VGA to S Video/ S Video to RCA

Mitch,

I might be telling you somehing you already know.

If you want to see a VHS composite video signal on a computer VGA type monitor, you will need something more than just a "cable." There would need to be some active electronics to make the NTSC (or PAL) to RGB conversion.

If you could give us more details of what and why you are trying to do this, we could be of more help.

Is it that you have a spare VGA monitor and you want to use it on your VCR? Is a PC part of the mix?

Aud_Mot
 
Mitch,

What you need to shop for is a composite video to VGA converter.

Assuming you live in North America, you are talking about NTSC composite video. That means all the video information comes down a single coaxial cable. All mixed together on this cable are several discrete signals needed to generate an image on a TV screen.

A computer monitor needs those different signals on individual wires, that is why you use a 15 pin monitor connector.

Add in that your computer monitor displays it's image with 3 important differences. a) It redraws the screen at a faster rate b) It does it from top to bottom, (the non-interlaced spec you see) TVs do it very other line line then goes back to the top and does the lines it missed first time (called interlaced) c) your computer monitor has roughly 2x the lines of resoultion of a Standard NTSC TV signal. 1024 lines computer Vs 525 lines TV.

A broadcast engineer could take me to task for some small errors in the above, but I simplified things for easier understanding.

That explains why just a cable will not work. You need an active converter. I would be suprised if you can get one for under USD $100.00. Broadcast ones cost thousands.

You might be disapointed with the results. "Blowing up" 525 video lines to 1024 lines might sound like a good idea, but you will just be seeing more of the imperfections and noise of your source. It is very much the same as enlarging an old snap shot.

If you do buy something, see if the store will let you try it out first, or let you return it for a refund.

Good luck,

Aud_Mot
 
Mitch said:
well see, they have these composite video to VGA adapters that are these yellow boxes for about $80.00 USD. These are the only ones I have been able to find.

Heres something else I just found.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1371065458

The E-bay item won't do what you want. It goes the wrong way. Besides, its still not a composite signal. I really don't think you're going to find a passive cable to do what you want. In addition to the items that Aud_Mot mentioned, you have several steps to go through just to get the VGA signals. You have to first separate out the chroma and the intensity (I think that's what its called, I'm blanking on it right now) signals. Then you have to figure out how to separate that into an RGB signal. Next you have to get the horizontal and veritcal sync pulses out of the stream and separate those onto their own lines. (Yes, it could be re-generated, but then you need a gen-lock to make sure its synched to the original signal)

So, as you can see, its pretty complicated and not easy to do. It can be done, but not with a passive cable or set of cables. Your best bet is one of those $80 boxes. Although I have to question spending $80 on a box to convert a crappy image onto a probably small monitor, when you can spend the same $80 (or maybe a little more) and just buy a TV with a tuner and everything else!
 
You could connect an AD7185 to ADV7190... the video will go through an A-D / D-A cycle, but it will do what you want. You could also use the comparable Philips parts (SAA711x series and the like) or one of the other AD parts if you can't get your hands on those specific chips, but those are the ones which came to mind. I'm afraid I don't know of a chip that will do what in the analog domain.
 
hifiZen said:
You could connect an AD7185 to ADV7190... the video will go through an A-D / D-A cycle, but it will do what you want. You could also use the comparable Philips parts (SAA711x series and the like) or one of the other AD parts if you can't get your hands on those specific chips, but those are the ones which came to mind. I'm afraid I don't know of a chip that will do what in the analog domain.

hifiZen,

That is is an interesting chip set. I have always been disappointed by the video/audio routing options of HT receivers. The ones I have looked at have Composite and S-Video inputs and outputs, but don't convert a composite input into an S-Video output (or vise-versa). This means that you end up having to connect the both the Component and S-Video outputs to the TV and switch the TV between them (assuming you are using a mix of input sources). Add component video to the mix and it gets even uglier.

I would think that a HT preamp that converted any video input to the best output format your TV supports would be way cool. You would no longer need to switch both the HT receiver and the TV when changing input sources.

I also noticed that the ADV7190 has Macrovision control registers (and the ADV7191 doesn't support Macrovision). This could also be a way to get around pesky Macrovision compatibility issues.

I have been working intermitantly on a 4 X 4 S-Video crosspoint switch (MAX456) and this could end up being expanded to include signal conversion as well. Got to think further about this.

Phil
 
S video to composite is the only simple conversion in the bunch
- I cannot vouch for the quality

lifted from:
http://www.hut.fi/Misc/Electronics/circuits/svideo2cvideo.html

(line up the plus signs in the ascii diagram-its not pasting well)
--snip---
S-video to composite video adapter
This simple adapter can be used to convert Y/C video (S-video) to a composite video. This adapter is useful in cases where your video output device has only S-video output but your signal source accepts only composite video input. This circuit works with both PAL and NTSC video standards.


Y-ground------------------+
+---------- RCA/composite ground
C-ground------------------+

Y-------------------------+
+--------- RCA/composite video
C------------||-----------+
470pF