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High Definition Multimedia Interface (HDMI®) is a digital audio interface that also carries multi-channel or surround sound digital audio signals. HDMI® improves upon previous analog technologies while requiring only a single 19-pin HDMI® cable to carry audio and video. An HDMI® converter is a standalone middleman device that digitally processes analog signals to HDMI®.
For example, many older DVD players have analog component video outputs (YPbPr) for connecting to a standard definition TV (SDTV) or high-definition TV (HDTV). Component video separates the video signal into chroma and luma signals which carry separate color and synchronization data streams. The RCA-type component ports on commercial products are color-coded red, green and blue, as is the designated three-headed component video cable. Component video requires a separate audio cable, which can be either multi-channel digital audio if available, or stereo RCA analog audio.
As HDTVs have overtaken SDTVs, many people prefer to use their HDTV HDMI® connections over alternate and inferior analog connections. In the example above, an HDMI® converter would sit between the DVD player and HDTV receiving the outgoing component and audio cables from the DVD. The HDMI® converter internally converts the signals to the digital HDMI® format, and processes the stereo audio into multi-channel digital audio (if required), outputting these streams to an HDMI® port on the converter. An HDMI® cable then runs from the converter to the HDMI® input port on the HDTV.
There are several different types of HDMI® converters available to handle a variety of scenarios and connections. An HDMI® converter made for S-Video and composite video signals can upscale standard definition video resolution to the high-definition 720p format. The original aspect ratio may remain unchanged, in this case 4:3 verses the high-definition 16:9 aspect ratio. Watching 4:3 upscaled signals in a 16:9 footprint is possible by using the manual aspect ratio control on the HDTV, however, the picture will be unnaturally stretched in some manner to fill the screen, as the original signal simply doesn’t have the data available to extrapolate a larger picture.
Digital Video Interface (DVI) used on current computer monitors is already compatible with HDMI®, but does not carry audio. An HDMI® converter can be used to merge DVI and outgoing digital or analog audio signals for HDMI® output as well.
In some cases, you might require the reverse setup, when for example, you want to output an HDMI® signal to an analog device that only has analog inputs. This flavor of HDMI® converter is also available, reversing the processing to reformat HDMI® into the appropriate analog signals for outgoing analog cabling. This converter includes a downscaler, where the converter will accept 480i through 1080i input, and output 480i (NTSC) or 576i (PAL) SDTV for those devices that only support standard definition resolutions.
HDMI® converters are available online and at many local retailers that sell HDTV and home entertainment equipment. The technology used to upscale or downscale signals can make a significant difference in picture quality, so it pays to read customer reviews to see which products have high satisfaction ratings.