Editing Composite video

{{short description|Baseband analog video signal format}}
{{distinguish|Component video}}
{{Use dmy dates|date=August 2020}}
{{Use American English|date=March 2020}}

{{Infobox connector
| name = Composite Video Baseband Signal (CVBS)
| type = Analog video connector
| image = [[File:Composite-video-cable.jpg|300px]]
| logo = 
| caption = On consumer products a yellow [[RCA connector]] is typically used for composite video.
| designer = 
| design_date = 1954<ref>{{cite web |title=Definition: composite video |url=https://www.computerlanguage.com/results.php?definition=composite+video |publisher=computer language |access-date=23 May 2019}}</ref>–1956<ref>{{cite web|title=the cable bible |url=https://amiaopensource.github.io/cable-bible/#composite |access-date=23 May 2019}}</ref>
| manufacturer = 
| production_date = 
| superseded = 
| superseded_by = Analog: [[S-Video]] & [[Component video|Component]] 
Digital: [[Serial digital interface|SDI]] & [[HDMI]]
| superseded_by_date = 
| external = Yes
| length = Maximum of {{val|50|u=meters}}{{citation needed|date=August 2022}}
| width = 
| height = 
| electrical = {{val|1|u=volt}}<ref>{{cite web|title=Understanding composite video|date=21 May 2023 |url=https://clearview-communications.com/insights/understanding-composite-video-signals|publisher=[[ClearView Communications Ltd]]}} </ref>
| ground = 
| maximum_voltage = 
| maximum_current = 
| audio_signal = 
| video_signal = NTSC, PAL or SECAM video
| data_signal = 
| data_bit_width = 
| data_bandwidth = 
| data_devices = 
| data_style = 
| cable = Coaxial
| physical_connector = [[RCA connector]] & [[BNC connector]]
| num_pins = 1 plus grounding shield
| pinout_col1_name = 
| pinout_col2_name = 
| pinout_image = 
| pinout_caption = 
| pin1 = video
| pin1_name = center
| pin2 = ground
| pin2_name = sheath
| pinout_notes = 
}}

'''Composite video''' is a [[Video#Analog video|baseband analog video]] format that typically carries a [[405 lines|405]], [[525 lines|525]] or [[625 lines|625 line]] [[interlaced]] black and white or color signal, on a single channel, unlike the higher-quality [[S-Video]] (two channels) and the even higher-quality [[YPbPr]] (three channels).

A yellow [[RCA connector]] is typically used for composite video, with left- and right-channel audio carried on separate, additional RCA connectors. In professional settings, or on devices that are too small for an RCA connector, such as digital cameras, other types of connectors can be used.

Composite video is also known by the acronym '''CVBS''', for '''composite video baseband signal''' or '''color, video, blanking and sync''',<ref>{{cite web |date=2002 |title=TUTORIAL 734 Video Basics |url=https://www.maximintegrated.com/en/app-notes/index.mvp/id/734 |url-status=dead |archive-url=https://web.archive.org/web/20180714164333/https://www.maximintegrated.com/en/app-notes/index.mvp/id/734 |archive-date=14 July 2018 |access-date=14 July 2018 |website=Maxim Integrated |publisher=[[Maxim Integrated]]}}</ref><ref>{{cite web |author=Silva |first=Robert |date=September 11, 2020 |title=Composite Video Connections Explained - Many home theater devices still support composite video inputs |url=https://www.lifewire.com/composite-video-the-basics-1846869 |access-date= |website=Lifewire Tech for Humans |publisher=[[Lifewire]]}}</ref> or is simply referred to as ''SD video'' for the standard-definition television signal it conveys.

There are three dominant variants of composite video signals, corresponding to the analog color system used ([[NTSC]], [[PAL]], and [[SECAM]]), but purely monochrome signals can also be used.

== Signal components ==
[[File:Composite Video.svg|thumb|right|upright=1.36|Composite video signal graphic]]
[[File:NTSC Signal.png|thumb|[[NTSC]] composite video signal (analog) displayed on a [[Digital storage and sampling oscilloscope|DSO]].]]

A composite video signal combines, on one wire, the video information required to recreate a color picture, as well as line and [[frame synchronization]] pulses. The color video signal is a linear combination of the ''[[luminance]]'' (Y) of the picture and a [[chrominance subcarrier]] which carries the color information (C), a combination of [[hue]] and [[Colorfulness|saturation]]. Details of the combining process vary between the NTSC, PAL and SECAM systems.

The [[frequency spectrum]] of the modulated color signal overlaps that of the baseband signal, and separation relies on the fact that frequency components of the baseband signal tend to be near [[harmonic]]s of the horizontal scanning rate, while the color carrier is selected to be an odd multiple of half the horizontal scanning rate; this produces a modulated color signal that consists mainly of harmonic frequencies that fall between the harmonics in the baseband [[Luma (video)|luma]] signal, rather than both being in separate continuous frequency bands alongside each other in the frequency domain. The signals may be separated using a [[comb filter]].<ref>{{Cite news |title=Understanding Video Comb Filters |work=Sencore Tech Tips |issue=201 |url=http://www.broadcaststore.com/pdf/model/793698/TT201%20-%204918.pdf}}</ref> In other words, the combination of luma and chrominance is indeed a frequency-division technique, but it is much more complex than typical [[frequency-division multiplexing]] systems like the one used to multiplex analog radio stations on both the AM and FM bands.

A gated and filtered signal derived from the color [[subcarrier]], called the burst or [[colorburst]], is added to the [[horizontal blanking interval]] of each line (excluding lines in the [[vertical sync interval]]) as a synchronizing signal and amplitude reference for the chrominance signals. In NTSC composite video, the {{val|3.58|u=MHz}} burst signal is inverted in phase (180° out of phase) from the reference subcarrier.<ref name="SMPTE 170M-2004">{{cite book |url=https://ieeexplore.ieee.org/document/7291416 |archive-url=https://web.archive.org/web/20180608112731/https://ieeexplore.ieee.org/document/7291416/ |url-status=dead |archive-date=8 June 2018 |title=SMPTE STANDARD for Television – Composite Analog Video Signal – NTSC for Studio Applications |journal=St 170:2004 |date=2004|pages=1–21 |doi=10.5594/SMPTE.ST170.2004 |isbn=978-1-61482-335-3 }}</ref> In PAL, the phase of the {{val|4.43|u=MHz}} color subcarrier alternates on successive lines. In SECAM, no colorburst is used since phase information is irrelevant.

===Composite artifacts===
[[Image:Crawl.jpg|right|thumb|upright=1.36|Enlarged detail from a video source exhibiting [[dot crawl]]. Note the distinctive checkerboard pattern on the vertical edges between yellow and blue areas.]]
The combining of component signals to form the composite signal does the same, causing a checkerboard video artifact known as [[dot crawl]]. Dot crawl is a defect that results from crosstalk due to the intermodulation of the chrominance and luminance components of the signal. This is usually seen when chrominance is transmitted with high bandwidth, and its spectrum reaches into the band of the luminance frequencies. [[Comb filter]]s are commonly used to separate signals and eliminate these artifacts from composite sources. [[S-Video]] and [[component video]] avoid this problem as they maintain the component signals physically separate.

=== Recording ===
Most home [[analog video]] equipment record a signal in (roughly) composite format: [[LaserDisc]]s and [[type C videotape]] for example store a true composite signal modulated, while consumer videotape formats (including [[VHS]] and [[Betamax]]) and commercial and industrial tape formats (including [[U-matic]]) use modified composite signals [[FM (modulation)|FM encoded]] (generally known as ''color-under'').<ref>{{cite web|title=US Patent 4323915|url=http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=4323915.PN.&OS=PN/4323915&RS=PN/4323915|publisher=US Patent and Trademark Office|access-date=12 May 2014|url-status=live|archive-url=https://web.archive.org/web/20161220125824/http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=4323915.PN.&OS=PN%2F4323915&RS=PN%2F4323915|archive-date=20 December 2016}}</ref> The professional [[D-2 (video)|D-2]] videocassette format [[digital recording|digitally stores]] a sampled [[analog signal|analog]] composite video signal on [[magnetic tape]]. With the advent of affordable higher sampling speed analog to digital converters, realtime composite to YUV sampled digital sampling has been possible since the 1980s and raw waveform sampling and software decoding since the 2010s.<ref name="CVBS-Decode">{{Cite web |last=Munday |first=Harry |date=2021 |title=CVBS-Decode - Software Defined Composite Video Decoder |url=https://github.com/oyvindln/vhs-decode/wiki/CVBS-Composite-Decode |website=[[GitHub]]}}</ref>

=== Extensions ===
A number of so-called ''extensions'' to the visible TV image can be transmitted using composite video. Since TV screens hide the [[vertical blanking interval]] of a composite video signal, these take advantage of the unseen parts of the signal. Examples of extensions include [[teletext]], [[closed captioning]], information regarding the show title, a set of reference colors that allows TV sets to automatically correct NTSC hue maladjustments, [[widescreen signaling]] (WSS) for switching between [[4:3]] and [[16:9]] display formats, etc.

== Connectors and cable ==
[[File:Elwro_800_Junior_jednostka_centralna_tyl.jpg|thumb|right|Rear of the [[Poland|Polish]] Elwro 800 Junior computer. DIN output carries a composite video signal to an external monitor.<ref>{{cite web|url=http://oldcomputer.info/8bit/elwro800/index.htm|title=Elwro 800 Junior - MCbx|website=oldcomputer.info|access-date=5 May 2018|url-status=live|archive-url=https://web.archive.org/web/20170318162308/http://oldcomputer.info/8bit/elwro800/index.htm|archive-date=18 March 2017}}</ref>]]
[[File:IntergraphVoodooRush.jpg|thumb|[[Intergraph]] Intense3D [[Voodoo Rush]] with [[TV-out]]; [[S-video]] (topmost connector) and composite video (yellow RCA connector below)]]

In home applications, the composite video signal is typically connected using an RCA connector, normally yellow. It is often accompanied with red and white connectors for right and left audio channels respectively. [[BNC connector]]s and higher quality [[coaxial cable]] are often used in professional [[television studio]]s and [[post-production]] applications. BNC connectors were also used for composite video connections on early home [[VCR]]s, often accompanied by either RCA connector or a 5-pin [[DIN connector]] for audio. The BNC connector, in turn, post dated the [[PL-259]] connector featured on first-generation VCRs.

Video cables are 75 ohm impedance, low in capacitance. Typical values run from 52&nbsp;pF/m for an [[HDPE]]-foamed dielectric precision video cable to 69&nbsp;pF/m for a solid PE dielectric cable.<ref>{{cite web |url=http://www.bluejeanscable.com/store/subwoofer/LC1-design-notes.htm |title=LC-1 Audio Cable Design Notes |publisher=Blue Jeans Cable |access-date=21 January 2012 |url-status=live |archive-url=https://web.archive.org/web/20111128085452/http://www.bluejeanscable.com/store/subwoofer/LC1-design-notes.htm |archive-date=28 November 2011 }}</ref>

== Digital sampling and modern usage ==
The active image area of composite and S-Video signals are digitally stored at {{times|720x576}} i25 PAL and {{times|720x480}} i29.7 (or {{times|720x488}}) pixels. This does not represent the whole signal. Hardware typically samples at four times the color subcarrier frequency (4fsc) that includes the [[vertical blanking interval]] (VBI). Only commercial video capture devices used in broadcast output images with the extra VBI space. Direct sampling with high-speed [[Analog-to-digital converter|ADCs]] and software [[time base correction]] has allowed projects like the [[open-source]] CVBS-Decode<ref name="CVBS-Decode" /> to create a [[D-2 (video)|D-2]] like a 4fsc stream that preserves and allows full presentation and inspection of the entire composite signal. This can then be chroma-decoded to a color image on a standard computer or via [[Digital-to-analog converter|DAC]] played back to a TV. 

Due to the development of digital video technologies, composite video is no longer a universal feature on consumer video products. Analog [[CRT display]]s have been displaced by digital displays, and virtually all newer consumer video devices instead use [[HDMI]]. Despite this, modified versions of composite video, such as 960H ({{times|960×576}}), remain in wide consumer use for [[CCTV]] systems and [[Drone racing|FPV drones]].{{cn|date=May 2024}}

== Modulators ==
{{Unreferenced section|date=August 2023}}
Some devices, such as [[videocassette recorder]]s (VCRs), [[video game console]]s, and [[home computer]]s output composite video. This may then be converted to FM RF with an [[RF modulator]] that generates the proper carrier (often for channel 3 or 4 in [[North America]], channel 36 in [[Europe]]). Sometimes this modulator is built into the product (such as video game consoles, VCRs, or the [[Atari]], [[Commodore 64]], or [[TRS-80 CoCo]] home-computers), is an external unit powered by the computer ([[TI-99/4A]]), or with an independent power supply.{{efn|In the United States, using an external RF modulator frees the manufacturer from obtaining FCC approval for each variation of a device. Through the early 1980s, electronics that output a television channel signal were required to meet the same shielding requirements as broadcast television equipment, thus forcing manufacturers such as Apple to omit an RF modulator, and [[Texas Instruments]] to have their RF modulator as an external unit, which they had certified by the FCC without mentioning they were planning to sell it with a computer. In Europe, while most countries used the same broadcast standard, there were different modulation standards (PAL-G versus PAL-I, for example), and using an external modulator allowed manufacturers to make a single product and easily sell it to different countries by changing the modulator.}}

Because of the [[digital television transition]] most television sets no longer have analog television tuners but DVB-T and ATSC digital ones. They therefore cannot accept a signal from an analog modulator. However, composite video has an established market for both devices that convert it to [[channel 3/4 output]]s, as well as devices that convert standards like [[VGA]] to composite, therefore it has offered opportunities to [[repurpose]] older [[composite monitor]]s for newer devices.

=== Demodulation loss ===
The process of modulating RF with the original video signal, and then demodulating the original signal again in the TV, introduces losses including added noise or interference. For these reasons, it is best to use composite connections instead of RF connections if possible for live signals and sample the source FM RF signal for recorded formats. Some video equipment and modern televisions have only RF input.

== See also ==
* [[List of video connectors]]
* [[NTSC#Color encoding|NTSC color encoding]]
* [[PAL#Colour encoding|PAL color encoding]]

==Notes==
{{Notelist}}

==References==
{{Reflist}}

== External links ==
* [https://pdfserv.maximintegrated.com/en/an/AN734.pdf Maxim - Apr 8, 2002 - Video Basics] Tutorial covering CVBS format structure.
* {{cite web |url=http://electronics.howstuffworks.com/tv9.htm |title=Composite Video Signal |author=Marshall Brain |date=26 November 2006 |access-date=1 May 2020}}

{{Analogvideo}}
{{Analogue TV transmitter topics}}
{{AVconn}}
{{Audio_and_video_interfaces_and connectors}}

[[Category:Video signal| ]]
[[Category:Analog video connectors]]
[[Category:Television technology]]
[[Category:Repurposing]]
[[Category:Composite video formats| ]]