[sci.electronics] Video inversion

cyamamot@nunki.usc.edu (Cliff Yamamoto) (04/04/88)

Greetings A/V do-it-yourselfers,

    This circuit that I'm trying to build seems so simple, I'm surprised I
can't find anything on it.  I'm interested in building (or locating a cheap
source of) video inverters.  I've been searching through my IC ref books, but
most of the chips I see are for TV's and the like.  All I want it to do is
take a 75-ohm NTSC video signal w/ negative sync, invert the picture portion
on the signal while keeping all the sync, color burst, etc. intact, then
output it.  Essentially I'd like to use my color negatives and move them to
video by camera but invert all the color/luminance values.
    I went down to my local TV store(s) and I saw a gadget by Sony that 
(aaacckk!) went for $800.  It had this Neg/Pos switch but I don't need all
that computerized wiping and color correction junk.  If anyone can direct me
to a manufacturer (or a mag/book with a simple circuit) that can perform this
inexpensively (under $50) I'd appreciate it.

Thanx in adv!
--------------------
Clifford K. Yamamoto
ARPA:  cyamamot%nunki.usc.edu@oberon.usc.edu
UUCP:  cit-vax!oberon.usc.edu!cyamamot@nunki.usc.edu
CSNET: cyamamot%nunki.usc.edu@relay.cs.net

snyderw@pawl17.pawl.rpi.edu (Wilson P. Snyder II) (04/05/88)

In article <637@nunki.usc.edu> cyamamot@nunki.usc.edu (Cliff Yamamoto) writes:
>    This circuit that I'm trying to build seems so simple, I'm surprised I
>can't find anything on it.  I'm interested in building (or locating a cheap
>source of) video inverters.  I've been searching through my IC ref books, but
>most of the chips I see are for TV's and the like.  All I want it to do is
>take a 75-ohm NTSC video signal w/ negative sync, invert the picture portion
>on the signal while keeping all the sync, color burst, etc. intact, then
>output it.  Essentially I'd like to use my color negatives and move them to
>video by camera but invert all the color/luminance values.
>--------------------
>Clifford K. Yamamoto
>ARPA:  cyamamot%nunki.usc.edu@oberon.usc.edu
>UUCP:  cit-vax!oberon.usc.edu!cyamamot@nunki.usc.edu
>CSNET: cyamamot%nunki.usc.edu@relay.cs.net

Several months ago "Radio-Electronics" had the plans for a project that
did this and much more, a video-effects generator.  It should not be hard
to delete sone of the extranious stuff you do not need.  Sorry I don't
have the date (was 1987 or 1988 issue.)


______________________________________________________________________
Wilson P. Snyder II		beowulf!lunge!snyderw@steinmez.UUCP
318 Crockett Hall, RPI		(uunet!steinmez!bewulf!lunge!snyderw)
Troy, NY 12180-3590		518-276-2764, 802-658-3799 in summer
______________________________________________________________________

markz@ssc.UUCP (Mark Zenier) (04/06/88)

In article <637@nunki.usc.edu>, cyamamot@nunki.usc.edu (Cliff Yamamoto) writes:
> 
> 
>     This circuit that I'm trying to build seems so simple, I'm surprised I
> can't find anything on it.  I'm interested in building (or locating a cheap
> source of) video inverters.  ...

The uA733 and NE592 are 50-100 mhz video amps that are cheap $1 - $1.50
that have an inverted and non inverted output.  They are pin compatible
differential amps with the gain set by a resistor.  I used one as a video
output to convert from a MC6847 to a TTL monitor and found that they
drift a bit for a DC amp, but they were spec'd as an AC amp anyway.  The
output is limited in amplitude but is a couple of volts.

Maxim has some new video opamp chips that look hot.  The max452 and the
max455.

Mark Zenier

brown@nicmad.UUCP (Mr. Video) (04/06/88)

In article <637@nunki.usc.edu> cyamamot@nunki.usc.edu (Cliff Yamamoto) writes:
<      [...]                                         All I want it to do is
<take a 75-ohm NTSC video signal w/ negative sync, invert the picture portion
<on the signal while keeping all the sync, color burst, etc. intact, then
<output it.  Essentially I'd like to use my color negatives and move them to
<video by camera but invert all the color/luminance values.

Someone who knows more about color will have to clarify this, but inverting
the video is fine, but you will have to be careful with the color burst
phasing.  Also, something that may get in your way is the orange mask that
is used on all color negs.  It WILL get in the way of the color camera.
You may or may not be able to work it out with a color corrector, which
will need to get the negative color balanced correctly.  So, the end result
is that you may have to spend the $800, as long as the Sony box has color
correction built in as well.
-- 
	       harvard-\	       ihnp4--\
Mr. Video               !uwvax.................!nicmad!brown
	       rutgers-/  terminus-/  decvax--/

dya@unccvax.UUCP (Edison Carter) (04/06/88)

In article <1155@ssc.UUCP>, markz@ssc.UUCP (Mark Zenier) writes:
> In article <637@nunki.usc.edu>, cyamamot@nunki.usc.edu (Cliff Yamamoto) writes:

> > can't find anything on it.  I'm interested in building (or locating a cheap
> > source of) video inverters.  ...

> The uA733 and NE592 are 50-100 mhz video amps that are cheap $1 - $1.50


     The Elantec EL-2020 operational amplifier is a current mode op
amp which has excellent video performance.  It can drive two 75 ohm
lines to 2 v p-p  with no problem.  It is about $ 5.50.

     Its primary advantage over the NE 592 are an order of magnitude
better differential gain and phase performance, and a much lower 
component count (say, 2 resistors, Vcc and Vee, and the chip) for
inverting gain.  It is also much more stable than the 592, or the
Plessey SL541 (yukkk) or the NE 5539 (a nice video amp, but a mean
oscillator).  You could get the EL 2020 to work nicely in a breadboard.

     Still another possibility (for crudity, anyway) is using a TL 084
and a 74LS221 to do your gating timing, etc.  The last thing you'll
need is an FET switch.  Make it an Analog Devices ADG 201.  The TL 084
doesn't make such a bad sync separator, and at unity gain inversion,
won't be gross for home use. You might want a real comparator, though,
to drive your gate (you want to preserve the burst and sync, I think).

     Maxim supposedly has some really neat stuff, too.


David Anthony
WLQV Detroit

phd@SPEECH1.CS.CMU.EDU (Paul Dietz) (04/07/88)

In article <944@unccvax.UUCP> dya@unccvax.UUCP (Edison Carter) writes:
>The last thing you'll
>need is an FET switch.  Make it an Analog Devices ADG 201.  

Why? Lot's of companies make versions of this part, and most of them
are cheaper. Siliconix and National are the two biggest players in this
market, and probably have the cheapest prices. Harris is also a pretty
big switch maker.

While I have infinite respect for Analog Devices, I think their prices
are much too high for these jelly-bean sorts of parts. Especially for
the hobbist.

Disclaimer: I used to work for National designing analog switches. However,
until my parts come to market, I don't care who's you buy. I no longer
have any affliation with National Semiconductor, except to occasionally
ask what the heck is holding up these parts...

bfalcon@lgnp1.LS.COM (Bob Falcon) (11/05/89)

Hello Net,
 
 I am looking for a  chip  or discrete circuit that I could use to
invert the video(and sync) from the video output of a vcr to the
video input of a (wireless/uhfch14) 'rabbit' device.
and at the other end  re-invert it between the 2nd vcr & the monitor.
 
My neighbors have mentioned to me that they are receiving a channel 14
some nights :-) ... well ... Maybe I don't want them to know what movies
I watch ;-) :-) 
 
I'd prefer a chip that don't need too much  support  circuitry, but a 
simple discrete circuit would be just as good.   I'm not picky ! :-)
 
I checked an  'RCA' 'SK'  cross reference book , but didn't see anything 
close... how about it? anyone have a GTE/Sylvania  Motorola or other
cross ref books to see if they carry anything?
 
Please  email to  :  bfalcon@ls.com    or   [uunet,rutgers]!lgnp1!bfalcon
 I'll repost , if there's any  interest.
 
Thanks much guys/gals/??  
 
anyhoo, have agood one, and I'll catchya later,  Bob Falcon 
Fidonet 1:273/906 Turbo XT QBBS 215-745-9774 HST/DS

-- 
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