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From: Richard Dungan
Subject: Re: Help? Ways to build RGB divider to NTSC UHF transmitter?
Date: Wed, 13 Nov 2002 18:25:19 +0000
Organization: Radix Electronic Designs
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Dan Barlow wrote:
>> I want to take a 1600x1200 rgb signal. cut it into to 320x240 pieces.
>> Then broadcast each piece to a separate uhf channel.
>> What's the easiest way to do something like this. How much would it
>> cost to prototype such a device.
>> right now it's for a science project at my school, and I'll be seeking
>> grant funding to build it.
>It would be very hard to do this in the way you describe.
>First you would need very fast Analog to Digital converters
>to sample the source RGB. In the range 250 - 300 MHz I would think.
>Then you would need a frame buffer for each output, and a NTSC encoder
>for each output. The logic to steer the samples coming in at 300
>MBytes/sec * 3 channels will have to be extremely well laid out.
>You might need to double-buffer each output to allow one buffer to be
>filled at high speed while the other is output at NTSC speed.
>Hmm, you might be able to do it all in a fast FPGA with outboard
>static RAM and ADCs and daughterboards for the outputs...
>I think you would be better off buying a quantity of TVout
>cards and doing the image breakup in software. You can get
>video cards with up to 8 VGA outs and do vga to TV with an
>external box... but you're looking at 25 outputs so it will
>get expensive whichever way you look at it.
As Dan B. says, this is not a project for the faint-hearted. My
suggestion is that you get your digitizer ready-made as an LCD
controller. DigitalView sell suitable products although here in the UK
their customer sevice beggars belief. There are others.
After that, Dan B is pretty well on the money. A fast FPGA, emulating an
LCD input, for mapping and timing, and some dual port RAMs to buffer the
sub-displays. AFAIR you can download suitable FPGA design software from
both Altera and Xilinx. The dual-port RAMs could come from IDT, among
Then, fast ADCs and ready-made NTSC modulators (Astec?) to generate your
I hope this helps.
Richard (who has been involved with something similar)
I may be able to help more if you email me privately, avoiding the spam
Radix Electronic Designs, Orpington, UK
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