Audio and video interfaces and connectors

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Audio connectors and video connectors are electrical or optical connectors for carrying audio and video signals. Audio interfaces and video interfaces define physical parameters and interpretation of signals. For digital audio and digital video, this can be thought of as defining the physical layer, data link layer, and most or all of the application layer. For analog audio and analog video these functions are all represented in a single signal specification like NTSC or the direct speaker-driving signal of analog audio. Physical characteristics of the electrical or optical equipment includes the types and numbers of wires required, voltages, frequencies, optical intensity, and the physical design of the connectors. Any data link layer details define how application data is encapsulated (for example for synchronization or error-correction). Application layer details define the actual audio or video format being transmitted, often incorporating a codecs not specific to the interface, such as PCM, MPEG-2, or the DTS Coherent Acoustics codec. In some cases, the application layer is left open; for example, HDMI contains an Ethernet channel for general data transmission.

Electrical connector electro-mechanical device

An electrical connector is an electro-mechanical device used to join electrical terminations and create an electrical circuit. Electrical connectors consist of plugs (male-ended) and jacks (female-ended). The connection may be temporary, as for portable equipment, require a tool for assembly and removal, or serve as a permanent electrical joint between two wires or devices. An adapter can be used to effectively bring together dissimilar connectors.

Optical fiber connector

An optical fiber connector terminates the end of an optical fiber, and enables quicker connection and disconnection than splicing. The connectors mechanically couple and align the cores of fibers so light can pass. Better connectors lose very little light due to reflection or misalignment of the fibers. In all, about 100 different types of fiber optic connectors have been introduced to the market.

An audio signal is a representation of sound, typically using a level of electrical voltage for analog signals, and a series of binary numbers for digital signals. Audio signals have frequencies in the audio frequency range of roughly 20 to 20,000 Hz, which corresponds to the upper and lower limits of human hearing. Audio signals may be synthesized directly, or may originate at a transducer such as a microphone, musical instrument pickup, phonograph cartridge, or tape head. Loudspeakers or headphones convert an electrical audio signal back into sound.

Contents

Some types of connectors are used by multiple hardware interfaces; for example, RCA connectors are defined both by the composite video and component video interfaces, but DVI is the only interface that uses the DVI connector. This means that in some cases not all components with physically compatible connectors will actually work together.

RCA connector

An RCA connector, sometimes called a phono connector or Cinch connector, is a type of electrical connector commonly used to carry audio and video signals. The name RCA derives from the Radio Corporation of America, which introduced the design by the early 1940s for internal connection of the pickup to the chassis in home radio-phonograph consoles. It was originally a low-cost, simple design, intended only for mating and disconnection when servicing the console. Refinement came with later designs, although they remained compatible.

Composite video analog video transmission

Composite video is an analog video transmission that carries standard definition video typically at 480i or 576i resolution as a single channel. Video information is encoded on one channel, unlike the higher-quality S-video and the even higher-quality component video. In all of these video formats, audio is carried on a separate connection.

Component video video signal that has been split into two or more component channels

Component video is a video signal that has been split into two or more component channels. In popular use, it refers to a type of component analog video (CAV) information that is transmitted or stored as three separate signals. Component video can be contrasted with composite video in which all the video information is combined into a single line level signal that is used in analog television. Like composite, component-video cables do not carry audio and are often paired with audio cables.

Some of these connectors, and other types of connectors, are also used at radio frequency (RF) to connect a radio or television receiver to an antenna or to a cable system; RF connector applications are not further described here. Analog A/V connectors often use shielded cables to inhibit radio frequency interference (RFI) and noise.

Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around twenty thousand times per second to around three hundred billion times per second. This is roughly between the upper limit of audio frequencies and the lower limit of infrared frequencies; these are the frequencies at which energy from an oscillating current can radiate off a conductor into space as radio waves. Different sources specify different upper and lower bounds for the frequency range.

Shielded cable electrical conductors enclosed by a conductive layer

A shielded cable or screened cable is an electrical cable of one or more insulated conductors enclosed by a common conductive layer. The shield may be composed of braided strands of copper, a non-braided spiral winding of copper tape, or a layer of conducting polymer. Usually this shield is covered with a jacket.

Noise unwanted sound,difference from sound - when the brain receives and perceives a sound;random fluctuations of data that hinders perception of an expected signal;unwanted residual electronic noise signal that gives rise to acoustic noise heard as a hiss

Noise is unwanted sound judged to be unpleasant, loud or disruptive to hearing. From a physics standpoint, noise is indistinguishable from sound, as both are vibrations through a medium, such as air or water. The difference arises when the brain receives and perceives a sound.

For efficiency and simplicity, the same codec or signal convention is used by the storage medium. For example, VHS tapes can store a magnetic representation of an NTSC signal, and the specification for Blu-ray Discs incorporates PCM, MPEG-2, and DTS. Some playback devices can re-encode audio or video so that the format used for storage does not have to be the same as the format transmitted over the A/V interface (which is helpful if a projector or monitor cannot handle a newer codec).

VHS Consumer-level analog video tape recording and cassette form factor standard

VHS is a standard for consumer-level analog video recording on tape cassettes. Developed by Victor Company of Japan (JVC) in the early 1970s, it was released in Japan on September 9, 1976 and in the United States on August 23, 1977.

Interfaces and their connectors

InterfaceConnectors
Audio or videoDigital or analogDescription
Audio onlyAnalogOften unmarked on consumer audio equipment since it is so common, or labelled with headphones symbol or as "line out". Computers and other equipment sometimes use Microsoft-Intel color coding scheme, especially when there are multiple input/output plugs. 3.5 mm TRS minijack
Balanced audio 6.35 mm TRS audio jack (shielded twisted pair),
XLR (shielded twisted pair)
Digital S/PDIF (Sony/Philips Digital Interconnect Format). Via coaxial or optical cables. RCA Jack (coaxial),
TOSLINK (optical),
BNC (rare)
AES3 (also known as AES/EBU) RCA Jack (coaxial),
XLR (shielded twisted pair),
TOSLINK (optical),
BNC
MADI BNC (coaxial),
ST (optical)
Video onlyAnalog Video Graphics Array (VGA) D-subminiature 15-pin
Composite. Often designated by the CVBS acronym, meaning "Color, Video, Blank and Sync". RCA jack, normally yellow (often accompanied with red and white for right and left audio channels respectively)
S-Video (Separate Video). Carries standard definition video and does not carry audio on the same cable. Mini-DIN 4-pin
Component. In popular use, it refers to a type of analog video information that is transmitted or stored as three separate signals. Either RGB interfaces or YPbPr 3 RCA Jacks
Composite, S-Video, and Component VIVO = Mini-DIN 9-pin with breakout cable.
Digital and analog Digital Visual Interface (DVI)DVI connector
Video and audioAnalog SCART (Peritel)SCART
Digital High-Definition Multimedia Interface (HDMI),BNCHDMI connector
DisplayPort DisplayPort connector
HDBaseT 8P8C connector
IEEE 1394 "FireWire" FireWire or i.LINK connectors

Multiple signals

Several generic digital data connection standards are designed to carry audio/video data along with other data and power:

USB industry standard

USB is an industry standard that establishes specifications for cables, connectors and protocols for connection, communication and power supply between personal computers and their peripheral devices. Released in 1996, the USB standard is currently maintained by the USB Implementers Forum. There have been three generations of USB specifications: USB 1.x, USB 2.0 and USB 3.x; the fourth called USB4 is scheduled to be published in the middle of 2019.

DisplayLink

DisplayLink is a semiconductor and software technology company. DisplayLink USB graphics technology is designed to connect computers and displays using USB, Ethernet, and WiFi. It also allows multiple displays to be connected to a single computer. DisplayLink's primary customers are notebook OEMs, LCD monitor manufacturers and PC accessory vendors, supporting the Microsoft Windows, macOS, Android, ChromeOS and Linux operating systems.

USB-C 24-pin reversible-plug serial digital connector system

USB-C, formally known as USB Type-C, is a 24-pin USB connector system, which is distinguished by its two-fold rotationally-symmetrical connector.

Some digital connection standards were designed from the beginning to primarily carry audio and video signals simultaneously:

HDMI communications protocol

HDMI is a proprietary audio/video interface for transmitting uncompressed video data and compressed or uncompressed digital audio data from an HDMI-compliant source device, such as a display controller, to a compatible computer monitor, video projector, digital television, or digital audio device. HDMI is a digital replacement for analog video standards.

Mobile High-Definition Link (MHL) is an industry standard for a mobile audio/video interface that allows the connection of smartphones, tablets, and other portable consumer electronics devices to high-definition televisions (HDTVs), audio receivers, and projectors. The standard was designed to share existing mobile device connectors, such as Micro-USB, and avoid the need to add additional video connectors on devices with limited space for them.

Many analog connectors carry both:

S/PDIF

The electrical coaxial cable (with RCA jacks) or optical fibre (TOSLINK).

Note that there are no differences in the signals transmitted over optical or coaxial S/PDIF connectors—both carry exactly the same information. Selection of one over the other rests mainly on the availability of appropriate connectors on the chosen equipment and the preference and convenience of the user. Connections longer than 6 meters or so, or those requiring tight bends, should use coaxial cable, since the high light signal attenuation of TOSLINK cables limits its effective range.

HDMI

HDMI Type A socket HDMI.socket.png
HDMI Type A socket

High-Definition Multimedia Interface (HDMI) is a compact audio/video standard for transmitting uncompressed digital data.

There are three HDMI connector types. Type A and Type B were defined by the HDMI 1.0 specification. Type C was defined by the HDMI 1.3 specification.

Type A is electrically compatible with single link DVI-D. Type B is electrically compatible with dual link DVI-D but has not yet been used in any products.

IEEE 1394 "FireWire"

The 6-circuit and 4-circuit alpha FireWire 400 connectors FireWire-46 Diagram.svg
The 6-circuit and 4-circuit alpha FireWire 400 connectors

IEEE 1394 FireWire is a digital data transfer protocol commonly used for digital cameras (common on MiniDV tape camcorders), but also used for computer data and audio data transfers. In the United States, cable TV converter set top boxes by law [1] also have the connection for transferring content directly to a TV (if equipped with a port) or computer for viewing. 1394 can also use coaxial cable as a medium for longer runs.

Unlike Point-to-Point connections listed above, IEEE 1394 is able to host several signals on the same wire, with the data delivered and shown on the destination set. It is also fully bi-directional, with its full bandwidth used in one direction or the other, or split directions up to its maximum. [2]

DisplayPort

pinout_caption=External connector (source-side) on PCB DisplayPort Connector.svg
pinout_caption=External connector (source-side) on PCB

DisplayPort is a digital display interface standard (approved May 2006, current version 1.4 published on March 1 2016). It defines a new license-free, royalty-free, digital audio/video interconnect, intended to be used primarily between a computer and its display monitor, or a computer and a home-theater system.

The video signal is not compatible with DVI or HDMI, but a DisplayPort connector can pass these signals through. DisplayPort is a competitor to the HDMI connector, the de facto digital connection for high-definition consumer electronics devices.

Audio connectors

Audio connectors are used for audio frequencies. They can be analog or digital.

Single-wire connectors used frequently for analog audio include:

Phone connector

2.5 mm (3/32") mono (TS), 3.5 mm (1/8") mono and stereo (TRS), and 6.3 mm (1/4") stereo (TRS) phone connectors Photo-audiojacks.jpg
2.5 mm (3/32") mono (TS), 3.5 mm (1/8") mono and stereo (TRS), and 6.3 mm (1/4") stereo (TRS) phone connectors

A phone connector (tip, ring, sleeve) also called an audio jack, phone plug, jack plug, stereo plug, mini-jack, or mini-stereo. This includes the original 6.35mm (quarter inch) jack and the more recent 3.5mm (miniature or 1/8 inch) and 2.5mm (subminiature) jacks, both mono and stereo versions.

DIN

Five-pin male 180deg DIN connector 5pin180dinplug.jpg
Five-pin male 180° DIN connector

A DIN connector is a connector that was originally standardized by the Deutsches Institut für Normung (DIN). Mini-DIN is a variation.

BNC

Male 50 ohm BNC connector BNC connector.jpg
Male 50 ohm BNC connector

The BNC (Bayonet Neill Concelman) connector is a very common type of RF connector used for terminating coaxial cable.

Clear TOSLINK cable with a round connector TOS LINK clear cable.jpg
Clear TOSLINK cable with a round connector

TOSLINK or Optical Cable is a standardized optical fiber connection system.

XLR

XLR3 cable connectors, female on left and male on right Xlr-connectors.jpg
XLR3 cable connectors, female on left and male on right

XLR connector plugs and sockets are used mostly in professional audio and video electronics cabling applications. XLR connector are also known as Cannon plugs after their original manufacturer. They are used for analog or digital balanced audio with a balanced line

Digital audio interfaces and interconnects with the AES/EBU interface also normally use an XLR connector.

RCA

RCA Plugs for composite video (yellow) and stereo audio (white and red) Composite-cables.jpg
RCA Plugs for composite video (yellow) and stereo audio (white and red)

RCA connectors, also known as phono connectors or phono plugs, are used for analog or digital audio or analog video. These were first used inside pre–World War II radio-phonographs to connect the turntable pickup to the radio chassis. They were not intended to be disconnected and reconnected frequently, and their retaining friction was quite sufficient for their original purpose. Furthermore, the design of both cable and chassis connectors was for minimum cost. Initially intended for audio-frequency connections only, the RCA plug was also used for analog composite video and non-critical radio-frequency applications.

Video connectors

A VGA connector SVGA port.jpg
A VGA connector

Video connectors carry only video signals. Common video-only connectors include:

Mini-DIN

mini-DIN 4 pin for S-Video SVideoConnector.jpg
mini-DIN 4 pin for S-Video

The Mini-DIN connectors are a family of multi-pin electrical connectors used in a variety of applications. Mini-DIN is similar to the larger, older DIN connector. Both are standards of the Deutsches Institut für Normung, the German standards body.

D-subminiature

DA, DB, DC, DD, and DE sized connectors DSubminiatures.svg
DA, DB, DC, DD, and DE sized connectors

D-subminiature or D-sub is a common type of electrical connector used particularly in computers. Calling them "sub-miniature" was appropriate when they were first introduced, but today they are among the largest common connectors used in computers. The DB25 is used for multi-track recording and other multi-channel audio, analog or digital (ADAT interface (DB25)), and was the standard connector for IBM compatible PC printer connection before USB and other connections became popular. It offered 8 simultaneous data pathways to the printer.

Video In Video Out

A graphics card with VIVO, DVI and VGA outputs Gpu-connector.jpg
A graphics card with VIVO, DVI and VGA outputs
A 6-connector VIVO splitter cable. From left to right: S-Video In, Component Pb out, Component Pr out, Component Y out/Composite out, Composite in, S-Video Out Vivo splitter cable.jpg
A 6-connector VIVO splitter cable. From left to right: S-Video In, Component Pb out, Component Pr out, Component Y out/Composite out, Composite in, S-Video Out

Video In Video Out, usually seen as the acronym VIVO (commonly pronounced vee-voh), is a graphics card port which enables some video cards to have bidirectional (input and output) video transfer through a Mini-DIN, usually of the 9-pin variety, and a specialised splitter cable (which can sometimes also transfer sound).

VIVO is found predominantly on high-end ATI video cards, although a few high-end NVIDIA video cards also have this port. VIVO on these graphics cards typically supports Composite, S-Video, and Component as outputs, and composite and S-Video as inputs. Many other video cards only support component and/or S-Video outputs to complement Video Graphics Array or DVI, typically using a component breakout cable and an S-Video cable.

DVI Connector

Color codes

Audio

white RCA/TSanalogue audio, left channel;
also mono (RCA/TS), stereo (TRS only),
or undefined/other
black RCA/TS/TRS
grey RCA/TS/TRS
red RCA/TSanalogue audio, right channel
orange RCA S/PDIF digital audio

For computers:

green TRS 3.5 mmstereo output, front channels
black TRS 3.5 mmstereo output, rear channels
grey TRS 3.5 mmstereo output, side channels
gold TRS 3.5 mmdual output, center and subwoofer
blue TRS 3.5 mmstereo input, line level
pink TRS† 3.5 mmmono microphone input
† Although the mic input is usually mono, the input is still a TRS phone socket. Many mono 'computer' mics are fitted with TRS plugs. The tip is for the MIC and the ring is for power (to power an electret-condenser style MIC).

There are exceptions to the above:

PC System Design Guide audio

Older sound cards had no common standard color codes until after PC 99. The PC System Design Guide (also known as the PC 97, PC 98, PC 99, or PC 2001 specification) is a series of hardware design requirements and recommendations for IBM PC compatible personal computers, compiled by Microsoft and Intel Corporation during 1997–2001. PC 99 introduced a color code for the various standard types of plugs and connectors used on PCs.

The color codes for audio plugs follow: [4]

Orange TRS 3.5 mmOutput, subwoofer
Blue TRS 3.5 mmInput, line level
Pink TRS† 3.5 mm microphone input
Lime TRS 3.5 mmOutput, front channels
Brown TRS 3.5 mmOutput, 'Right-to-left speaker'
Gold TRS 3.5 mm MIDI/game
† Though the input is often mono, the actual connector is usually still a 3-conductor TRS phone minijack. Many mono computer microphones have 3-conductor TRS plugs.

Video

yellow RCA/BNCcomposite video
red RCA/BNCred or Pr/Cr chrominance
green RCA/BNCgreen or luminance
blue RCA/BNCblue or Pb/Cb chrominance
white BNChorizontal sync
black BNCvertical sync

Newer connectors are identified by their shape and not their colour.

See also

Related Research Articles

Digital Visual Interface standard for transmitting digital video to a display (such as a monitor)

Digital Visual Interface (DVI) is a video display interface developed by the Digital Display Working Group (DDWG). The digital interface is used to connect a video source, such as a video display controller, to a display device, such as a computer monitor. It was developed with the intention of creating an industry standard for the transfer of digital video content.

BNC connector

The BNC connector is a miniature quick connect/disconnect radio frequency connector used for coaxial cable. The interface specifications for the BNC and many other connectors are referenced in MIL-STD-348. It features two bayonet lugs on the female connector; mating is fully achieved with a quarter turn of the coupling nut. BNC connectors are used with miniature-to-subminiature coaxial cable in radio, television, and other radio-frequency electronic equipment, test instruments, and video signals. The BNC was commonly used for early computer networks, including ARCnet, the IBM PC Network, and the 10BASE2 variant of Ethernet. BNC connectors are made to match the characteristic impedance of cable at either 50 ohms or 75 ohms. They are usually applied for frequencies below 4 GHz and voltages below 500 volts.

A video card is an expansion card which generates a feed of output images to a display device. Frequently, these are advertised as discrete or dedicated graphics cards, emphasizing the distinction between these and integrated graphics. At the core of both is the graphics processing unit (GPU), which is the main part that does the actual computations, but should not be confused as the video card as a whole, although "GPU" is often used to refer to video cards.

S/PDIF standardized optical fiber connection system

S/PDIF is a type of digital audio interconnect used in consumer audio equipment to output audio over reasonably short distances. The signal is transmitted over either a coaxial cable with RCA connectors or a fibre optic cable with TOSLINK connectors. S/PDIF interconnects components in home theatres and other digital high-fidelity systems.

A de facto standard is a custom or convention that has achieved a dominant position by public acceptance or market forces. De facto is a Latin phrase that means in fact in the sense of "in practice but not necessarily ordained by law" or "in practice or actuality, but not officially established", as opposed to de jure.

DVD player device playing DVD discs

A DVD player is a device that plays DVD discs produced under both the DVD-Video and DVD-Audio technical standards, two different and incompatible standards. Some DVD players will also play audio CDs. DVD players are connected to a television to watch the DVD content, which could be a movie, a recorded TV show, or other content.

D-subminiature type of electrical connector

The D-subminiature or D-sub is a common type of electrical connector. They are named for their characteristic D-shaped metal shield. When they were introduced, D-subs were among the smallest connectors used on computer systems.

VGA connector

A Video Graphics Array (VGA) connector is a three-row 15-pin DE-15 connector. The 15-pin VGA connector was provided on many video cards, computer monitors, laptop computers, projectors, and high definition television sets. On laptop computers or other small devices, a mini-VGA port was sometimes used in place of the full-sized VGA connector.

DB13W3 style of D-subminiature connector used as an analog video interface

DB13W3 (13W3) is a style of D-subminiature connector commonly used for analog video interfaces. It was used primarily on Sun Microsystems, Silicon Graphics (SGI) and IBM RISC workstations, as well as some displays from Apple Computer, NeXT Computer and Intergraph Corporation. The 13W3 connector is no longer used with modern displays; it was superseded for use with analog displays by the VGA connector, and as the display market has moved to digital flat panel displays that has in turn been replaced almost entirely by digital connections.

DisplayPort digital display interface

DisplayPort (DP) is a digital display interface developed by a consortium of PC and chip manufacturers and standardized by the Video Electronics Standards Association (VESA). The interface is primarily used to connect a video source to a display device such as a computer monitor, and it can also carry audio, USB, and other forms of data.

AV input is a common label on a connector to receive (AV) audio/visual signals from electronic equipment that generates AV signals.

Computer port (hardware) hardware

In computer hardware, a port serves as an interface between the computer and other computers or peripheral devices. In computer terms, a port generally refers to the part of a computing device available for connection to peripherals such as input and output devices. Computer ports have many uses, to connect a monitor, webcam, speakers, or other peripheral devices. On the physical layer, a computer port is a specialized outlet on a piece of equipment to which a plug or cable connects. Electronically, the several conductors where the port and cable contacts connect, provide a method to transfer signals between devices.

An audio/video receiver (AVR) is a consumer electronics component used in a home theater. Its purpose is to receive audio and video signals from a number of sources, and to process them to drive loudspeakers and displays such as a television, monitor or video projector. Inputs may come from a satellite receiver, radio, DVD players, Blu-ray Disc players, VCRs or video game consoles. The AVR source selection and settings such as volume, are typically set by a remote controller.

Mini DisplayPort Audio/video interface for transmitting digital signals

The Mini DisplayPort is a miniaturized version of the DisplayPort audio-visual digital interface.

TOSLINK standardized optical fiber connection system

TOSLINK is a standardized optical fiber connector system. Also known generically as an "optical audio cable" or just "optical cable", its most common use is in consumer audio equipment, where it carries a digital audio stream from components such as CD and DVD players, DAT recorders, computers, and modern video game consoles, to an AV receiver that can decode two channels of uncompressed lossless PCM audio or compressed 5.1/7.1 surround sound such as Dolby Digital or DTS Surround System. Unlike HDMI, TOSLINK does not have the bandwidth to carry the lossless versions of Dolby TrueHD, DTS-HD Master Audio, or more than two channels of PCM audio.

References

  1. "Archived copy". Archived from the original on 2010-07-31. Retrieved 2010-06-04.CS1 maint: Archived copy as title (link) All Cable TV box have working 1394 ports, FCC rule CS Docket 97-80" and "section 47 C.F.R. 76.640(b)(4)
  2. "Archived copy" (PDF). Archived from the original (PDF) on 2011-06-06. Retrieved 2010-06-04.CS1 maint: Archived copy as title (link) Demonstrating the multi-device capabilities of IEEE A/V network.
  3. 2.5mm Audio Cables Archived September 26, 2013, at the Wayback Machine
  4. PC 99 System Design Guide, Intel Corporation and Microsoft Corporation, 14 July 1999. Chapter 3: PC 99 basic requirements (PC 99 System Design Guide (Self extracting .exe). Requirement 3.18.3: Systems use a color-coding scheme for connectors and ports. Accessed 2009-02-05