What is RGB and sync on green?

What it is

Sync tells the display when each line and each frame begins. It can travel in four common ways. Separate horizontal and vertical sync on their own wires is RGBHV, as on a VGA cable. Composite sync on one wire is RGBS. Sync carried on the green signal is RGsB, called sync on green. Component YPbPr carries sync on the luma signal, Y.

Professional monitors such as Sony PVM and BVM units accept RGBS and often sync on green. Consumer sets with SCART inputs generally expect composite sync. A CRT display with the right input can show these signals directly. A converter such as an OSSC also accepts them, but its input settings must match the sync type.

Why it matters

• No picture: a monitor that wants separate sync gets none from a sync-on-green source, and it shows a blank or unstable image.
• Green tint: a display that does not expect sync on green can read the extra pulse on the green line as color and tint the picture.
• Adapters: a sync stripper or converter can move sync from one form to another. Find out what your source outputs and your monitor accepts before buying one.
• Cables: a cable wired for RGBS will not carry sync on green, and the reverse. Check which wire or pin carries sync.

How this shows up in our work

Sync matters when we test the CRT televisions and monitors we collect. Each set is checked with real video sources before it is rehomed, so we know which sync types it accepts.

We also pay for rare professional ones. See the CRT recycling page for how collection works.

Learn more

• Component video on WikipediaDescribes YPbPr and how sync is carried in each analog video format.
• Analog television on WikipediaBackground on line and frame timing, the reason sync exists.