Unusual software carriers. (Was :Vinyl Data- Classic Computers ) counting syncs

[Bob Rosenbloom]

--- On Thu, 10/2/08, Roy J. Tellason <rtellason at verizon.net> wrote:
From: Roy J. Tellason <rtellason at verizon.net>
Subject: Re: Unusual software carriers. (Was :Vinyl Data- Classic Computers )
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
Date: Thursday, October 2, 2008, 10:23 AM

On Thursday 02 October 2008 05:27, Gordon J. C. Pearce MM3YEQ wrote:
> On Thu, 2008-10-02 at 00:02 -0400, Roy J. Tellason wrote:
> > I've also been curious for some time as to how one could
"pick off" a
> > specific scan line to get at whatever data was in there,  so if that
> > circuit is online anyplace I'd be interested in taking a look at
it, 
> > even if it's not precisely the same thing.
>
> Detect vsync then count hsync pulses.  Or, if you can make it accurate
> and stable enough, a monostable.

Maybe my grasp of current and recent signal processing techniques is a little 
too tenouous.  My recollection of vertical sync is the composite sync pulses 
fed into an integrator which put out a fairly rounded waveform,  giving 
a "start of sync" point that was fairly ambiguous.  Maybe I oughta
study up 
on that there digital stuff.  :-)

An LM1881 sync separator chip and a counter (or PIC type chip)
is all that you need to select a line, or group of lines.

Bob