moving parts of the image when viewed on an interlaced CRT display.
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 described as 576i50, where 576 indicates the total number of horizontal scan lines, i indicates interlacing, and 50 indicates 50 fields (half-frames) per second.
When displaying a natively interlaced signal on a progressive scan device, the overall spatial resolution is degraded by simple line doubling—artifacts, such as flickering or "comb" effects in moving parts of the image that appear unless special signal processing eliminates them. A procedure known as deinterlacing can optimize the display of an interlaced video signal from an analog, DVD, or satellite source on a progressive scan device such as an LCD television, digital video projector, or plasma panel. Deinterlacing cannot, however, produce video quality that is equivalent to true progressive scan source material.
Aspect ratio
Aspect ratio describes the proportional relationship between the width and height of video screens and video picture elements. All popular video formats are rectangular, and this can be described by a ratio between width and height. The ratio of width to height for a traditional television screen is 4:3, or about 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 (also known as the Academy ratio) is 1.375:1.
Pixels on computer monitors are usually square, but pixels used in digital video often 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. The 720 by 480 pixel raster uses thin pixels on a 4:3 aspect ratio display and fat pixels on a 16:9 display.
The popularity of viewing video on mobile phones has led to the growth of vertical video. Mary Meeker, a partner at Silicon Valley venture capital firm Kleiner Perkins Caufield & Byers, highlighted the growth of vertical video viewing in her 2015 Internet Trends Report – growing from 5% of video viewing in 2010 to 29% in 2015. Vertical video ads like Snapchat's are watched in their entirety nine times more frequently than landscape video ads.
Color model and depth
The color model uses the video color representation and maps encoded color values to visible colors reproduced by the system. There are several such representations in common use: typically, YIQ is used in NTSC television, YUV is used in PAL television, YDbDr is used by SECAM television, and YCbCr is used for digital video.
The number of distinct colors a pixel can represent depends on the color depth expressed in the number of bits per pixel. A common way to reduce the amount of data required in digital video is by chroma subsampling (e.g., 4:4:4, 4:2:2, etc.). Because the human eye is less sensitive to details in color than brightness, the luminance data for all pixels is maintained, while the chrominance data is averaged for a number of pixels in a block, and the same value is used for all of them. For example, this results in a 50% reduction in chrominance data using 2-pixel blocks (4:2:2) or 75% using 4-pixel blocks (4:2:0). This process does not reduce the number of possible color values that can be displayed, but it reduces the number of distinct points at which the color changes.
Video quality
Video quality can be measured with formal metrics like peak signal-to-noise ratio (PSNR) or through subjective video quality assessment using expert observation. Many subjective video quality methods are described in the ITU-T recommendation . One of the standardized methods is the Double Stimulus Impairment Scale (DSIS). 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 (digital only)
Uncompressed video delivers maximum quality, but at a very high data rate. A variety of methods are used to compress video streams, with the most effective ones using a group of pictures (GOP) to reduce spatial and temporal redundancy. 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 compression standards are MPEG-2, used for DVD, Blu-ray, and satellite television, and MPEG-4, used for AVCHD, mobile phones (3GP), and the Internet.
Stereoscopic
Stereoscopic video for 3D film and other applications can be displayed using several different methods:
- Two channels: a right channel for the right eye and a left channel for the left eye. Both channels may be viewed simultaneously by using light-polarizing filters 90 degrees off-axis from each other on two video projectors. These separately polarized channels are viewed wearing eyeglasses with matching polarization filters.
- Anaglyph 3D, where one channel is overlaid with two color-coded layers. This left and right layer technique is occasionally used for network broadcasts 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.
- One channel with alternating left and right frames for the corresponding eye, using LCD shutter glasses that synchronize to the video to alternately block the image for each eye, so the appropriate eye sees the correct frame. This method is most common in computer virtual reality applications, such as in a Cave Automatic Virtual Environment, but reduces effective video framerate by a factor of two.
Formats
Different layers of video transmission and storage each provide their own set of formats to choose from.
For transmission, there is a physical connector and signal protocol (see List of video connectors). A given physical link can carry certain display standards that specify a particular refresh rate, display resolution, and color space.
Many analog and digital recording formats are in use, and digital video clips can also be stored on a computer file system as files, which have their own formats. In addition to the physical format used by the data storage device or transmission medium, the stream of ones and zeros that is sent must be in a particular digital video coding format, for which a number is available.
Analog video
Analog video is a video signal represented by one or more analog signals. Analog color video signals include luminance (Y) and chrominance (C). When combined into one channel, as is the case among others with NTSC, PAL, and SECAM, it is called composite video. Analog video may be carried in separate channels, as in two-channel S-Video (YC) and multi-channel component video formats.
Analog video is used in both consumer and professional television production applications.
- Composite video
(single channel RCA) - S-Video
(2-channel YC) - Component video
(3-channel YPbPr) - SCART
- VGA
- TRRS
- D-Terminal
Digital video
Digital video signal formats have been adopted, including serial digital interface (SDI), Digital Visual Interface (DVI), High-Definition Multimedia Interface (HDMI) and DisplayPort Interface.
- Serial digital interface (SDI)
- Digital Visual Interface (DVI)
- HDMI
- DisplayPort
Transport medium
Video can be transmitted or transported in a variety of ways including wireless terrestrial television as an analog or digital signal, coaxial cable in a closed-circuit system as an analog signal. Broadcast or studio cameras use a single or dual coaxial cable system using serial digital interface (SDI). See List of video connectors for information about physical connectors and related signal standards.
Video may be transported over networks and other shared digital communications links using, for instance, MPEG transport stream, SMPTE 2022 and SMPTE 2110.
Display standards
Digital television
Digital television broadcasts use the MPEG-2 and other video coding formats and include:
- ATSC – United States, Canada, Mexico, Korea
- Digital Video Broadcasting (DVB) – Europe
- ISDB – Japan
- Digital multimedia broadcasting (DMB) – Korea
Analog television
Analog television broadcast standards include:
- Field-sequential color system (FCS) – US, Russia; obsolete
- Multiplexed Analogue Components (MAC) – Europe; obsolete
- Multiple sub-Nyquist sampling encoding (MUSE) – Japan
- NTSC – United States, Canada, Japan
- EDTV-II "Clear-Vision" - NTSC extension, Japan
- PAL – Europe, Asia, Oceania
- RS-343 (military)
- SECAM – France, former Soviet Union, Central Africa
- CCIR System A
- CCIR System B
- CCIR System G
- CCIR System H
- CCIR System I
- CCIR System M
An analog video format consists of more information than the visible content of the frame. Preceding and following the image are lines and pixels containing metadata and synchronization information. This surrounding margin is known as a blanking interval or blanking region; the horizontal and vertical front porch and back porch are the building blocks of the blanking interval.
Computer displays
Computer display standards specify a combination of aspect ratio, display size, display resolution, color depth, and refresh rate. A list of common resolutions is available.
Recording
Early television was almost exclusively a live medium, with some programs recorded to film for historical purposes using Kinescope. The analog video tape recorder was commercially introduced in 1951. The following list is in rough chronological order. All formats listed were sold to and used by broadcasters, video producers, or consumers; or were important historically.
- VERA (BBC experimental format ca. 1952)
- 2" Quadruplex videotape (Ampex 1956)
- 1" Type A videotape (Ampex)
- 1/2" EIAJ (1969)
- U-matic 3/4" (Sony)
- 1/2" Cartrivision (Avco)
- VCR, VCR-LP, SVR
- 1" Type B videotape (Robert Bosch GmbH)
- 1" Type C videotape (Ampex, Marconi and Sony)
- 2" Helical Scan Videotape (IVC) (1975)
- Betamax (Sony) (1975)
- VHS (JVC) (1976)
- Video 2000 (Philips) (1979)
- 1/4" CVC (Funai) (1980)
- Betacam (Sony) (1982)
- VHS-C (JVC) (1982)
- HDVS (Sony) (1984)
- Video8 (Sony) (1986)
- Betacam SP (Sony) (1987)
- S-VHS (JVC) (1987)
- Pixelvision (Fisher-Price) (1987)
- (1988)
- Hi8 (Sony) (mid-1990s)
- W-VHS (JVC) (1994)
Digital video tape recorders offered improved quality compared to analog recorders.
- Betacam IMX (Sony)
- D-VHS (JVC)
- D-Theater
- D1 (Sony)
- D2 (Sony)
- D3
- D5 HD
- D6 (Philips)
- Digital-S D9 (JVC)
- Digital Betacam (Sony)
- Digital8 (Sony)
- DV (including DVC-Pro)
- HDCAM (Sony)
- HDV
- ProHD (JVC)
- MicroMV
- MiniDV
Optical storage mediums offered an alternative, especially in consumer applications, to bulky tape formats.
- Blu-ray Disc (Sony)
- China Blue High-definition Disc (CBHD)
- DVD (was Super Density Disc, DVD Forum)
- Professional Disc
- Universal Media Disc (UMD) (Sony)
- Enhanced Versatile Disc (EVD, Chinese government-sponsored)
- HD DVD (NEC and Toshiba)
- HD-VMD
- Capacitance Electronic Disc
- Laserdisc (MCA and Philips)
- Television Electronic Disc (Teldec and Telefunken)
- VHD (JVC)
- Video CD
Digital encoding formats
A video codec is software or hardware that compresses and decompresses digital video. In the context of video compression, codec is a portmanteau of encoder and decoder, while a device that only compresses is typically called an encoder, and one that only decompresses is a decoder. The compressed data format usually conforms to a standard video coding format. The compression is typically lossy, meaning that the compressed video lacks some information present in the original video. A consequence of this is that decompressed video has lower quality than the original, uncompressed video because there is insufficient information to accurately reconstruct the original video.
- CCIR 601 (ITU-T)
- H.261 (ITU-T)
- H.263 (ITU-T)
- H.264/MPEG-4 AVC (ITU-T + ISO)
- H.265
- M-JPEG (ISO)
- MPEG-1 (ISO)
- MPEG-2 (ITU-T + ISO)
- MPEG-4 (ISO)
- Ogg-Theora
- VP8-WebM
- VC-1 (SMPTE)
See also
- General
- Index of video-related articles
- Sound recording and reproduction
- Video editing
- Videography
- Video format
- 360-degree video
- Cable television
- Color television
- Telecine
- Timecode
- Volumetric capture
- Video usage
- Closed-circuit television
- Fulldome
- Interactive video
- Video art
- Video feedback
- Video sender
- Video synthesizer
- Videotelephony
- Video screen recording software
- Bandicam
- CamStudio
- Camtasia
- Zight App
- Fraps
References
- "Video – HiDef Audio and Video". hidefnj.com. Archived from the original on May 14, 2017. Retrieved March 30, 2017.
- "video", Online Etymology Dictionary
- Amidon, Audrey (June 25, 2013). "Film Preservation 101: What's the Difference Between a Film and a Video?". The Unwritten Record. US National Archives.
- "Vocademy - Learn for Free - Electronics Technology - Analog Circuits - Analog Television". vocademy.net. Retrieved 2024-06-29.
- Elen, Richard. "TV Technology 10. Roll VTR". Archived from the original on October 27, 2011.
- "Vintage Umatic VCR – Sony VO-1600. The worlds first VCR. 1971". Rewind Museum. Archived from the original on February 22, 2014. Retrieved February 21, 2014.
- Follows, Stephen (February 11, 2019). "The use of digital vs celluloid film on Hollywood movies". Archived from the original on April 11, 2022. Retrieved February 19, 2022.
- Soseman, Ned. "What's the difference between 59.94fps and 60fps?". Archived from the original on June 29, 2017. Retrieved July 12, 2017.
- Watson, Andrew B. (1986). "Temporal Sensitivity" (PDF). Sensory Processes and Perception. Archived from the original (PDF) on March 8, 2016.
- Bovik, Alan C. (2005). Handbook of image and video processing (2nd ed.). Amsterdam: Elsevier Academic Press. pp. 14–21. ISBN 978-0-08-053361-2. OCLC 190789775. Archived from the original on August 25, 2022. Retrieved August 25, 2022.
- Wright, Steve (2002). Digital compositing for film and video. Boston: Focal Press. ISBN 978-0-08-050436-0. OCLC 499054489. Archived from the original on August 25, 2022. Retrieved August 25, 2022.
- Brown, Blain (2013). Cinematography: Theory and Practice: Image Making for Cinematographers and Directors. Taylor & Francis. pp. 159–166. ISBN 9781136047381.
- Parker, Michael (2013). Digital Video Processing for Engineers : a Foundation for Embedded Systems Design. Suhel Dhanani. Amsterdam. ISBN 978-0-12-415761-3. OCLC 815408915. Archived from the original on August 25, 2022. Retrieved August 25, 2022.
{{cite book}}
: CS1 maint: location missing publisher (link) - Bing, Benny (2010). 3D and HD broadband video networking. Boston: Artech House. pp. 57–70. ISBN 978-1-60807-052-7. OCLC 672322796. Archived from the original on August 25, 2022. Retrieved August 25, 2022.
- Stump, David (2022). Digital cinematography : fundamentals, tools, techniques, and workflows (2nd ed.). New York, NY: Routledge. pp. 125–139. ISBN 978-0-429-46885-8. OCLC 1233023513. Archived from the original on August 25, 2022. Retrieved August 25, 2022.
- Constine, Josh (May 27, 2015). "The Most Important Insights From Mary Meeker's 2015 Internet Trends Report". TechCrunch. Archived from the original on August 4, 2015. Retrieved August 6, 2015.
- Li, Ze-Nian; Drew, Mark S.; Liu, Jiangchun (2021). Fundamentals of multimedia (3rd ed.). Cham, Switzerland: Springer. pp. 108–117. ISBN 978-3-030-62124-7. OCLC 1243420273. Archived from the original on August 25, 2022. Retrieved August 25, 2022.
- Banerjee, Sreeparna (2019). "Video in Multimedia". Elements of multimedia. Boca Raton: CRC Press. ISBN 978-0-429-43320-7. OCLC 1098279086. Archived from the original on August 25, 2022. Retrieved August 25, 2022.
- Andy Beach (2008). Real World Video Compression. Peachpit Press. ISBN 978-0-13-208951-7. OCLC 1302274863. Archived from the original on August 25, 2022. Retrieved August 25, 2022.
- Sanz, Jorge L. C. (1996). Image Technology : Advances in Image Processing, Multimedia and Machine Vision. Berlin, Heidelberg: Springer Berlin Heidelberg. ISBN 978-3-642-58288-2. OCLC 840292528. Archived from the original on August 25, 2022. Retrieved August 25, 2022.
- Ekmekcioglu, Erhan; Fernando, Anil; Worrall, Stewart (2013). 3DTV : processing and transmission of 3D video signals. Chichester, West Sussex, United Kingdom: Wiley & Sons. ISBN 978-1-118-70573-5. OCLC 844775006. Archived from the original on August 25, 2022. Retrieved August 25, 2022.
- Block, Bruce A.; McNally, Phillip (2013). 3D storytelling : how stereoscopic 3D works and how to use it. Burlington, MA: Taylor & Francis. ISBN 978-1-136-03881-5. OCLC 858027807. Archived from the original on August 25, 2022. Retrieved August 25, 2022.
- Tozer, E.P.J. (2013). Broadcast engineer's reference book (1st ed.). New York. pp. 470–476. ISBN 978-1-136-02417-7. OCLC 1300579454. Archived from the original on August 25, 2022. Retrieved August 25, 2022.
{{cite book}}
: CS1 maint: location missing publisher (link) - Pizzi, Skip; Jones, Graham (2014). A Broadcast Engineering Tutorial for Non-Engineers (4th ed.). Hoboken: Taylor and Francis. pp. 145–152. ISBN 978-1-317-90683-4. OCLC 879025861. Archived from the original on August 25, 2022. Retrieved August 25, 2022.
- "Sony HD Formats Guide (2008)" (PDF). pro.sony.com. Archived (PDF) from the original on March 6, 2015. Retrieved November 16, 2014.
- Ward, Peter (2015). "Video Recording Formats". Multiskilling for television production. Alan Bermingham, Chris Wherry. New York: Focal Press. ISBN 978-0-08-051230-3. OCLC 958102392. Archived from the original on August 25, 2022. Retrieved August 25, 2022.
- Merskin, Debra L., ed. (2020). The Sage international encyclopedia of mass media and society. Thousand Oaks, California. ISBN 978-1-4833-7551-9. OCLC 1130315057. Archived from the original on June 3, 2020. Retrieved August 25, 2022.
{{cite book}}
: CS1 maint: location missing publisher (link) - Ghanbari, Mohammed (2003). Standard Codecs: Image Compression to Advanced Video Coding. Institution of Engineering and Technology. pp. 1–12. ISBN 9780852967102. Archived from the original on August 8, 2019. Retrieved November 27, 2019.
External links
- Format Descriptions for Moving Images
This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Video news newspapers books scholar JSTOR January 2025 Learn how and when to remove this message Video is an electronic medium for the recording copying playback broadcasting and display of moving visual media Video was first developed for mechanical television systems which were quickly replaced by cathode ray tube CRT systems which in turn were replaced by flat panel displays of several types source source source source source source source source track A one minute animated video showing an example of a media production process Video systems vary in display resolution aspect ratio refresh rate color capabilities and other qualities Analog and digital variants exist and can be carried on a variety of media including radio broadcasts magnetic tape optical discs computer files and network streaming EtymologyThe word video comes from the Latin verb video I see HistoryAnalog video NTSC composite video signal analog Video developed from facsimile systems developed in the mid 19th century Early mechanical video scanners such as the Nipkow disk were patented as early as 1884 however it took several decades before practical video systems could be developed many decades after film Film records using a sequence of miniature photographic images visible to the eye when the film is physically examined Video by contrast encodes images electronically turning the images into analog or digital electronic signals for transmission or recording Video technology was first developed for mechanical television systems which were quickly replaced by cathode ray tube CRT television systems Video was originally exclusively live technology Live video cameras used an electron beam which would scan a photoconductive plate with the desired image and produce a voltage signal proportional to the brightness in each part of the image The signal could then be sent to televisions where another beam would receive and display the image Charles Ginsburg led an Ampex research team to develop one of the first practical video tape recorders VTR In 1951 the first VTR captured live images from television cameras by writing the camera s electrical signal onto magnetic videotape Video recorders were sold for 50 000 in 1956 and videotapes cost US 300 per one hour reel However prices gradually dropped over the years in 1971 Sony began selling videocassette recorder VCR decks and tapes into the consumer market Digital video Digital video is capable of higher quality and eventually a much lower cost than earlier analog technology After the commercial introduction of the DVD in 1997 and later the Blu ray Disc in 2006 sales of videotape and recording equipment plummeted Advances in computer technology allow even inexpensive personal computers and smartphones to capture store edit and transmit digital video further reducing the cost of video production and allowing programmers and broadcasters to move to tapeless production The advent of digital broadcasting and the subsequent digital television transition are in the process of relegating analog video to the status of a legacy technology in most parts of the world The development of high resolution video cameras with improved dynamic range and color gamuts along with the introduction of high dynamic range digital intermediate data formats with improved color depth has caused digital video technology to converge with film technology Since 2013 update the use of digital cameras in Hollywood has surpassed the use of film cameras Characteristics of video streamsNumber 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 frame s for old mechanical cameras to 120 or more frames per second for new professional cameras PAL standards Europe Asia Australia etc and SECAM France Russia parts of Africa etc specify 25 frame s while NTSC standards United States Canada Japan etc specify 29 97 frame s Film is shot at a slower frame rate of 24 frames per second which slightly complicates the process of transferring a cinematic motion picture to video The minimum frame rate to achieve a comfortable illusion of a moving image is about sixteen frames per second Interlaced vs progressive Video can be interlaced or progressive In progressive scan systems each refresh period updates all scan lines in each frame in sequence When displaying a natively progressive broadcast or recorded signal the result is the optimum spatial resolution of both the stationary and moving parts of the image Interlacing was invented as a way to reduce flicker in early mechanical and CRT video displays without increasing the number of complete frames per second Interlacing retains detail while requiring lower bandwidth compared to progressive scanning In interlaced video the horizontal scan lines of each complete frame are treated as if numbered consecutively and captured as two fields an odd field upper field consisting of the odd numbered lines and an even field lower field consisting of the even numbered lines Analog display devices reproduce each frame effectively doubling the frame rate as far as perceptible overall flicker is concerned When the image capture device acquires the fields one at a time rather than dividing up a complete frame after it is captured the frame rate for motion is effectively doubled as well resulting in smoother more lifelike reproduction of rapidly moving parts of the image when viewed on an interlaced CRT display 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 described as 576i50 where 576 indicates the total number of horizontal scan lines i indicates interlacing and 50 indicates 50 fields half frames per second When displaying a natively interlaced signal on a progressive scan device the overall spatial resolution is degraded by simple line doubling artifacts such as flickering or comb effects in moving parts of the image that appear unless special signal processing eliminates them A procedure known as deinterlacing can optimize the display of an interlaced video signal from an analog DVD or satellite source on a progressive scan device such as an LCD television digital video projector or plasma panel Deinterlacing cannot however produce video quality that is equivalent to true progressive scan source material Aspect ratio Comparison of common cinematography and traditional television green aspect ratios Aspect ratio describes the proportional relationship between the width and height of video screens and video picture elements All popular video formats are rectangular and this can be described by a ratio between width and height The ratio of width to height for a traditional television screen is 4 3 or about 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 also known as the Academy ratio is 1 375 1 Pixels on computer monitors are usually square but pixels used in digital video often 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 The 720 by 480 pixel raster uses thin pixels on a 4 3 aspect ratio display and fat pixels on a 16 9 display The popularity of viewing video on mobile phones has led to the growth of vertical video Mary Meeker a partner at Silicon Valley venture capital firm Kleiner Perkins Caufield amp Byers highlighted the growth of vertical video viewing in her 2015 Internet Trends Report growing from 5 of video viewing in 2010 to 29 in 2015 Vertical video ads like Snapchat s are watched in their entirety nine times more frequently than landscape video ads Color model and depth Example of U V color plane Y value 0 5 The color model uses the video color representation and maps encoded color values to visible colors reproduced by the system There are several such representations in common use typically YIQ is used in NTSC television YUV is used in PAL television YDbDr is used by SECAM television and YCbCr is used for digital video The number of distinct colors a pixel can represent depends on the color depth expressed in the number of bits per pixel A common way to reduce the amount of data required in digital video is by chroma subsampling e g 4 4 4 4 2 2 etc Because the human eye is less sensitive to details in color than brightness the luminance data for all pixels is maintained while the chrominance data is averaged for a number of pixels in a block and the same value is used for all of them For example this results in a 50 reduction in chrominance data using 2 pixel blocks 4 2 2 or 75 using 4 pixel blocks 4 2 0 This process does not reduce the number of possible color values that can be displayed but it reduces the number of distinct points at which the color changes Video quality Video quality can be measured with formal metrics like peak signal to noise ratio PSNR or through subjective video quality assessment using expert observation Many subjective video quality methods are described in the ITU T recommendation One of the standardized methods is the Double Stimulus Impairment Scale DSIS 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 digital only Uncompressed video delivers maximum quality but at a very high data rate A variety of methods are used to compress video streams with the most effective ones using a group of pictures GOP to reduce spatial and temporal redundancy 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 compression standards are MPEG 2 used for DVD Blu ray and satellite television and MPEG 4 used for AVCHD mobile phones 3GP and the Internet Stereoscopic Stereoscopic video for 3D film and other applications can be displayed using several different methods Two channels a right channel for the right eye and a left channel for the left eye Both channels may be viewed simultaneously by using light polarizing filters 90 degrees off axis from each other on two video projectors These separately polarized channels are viewed wearing eyeglasses with matching polarization filters Anaglyph 3D where one channel is overlaid with two color coded layers This left and right layer technique is occasionally used for network broadcasts 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 One channel with alternating left and right frames for the corresponding eye using LCD shutter glasses that synchronize to the video to alternately block the image for each eye so the appropriate eye sees the correct frame This method is most common in computer virtual reality applications such as in a Cave Automatic Virtual Environment but reduces effective video framerate by a factor of two FormatsDifferent layers of video transmission and storage each provide their own set of formats to choose from For transmission there is a physical connector and signal protocol see List of video connectors A given physical link can carry certain display standards that specify a particular refresh rate display resolution and color space Many analog and digital recording formats are in use and digital video clips can also be stored on a computer file system as files which have their own formats In addition to the physical format used by the data storage device or transmission medium the stream of ones and zeros that is sent must be in a particular digital video coding format for which a number is available Analog video Analog video is a video signal represented by one or more analog signals Analog color video signals include luminance Y and chrominance C When combined into one channel as is the case among others with NTSC PAL and SECAM it is called composite video Analog video may be carried in separate channels as in two channel S Video YC and multi channel component video formats Analog video is used in both consumer and professional television production applications Composite video single channel RCA S Video 2 channel YC Component video 3 channel YPbPr SCART VGA TRRS D TerminalDigital video Digital video signal formats have been adopted including serial digital interface SDI Digital Visual Interface DVI High Definition Multimedia Interface HDMI and DisplayPort Interface Serial digital interface SDI Digital Visual Interface DVI HDMI DisplayPortTransport mediumVideo can be transmitted or transported in a variety of ways including wireless terrestrial television as an analog or digital signal coaxial cable in a closed circuit system as an analog signal Broadcast or studio cameras use a single or dual coaxial cable system using serial digital interface SDI See List of video connectors for information about physical connectors and related signal standards Video may be transported over networks and other shared digital communications links using for instance MPEG transport stream SMPTE 2022 and SMPTE 2110 Display standardsDigital television Digital television broadcasts use the MPEG 2 and other video coding formats and include ATSC United States Canada Mexico Korea Digital Video Broadcasting DVB Europe ISDB Japan ISDB Tb uses the MPEG 4 video coding format Brazil Argentina Digital multimedia broadcasting DMB KoreaAnalog television Analog television broadcast standards include Field sequential color system FCS US Russia obsolete Multiplexed Analogue Components MAC Europe obsolete Multiple sub Nyquist sampling encoding MUSE Japan NTSC United States Canada Japan EDTV II Clear Vision NTSC extension Japan PAL Europe Asia Oceania PAL M PAL variation Brazil PAL N PAL variation Argentina Paraguay and Uruguay PALplus PAL extension Europe RS 343 military SECAM France former Soviet Union Central Africa CCIR System A CCIR System B CCIR System G CCIR System H CCIR System I CCIR System M An analog video format consists of more information than the visible content of the frame Preceding and following the image are lines and pixels containing metadata and synchronization information This surrounding margin is known as a blanking interval or blanking region the horizontal and vertical front porch and back porch are the building blocks of the blanking interval Computer displays Computer display standards specify a combination of aspect ratio display size display resolution color depth and refresh rate A list of common resolutions is available RecordingA VHS video cassette tape Early television was almost exclusively a live medium with some programs recorded to film for historical purposes using Kinescope The analog video tape recorder was commercially introduced in 1951 The following list is in rough chronological order All formats listed were sold to and used by broadcasters video producers or consumers or were important historically VERA BBC experimental format ca 1952 2 Quadruplex videotape Ampex 1956 1 Type A videotape Ampex 1 2 EIAJ 1969 U matic 3 4 Sony 1 2 Cartrivision Avco VCR VCR LP SVR 1 Type B videotape Robert Bosch GmbH 1 Type C videotape Ampex Marconi and Sony 2 Helical Scan Videotape IVC 1975 Betamax Sony 1975 VHS JVC 1976 Video 2000 Philips 1979 1 4 CVC Funai 1980 Betacam Sony 1982 VHS C JVC 1982 HDVS Sony 1984 Video8 Sony 1986 Betacam SP Sony 1987 S VHS JVC 1987 Pixelvision Fisher Price 1987 1988 Hi8 Sony mid 1990s W VHS JVC 1994 Digital video tape recorders offered improved quality compared to analog recorders Betacam IMX Sony D VHS JVC D Theater D1 Sony D2 Sony D3 D5 HD D6 Philips Digital S D9 JVC Digital Betacam Sony Digital8 Sony DV including DVC Pro HDCAM Sony HDV ProHD JVC MicroMV MiniDV Optical storage mediums offered an alternative especially in consumer applications to bulky tape formats Blu ray Disc Sony China Blue High definition Disc CBHD DVD was Super Density Disc DVD Forum Professional Disc Universal Media Disc UMD Sony Enhanced Versatile Disc EVD Chinese government sponsored HD DVD NEC and Toshiba HD VMD Capacitance Electronic Disc Laserdisc MCA and Philips Television Electronic Disc Teldec and Telefunken VHD JVC Video CDDigital encoding formatsA video codec is software or hardware that compresses and decompresses digital video In the context of video compression codec is a portmanteau of encoder and decoder while a device that only compresses is typically called an encoder and one that only decompresses is a decoder The compressed data format usually conforms to a standard video coding format The compression is typically lossy meaning that the compressed video lacks some information present in the original video A consequence of this is that decompressed video has lower quality than the original uncompressed video because there is insufficient information to accurately reconstruct the original video CCIR 601 ITU T H 261 ITU T H 263 ITU T H 264 MPEG 4 AVC ITU T ISO H 265 M JPEG ISO MPEG 1 ISO MPEG 2 ITU T ISO MPEG 4 ISO Ogg Theora VP8 WebM VC 1 SMPTE See alsoGeneralIndex of video related articles Sound recording and reproduction Video editing Videography Video format360 degree video Cable television Color television Telecine Timecode Volumetric capture Video usageClosed circuit television Fulldome Interactive video Video art Video feedback Video sender Video synthesizer Videotelephony Video screen recording softwareBandicam CamStudio Camtasia Zight App FrapsReferences Video HiDef Audio and Video hidefnj com Archived from the original on May 14 2017 Retrieved March 30 2017 video Online Etymology Dictionary Amidon Audrey June 25 2013 Film Preservation 101 What s the Difference Between a Film and a Video The Unwritten Record US National Archives Vocademy Learn for Free Electronics Technology Analog Circuits Analog Television vocademy net Retrieved 2024 06 29 Elen Richard TV Technology 10 Roll VTR Archived from the original on October 27 2011 Vintage Umatic VCR Sony VO 1600 The worlds first VCR 1971 Rewind Museum Archived from the original on February 22 2014 Retrieved February 21 2014 Follows Stephen February 11 2019 The use of digital vs celluloid film on Hollywood movies Archived from the original on April 11 2022 Retrieved February 19 2022 Soseman Ned What s the difference between 59 94fps and 60fps Archived from the original on June 29 2017 Retrieved July 12 2017 Watson Andrew B 1986 Temporal Sensitivity PDF Sensory Processes and Perception Archived from the original PDF on March 8 2016 Bovik Alan C 2005 Handbook of image and video processing 2nd ed Amsterdam Elsevier Academic Press pp 14 21 ISBN 978 0 08 053361 2 OCLC 190789775 Archived from the original on August 25 2022 Retrieved August 25 2022 Wright Steve 2002 Digital compositing for film and video Boston Focal Press ISBN 978 0 08 050436 0 OCLC 499054489 Archived from the original on August 25 2022 Retrieved August 25 2022 Brown Blain 2013 Cinematography Theory and Practice Image Making for Cinematographers and Directors Taylor amp Francis pp 159 166 ISBN 9781136047381 Parker Michael 2013 Digital Video Processing for Engineers a Foundation for Embedded Systems Design Suhel Dhanani Amsterdam ISBN 978 0 12 415761 3 OCLC 815408915 Archived from the original on August 25 2022 Retrieved August 25 2022 a href wiki Template Cite book title Template Cite book cite book a CS1 maint location missing publisher link Bing Benny 2010 3D and HD broadband video networking Boston Artech House pp 57 70 ISBN 978 1 60807 052 7 OCLC 672322796 Archived from the original on August 25 2022 Retrieved August 25 2022 Stump David 2022 Digital cinematography fundamentals tools techniques and workflows 2nd ed New York NY Routledge pp 125 139 ISBN 978 0 429 46885 8 OCLC 1233023513 Archived from the original on August 25 2022 Retrieved August 25 2022 Constine Josh May 27 2015 The Most Important Insights From Mary Meeker s 2015 Internet Trends Report TechCrunch Archived from the original on August 4 2015 Retrieved August 6 2015 Li Ze Nian Drew Mark S Liu Jiangchun 2021 Fundamentals of multimedia 3rd ed Cham Switzerland Springer pp 108 117 ISBN 978 3 030 62124 7 OCLC 1243420273 Archived from the original on August 25 2022 Retrieved August 25 2022 Banerjee Sreeparna 2019 Video in Multimedia Elements of multimedia Boca Raton CRC Press ISBN 978 0 429 43320 7 OCLC 1098279086 Archived from the original on August 25 2022 Retrieved August 25 2022 Andy Beach 2008 Real World Video Compression Peachpit Press ISBN 978 0 13 208951 7 OCLC 1302274863 Archived from the original on August 25 2022 Retrieved August 25 2022 Sanz Jorge L C 1996 Image Technology Advances in Image Processing Multimedia and Machine Vision Berlin Heidelberg Springer Berlin Heidelberg ISBN 978 3 642 58288 2 OCLC 840292528 Archived from the original on August 25 2022 Retrieved August 25 2022 Ekmekcioglu Erhan Fernando Anil Worrall Stewart 2013 3DTV processing and transmission of 3D video signals Chichester West Sussex United Kingdom Wiley amp Sons ISBN 978 1 118 70573 5 OCLC 844775006 Archived from the original on August 25 2022 Retrieved August 25 2022 Block Bruce A McNally Phillip 2013 3D storytelling how stereoscopic 3D works and how to use it Burlington MA Taylor amp Francis ISBN 978 1 136 03881 5 OCLC 858027807 Archived from the original on August 25 2022 Retrieved August 25 2022 Tozer E P J 2013 Broadcast engineer s reference book 1st ed New York pp 470 476 ISBN 978 1 136 02417 7 OCLC 1300579454 Archived from the original on August 25 2022 Retrieved August 25 2022 a href wiki Template Cite book title Template Cite book cite book a CS1 maint location missing publisher link Pizzi Skip Jones Graham 2014 A Broadcast Engineering Tutorial for Non Engineers 4th ed Hoboken Taylor and Francis pp 145 152 ISBN 978 1 317 90683 4 OCLC 879025861 Archived from the original on August 25 2022 Retrieved August 25 2022 Sony HD Formats Guide 2008 PDF pro sony com Archived PDF from the original on March 6 2015 Retrieved November 16 2014 Ward Peter 2015 Video Recording Formats Multiskilling for television production Alan Bermingham Chris Wherry New York Focal Press ISBN 978 0 08 051230 3 OCLC 958102392 Archived from the original on August 25 2022 Retrieved August 25 2022 Merskin Debra L ed 2020 The Sage international encyclopedia of mass media and society Thousand Oaks California ISBN 978 1 4833 7551 9 OCLC 1130315057 Archived from the original on June 3 2020 Retrieved August 25 2022 a href wiki Template Cite book title Template Cite book cite book a CS1 maint location missing publisher link Ghanbari Mohammed 2003 Standard Codecs Image Compression to Advanced Video Coding Institution of Engineering and Technology pp 1 12 ISBN 9780852967102 Archived from the original on August 8 2019 Retrieved November 27 2019 External linksWikimedia Commons has media related to Video Wikiquote has quotations related to Video Library resources about Video Resources in your library Format Descriptions for Moving Images