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HDMI, which stands for "High-Definition Multimedia Interface", is the consumer electronic industry's first connection capable of transmitting uncompressed digital audio/video signals. Components featuring HDMI can transmit both digital audio and video over one convenient cable, replacing the tangled mess that resides behind many home theater components.
HDMI also offers improved quality over traditional analog connections thanks to all-digital transmission. Digital sources like DVDs and HDTV programming can now be transferred digitally from source to display without analog conversions that can degrade the original signal.
Unlike the HDMI interface, DVI only handles digital video. Through the use of an adapter(HDMI-DVI Conversion Cable), a DVI device can be connected to an HDMI device, but only video content can be transmitted. The audio signal would have to be transmitted through other methods such as analog RCA outputs or an optical digital output.