An audio visual or AV source is basically a device that outputs an audio and video signal to a secondary device such as a monitor, TV or other external displays.
While there are a multitude of AV sources out there, the most common ones used today are HDMI and DisplayPort (Thunderbolt) with the latter becoming increasingly popular thanks to its one stop shop ability to transfer audio, video, power and data.
However, even with Thunderbolt being the obvious future for any kind of data transmission, as of now, we are still reliant on HDMI and even a few older AV standards.
While there might be some AV standards here that you haven’t heard of before, they do have their specific use cases and can actually have better results than modern AV standards in those specific cases.
There are also devices that can only do audio or video outputs such as soundbars or speakers and monitors without built-in speakers.
With the basics out of the way, let’s go into detail about AV sources.
An AV source is essentially a device that transmits both audio and video source to, such as a DVD player, or Playstation with an output device like your TV or monitor.
Understanding AV Signals and Devices
There are two types of AV signals, input and output.
Input devices include PC’s, gaming consoles, and set top boxes to name a few, while output devices include TV’s, monitors, and speakers.
For example, you can’t use your PC without an output device like a TV or monitor, and you can’t use your monitor without an input device.
We also have devices that have both input and output capabilities such as smartphones, tablets, and smart TVs.
While these devices can perform certain tasks such as streaming, which makes devices like DVD players obsolete, they can’t perform tasks like gaming as well as a dedicated input device such as a PC or console.
Composite Video (RCA jack plug)
One of the earliest AV Standards was developed by the Radio Corporation of America. The standard is known as Composite Video.
The signals are analog and the video is transmitted as a single signal.
Signals are transmitted through RCA cables that have connectors for 2 channels, left and right, of audio and one for video.
Older TV sets, video game consoles, audio players and VCRs are usually equipped with RCA plugs.
There have also been variations to this standard over time like YPbPr and YCbCr which essentially used a different color space to the standard RGB.
Having been introduced in 1940, this standard is slowly getting redundant as the highest supported resolution is standard definition video(480p).
Apart from this, RCA Cables are also prone to a lot of interference and noise.
These drawbacks have led to the development of better and more advanced standards. The S- Video (Super-Video) is one such signal.
However, there is still a huge retro gaming community that keeps the composite video market alive.
SCART/EIA Multiport
SCART was developed in 1976 in France by the Radio and Television Receiver Manufacturers’ Association.
It was a single connector AV port and was one of the first types of AV connections that allowed daisy chaining devices.
Additionally, since it was a single port that combined all audio and video signals, it was nearly impossible to make an incorrect connection between devices.
It supported both composite and RGB video and by the 1980’s it was adapted to support S-video signals as well.
SCART devices also introduced an earlier form of HDMI-CEC, which allowed for features such as automatically turning on the TV when your connected device is turned on, and automatically switching to the AV channel that your device is connected to.
S-Video (Separate Video) or Y/C Video
S-Video is another analog AV standard that was introduced in 1987.
Developed as an improvement over composite video standard, the S-Video separated the Luma (Brightness) and Chrominance (Color) and hence required 3 wires to transmit the video signals.
The biggest benefit of this separation was a highly improved video signal.
However, the drawback is that S-Video requires RCA connectors for transmitting audio.
S-Video was also more resistant to noise and had remarkably less signal loss.
The device sending the video signals must be equipped with the S-Video output jacks and those that receive the signal must have the S-Video input jacks.
Just like the Composite Video, most of the older devices come equipped with the capability to play S-Video.
Coaxial Cable
The Coaxial Cable consists of a thick conductor surrounded by an insulator (a dielectric).
The insulator is surrounded by a copper mesh that acts as an electrostatic shield and the structure is enclosed by a PVC jacket.
Coaxial cables have been in use for a very long time.
They are used in cable television, satellite cable boxes, home video devices, broadband internet and measuring devices.
Unlike S-Video and Composite video cables, Coaxial cables support both digital and analog signals.
The advantage of coaxial cable over other types of cables is that it offers a very high bandwidth. It is also more resistant to interference and noise by virtue of its design.
S/PDIF (Sony/Philips Digital Interface)
The S/PDIF is an audio standard developed by Sony and Philips in 1980 for the purpose of transmitting superior quality digital audio.
S/PDIF standard is based on the AES3 interconnect standard. S/PDIF cables carry two channels of uncompressed PCM audio or compressed 5.1/7.1 surround sound.(e.g.: DTS audio).
It is widely used for connecting various devices like home entertainment systems, game consoles, set top boxes and computers.
The advantage of the S/PDIF standard is that it can be implemented with both optical and coaxial cables.
Optical or TOSLINK
TOSLINK (Toshiba Link) also known as Optical Digital, uses fiber optics to transmit digital audio between various devices. TOSLINK cables and the ports were developed by Toshiba in 1983.
Unlike other cables, TOSLINK utilizes light signals to transmit the audio information while the software interface is S/PDIF.
Another positive is, apart from S/PDIF, optical cables are capable of transmitting 8 channels of digital audio at 24-Bit resolution at 48 KHz when used with the DAT Light Pipe optical interface.
Toshiba came up with the TOSLINK connectors to be fitted in the CD players developed by them.
The TOSLINK connector is very common in TV Sets, Blu-Ray Players, AV receivers, Computers and Video Game Consoles.
One of the major drawbacks of TOSLINK was the 10m limit on the cable since at the time there wasn’t a viable option to build longer cables and still transfer data at high speeds.
HDMI (High Definition Multimedia Interface)
HDMI is an digital AV interface that allows simultaneous transmission of uncompressed video and uncompressed or compressed audio between HDMI compatible transmitting and receiving devices at the highest available speed.
HDMI was developed by leading electronic equipment manufacturers that include Philips, Sony, Thomson, Toshiba, Hitachi and others as an alternative for analog video.
The HDMI standard was released in 2002 and more than 10 billion devices have been shipped globally with HDMI interfaces.
The HDMI 1.0 specification itself allowed the transmission of 1080p video at 60 Hz.
The latest version, HDMI 2.1a allows the transmission of 8K resolution video at a refresh rate of 60 Hz.
The bandwidth supported is up to 48 Gbps and with support for Dynamic HDR formats.
Coming to audio, HDMI allows the transmission of uncompressed, full-resolution audio. This inturn enables you to enjoy Dolby Atmos Sound or 3D sound if you use HDMI.
Being a digital signal, HDMI signals don’t need the A/D and D/A conversions that adversely affect the signal quality. This inturn ensures high quality audio and video.
HDMI 2.1a incorporates eARC (Enhanced Audio Return Channel), simplifies connectivity and enables the connection of multiple components and their discovery.
eARC is capable of delivering up to 32 channels of audio, that can include eight-channel, 24bit/192kHz uncompressed data streams.
The other advantages of HDMI include backward compatibility. HDMI supports DVI, PCM Audio, DTS Surround and Dolby Digital and also S/PDIF Audio.
The biggest advantage of HDMI is that both audio and video could be sent over a single cable. The add-on benefits include less complexity while connecting multiple devices, cost savings and better cable management in home theater systems.
DisplayPort
DisplayPort (DP) is very similar to HDMI in that it was developed to succeed VGA, DVI, RGB Component, and SCART.
It can carry both audio and video signals and while the earliest version supported only up to 1080p, version 1.3 added support for multiple resolutions up to 8K and support for high refresh rate up to 120Hz.
This was further developed by version 2.0 to support higher than 8K resolution, as well as multiple high resolution monitor setups.
Although both HDMI and DisplayPort are commonly used on many devices, you’ll usually find DP connectors on computer hardware such as graphics cards.
The main difference between the two standards is that HDMI supports ARC as mentioned in the previous section while DP does not.
Thunderbolt
Thunderbolt is an interface standard developed by Intel and Apple.
While it was originally developed on the Mini DisplayPort standard, by Thunderbolt 3, it was switched to USB-C.
Thunderbolt is considered to be the future of transmitting signals as in theory they are capable of transmitting any kind of signal, be it audio, video, data or power.
Coupled with the fact that it also supports high refresh rate and high resolution displays along with high resolution audio and multi monitor capabilities, makes it one of the reasons why manufacturers have started including Thunderbolt in newer setups.
Picking The Right AV Source
Over the years, a lot of different AV sources and standards have been developed. This has led to a lot of confusion among users when it comes to connecting different devices.
The standards too have evolved from analog Composite video to S/PDIF to HDMI. Each standard has brought with it a set of improvements and this has made it possible for us to enjoy 8K video on our TV screens.
With the development of HDMI, the number of cables required to transmit high quality video and audio has been limited to just a single cable.
Any one facing any difficulties or confusion regarding the various AV signals with respect to their Home Entertainment system should read this article. This article briefly describes the different types of AV sources and signal types along with their applications.
Frequently Asked Questions
What is the advantage of using HDMI?
While HDMI and DisplayPort support very similar features, HDMI supports Audio Return Channel or ARC which eliminates the need for a dedicated audio cable.
Is composite better than S-Video?
Composite video transmits the Video information as single signal while S-Video transmits the video over two signals. This inturn results in much better and clearer quality images with S-Video.
What is S/PDIF?
S/PDIF is a digital interface that allows for transmission of high quality audio either through a coaxial or optical cable. S/PDIF sends high quality audio as electric signals and supports 2 channels of uncompressed PCM Audio or compressed 5.1 channel surround sound.
