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Message
From: Mark McDougall<markm@v...>
Date: Thu Jul 14 01:59:37 CEST 2005
Subject: [oc] NTSC Video Encoding/Generation
Mike Delaney wrote:> Has anyone seen a free core for NTSC video generation (or something
> like a tutorial that I could at least use as a starting point)? I
> haven't had much luck yet, I can get a nice zigzag pattern that's
> supposed to be verticle lines ....
There's a site where someone has done some NTSC generation in a PIC - I
used that as a basis for my experiments with video generation at the end
of last year.
<http://www.rickard.gunee.com/projects/video/sx/howto.php>
> Also, it seems like most of the designs or eval boards I've found
> online use an external NTSC encoder, typically from Phillips. Is
> generating color NTSC (with a parellel DAC) that hard, or is it just
> people being lazy? :)
From what I understand, you need quite a high clock to give you the
resolution to generate the colour information for more than a few
colours. It determines how 'fast' you can change the raster colour (as
it is encoded as a phase shift IIRC) and hence limits your effective
horizontal resolution.
You'll also need an accurate clock to generate the burst signal as
displays tend to be quite fussy when it comes to locking onto the burst.
Even experiments with a programmable clock didn't produce satisfactory
results for me - I bought some PAL/NTSC crystal oscillators but am yet
to plug them into my design...
Regards,
--
Mark McDougall, Software Engineer
Virtual Logic Pty Ltd, <http://www.vl.com.au>
21-25 King St, Rockdale, 2216
Ph: +612-9599-3255 Fax: +612-9599-3266
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