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Old 15 April 2008, 18:49   #1
rkauer
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Lightbulb Creating Component Video inside the Amiga

Hi ppl.

Reading other thread, I had an idea: since the Amiga (at least the ones who have composite out) have "almost" all signals present (Y, C, R, B), I think there is only one thing to do...

We need to "create" the missing signals!

Since the missing ones are only Pb (difference between Y and blue) and Pr (same, but red), those are just the necessary to make a "YUV" out inside the Miggy!

So the question is: can I create the necessary signals using the R, B and Y, plus a pair of low noise op-amps?
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Old 15 April 2008, 20:16   #2
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@rkauer

you would need a small component IC from the RGB to actualy pump out the YPbPr encoded signal... i shall hit my tech specs.
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Old 15 April 2008, 20:25   #3
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You've got YC though for SVideo, a couple of wires and voila.
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Old 15 April 2008, 21:07   #4
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Quote:
Originally Posted by Zetr0 View Post
@rkauer

you would need a small component IC from the RGB to actualy pump out the YPbPr encoded signal... i shall hit my tech specs.
That's what I mean. Using a pair of op-amps, configured to gain=1, and using the differencial ins, I thnik we can make a winner!

YUV (Y-Pb-Pr) is only those 3 signals. Since R, B and Y are present, it's just a matter of generating the two diff signals to achieve Pb-Pr.

And Alexh is right, YC is already in there. But I don't want S-VHS (=super-video, as someone can say), but component.
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Old 15 April 2008, 22:27   #5
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Sounds interesting - let me know how you get on!
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Old 15 April 2008, 22:56   #6
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@rkauer

hmmm this is VERY interesting.... tell me how i can help you got an idea on what if any specific OPAMPS
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Old 15 April 2008, 22:58   #7
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Commodore Amiga 1000 S-Video hack

While reading this thread I remembered a youtube video I recently watched and which is somehow related: http://de.youtube.com/watch?v=LDP8cvIXtFY
But speaking for myself, I wouldn't DARE cutting my A1000 case and fumbling around with the interiors (as a owner of 2 left hands)
Nevertheless, this video's really fascinating, so take a look...
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Old 16 April 2008, 00:15   #8
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Quote:
Originally Posted by microslave View Post
While reading this thread I remembered a youtube video I recently watched and which is somehow related: http://de.youtube.com/watch?v=LDP8cvIXtFY
But speaking for myself, I wouldn't DARE cutting my A1000 case and fumbling around with the interiors (as a owner of 2 left hands)
Nevertheless, this video's really fascinating, so take a look...

Not sure about the A1k, but in the 1200 we always have that back cover to create custom connectors. And the youtoob video is for S-VHS only. My goal is Video Component (YUV).

Back to the topic: I wonder if feeding the each op-amp positive input with R or B (before the CI clamp circuit to match the propagation times), then put Y in the negative inputs and set the gain to "1" with proper retrofeeding is enough to generate the Pr and Pb signals. Am I wrong?

BTW: I am left-handed (my right hand is useful only to hold something or when typing or playing in keyboards (I'm an ex-musician, too).

Last edited by rkauer; 16 April 2008 at 00:17. Reason: complementing
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Old 16 April 2008, 00:32   #9
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@rkauer

my friend, this is moving away (quickly) from my little knowledge and into the realms of RESEARCH

if you can tell me what you need, if i have i will post it
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Old 16 April 2008, 00:37   #10
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Post

Quote:
Originally Posted by Zetr0 View Post
@rkauer

my friend, this is moving away (quickly) from my little knowledge and into the realms of RESEARCH

if you can tell me what you need, if i have i will post it
Thanks, Zetro.

My only concern at the moment is what op-amp I'll use. Need to be very cheap and with very low noise.

Then I'll start the research on the little copper board.
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Old 16 April 2008, 00:45   #11
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well i have been toying with the 8073 tripple line Op Amps for boosting the RGB, but there is also another on the tip of my fingers that cannot remember... thats arround $4 each... and is a quad OpAmp... its slight higher rated than the 8073 too....

damn it.... wheres my brain this week.
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Old 16 April 2008, 01:04   #12
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Maplin.co.uk

http://www.maplin.co.uk/Module.aspx?...12224&doy=16m4

http://www.maplin.co.uk/Module.aspx?...=2856&doy=16m4

and several other quad op-amp packages. Not that I know which one you really need.
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Old 16 April 2008, 01:13   #13
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Question

Quote:
Originally Posted by alphonsus View Post
http://www.maplin.co.uk/Module.aspx?...12224&doy=16m4

http://www.maplin.co.uk/Module.aspx?...=2856&doy=16m4

and several other quad op-amp packages. Not that I know which one you really need.

A simple dual op-amp will be enough for the hack, thanks Alphonsus and Zetro!


We only need a way to use retrofeeding and differential at the same time on each op-amp to make the hack works. Plus I need to remember how can I set the gain to 1, since any amplification of the signals are not desired (really bad colour distortions).
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Old 16 April 2008, 01:17   #14
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Quote:
Originally Posted by rkauer View Post
And Alexh is right, YC is already in there. But I don't want S-VHS (=super-video, as someone can say), but component.
S-VHS is a type of video cassette recording system.

Svideo (Separate Video) is an analog video interface specification.

Super-video is erm.. a slang English phrase first used in the early 1970's, by exceptionally "camp" people at the end of home movies?
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Old 16 April 2008, 01:28   #15
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Quote:
Originally Posted by alexh View Post
....
Super-video is erm.. a slang English phrase first used in the early 1970's, by exceptionally "camp" people at the end of home movies?



You know this how..... were you staring in them again.... you know you will make Dreamcast Kat Dizzy very jealous!!!


anyway my brain died.... is there an OP AMP 97xx tripple or quad line ? i cannot remember... i cannot find it in my favs.... it was $4 from digikey i think... it might help RK out here....
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Old 16 April 2008, 02:27   #16
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Quote:
Originally Posted by Zetr0 View Post


You know this how..... were you staring in them again.... you know you will make Dreamcast Kat Dizzy very jealous!!!


anyway my brain died.... is there an OP AMP 97xx tripple or quad line ? i cannot remember... i cannot find it in my favs.... it was $4 from digikey i think... it might help RK out here....

Since I'm on this side of the pond (Brazil, remember?), I'll make contact with some local distributors too see what I can put my hands on.

The AD8072 (dual op-amp) sounds nice to me.
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Old 16 April 2008, 06:14   #17
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I know nothing about constructing hardware, but not sure if these equations in this post for converting to YUV from RGB will be relevant for you:

http://eab.abime.net/showpost.php?p=402395&postcount=5
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Old 16 April 2008, 19:11   #18
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Perhaps a circuit like this one is the sort of thing you are looking for? Let me know if you would like a copy of the article.
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Old 16 April 2008, 19:45   #19
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indeed, i would like a copy of the article
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Old 16 April 2008, 20:39   #20
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Zoned for your reading pleasure, hope you find a suitably devious use for it.
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