Overview of HDMI Cables
High-Definition Multimedia Interface (HDMI) cables are audio/video cables that transmit high-definition data in a digital format. HDMI cables connect media sources, such as cable boxes, DVD players, personal computers and video game consoles, to audio/video players, such as televisions and AV receivers. HDMI cables are the digital equivalent of analog cables, such as S-video, coaxial and radio frequency cables. HDMI cables convert analog signals to digital signals, which improves picture quality on high-definition televisions. Essentially, HDMI cables facilitate electronic communication between high-definition media devices.
Inside an HDMI Cable
A typical HDMI cable has 19 pins in the female end of the cable plug, each of which serves a different purpose. The first nine pins convert analog signals into digital data packets that are transmitted across various data channels. Three pins are collectively needed to convert and transmit digital data through a given channel, meaning the first nine pins in an HDMI cable provide data for a total of three channels. Pins 10 through 12 regulate the flow of data through the first nine pins and ensure that the data signals are synchronized with one another. The remaining pins serve a variety of functions, including providing power to the HDMI cable and ensuring seamless communication between the media devices.
Coding of Digital Data
An HDMI cable consists of a pair of twisted wires, which are responsible for the core transmission functionality of the HDMI cable. Before transmitting a signal from a media source (such as a cable box) to a media player (such as a television), the HDMI cable converts and encodes the signal to prevent it from degrading as it moves through the cable. The media source transmits a data signal in either analog or digital format, depending upon whether the media source is a high-definition device. The HDMI cable receives the signal, and one of the wires in the pair transmits the signal to the media player. The second wire transmits an inverse copy (or mirror image) of the signal. The media player receives the original and inverse signals and measures the difference between the two. The media player then uses this difference to compensate for any signal degradation that may have occurred during transmission.
Although there is no maximum length for HDMI cables, longer cables have significantly more potential for signal degradation. Consequently, most HDMI cable manufacturers will not produce cables longer than16 feet. Some cables used in large theaters are much longer, but these cables are generally made from high-quality materials and are quite expensive.