RGB Scart

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Revision as of 03:09, 11 September 2006 by Icd (talk | contribs) (Example xorg.conf)

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SCART is a European standard for connecting audio-visual equipment together. Different methods of transmitting video such as composite, Y/C (S-video) and RGB are supported on the same cable. The RGB method of transmission is of particular interest as it uses Red, Green, Blue and Composite Sync pins, which is very close to the way signal is carried over a VGA cable, Red, Green, Blue, Horizontal Sync and Vertical Sync. This makes is possible to adapt a VGA output to drive a RGB-capable SCART television directly.

Driving a TV directly has some advantages. The quality is superior to composite or S-video, and as the video card's TV encoder is completely bypassed, custom resolutions and refresh rates can be programmed. On the down side, this method can require some experimentation to get right.


As these types of cables are directly driving the television, there exists potential for damage through mistakes in cabling or even sending an out-of-spec signal to the television. Consider yourself warned and proceed at your own risk.


  • A television with an RGB capable SCART socket. Just the presence of a SCART socket does not mean the television accepts RGB. Check the manual.
  • A video card capable of supporting interlaced resolutions.
  • A video card capable of supporting a very low dot-clock frequency (14.76 MHz for PAL, 13.34 MHz for NTSC.)

Cable types

These fall into two groups. Some Radeon video cards are capable of generating composite sync directly and therefore need only a simple cable connecting the pins together. All other cards require a small circuit to convert the horizontal/vertical sync into composite sync. You can tell the circuits apart by the because the more complex version will have at least one transistor.

Video cards

Cards known to support interlaced resolutions and TV frequency dot clocks
Name Interlacing? <15 MHz dot clock?
nVidia GeForce4 MX YES YES
nVidia FX 5200 series YES YES
ATI Radeon 8000 series
ATI Radeon X300SE
(RV370 - Dell Optiplex GX280)
Via Unichrome IGP
Intel GMA950

Xorg Configuration

X Windows needs to be configured to generate the signals at the right frequencies for your TV.

Example xorg.conf

This is a working Interlaced PAL TV setup. The relevant sections of xorg.conf are below. Note the "composite" keyword which causes the Radeon to generate composite sync directly.

 Section "Monitor"
       Identifier   "Generic Monitor"
       HorizSync    14.0 - 18.0
       VertRefresh  45.0  - 65.0
       Option      "DPMS"
       Modeline     "720x576" 15.125 720 778 834 968 576 579 607 625 composite interlace +hsync +vsync
 Section "Device"
       Identifier  "ATI Technologies, Inc. RV370 5B60 [Radeon X300 (PCIE)]"
       Driver      "ati"
       Option      "DynamicClocks" "true"
       Option      "ForceMinDotClock" "14MHz"
       Option      "MergedFB" "false"
       Option      "IgnoreEDID" "true"
       Option      "VGAAccess" "false"
       BusID       "PCI:1:0:0"


Here are some links to information on how to convert the VGA out signal to a suitable signal for a RGB Scart input.