This page gives a general description of "sync" and how
it relates to game consoles in an RGBs signal.
Sync literally means the synchronization of lines on the
screen. All analog video signals carry some type of sync signal; Composite video carries all of the video information (all of the colors and
brightness combined), as well as the sync information to your TV. S-Video is similar to composite, but
separates the signal into two parts: Chroma (color information) and Luma (brightness information and sync).
RGB signals separate each color into their own
channel (Red, Green and Blue) and carry both the horizontal and vertical sync information in it’s own separate
channel called "composite sync" (totaling 4 channels). This is called "RGBs".
Here’s a good example of what happens if you remove the sync
cable (it’s usually much worse than this, but since I’m only on a title screen with no movement, it’s not as
Also, here’s a short clip of the same thing (once again, it’s
usually much worse than this):
It's common to stumble across articles or forums posts where
people use different names to describe sync (“regular sync”, "pure sync" “raw sync” , etc). This was
extremely confusing to me when I first started learning about sync in game consoles and I want to make
sure this page clarifies that! In the context of game consoles, there's really only three types of sync any
beginner or intermediate retro-gamer needs to know:
csync - This is just
the composite sync info with nothing else on the line.
composite video as sync -
This uses the composite video line as sync.
sync on luma - This is
using S-Video's luma pin as sync
In most cases, it's best to use csync, as there's no other information in the
signal which could cause possible interference, or incompatibilities with your setup. Certain consoles (PAL
SNES & N64) don't have csync as an option and in this case, it's best to use luma, since it
contains the sync signal, but not as much information as composite video. You can also
use composite video as sync, but interference could occur, since there's so much information traveling through
that line; The most common result of that is colors “bleeding” between pixels on the screen, causing the
picture to lose sharpness (and on some displays, it may cause interference nicknamed jailbars). In either
case, if your setup requires csync, but you only have luma or composite video to work with, you can still
accomplish that with the help of a small circuit called a Sync Stripper:
As an FYI, you may come across terms similar to RGBs,
such as "RGBHV" and "RGsB". Just to clarify, here is a basic description of each:
- RGBs is simply Red, Green, Blue and sync. In RGBs,
both the horizontal and vertical sync signals are combined into this one line.
- RGBHV is essentially the same as VGA. The "HV" means there are two
cables for sync, one for horizontal and one for vertical, totaling 5 channels.
- RGsB is "Sync on green": Literally, the green
cable also carries the horizontal and vertical sync signals, totaling only three cables. Most
displays are not compatible with RGsB, so you'd need to pass it through a device that will separate the sync
signals into a more common signal, such as an Extron RXi.
Hopefully this page covered all the basics you'd need to know about sync. I purposely over-simplified a
few of the details in hopes that it would make this page easier to understand, but if you'd like more information, I suggest watching My Life In Gaming's great video about sync: