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SVGA to composite video

A

Another Nick

Jan 1, 1970
0
Hi,

I have an application where I need to replace a CCTV image on a monitor
with a 800x600 computer-generated image at certain times. The CCTV images
are usually composite (PAL) video. The easiest way as I see it is to
convert the SVGA RGB to PAL using an AD725 or something like that and
switch between the two PAL sources.

Most of the screens in use (15" TFT) will take either VGA or composite
video either by a separate interface option or a menu, so should
handle the non-interlaced video at the higher refresh rates and higher
lines-per-field than standard TV systems.

My feeling is this should work, but is there any complication I might've
overlooked? Is there a better NG to ask this question?

(This is an embedded PC/104 system, so I don't have the luxury of buying a
PC/TV card etc)

Thanks
Nick
 
x-no-archive:yes
Hi,

I have an application where I need to replace a CCTV image on a monitor
with a 800x600 computer-generated image at certain times. The CCTV images
are usually composite (PAL) video. The easiest way as I see it is to
convert the SVGA RGB to PAL using an AD725 or something like that and
switch between the two PAL sources.

That chip won't help you.
Most of the screens in use (15" TFT) will take either VGA or composite
video either by a separate interface option or a menu, so should
handle the non-interlaced video at the higher refresh rates and higher
lines-per-field than standard TV systems.

That's not a given, but a good bet.
My feeling is this should work, but is there any complication I might've
overlooked? Is there a better NG to ask this question?

Yes, you overlooked the fact that "RGB" just refers to how colors are
encoded, not to any particular overall video standard.
That chip is just a modulator, it will take 15KHz RGB data and create
a modulated video signal. It won't convert frame rates or re-size
pixels.
If you feed it 800 x 600 non-interlaced RGB, it will try to modulate
that color information into a 800 x 600 non-interlaced "PAL" or "NTSC"
signal which no TV will understand.
(This is an embedded PC/104 system, so I don't have the luxury of buying a
PC/TV card etc)

Thanks
Nick

Check your local computer store, there are VGA to NTSC boxes, maybe
some will work at 800x600. If my 10 year old Voodoo 3 3000 has a chip
that lets me see "800x600" on my NTSC TV, surely it exists.

If you have your heart set on on a project, look into these guys:
http://www.chrontel.com/
 
M

Martin Griffith

Jan 1, 1970
0
Hi,

I have an application where I need to replace a CCTV image on a monitor
with a 800x600 computer-generated image at certain times. The CCTV images
are usually composite (PAL) video. The easiest way as I see it is to
convert the SVGA RGB to PAL using an AD725 or something like that and
switch between the two PAL sources.

Most of the screens in use (15" TFT) will take either VGA or composite
video either by a separate interface option or a menu, so should
handle the non-interlaced video at the higher refresh rates and higher
lines-per-field than standard TV systems.

My feeling is this should work, but is there any complication I might've
overlooked? Is there a better NG to ask this question?

(This is an embedded PC/104 system, so I don't have the luxury of buying a
PC/TV card etc)

Thanks
Nick
This is not a trivial problem
http://epanorama.net/links/videosignal.html#conversion

I would use something like this
http://www.kitmondo.com/ViewListing.aspx?lid=46279&prodName=Sony_DSC-1024G-scan-converter


martin
 

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