What Is HDMI?

 

High Definition Multimedia Interface (HDMI) is arelatively new digital cable specification that is bettersuited for the unique needs of the consumer electronicsmarket. It's design is built upon many of the featuresand benefits of DVI (Digital Visual Interface).HDMI is similar to DVI in many aspects. It provides ahigh-bandwidth, all digital connection with encryption(HDCP - High-bandwidth Digital Content Protection)for use between digital sources and displays. DVI andHDMI are both 24 bit digital RGBHV interfaces basedupon a technology called Transition Minimized DifferentialSignaling (TMDS). An explanation of TMDS isa bit complicated and lengthy for this bulletin, butgood one can be found in the February 2003 issue ofWidescreen Review . HDMI supports bi-directionalcommunication between devices, as does DVI. Thisallows the digital TV to communicate it's preferredvideo and audio formats to the source, and the sourcecan communicate what video and audio format it isproviding (16:9 or 4:3, 2 channel audio, etc.) DVI andHDMI are capable of supporting all current High Definitionformats.There are a number of differences between HDMIand DVI interfaces.

 

 

 

1. HDMI is more user-friendly for consumer electronics.The physical size of the connector is one of themost immediate differences. DVI uses a bulky 29pin connector, while HDMI utilizes a smaller 19pin connector about the size of a USB plug (seeillustration below).

The size of the HDMI connectormakes it ideal for custom installation applications.2. Another difference is digital audio. HDMI is designedto carry eight channels of uncompressed digitalaudio (PCM audio). It also supports compressedaudio formats such as Dolby Digital, Dolby DigitalEX, DTS, and DTS EX.3. Control over HDMI devices is possible using an embeddedCE control bus. This will allow one remote tocontrol all HDMI devices in an AV system. Instructionssuch as “pause” or “stop” can be sent, simplifyingease of use.4. Cable length is improved with HDMI. The designerof HDMI, Silicon Image, has demonstrated HDMIover 20 meter cable lengths. TRIBUTARIES offers alimited selection of HDMI cables and is currentlyworking on adding more to the product line.5. Although the pin configurations and sizes are different,HDMI is fully backward compatible with DVI.An HDMI device, when plugged in to a DVI deviceusing a DVI-HDMI adapter ( offered by TRIBUTARIES)will support digital video over the link. The additionalfeatures supported by HDMI are not availableto devices using a DVIinput or output.