Re: Video overlay generator
- From: MooseFET <kensmith@xxxxxxxxx>
- Date: Wed, 15 Aug 2007 18:16:27 -0700
On Aug 15, 8:46 am, pantel...@xxxxxxxxx wrote:
On 15 aug, 14:34, Frank Raffaeli <SNIPrf_man_frT...@xxxxxxxxx> wrote:
[....Video overlay...]
Yes, this is very possible, I have done it with some simple analog
switches (HC4053).
You don't want to use a HC4053. They switch very quickly. This makes
frequencies up into the chroma carrier frequency. You want a softer
switching so that you stop short of that.
In case of color, you also need to insert the right chroma phase, that
means in PAL
that you need to phase lock a 4.43 MHz xtal and get the H/2 info too,
apart
from the H PLL and V sync.
You want to go up to 4 times the normal frequency. It is still low
enough that HC counters will work and you can get you phase shifted
components by using a Johnson counter.
[...]
It is all low power analog stuff, could easily fit on one board, if
I've seen boards up to 12 x 18 inches. You are right it is small but
perhaps you should have used a different way to express it.
.
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