HDMI is a one-cable way to connect high-definition AV components and is currently the most common connection method used on Blu-ray players, AV receivers, cable/satellite set-top boxes, gaming consoles, and video displays such as plasma/LCD TVs and front projectors. HDMI can pass high-definition video and high-resolution, multichannel audio (including the DTS Master Audio and Dolby True HD soundtracks found on many Blu-ray discs) over a single cable, providing an easy, uncluttered way to connect your devices.
HDMI has been through many upgrades in its lifetime. You can read about previous versions through the HDMI Wikipedia page or at HDMI.org. The current spec, released in September 2013, is HDMI 2.0, which increases bandwidth up to 18 Gbps and supports the passage of a 4K/Ultra HD resolution at up to 60 frames per second. Other enhancements in the 2.0 spec include support for the 21:9 video aspect ratio, support for up to 32 audio channels and up to a 1536-kHz audio sample frequency, simultaneous delivery of dual video streams on the same screen, and simultaneous delivery of multi-stream audio to up to four users. HDMI 2.0 is now appearing on the new crop of Ultra HD TVs and projectors and will likely be the connection format of choice for any upcoming Ultra HD disc format. (Another connector you might find on a new Ultra HD component is DisplayPort. The HDMI 2.0 spec is backwards compatible with previous HDMI versions and does not require the use of new cables.
Speaking of cables, HDMI Licensing, LLC has defined five different types of HDMI cables; officially licensed HDMI cables should clearly identify their type on the packaging to help you select the kind you need:
Standard HDMI Cable with Ethernet: offers the same baseline performance as the Standard HDMI Cable with an additional, dedicated data channel, known as the HDMI Ethernet Channel, for device networking.
Standard Automotive HDMI Cable: supports up to 720p/1080i. Since an automotive system may be wired with one or more internal relays that can affect signal strength, the Standard Automotive HDMI Cable needs to send a stronger signal than other cables types, so it is tested to higher performance standards.
High Speed HDMI Cable: tested to handle video resolutions of 1080p and beyond, including 4K, 3D, and Deep Color. This type of cable is recommended for use with a 1080p Blu-ray player or gaming console, as well as new Ultra HD gear.
High Speed HDMI Cable with Ethernet: offers the same baseline performance as the High Speed HDMI Cable with an additional, dedicated data channel, known as the HDMI Ethernet Channel, for device networking.
While HDMI is a very convenient way to connect devices, the technology is not problem-free. HDMI employs HDCP copy protection to protect the digital information transferred between devices; the connected devices must establish HDCP authentication in order to transmit the signal, which is sometimes called the HDCP handshake. If the handshake is unsuccessful, you may see a blue or otherwise discolored image, or you may just see snow on the screen. Handshake issues are less common than they were in the early days of HDMI, but they still occur. To re-establish the HDCP handshake between two devices, you can try disconnecting and reconnecting the HDMI cable at each end and/or powering down the components and restarting.
HDMI can also be less reliable over long runs. If your AV gear sits only a few feet away from your TV, then a basic, inexpensive HDMI cable will likely do the job just fine. However, if you need to run HDMI across the room to a projector or through walls to an equipment room, then you'll probably need to step up to a well-built active HDMI cable that boosts the signal to extend the range, up to about 100 feet. RedMere is one chipset used in some active HDMI cables. For even longer runs, consider an HDMI Extender Kit from a company like Gefen, Atlona, or WireWorld that can send the signal over CAT5/6, coaxial, or fiberoptic cable.