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PICList Thread
'Time information on video signal'
1999\04\08@194941 by Peter Grey

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I have a video signal (PAL 1 volt P-P) and I need to superimpose time and
date information onto it and then retransmit it to a VCR. Has anyone done
this or similar and can provide a few tips?


TIA


Peter

1999\04\08@195622 by Wagner Lipnharski

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Peter, take a look at http://www.ustr.net click [NEWBIE] and select
"Download PAL-M Sync Timming Chart" if you don't have it yet... perhaps
can help you a bit.  What you want to do is just a matter of counting
the HSyncs at the Even or Odd frames, and just "And" or "Or" your
Data... just take in consideration the Horizontal speed...
Wagner.

Peter Grey wrote:
>
> I have a video signal (PAL 1 volt P-P) and I need to superimpose time and
> date information onto it and then retransmit it to a VCR. Has anyone done
> this or similar and can provide a few tips?

1999\04\08@210958 by Ron Fial

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face
If your video source is a network or cable TV box, then the stability should be
good enough to sync to it and overlay stable letters and numbers.   But if the s
ource of the signal is another VCR, then the wobble and variation of the sync re
lative to your local character generator sync oscillator will cause the letters
and numbers superimposed to jitter back and forth a little, due to the VCR servo
loop error.

I had this problem in computer controlled unit I designed for adding captions to
instructional video for a state school for the deaf.  Despite heroic efforts at
PLL stabilization, the only solution was to run the source VCR signal through a
time domain corrector, then into the title unit, then to the final VCR recorder
.

 Regards,
 Ron Fial
--------------------------
At 09:48 AM 4/9/99 +1000, you wrote:
>I have a video signal (PAL 1 volt P-P) and I need to superimpose time and
>date information onto it and then retransmit it to a VCR. Has anyone done
>this or similar and can provide a few tips?
>
>TIA
>
>Peter

1999\04\08@223824 by Wagner Lipnharski

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Dear Ron, despite your efforts to get a stable sync signal, or at least,
in sync with the image, you needed to recreate a stable sync to get a
stable final image.  I can imagine that you may exhausted all the other
possibilities, and I understand how difficult this task can be
sometimes, no doubt about that, we technicians and engineers already
lived that situation a hundred times, but, a simple $120 color TV can do
that and show a stable image from a VCR generating a jittered sync due
the servo loop error.  How the TV does that?

Without any criticism to your job, please, I am trying to see the real
possibilities to avoid to use the external time domain correction in a
possible future. Does your previous solutions got software locked into
the odd or even frame and horizontal pulses for a vertical positioning,
then a fixed time delay for horizontal targeting?  Actual close caption
microchips does a pretty good job even with a not so stable image, and
the generated text is way to stable.

Mr. Richard Ottosen from Rho Enterprises in Denver (CO) made a pretty
nice project design with a PIC16C84 and a video sync separator EL4581 to
build a close caption decoder back in 1995. Probably this could be a
solution for this subject.

Just take a look at:
http://www.brouhaha.com/~eric/pic/caption.html
:)

Wagner

Ron Fial wrote:
> I had this problem in computer controlled unit I designed for adding captions
to instructional video for a state school for the deaf.  Despite heroic efforts
at PLL stabilization, the only solution was to run the source VCR signal through
a time domain corrector, then into the title unit, then to the final VCR record
er.

1999\04\08@225023 by Wagner Lipnharski

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There is another example, this one he just put the clock time of the day
on the TV image using a PIC and few other microchips:

http://www.rt66.com/dthomas/pic/vidclock.html

Wagner.

1999\04\08@231200 by Peter Grey

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At 06:07 PM 8/04/99 -0700, you wrote:

My source is a CCD camera. Preferably I would like a "chip" that took PAL
video in and another input was ASCII data in (serial) and the output was a
mix of the two. Just a wish!

thanks for the advice

Peter
>If your video source is a network or cable TV box, then the stability
should be good enough to sync to it and overlay stable letters and numbers.
But if the source of the signal is another VCR, then the wobble and
variation of the sync relative to your local character generator sync
oscillator will cause the letters and numbers superimposed to jitter back
and forth a little, due to the VCR servo loop error.
>
>I had this problem in computer controlled unit I designed for adding
captions to instructional video for a state school for the deaf.  Despite
heroic efforts at PLL stabilization, the only solution was to run the source
VCR signal through a time domain corrector, then into the title unit, then
to the final VCR recorder.
{Quote hidden}

1999\04\09@032857 by Andy Stephenson

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I think that you should be looking at OSD chips. NEC, ROHM and ST do them,
plus some others no doubt.

They take you data to be displayed serially (SPI I think). You usually have
to provide sync signals, and sometimes the overlay is done external to the
device. A 4051 will do the job here. Make sure that the chip you choose can
clamp the signal. If not, you have to do it yourself. Again, a 4051 will do
the job.

Search the manuf's sites for OSD and take it from there.

I think that one of the PICLIST regulars sells a board to do this - I may
be totally wrong here but BOBCAT or something like rings a bell.

Rgds...

...Andy
>
>My source is a CCD camera. Preferably I would like a "chip" that took PAL
>video in and another input was ASCII data in (serial) and the output was a
>mix of the two. Just a wish!
>

1999\04\09@051713 by Nigel Orr

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At 09:48 09/04/99 +1000, you wrote:
>I have a video signal (PAL 1 volt P-P) and I need to superimpose time and
>date information onto it and then retransmit it to a VCR. Has anyone done
>this or similar and can provide a few tips?

This page has 2 PIC-based PAL output projects (pong and tetris) and some
pointers to useful info about video signals- it might be of use to you... I
would expect the time bit to be _fairly_ easy.

http://www.efd.lth.se/~e96rg/pic.html

Nigel

1999\04\09@091051 by Paul Fletcher

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Peter,

The UK mag EPE ran a project along these lines a few months ago - It is
a PIC based video signal date/time stamper based on a PIC, the code for
it can be found on their ftp site at
ftp://ftp.epemag.wimborne.co.uk:21/pub/PICS/timedate
a back issue of the mag is available from their web site at
http://www.epemag.wimborne.co.uk/
I'm not sure if is what you want, but sounds something like it.

Paul Fletcher.

Peter Grey wrote:
>
> I have a video signal (PAL 1 volt P-P) and I need to superimpose time and
> date information onto it and then retransmit it to a VCR. Has anyone done
> this or similar and can provide a few tips?
>
> TIA
>
> Peter

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