VGA to S-video - can't be this simple can it?

**mitaux8030** · 11-12-15, 06:56 AM

I've seen a quick and dirty cable diagram for a VGA to S-video converter, where the red & blue pins of VGA are connected together to the S-video Luma, and VGA green goes to S-video Chroma. How can this possibly work, and if it does - how 'dirty' is it?

I'm hoping to connect an old device with a 4-pin S-video output to a VGA input (or Pr Pb Y component or HDMI input) - without the use of a converter box if possible. If a converter is needed, I'd like to build it myself... schematics anyone?

**SpankedHam** · 11-12-15, 07:47 AM

Originally Posted by 6502

I've seen a quick and dirty cable diagram for a VGA to S-video converter, where the red & blue pins of VGA are connected together to the S-video Luma, and VGA green goes to S-video Chroma. How can this possibly work, and if it does - how 'dirty' is it?

I'm hoping to connect an old device with a 4-pin S-video output to a VGA input (or Pr Pb Y component or HDMI input) - without the use of a converter box if possible. If a converter is needed, I'd like to build it myself... schematics anyone?

It's not that simple. Whilst it's possible there's always one out there, I haven't come across a single card that outputs colourburst on any of the pins on the VGA plug, let alone the pins that actually carry the picture. The green pin usually does have syncs on it. Crash mixing the other colour channels and hoping to get the PAL QAM colour component out, well that's just plain dreaming.

If you want s-video out you will need a card that has hardware on board to provide it, but even then there's more to it than just that. The horizontal and vertical timing needs to be correct if you want to be able to use the s-video output as if it were 'normal'. If you only want to plug it into a TV you can probably get away with what comes out of the typical AMD (ATI)/nVidia or (cringe) Intel video chips. If you want to do things like plug it into a VCR and record to tape (God only knows why but hey....) all those devices fall short. None of them are tweakable enough to output proper PAL timing. The only series of cards I've ever come across that can do accurate PAL (or NTSC for that matter) timings (syncs, front / back porch, colour burst you name it) are Matrox's.

**mtv** · 11-12-15, 09:44 AM

+1 for Matrox.

Your description actually requires conversion the other way around... S-Video to VGA

Here's a circuit diagram.

**mitaux8030** · 13-12-15, 07:20 PM

Thanks! Sadly, some of those parts might be a bit hard to get at the local Jaycar. Looks like a commercial S-video to VGA dongle would be less hassle, and it can be hidden inside the cabinet to keep the clutter down - which was the ultimate aim. For the time being, I've done another 'quick & dirty' by ripping out an analogue modulator from an old VCR, and tuning in via ye olde analogue TV - it works enough to be useful for the moment.