On Sun, 3 Dec 2000 18:17:16 -0500 Olin Lathrop
<olin_piclist@EMBEDINC.COM> writes:
> > As for DC restoration, I'm afraid I don't understand what is being
> > suggested. My thought was to capacitively couple the input, sample
> the
> > signal level when the LM1881 says that the negative sync tip
> should
> > occur(or just use a negative peak detector),
>
> You shouldn't use the sync tip for DC restoration.  It can work if
> you're
> always receiving video from the same known device, but I would
> definitely
> not use it accross video sources.  The scan line front porch is
> provided for
> the purpose of DC restoration.  It occurs after the sync tip and
> before the
> displayable part of the scan line.  This is also where the color
> burst is,
> so you have to be a little careful.  You can also use the back
> porch, but
> usually finding the front porch is a little easier with simple
> circuitry.
>
>

        By the way, waveforms for NTSC television are shown in section 73.699 of
the FCC rules. This is available as text (without the images) at
http://www.hallikainen.com/cgi-bin/section.pl?section=73.699
and as a pdf (with images) at
http://frwebgate.access.gpo.gov/cgi-bin/get-cfr.cgi?TITLE=47&PART=73&SECT
ION=699&TYPE=PDF

Watch for URL wrap. Also, on the pdf, you may have to save the file, then
rename it with pdf extension to view it.

Harold


FCC Rules Online at http://www.hallikainen.com/FccRules/

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