HDMI stands for High-Definition Multimedia Interface. HDMI is a type of digital connection capable of transmitting both high-definition (HD) video and high-resolution audio over a single cable. With HDMI cables, you eliminate the cost, complexity, and confusion of using multiple cables for audio and video. The development of HDMI cables began on April 16, 2002, and version 1.0 HDMI cables were in stores by late 2003.

Uses of HDMI Cables

HDMI is used to connect high-definition devices. For example, HDMI cables can connect a HDTV to a Blu-ray disc player, PlayStation 3, Xbox 360, cable box, and other HD devices. HDMI also reduces the number of cables needed to deliver audio. Instead of handling three different A/V cables, you can simplify your life by using only one HDMI cable.

HDMI Cables and Digital Video

It is common to see HDTVs with "1080p display" or "720p display," so let's break down what that means. The display specification of an HDTV consists of a number followed by either a "p" or an "i." The number signifies the vertical height of the TV screen in pixel lines. An HDTV with a display of 1080p or 1080i has a screen height of 1,080 lines. A 720p display refers to a screen that is 720 lines high. Larger numbers mean a bigger or more detailed display.

The letter – either p or i – refers to how the pixel rows are scanned to create a picture. P stands for "progressive" and I stands for "interlaced."

• A progressive scan means that all pixel lines are scanned at the same time. Progressive scans offer you a better picture.
• An interlaced scan means that the pixel lines are scanned in alternation. Odd-numbered lines are scanned first, and even lines are scanned on the next pass.

Because HDMI is a digital interface it provides noticeable higher resolutions and sharper displays. HDMI cables deliver better image quality than any other cable, capable of a 1080p display at 60 frames per second (60 progressive scans per second). More frames per second means a smoother-looking picture. Digital video with HDMI is sharper than video signals sent through component cables, which often suffer from softness and ghosting. This difference really stands out with small, high contrast details like text.

A device using HDMI cables automatically delivers the most effective format for the display that it is connected to, eliminating the need for the consumer to scroll through all the format options to guess what looks best. Video resolution is very important; even if your HDTV is capable of 1080p display, its functional resolution will change based on the device that it is connected to. For example, if a 1080p HDTV is connected to a device that outputs video at 720p, your HDTV will display the video at 720p. Consequently, if you would like to consistently see that 1080p resolution you should make sure your TV is connected to devices with a matching resolution output. The new 3D TVs coming out on the market function the same way. Many current HDTVs have at least two HDMI output ports for connecting to other HDMI-compatible devices.

HDMI Audio

HDMI cables have the ability to carry 8 channels of 24-bit audio at 192 kHz. It can handle the highest level of audio such as Dolby TrueHD and Digital Theater System DTS-HD Master Audio.

Expensive vs Cheap HDMI Cables: Is There Really a Difference?

Retailers sell HDMI cables for a wide range of prices, and there are lots of slick and fancy branded HDMI cables out there promising to give you the best picture ever. However, many of these differences are purely cosmetic. The fact is that either an HDMI cable works or it doesn't. For example, it doesn't matter whether you buy Brand A's $50 HDMI High Speed cable or Brand B's $20 HDMI High Speed cable - you're going to get the same quality either way. Many people don't realize this and think expensive cables are always better, but they're really just paying for the cable's looks and packaging!

There will be no difference in the quality of your HD video if you decide to buy cheap HDMI cables – if the cables are the same, you may as well go with a lower price. Many consumers have been purchasing HDMI cables online to get a better price.

On the other hand, consumers need to pay attention to the type of HDMI cable. Each type of HDMI cable uses a different hardware schematic and transmission specification. Aside from length, HDMI cable type is the only legitimate reason to see a price difference. High Speed HDMI cables will be more expensive than standard HDMI cables, and HDMI cables with Ethernet will cost more than HDMI cables without Ethernet.

Types of HDMI Cables

There are five different types of HDMI cables. Each type of HDMI cable is described below.

Standard HDMI Cable

Standard HDMI cables are designed to handle most home applications. HDMI Standard cables are compatible with 1080i or 720p video and with surround sound. The Playstation 3 and Xbox 360 video game consoles can use HDMI Standard cables.

Standard HDMI Cable with Ethernet

HDMI Standard with Ethernet cables have the same functionality as HDMI Standard cables, but they include a built-in Ethernet channel that allows connection sharing and device networking. Standard HDMI cables with Ethernet work great for streaming to Samsung and Sony HDTVs.

Standard Automotive HDMI Cable

HDMI Standard Automotive cables are designed for internal cabling in motor vehicles with HD video systems, able to withstand the temperature and vibrations of a vehicle. Standard Automotive HDMI cables can transmit up to 720p and 1080i video displays and connect to camcorders, portable media players, and any other HD video device.

High Speed HDMI Cable

High Speed HDMI cables use the newest HDMI specifications. High Speed HDMI cables are designed to handle video resolutions of 1080p, 4K, 3D, and Deep Color as well as surround sound. High Speed HDMI cables are required for watching movies and playing video games in 3D. HDMI High Speed cables are compatible with the largest HDTVs, 3D TVs, Blu-Ray players, and the PlayStation 3 slim model.

High Speed HDMI Cable with Ethernet

HDMI High Speed with Ethernet cables have the same specifications as HDMI High Speed cables and include an Ethernet channel for Internet connection sharing and device networking. HDMI High Speed cables with Ethernet include shielding and gold-plated connectors for maintaining the digital signal and work great with new Samsung, LG, and Sony HDTVs.

Inside an HDMI cable

Typically there are 19 pins inside an HDMI cable. The diagram to the right identifies them.

• Pins 1 through 9 carry the three TMDS data channels (Transition Minimized Differential Signaling – the technology that allows DVI and HDMI to send high-speed digital data). There are three pins per channel. TMDS data includes both video and audio information, and each channel has three separate lines: + values, - values, and a ground or data shield.
• Pins 10 through 12 carry data for the TMDS clock channel, which helps synchronize the signals. As with the TMDS data channels, there are separate lines for + values, - values, and data shielding.
• Pin 13 carries the CEC (Consumer Electronics Control) channel, used for sending command and control data between connected devices.
• Pin 14 is reserved for future use.
• Pins 15 and 16 are dedicated to the DDC (Display Data Channel), used for communicating EDID (Extended Display Identification Channel) information between devices.
• Pin 17 is a data shield for the CEC and DDC channels.
• Pin 18 carries a low-voltage (+5V) power supply.
• Pin 19 is the Hot Plug Detect, dedicated to monitoring power up/down and plug/unplug events.

HDMI Micro Connector

The HDMI Micro Connector made its debut in late 2006. The HDMI Micro Connector enables users to send their images and videos in less time and with greater quality. The HDMI Micro Connector is small, user-friendly, and features gold-plated contacts and connectors that provide a solid bridge to reliably and quickly transport data. As of 2011, most camcorders and digital cameras use the HDMI Micro Connector for uploading pictures and video or viewing them on an HDTV. Many mobile phones and portable media players are compatible with the HDMI Micro Connector.