This channel of the interface is relatively small in bandwidth compared to other signal channels clocking in at only 100KHz. However, it can be as important as any High-Speed Video signal. Historically the DDC channel has been the most problematic channel within the entire interface. DDC is considered by many to be a “sleeper” when it comes to interoperability issues.
DDC is a two-channel information channel. It shares data between both the source (Set-Top Box, DVD, etc.) and the sink (Display or any input stage). It uses a half-duplex serial protocol and was designed by Philips Semiconductor in 1982 called Inter-Integrated Circuit or I²C for short. It serves as a serial communication bus between integrated circuits (IC) on printed circuit boards. Typically, these ICs are seldom more than a few inches apart. However, in digital video I²C communications over cable can be as short as .5 Meters and long as 100 Meters, far beyond its original intent. This is where the trouble begins.