What is HDCVI?
Tuesday 10th June 2014
HDCVI (High Definition Composite Video Interface) is a solution for megapixel high definition applications, featuring non-latent long-distance transmission at a lower cost. The name has to do with its baseband and quadrature amplitude modulation technology, which is able to avoid CVBS cross talk, completely separate brightness and hue signal, and further enhances video quality.
The HDCVI solution incorporates both cameras and DVRs. The system is star topology structured — the DVR serves as a node for an over coax P2P (Point-to-Point) transmission to the camera. The technology offers two specifications: 1080p (1920×1080) and 720p (1280×720). In addition, the technology features the Auto Signal Compensation (ASC) patent, which only allows an extremely low signal distortion along long-distance transmissions.
Transmitting data over 500m over a coaxial cable can be realized, depending on the cable selected. Cable 75-3 and 75-5 are recommended for transmissions within 500m, cable 75-5 and above for over 500m. Connectors and welding process also affect the transmission distance.
3 Signals in 1 Coaxial Cable
HDCVI composites video, audio, and control signals together and then transmits them over one coaxial cable, simplifying installation. To further realize multiple-signal transmission over one cable, both audio and dual-way data communication signals are embedded in a blanking zone. This enhances synchronization with the video signal and supports a max sampling rate of 44.1kHz thanks to ASC.
The forward and reverse data channels are composited in the frame blanking zone, realizing a two-way end-to-end transmission to support control commands such as camera focus, PTZ control, real-time alarm, etc. The forward outputting data supports a high transmission baud rate, as the sending time and electric signal baud rate are predictable, and the receiving end is of high ASC performance.
On the contrary, the reverse outputting data supports a lower baud rate due to its low signal frequency and limited data, which are affected by impedance matching and channel transmission uncertainty. However, by adopting ASC, the reverse channel can restore some degree of electrical signal during long-distance transmission.