CVBS

CVBS is a single analog video signal that carries picture information, synchronization pulses, and blanking intervals all mixed together on one coaxial cable. The signal rides at baseband, typically 1 volt peak-to-peak, and was the standard for consumer and broadcast video from the 1950s through the early 2000s. A CVBS output appears on older television sets, VCRs, DVD players, and security cameras as a yellow RCA jack (often paired with red and white audio connectors).

The signal structure divides each frame into horizontal lines, with each line containing active video data followed by a blanking interval. During blanking, the electron beam in a CRT resets to the start of the next line; synchronization pulses (sync) embedded in the signal tell the display when to perform this reset. The composite format keeps these three elements, video, blanking, sync, inseparable in a single waveform, which simplifies wiring but sacrifices picture quality compared to separated component signals.

Variants and practical constraints

CVBS exists in regional standards that differ in line count and refresh rate. NTSC (North America, Japan) uses 525 lines at 59.94 Hz; PAL (Europe, Africa, Asia) uses 625 lines at 50 Hz; SECAM (France, parts of Africa) also uses 625 lines but with different color encoding. These standards are incompatible; a NTSC camera connected to a PAL display will show no color or a distorted picture. Cable length matters: runs beyond 20 meters degrade the signal noticeably, and poor shielding allows hum and RF interference to corrupt the image as dark lines or snow.

The composite approach bundled everything for cost and simplicity in an era of limited bandwidth and component count. Separating luminance (Y) from chrominance (C) in S-Video, or splitting into full component video (separate R, G, B or Y, Pb, Pr), eliminates crosstalk between color and brightness information and produces sharper pictures. Most modern equipment abandoned CVBS in favor of digital signals like HDMI, but CVBS persists in closed-circuit video, legacy broadcast chains, and retrofit installations where replacing wiring is impractical.