HDMI and DVI actually are more alike than they are different. Both of these support the transmission of digital signals. Both DVI and HDMI are based on specifications that are similar, because HDMI specification was derived from the specification for DVI.
There are two important differences between DVI and HDMI. The first difference is that HDMI technology incorporates content security that is called High Definition Content Protection, also known as HDCP. The other huge difference between Digital Video Interface and High Definition Multimedia Interface is that DVI can only support digital video, and HDMI can support audio and video on the same cable.
This leads to another big difference between HDMI and DVI. The number of cables that need to be used and run during installation. With Digital Video Interface at least two cables are needed. One cable is needed to support the video signal, and one cable or cord is needed to support the audio signal, because DVI can only support video, not audio. With HDMI only one cable is needed for the installation. This is because the HDMI can support all formats of digital video plus it can support multiple channels of audio signal as well.
The good news is that despite their differences, a backward compatibility for video exists between HDMI and DVI. Because HDMI evolved from DVI, they are both identical when it comes to video. But remember, DVI can not support digital audio. A good example is an older DVI connection on the source and an HDMI connector to the display. In this case, all that is needed to see the video is an HDMI to DVI cable. However, a separate cable for audio is needed to carry the the digital audio so the sound can be heard.
