HDMI

What Do TV Wires Do?

Before we can definitively explain what the wires connected to a television set do, we need to talk about the many kinds there have been and currently, are. We will end this journey with a very special wire, and undoubtedly the very reason you are reading. We will answer “What is HDMI?”, and give you a lot more information along the way, so that you truly understand the importance of this wire.

A television generally receives two different types of signals, video and audio.

To receive these signals, there is a wire (or optical cable, more on that later) connected to the television that also connects to another device that creates or collects the signal from media (VHS, DVD, radio waves, cable TV, etc).

The devices that can send a signal to a television vary, and have changed drastically since the invention of the television in the 1920s and becoming common in homes shortly after.

Here is a list of a few devices that send signals to TVs:

  • UHF Antenna
  • Cable TV
  • Digital Cable TV Receiver
  • Satellite Receiver
  • VCR, DVD or BluRay Player
  • Video Game Console (PlayStation, Xbox, Nintendo, etc)
  • Media Streaming Device (Apple TV, Roku, Android Box, etc)

These devices all collect or create signals from a media source and send them to the signal “monitor”, or television.

Without some type of wire, this would be almost impossible, as wireless technologies have not been able to keep up with the advancements of video and audio signals to the point where they would be excellent quality, with no noise, and in “sync” (audio and video playing at the same time so that they line up as they should). The best that wireless technology can provide is sending the media to a decoding device that is connected to the monitor, of which some are built in, in the case of smart televisions.


What Type of Wire Does What?


UHF Antennas

Back when UHF antennas were the most used media source, a very simple wire was used.

UHF Antenna

UHF stands for Ultra High Frequency. It falls in the range of 300 MHz and 3 GHz and has been used for television broadcast, cell and cordless phones, satellite communication, Wi-Fi, Bluetooth, and many other methods of signal transfer. It is heavily dependent on line-of-sight and can be difficult to receive a long distance from signal towers without very tall antennas.

UHF ConnectionUHF connected to the back of the television through a wire very much like a speaker wire or the wire in an extension cord or power plug. In fact, a lot of people would use such wires to connect their antenna to their television over long distances, since they were readily available, and there was no need for proprietary connections like we have today.

Unshielded Copper Wire

These wires were unshielded twisted copper wire and could very easily pick up noise from other electrical devices nearby, giving a poor quality signal to the television.

UHF eventually developed into much simpler connections that could be used inside a home, such as the following picture (I myself owned the exact same model at one point).

RF UHF DishThese types of antennas were popular when most people did not pay for cable or satellite television service, and generally only provided a few main, local broadcast stations (in Nova Scotia, where I grew up, there was CBC, CTV and Global).


Cable and SatelliteTV

The next step from UHF was cable and satellite television service. These were a much stronger signal, over a wire sent into your home, or directly from a satellite orbiting the Earth.

Satellite technology eliminated the issue of line-of-sight restriction with UHF signals. Each satellite could receive the signals from the last, and repeat the signal to everywhere on Earth (or wherever the company that owned them wanted coverage), creating a blanket of signal that satellite dishes could receive.

These new ways of receiving signals were connected to the television with a different kind of wire.

Coaxial CableCoaxial cable, or coax as it is commonly known, became the new standard for television signals (and early high-speed internet). They were quite similar to the wires being used for UHF antennas but were electrically shielded, greatly reducing the amount of noise being picked up and vastly improving the signal quality (one of the reasons it is acceptable for internet use). Coax consists of a few twisted or one solid copper wire, surrounded by an insulator, which is surrounded by a woven copper “shield” that accepts electrical noise and isolates it from the copper core that delivers the signal.


VCR, DVD, BluRay, Video Game Consoles

The VCR and Betamax Player both were able to be connected using UHF and coax, with the addition of RCA jacks on most.

RCA cables were developed by Radio Corporation of America, the makers of commonly known RCA televisions. They were originally used to connect a home radio and a phonograph console, or turntable.

RCA CableThese cables contain two wires each, a signal wire in the center, and a ground wire connected to the outer ring.

RCA cables have been widely used for video, analog audio and digital audio, mostly due to their ease of use, simple connections and durability. For most television applications, video (when using one video cable) is yellow, the right audio channel (for stereo) is red and the left audio channel is white.

There are many other configurations, such as component (analog) video, in which the video signal is split into two or more channels (three for the popular television variety) to give a much more precise signal, where black and white were largely the same on all channels, but red, green and blue were separated (in the RGB television type), and put back together by the television using another signal usually sent over the green wire.

Component VideoComponent video gave a much higher quality signal than composite video (just a yellow RCA cable), but still required audio to be sent separately, giving five wires for video and stereo sound, as pictured above.

S-Video was a cable that appeared shortly before component video became widely used, and was between composite and component video in quality, only using one cable. The cable contained four separate wires and separated the black and white from the colour signals. It provided better image quality than composite video, but lower colour resolution than the slightly better component video. It also required separate audio signal cables.

S-video


Digital Media and HD

When the media became more and more realistic, the cables carrying the signals needed to change. The standard definition signal that was carried over composite, s-video and component video cables was no longer enough.

The new signals were digital and contained a minimum of four times the information.

Also, people, on average, owned more devices that they were connecting to their televisions, making it complicated, messy and almost dangerous to have five or six wires connected to every device.

While signals grew more complicated, the means of connecting them to the television became simpler.

The first improvement came in the form of DVI, or Digital Visual Interface, which was simultaneously used on computer video cards to high-end CRT monitors. DVIDVI was very similar to the previously used VGA, or Video Graphics Array, which was designed to only carry an analog signal, but added was a digital connection in the same connector that was either single link (up to 1920 x 1200 at 60 Hz), or dual link (up to 2560 x 1600 at 60 Hz).

VGA and DVI both lacked the ability to carry audio signals, so there was still the need for separate cables.

DVI was more than capable of handling the original HD standards that televisions and computer monitors were able to handle since 720p was 1280 x 720 and 1080p was 1920 x 1080. However, that was where DVIs capabilities ended.


HDMI Was Created

HDMI

HDMI stands for High-Definition Multimedia Interface, a fancy term for a cable that can transport HD signals.

Not only can they transport HD video, but the sound is also sent over the same wire! This is something that was never done before and greatly simplified connecting devices to your entertainment center.

HDMI was developed starting April 16, 2002, by a collaborating Hitachi, Philips, Panasonic, Sony, Toshiba and Silicon Image, mixed with Digital Content Protection, LLC and Intel providing HDCP which is very similar to the copy protection that was developed for VHS (that would modify the image when played through a second VCR, diminishing the illegal copying of copyrighted work).

The cable itself has a connector with 19 pins (meaning 19 separate wires), which carry SD, ED (Enhanced Definition, 480 like SD with progressive scan, making it 480p), HD, UHD and 4k, along with (since HDMI 1.4) ARC and HEC.

HDMI Wires

ARC, or Audio Return Channel, became necessary with the advent of smart televisions. It makes it so that an audio signal can be sent back from the television to the audio device connected to external speakers. Otherwise, you would need to use another cable to send sound from apps like Netflix through the “Audio Out” on your TV, into your “Audio In” in your receiver, then out to your speakers.

HEC, or HDMI Ethernet Channel, is used for IP-based communication with devices and provides bidirectional communication. This allows your devices to connect to the internet without each device requiring its own Ethernet cable from the router, creating a single, Internet-connected entertainment center. This further simplifies connections to your devices by vastly reducing the number of cables connected.

So, there you have it.

HDMI has effectively replaced, with one cable, what once required up to ten (component video, separate surround channels via RCA cables and an Ethernet cable).


HDMI and the Future

HDMI started with version 1.0 being able to support up to 165 MHz signal speed, with resolutions up to 1920 x 1080 or 1920 x 1200 at 60 Hz (which you may recall is what DVI was able to do without the ability to also carry audio signals). Version 1.0 was able to produce signals with up to 24 bit/pixel colour depth, meaning 16,777,216 colours were able to be reproduced by the video signal being sent over an HDMI 1.0 cable.

As of January 4, 2017, with the release of HDMI 2.1, signals up to 10k resolution (not a standard ratio signal, at approximately 21:9, and pixel count of 10240 x 4320) at 100 Hz, or 8k (7680 × 4320, see Samsung 8k QLED TV Review) at an incredible 120 Hz refresh rate, using up to 12 GHz signals.

HDMI 2.1 also supports Dynamic HDR (see What is HDR?), eARC (Enhanced Audio Return Channel, which allows for Dolby Atmos and DTS:X), and Dolby Vision (a superior version of HDR).

To make Dolby Vision and HDR10+ possible, version 2.1 has an amazing colour depth of 48 bits/pixel, or 281 trillion possible colours.

The newest HDMI cables (available on Amazon) will remain relevant far into the technology of the next generation televisions. To ensure the best possible connection between all of your devices, it is greatly recommended upgrading to HDMI 2.1 and enjoy all the benefits of the newest technology.