What is the difference between analoge RGB and VGA connection? Can you
interface a device with RGB output to VGA input?(Video)

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Clarification of Question by varuni13-ga on 11 Oct 2004 17:53 PDT

I am trying to use new TFT monitors to use with Medical three chip
Camera system for endoscopy. These cameras have RGB-S output-( 4- BNC
connectors) Some TFT monitors seem to have 15 pin C type connectors
and mention that they are RGB in (not VGA). The connector looks
exactly like the older VGA.
Can I connect my Camera RGB out which has a separate sync signal to a
TFT monitor with 15 pin D sub( RGB in) connctor?

I think you may be slightly confused by the terms VGA and RGB. Doesn?t
make you a bad person :-) The question mentioned TFT so you may want
to clarify your question.

VGA, stands for ?video graphics array?, an IBM PC analogue standard
for text and graphics in 256 colours, 640 by 480 pixels. Incidentally,
SVGA (super) is an extension of the standard. Prior to that were CGA
and EGA. All these standards have been largely superseded.

RGB is the colour signal separated into the three primary *additive*
colours, red green and blue, for colour reproduction from light
sources such as CRT monitors. This is distinct from the subtractive
(or pigment colours) of magenta, cyan and yellow. Within the RGB
framework, sync signals can be added to one of the channels (usually
green) but alternatively as a separate signal.

The older style mini 15 pin ?D? connector is RGB but depending on
set-up can be any of the original IBM standards or the later higher
resolution ones.

Direct VGA to videos is not possible but some cards have an S-video
output for this purpose (amongst other purposes). Later cards also
have newer digital standards for more comprehensive integration to
compatible devices.

http://www.webopedia.com/TERM/V/VGA.html
http://www.webopedia.com/TERM/S/S_Video.html
http://www.epanorama.net/circuits/svideo2cvideo.html

Does this help?

Best

Ahhh, I see. Trouble with flat screens is that they prefer to be
driven at ?native? resolution because each pixel is addressed, as
opposed to CRTs where the beams are just thrown at the screen. When
installing for use with a PC, the driver disk sets the optimum
parameters. However, analogue input TFTs can generally accept quite a
wide range of horizontal and vertical sync frequencies, but it may be
that some of them won?t always display the correct aspect ratio or
full width. Not absolutely sure about this, just thinking of how the
circuitry would work. CRTs (almost) always have a width tweak.

As regards the signal levels (RGB and sync) there should be no problem
-- the standards and pin allocations were set centuries ago and are
mostly adhered to. There are different sync standards but the
circuitry should auto detect unless it is *really* stupid. The reason
that it?s not VGA is because the VGA is a subset of RGB, as is SVGA.
Kinda loose terms and it wouldn?t actually be dreadfully wrong to call
it SVGA. Thing is though that the mini 15 way D is not a VGA, RGB
connector or anything else like that, just that it is familiar to most
in that application.

What you want to do is track down the sync rates of the camera and the
TFTs to see if they are compatible. I?m assuming that the camera is
*not* interlaced -- I doubt that any TFT could cope with this. If all
seems OK, just wire up a 15 way mini D to the BNCs and it should be
fine. Won?t blow anything up. Not aware of off-the-shelf adapters
(though doubtless someone somewhere...) but easiest way is to make up
a transition box, preferably metal. All parts readily available.

If you need wiring details I can hunt down a page, but you?re likely
to be able to find one easily enough. The TFT should ?find? the sync
line OK but perhaps best to check that the input accepts separate sync
and not piggybacked sync on the green.

Best

Thanks Guzzi-ga. There are standard break out wires which has 15 pin D
type HD connection on one side and RGB and two sync BNC connectors on
the other. Should that work?

A great person once said ?think before you speak.? Wish I?d listened.

What you?ve got from the camera is RBGS -- as you said and I didn?t
think too hard. That?s composite sync (as opposed to composite video).
The link below are circuits for going from 5 wire to 4, opposite to
what you want but it might help with familiarisation.

http://www.hut.fi/Misc/Electronics/circuits/vga2rgbs.html

Next link defines (partially) RGBS

http://www.audioholics.com/techtips/specsformats/audiovideoconnections.php

Finally a product which converts RGBS to VGA with sync on the green.
Don?t worry about the VGA term -- loose usage.

http://www.inlineinc.com/products/special/2067.htm

Your breakout should work if the TFT can handle composite sync. If not
you?ll have to use a box like the one above (or build one) if it can
handle sync on the green. If it demands 5 wire (RGB plus H and V sync)
then you?ll need something else.

What?s got to be established first though is the spec of the camera.
Offhand I can?t remember the sync levels of RGBS but your spec sheets
should define it. You can get hold of the spec can?t you? It might
just be TV line and frame rate and even interlaced. TFTs won?t go down
that slow.

If you post the specs I can examine them and confuse you more :-)

Best

My camera user guide doesnot go in too many details It just says
output- 4 BNC RGB, Resolution > 750 Horizontal lines. But I will dig
up more detals and post it. thanks

That?s interesting, but of course >750 lines resolution doesn?t
necessarily relate at all to the scanning. But it would have to be
higher than 750 lines so it looks promising. If you can dig up the
info we can probably nail this one, but perhaps you can post the
camera make and model and I can look it up too. If it?s reasonably
recent, it?s likely to conform to modern standards but as you know,
some specialist stuff remains unchanged for yonks so date of
manufacture can be unhelpful.

I had a brief browse through catalogues today and found some equipment
orientated TFTs which accept RGBS. Not too pricey. If time permits
I?ll check out specs of these and others. (Lot of S-Video goods around
too just to confuse even more!)

Shall keep a watch out for updates :-)

Best

The camera is Made by Thales Angenieux France. Does not give much
information on the website. but Here is the website angenieux.com. The
Camera is ATC 3000.

Hi. Didn?t realise Angenieux made this type of stuff. Will be good and
pricey. Truly dorky web site though.

The PDF is a little confusing. For the BNCs it says :
1 RGB
1 composite
2 Y/C (S-VHS)

RGB needs 3 BNCs minimum so I don?t understand. For Y/C, two leads are
required -- this is also known as S-video. Composite will be composite
video. Dunno how they get RGB out of one BNC though, unless it?s a
multi contact BNC which are very rare.

Thing that bothers me is the line and frame, not TV standards. But
what?s more bothersome is that it?s NTSC {never the same colour :-) }
or PAL, both of which are interlaced. As I said, I don?t think modern
computer aimed TFTs can handle interlaced.

Could you sent them an email to ask what they mean by the single RGB
BNC and more details of the scan rates. Also ask what they recommend
for flat screen. I presume you have CRT monitors which were supplied
(or advised).

There are numerous standards converters out there BTW, but not too
cheap. I?ll keep watching, but I don?t think I?ve done any good so far
except offering solicitude.

Best

BTW I?d sent the email myself but they want user fields filled.

Best

BTW, could you post *exactly* the legend on the BNCs.

Best

I was out of station for a while so I could not get back. The Camera
has 4 BNC connectors for RGB out- Red Blue Green and one Sync. As for
the Sync.scan rates I have no information. I have sent them the mail
but not received the answer. If it is multifunction TFT (Like Samsung
170 MP) which supports S video should it not be able to handle
interlacsed signal?

This all a bit at odds with the pdf, isn?t it. Perhaps your camera was
a ?special?. Presume you sent the serial number with the inquiry -- if
they don?t reply, guess you?ll have to badger them. As you probably
know, RGB isn?t usually interlaced, but medical stuff (like military)
follows their own agenda.

Good searching, you finding the 170MP. I had trouble with the Samsung
web site -- there ain?t nothing more useless in this world than IT.
Anyway, the Samsung 170MP looks pretty handy but the pdf doesn?t say
specifically if it can accept non-interlaced. But with the RGB on the
15 way ?D?, I kinda suspect it does, meaning that it can be driven
from computer video cards. Another term you may have noticed is CVBS,
just to confuse. That?s composite video.

So basically, whatever your signal, interlaced or not, RGB, S-video
etc, this machine should handle it if. The horizontal scan goes from
30 to 80 kHz and your camera is probably lower than that. But it might
not be a problem because s-video etc are usually lower too and it?ll
do internal resampling. However, this feature might not respond to an
RGB input.

See what Angie come back with and Samsung could then be queried.

Best